Olefin Metathesis Reaction in Rubber Chemistry and Industry and

Subscriber access provided by - Access paid by the | UCSB Libraries

Review

Olefin Metathesis Reaction in Rubber Chemistry and Industry and Beyond Peng Liu, and Chunjin Ai Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b03830 • Publication Date (Web): 01 Mar 2018 Downloaded from http://pubs.acs.org on March 1, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Industrial & Engineering Chemistry Research is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

Olefin Metathesis Reaction in Rubber Chemistry and Industry and Beyond Peng Liua,*, Chunjin Aia,b a

State Key Laboratory of Applied Organic Chemistry and Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China b

Lanzhou Petrochemical Research Center, Petrochina, Lanzhou, 730060, China

ABSTRACT: Olefin metathesis reaction has showed promising application in rubber chemistry and industry in the last decades, for the production of specialty rubbers (polyene rubbers, lowmolecular-weight telechelic oligomers, hydrogenated diene-based rubbers, liquid rubbers and other functional rubbers) and characterization and recycling of rubber products (waste tyres, or others) via ring opening metathesis polymerization (ROMP) or cross metathesis (CM) degradation technique. Here, the recent advances in both molecular modeling and experimental investigations of the olefin metathesis reaction in the rubber chemistry and industry are reviewed, and the challenges in future application are also prospected. Keywords: Olefin Metathesis; rubber; ROMP; cross metathesis; functionalization; degradation

* Corresponding author at: State Key Laboratory of Applied Organic Chemistry and Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China. Fax: +86 931 8912582.

E-mail address: [email protected] (P. Liu).

ACS Paragon Plus Environment

1

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 48

Abbreviations CM

cross metathesis

COD

cyclooctadiene

CTA

chain transfer agent

DAB

butenediacetate

G1

Grubbs 1st generation catalyst

G2

Grubbs 2nd generation catalyst

G3

Grubbs 3rd generation catalyst

HG1

Hoveyda-Grubbs 1st generation catalyst

HG2

Hoveyda-Grubbs 2nd generation catalyst

NBE

norbornene

NBR

nitrile-butadiene rubber

NR

natural rubber

PEB

poly(ethylene-co-1,3-butadiene)

PB

polybutadiene

PI

polyisoprene

PIB

polyisobutylene

PNB

polynorbornene

RAFT

reversible addition/fragmentation chain transfer polymerization

ROMP

ring opening metathesis polymerization

SBR

styrene-butadiene rubber

TPEs

thermoplastic elastomers

XNBR

carboxylated nitrile-butadiene rubber


2

Page 3 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


INTRODUCTION Olefin metathesis reaction,1-3 as one kind of transition metal catalyzed reactions, in which both the cleaving and forming reactions of C=C double bonds occur (Scheme 1),4,5 results an efficient alkylidene exchange between two alkenes. Chauvin developed the generally accepted mechanism of metathesis, namely Chauvin mechanism, via metalla-cyclobutane intermediates by [2+2] cyclo-additions/cyclo-reversions consisting metal carbenes.6 Since all individual reaction steps are reversible in such catalytic cycle, as a result, an equilibrium olefin mixture is resulted. Therefore, it is desired to facilitate the equilibrium moving toward the target product. R1

R2 calatyst

+ R3

R1

R4

R2 +

R3

R4

Scheme 1. The principle of olefin metathesis.

Nowadays, it has been widely used in chemistry and industry, for examples, drug synthesis via ring closure metathesis,7 production of various chemical compounds with natural resources as raw materials via cross metathesis (CM),8,9 and polymer materials via ring opening metathesis polymerization (ROMP) or acyclic diene metathesis polycondensation.10-12 Especially in the rubber chemistry and industry, metathesis reaction also plays an important role, including the production of specialty rubbers, and characterization and recycling of rubber products.13 In the present review, the recent advances in ROMP, CM, and their modeling and simulation, and applications in rubber chemistry and industry are reviewed, and the future application is also prospected.


3


Page 4 of 48

ROMP ROMP, as an olefin metathesis chain-growth polymerization technique, has been widely used for the industrial manufacture of several important rubber products.10 It generate unsaturated polyalkenamers with cyclic olefin monomers by means of metathesis catalysts, with the relief of ring-strain energy in strained cyclic olefin monomers as the main driving force.14 It is significantly different from the olefin chain polymerizations, retaining the double bonds in the polymer backbones. And the cis or trans configuration of these double bonds would affect the performance of the products. For example, norbornene (NBE) and its derivatives are favorite monomers for ROMP, their polymers (polynorbornene (PNB)) spanning the whole cis content range could be designed by altering catalyst, co-catalyst, and solvent, or adding additives.15 Singh et al reported the first living ring opening metathesis polymerization and copolymerization of cyclo-propene, with 3,3-disubstituted cyclo-propenes as monomers and high oxidation-state molybdenum (Mo)-based initiator (Mo(NAr)(CHR’)(OR’)2).16 The poly(3-(2methoxyethyl)-3-methylcyclopropene) were obtained under the monomer/initiator ratio of 100, with yield, Mn, Mw/Mn, and Tg of 90%, 8990, < 1.05 and -20 °C or 92%, 9930, < 1.05 and -42 °C initiated by the Mo-based catalyst with R of CMe2Ph and R’ of C(CF3)2Me or R of t-Bu and R’ of t-Bu, respectively. Grubbs’ group reported the synthesis of perfect rubber with exclusively cis and 100% head-to-tail configuration, via the ROMP of 1-methylcyclobutene with welldefined alkylidene complex (Mo(CH(CH3)2Ph)(NAr)(OC(CH3)2CF3)2 (where Ar = 2,6diisopropylphenyl)) as catalyst.17 After that, various metathesis catalysts have been developed for the synthesis of polyenes via the cis-selective ROMP of NBE (Scheme 2) (Table 1).


4

Page 5 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Catalyst n

cis-PNB

NBE

Scheme 2. Cis-selective ROMP of NBE. Table 1. Conditions and results of the reported cis-selective ROMP of NBE. Conditions Catalyst (1 mol%) Solvent

N

N Mes

O Ru O O Pri

N

O

N

N

Ref.

Time (h)

Yield (%)

Mn (kDa)

THF

r.t

72

94

347

1.87

88

18

toluene

r.t.

0.5

-

114

2.34

>95

19a

THF

r.t.

1

79

605

1.41

>95

21

THF

r.t.

1

88

521

1.49

>95

21

THF

r.t.

1

84

424

1.45

>95

21

toluene

r.t.

1

98

133

1.8

79

22

benzene

25

1/3

-

950

1.15

97

22b

benzene

25

1/3

60

1550

1.19

98

24c

N MIPP

O Ru OO

But

cis (%)

Temp. (°C)

N Mes

O Ru O O Pri

But

Results Mw/Mn

Pri

N

But

N MIPP

O Ru OO Pri

Ar N Ar N

PMe2Ph

W Ph

N Ar

Ar = 2,6-iPr2C6H3

Cl

N

Me3P F3C

V

Cl SiMe3

O

F3C CF3

PMe3


5


Page 6 of 48

Continued Table 1. Conditions Catalyst (1 mol%) Solvent

N

Me3P

SiMe3

V

Results Mw/Mn

cis (%)

Ref.

Temp. (°C)

Time (h)

Yield (%)

Mn (kDa)

benzene

25

1/3

85

1390

1.22

98

24c

C6D6

60

15

76

-

-

85

25

CHCl3

r.t.

6

80

13.9

1.6

93

26

O

F3C

F3C CF3

PMe3

CF3 CF3 Ph

O N Nb O

Ph

CF3 CF3

Ph

B(ArF)4 C N

O

CH3 i

Pr

i

Pr

Mo N

N N

Dipp

a

Catalyst amount of 0.1 mol% of NBE. Catalyst amount of 1.0 µmol, with addition of PMe3. c Catalyst amount of 0.3 µmol, with addition of PMe3. b

Veige also reported that the initiator [tBuOCO]W≡CC-(CH3)3(THF)2, combining a nucleophilic alkylidyne and an electrophilic W6+ center, could release the ring-strain energy upon cyclo-addition in ynene metathesis, as a result, cyclic stereo-regular PNB was obtained with highly cis (>99%) and syndiotactic (>95%).19,20 In Tanahashi’s work, a mild and efficient ROMP was obtained with high yield by using CuCl2 (5 equiv to the W-catalyst) as a phosphine scavenger to generate coordinatively unsaturated alkylidene species.22 Hou and Nomura claimed that the modification of their vanadium (V)-based catalyst with both imido and anionic donor ligands would result in living ROMP with high cis-specificity.24 Furthermore, Higher reaction


6

Page 7 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


temperature lead to higher catalysis activity without decreasing the cis-selectivity. And the addition of chain transfer agent (CTA) did not affect the catalysis activity.24,27 The similar result has also been reported by Autnrieth and Schrock with the Mo-based biphenolate imido alkylidene catalysts (Mo(NR)-(CHCMe2Ph)(Biphen)) and W-based imido or oxo monoaryloxide pyrrolide catalysts (W(X)(CHR’)(Pyrrolide)(OTer)).28 Boydston and his coworkers developed the metal-free ROMP mediated by the oxidation of organic initiators in the absence of any transition metals (Scheme 3).29 It was reported that the vinyl ether one-electron oxidation could generate radical cations, which reacted with NBE to produce PNB with microstructures essentially identical to those via traditional metal-mediated ROMP. Such feature resulted in high yield generally good correlation between Mn and initial monomer/catalyst ratios. Most importantly, the on/off cycles of blue LED light could control the re-initiation of polymerization. OMe

BF4 O MeO

OMe OR'

NBE

R

OR'

R

CH2Cl2, LED

n

PNB

Scheme 3. Metal-free ROMP of NBE.

Hoveyda and his coworkers reported the all-Z polynorbornadiene by ROMP with a readily accessible Ru-based catalyst (Scheme 4).30 It is found that the non-metathesis based polytopal isomerization rate and syndio-tacticity level could be well-controlled by adjusting the monomer concentration and the steric and electronic characteristics of the catalysts.


7


Mes

N

N

Page 8 of 48

Mes

S

Ru S O i Pr

0.01 mol% benzene, 22 oC, 1 h

n

Scheme 4. All-Z polynorbornadiene by ROMP.

The chain transfer ROMP, namely the ROMP in the presence of CTA, has been developed for the design of telechelic α,ω-end-functionalized polymers. 1,4-Hydroxytelechelic polybutadiene with number average functionality near 2.0 was synthesized via the ROMP of 1,5-cyclooctadiene (COD) at high monomer concentrations and low catalyst/monomer ratios (~0.01 mol% catalyst to monomers) with butane diacetate (DAB) as a functional CTA molecule and the G1 catalyst, followed by alcoholysis.31 The proposed approach could also be used for the synthesis of α,ω-end-functionalized polyisoprene via the ROMP of 1,5-dimethyl-1,5-cyclo-octadiene (DMCOD) (Scheme 5).32 Such α,ω-end-functionalized telechelic polymers could be used for the synthesis of tri-block and multi-block copolymers as valuable precursors. + AcO

OAc

ROMP

deprotection

OAc AcO

n

OH HO

n

Scheme 5. Synthesis of α,ω-end-functionalized polyisoprene (PI).


8

Page 9 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Radlauer et al designed the block and hetero-telechelic polymers via the ROMP of 3substituted cyclooctene (3RCOE) in presence of an asymmetric allylically-functionalized CTA with Grubbs 2nd and 3rd catalysts (G2 and G3) (Figure 1) and a cross metathesis (CM) reaction between the resultant polymers during the ROMP (Scheme 6).33 The block polymers after a short CM reaction showed two Tg near the value of the starting homo-polymers (-55 °C and -34 °C), while a unique Tg was obtained of -49 °C after 24 h of CM reaction with the G2 or G3 catalyst. These results demonstrated that the multi-block or statistical polymers could be designed by combining two homo-polymers with different substituents, depending on the CM reaction time.

Cl Cl

PCy3 Ru PCy3

N

N

Mes

Mes Mes Cl Ru Cl PCy3

G1

X

N

N Cl Mes N Ru Cl N

X: H, Br

G3

G2

Cl Cl

PCy3 Ru

Mes

N Cl Cl

O

N Mes Ru O

HG1

HG2

Figure 1. Structures of the Grubbs catalysts (G1, G2 and G3) and the Hoveyda-Grubbs catalysts (HG1 and HG2).


9


EtO

OEt

G2 or G3

Page 10 of 48

OEt EtO

n

9

+ OAc

C5H11

9

OAc

G2 or G3 C5H11

n

5

5

ROMP n

G2 or G3

+

O

O

m

O

O

CM

Scheme 6. Synthesis of heterotelechelic polyolefin via ROMP and regioselective CM reaction.

Nomura and Hou synthesized end-functionalized polymers by the combination of cis-specific ROMP of NBE with terminal olefins as CTA for CM, with a V-based catalyst at 80 °C (Scheme 7).34 The activity was enhanced by adding PMe3, maintaining the high cis-selectivity. And the controlled molecular weight could be achieved by adjusting the CTA concentrations and/or polymerization temperature.

Cl

N

Me3P F 3C

V

SiMe3

O

F3C CF3 R

Cl

PMe3

R

o

n

benzenen, 80 C

R: -(CH2)mCH3 m = 3 or 5 -CH2SiMe3 cyclohexyl

Scheme 7. Synthesis of end-functionalized PNB via cis-specific ROMP with terminal olefins.


10

Page 11 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


α,ω-Bis(trialkoxysilyl) telechelic copolyolefins with tunable properties, as low viscosity liquids at room temperature for adhesive application, were synthesized via ROMP/CM of NBbased olefin with high yield of 85-98% and molecular weight of thousands with narrow dispersity of 1.4-1.9, using the G2 catalyst, with bis(trialkoxysilyl)-functionalized symmetric acyclic alkene-based CTA, (RO)3Si(CH2)3NHC(O)OCH2CH=CHCH2OC(O)NH(CH2)3Si(OR)3 (R = Me or Et) (Scheme 8).35 It was found the affinity of the CTA towards the mOLF rather than NB-OLF was observed in the CM, due to the steric hindrance around the C=C groups in the NBOLF units. Furthermore, the oxygen atom in the NB-OLF units could modulate the electronic density of the C=C groups, increasing the CM efficiency as a result. O R'' +

+

(RO)3Si

N H

O

R' NB type cycloolefin (NB-OLF)

H N

O O

Si(OR)3 R = Me or Et

CTA monocycloolefin (mOLF)

G2 CH2Cl2 24 h O

(RO)3Si

H N

O

O

N H

Si(OR)3

O

R'

R''

Scheme 8. Synthesis of copolyolefins by ROMP/CM of NB-OLF and mOLF.

Yang et al synthesized bottlebrush polyisobutylene (PIB)-based polymer via ROMP of norbornene- and oxanorbornene-functionalized PIB macromonomers initiated with G3 catalyst at room temperature with high yield of > 97% (Scheme 9), in a controlled/“living” polymerization manner with narrow dispersity (≤ 1.04).36 The propagation rate of the norbornene-functionalized PIB macromonomer was 2.9 times higher than that of the oxanorbornene-functionalized one with similar molecular weight, due to the complexation effect between G3 and the electron-rich


11


Page 12 of 48

oxygen atom, which interfered but didn’t inhibit the interaction of R=C with the polymerizable oxanorbornene moiety. O O

BIP O

Br

+

R

BIP

NH

O

O

N

R = O or CH2

R

O

G3 O BIP O

N

R

O n

Scheme 9. Synthesis of bottlebrush polymers via ROMP.

Additionally, the removal and recovery of the catalysts after the ROMP is still remained as challenge, because of their high cost, as well as the damage in the property of the resultant polymers. Lamberth et al reported two approaches for the removal of the residual G3 catalyst after the ROMP: coordinating with functionalized particles followed by filtration, or coordinating with small solubilizing agents for partitioning in a particular solvent.37 The final residual Ru content could be reduced to 10-60 ppm or 30-120 ppm with the two proposed methods, respectively. Al-Hashimi et al designed PIB-supported G2 catalyst as a phase selectively soluble polymerbased catalyst, for the ROMP of NBE and exo-norbornene derivatives (Figure 2).38 The PIBsupported G2 catalyst showed a comparable catalytic activity to the non-supported one. Furthermore, the bound catalyst exhibits similar catalytic activity to its non-supported counterpart. However, the polymers were obtained with reduced Ru contamination levels (0.983.45%) after multiple precipitations with hexane, much lower than those with the non-supported counterpart of 16.6-46.6%.


12

Page 13 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


N BIP

N PIB

Cl Ru Cl PCy3

Figure 2. PIB-supported G2 catalyst.

In particular, immobilizing the homogeneous catalyst onto solid supports as heterogeneous catalyst may be a simple method to solve the problem. Balcar et al prepared the RuCl2(pcymene)(PCy3) (Cy = cyclohexyl) adsorbed silica and mesoporous molecular sieves (SBA-15 and MCM-41) as heterogeneous catalysts for the ROMP of NBE and its derivatives.39 PNB with Mw of 200,000~400,000 were obtained with high yield of > 80%, with the molecular sieve-based catalysts, much higher than the silica-based one of only < 28% which was similar to the free catalyst. Such heterogeneous catalysts could be simply removed from the resultant solution in comparison with the corresponding homogeneous one. After centrifugation, the polymers with were obtained with maximum Ru contamination of 47 ppm. Costabile et al prepared the G1 and G2 catalyst-functionalized multiwalled carbon nanotubes (MWCNT) for the ROMP of NBE, with the similar catalytic activity of the free G1 and G2 catalysts.40 Furthermore, the functional MWCNT were well dispersed in the resultant PNB, indicating a facile preparation approach for the MWCNT/PNB composites. Larabi and coworkers synthesized silica-supported tungsten–oxo perhydrocarbyl catalysts for the ROMP of NBE (Figure 3).41 The catalyst 2 possessed the highest polymer yield within short reaction time (0.5 min), while the catalyst 3 showed a higher monomer conversion, both with high cis-selectivity > 65% attributed to both the ligands and the supports. And the molecular


13


Page 14 of 48

weight of resultant PNB was close to the theoretical values with the catalyst 2, but higher with the catalyst 3. The catalyst 3, bipodal tungsten oxo neosilyl material, showed a high catalytic activity (TON of 9000 after 1 h), five times higher than that in toluene (TON of 1800), demonstrating a promising industrial catalyst. SiMe3

O

O Me

W

Me3Si

SiMe3

O O

Me O

O

Si O

Si O

SiMe3

O

Me3Si

W

W

O Me O

O Si O

O

O

1

2

O

O

O Si

O

O

O

Si O

Si O

O

O

O

3

Figure 3. Silica-supported tungsten–oxo perhydrocarbyl catalysts.

Elbert et al designed the rodox-sensitive polyvinylferrocene-grafted silica nanoparticles to modulate the catalytic activity of the surface-immobilized G2 catalyst for the surface-initiated ROMP of NBE (Scheme 10),42 in which the deactivation of the surface-immobilized G2 catalyst in ROMP was switched upon chemical oxidation, while the catalyst’s reactivation was immediately achieved by the in-situ chemical reduction. In the deactivation-reactivation cycle, the shrinkage or stretching of the polyvinylferrocene brushes upon chemical oxidation or reduction was used to control the diffusion of the NBE monomers close to the active sites on the silica nanoparticles.


14

Page 15 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Mes

OEt O O Si O Si O OEt HO

OH

HO HO

OH

N

Cl

N Mes

Mes

OEt O O Si O Si O OEt

Ph

N Cl Ru N

PCy3

Cl Mes

M3

M1

OH OH

OH

OEt O O Si

N

Cl N

OEt O O Si

N Cl

Mes

M2

Cl

N

Mes

Ru PCy3

Ph

M4

Scheme 10. Synthesis of the silica nanoparticles supported G2 catalyst.

CM Olefin cross-metathesis (CM) reaction, formally described as the intermolecular mutual exchange of alkylidene fragments between two olefins promoted by metal-carbene complexes, has been widely used in organic synthesis.43 In polymer science, the telechelic polymers have attracted more and more interests due to their applications in the design of block copolymers and polymeric networks in last decades. The preparation of the low-molecular-weight telechelic oligomers with commercial rubbers as raw materials by using late transition metal-based catalysts shows potential application owing to its excellent tolerance to air and moisture, especially via the CM reaction catalyzed with the G1 and HG2 catalysts showing higher stability toward various functional groups such as carboxylic acid, alcohol, aldehyde, and even water, which exhibit quite efficient in terms of both activity and efficacy when compared with their predecessors. Telechelic oligomers. CM degradation of unsaturated polymers (USPs) with bi-functional CTAs (Figure 4) has been successfully established to synthesis of telechelic oligomers those are not easy to obtain via other organic methods, under different reaction conditions (Table 2).


15


O

O C12H25

S

Page 16 of 48

S

S

S C12H25

O

O

S

S Bistrithiocarbonyl-functionalized CTA

O Cl

Cl

O

O

DCB

O O O DEM

O O DMM

Figure 4. CTAs for the CM degradation of unsaturated polymers.

Table 2. Synthesis of telechelic oligomers via CM reaction. USP

CTA

Catalyst

Yield (%)

Mn (kDa)

Mw/Mn

Ref.

PI

DAB

G2

~98%

8-40

1.33-4.15

44

PEB

DAB

G1

-

1.1-2.1

-

45

G2

70-78%

8.2-23

1.67-1.83

46

G2

~93%

0.35-98

~2

47

-

1.125

1.82

48

BistrithiocarbonylNR

functionalized CTA

PI

DAB

Poly(ethyleneco-octene-co-

Ru-

CH2=CH2

indenylidene

butadiene).

PB

NR Crosslinked PB P(B-co-IP))

DCB

G2

-

0.48-660 1.09-2.05

DMM

G2

-

1.8-4.8 1.60-2.58

DEM

G2

-

1.9-4.4 1.44-2.42

DAB

G2

96-97%

26-38

1.83-2.26

50

DEM

G1

-

~2

-

51

G2

-

0.17-4.6

1.6-2.8

52

Difunctionalized CTA


49

16

Page 17 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Lucas et al designed the dihydroxytelechelic poly(ethylene-co-1,3-butadiene) via the metathetical depolymerization of poly(ethylene-co-1,3-butadiene) (PEB) with G1 catalyst and DAB as functional CTA, and the hydrolysis of the end acetoxy groups (Scheme 11).45 It was found that the back-biting reaction also occurred in the depolymerization, resulting to thermodynamically favored unsaturated six-membered ring. But fortunately, these macrocycles can be quantitatively re-opened to the linear telechelics at the [DAB]/[macrocycles] ratios ≥ 1. + n

m

OCOCH3

H3COCO

Mn = 45000

H3COCO

OCOCH3 q

p

Mn =1000-2000 OH HO

p

q

Scheme 11. Synthesis of dihydroxytelechelic copolymer via metathetical depolymerization of PEB.

Saetung et al established the one-pot approach for new α,ω-bistrithiocarbonyl-terminated telechelic cis-PI via the metathesis degradation of natural rubber (NR) with the G2 catalyst and a bistrithiocarbonyl-functionalized olefin (Figure 4) as CTA.46 And the well-defined telechelic cisPI could be achieved with higher CTA concentrations, without obvious difference in molecular weight and distribution. The authors also explored the application of the well-defined telechelic products as macromolecular chain transfer agents (macroCTAs) for the reversible addition/fragmentation chain transfer (RAFT) polymerization of tert-butyl acrylate (t-BA). Patil et al reported a facile one-step olefin metathesis-mediated ethenolysis reaction of 1,4butadiene contained polyolefins (for example, random copolymer of ethylene, α-olefin, and 1,4-


17


Page 18 of 48

butadiene) for the synthesis of α,ω-divinyl telechelic polymers, with Ru-indenylidene complexes as catalyst (Scheme 12).48 The proposed method was expected as efficient strategy for production of building blocks for the polyolefin-based block, graft, and star polymers, possessing the advantages of low cost, simple processing, and flexibility. CH2=CH2 m

l R

R = n-hexyl

n

p

o N

N

R Ph

Cl Ru Cl PCy3

Scheme 12. Ethenolysis of random copolymer of ethylene, α-olefin, and 1,4-butadiene.

Zou et al reported the degradation of industrial high molecular weight PB rubber using the G2 catalyst with several symmetrical olefins including cis-1,4-dichloro-2-butene (DCB), DAB, dimethyl maleate (DMM) and diethyl maleate (DEM) as CTAs (Figure 4).49 When DAB was introduced as a CTA, Mn of the degraded product decreased to 330 with the molar ratio of [PB]/[DAB]=2:1 and [PB]/[catalyst]=1000:1. Increasing the [PB]/[DAB] molar ratio to 1:1, an almost complete degradation procedure could be reached within a few hours. Mouawia et al reported the metathetic degradation reaction on waste tires to provide telechelic oligomers,50 which was efficient in the ionic liquid (IL) phase under soft conditions (low temperature, low IL quantity, short reaction time). High yields of acetoxy telechelic PI polymers with low Ru contamination (3.6 ppm) were obtained, and the degradation rate can be controlled with the PI concentration used in the reaction. The catalytic IL phase could be recycled five times, allowing in each cycle an efficient and controlled depolymerization of NR. The


18

Page 19 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


proposed method was also performed on waste tire ground powders, yielding 26% of acetoxy telechelic PI oligomers with average molecular weight of 400. Smith et al reprocessed the cross-linked rubbers via CM with the G2 catalyst to catalytic disassemble the polymer chains of the crosslinked PB to produce soluble oligomers (Mn about 2000).51 It was also found that the breakdown of the crosslinked styrene-butadiene rubber (SBR) sheets could be accelerated in the presence of diester (DEM) as CTA. The breakdown extent increased with increasing the reaction time and temperature. Two possible mechanisms were postulated as following: Two smaller molecules containing a cyclic one were produced by the CM reaction of backbone C=C bonds in a single linear polymer segment; then the pendant vinyl groups participated in a CM reaction with a backbone C=C group to produce a linear polymer. The proposed method is expected as a promising approach for the recycle of the waste vehicle tyres. Michel et al synthesized the low-viscosity α,ω-bis(trialkoxysilyl)-telechelic (co)polydienes with low Tg around -105 °C for potential adhesive application, by the functional CM depolymerization of the commercial (co)polydienes (PB or poly(butadiene-co-isoprene) (P(B-coIP)) with the G2 catalyst and an difunctionalized CTA (Scheme 13).52 High selectivity of 75% was achieved towards the α,ω-bis-telechelic (co)polydienes in the optimized reaction condition, with non-functionalized product.


19


O

+ (EtO)3Si

N H

H N

O

O

Page 20 of 48

Si(OEt)3

O

CTA

PB or P(B-co-IP) G2 O (EtO)3Si

N H

H N

O O

Si(OEt)3

O

Low-viscosity liquid Scheme 13. CM synthesis of low-viscosity α,ω-bis(trialkoxysilyl)-telechelic (co)polydienes.

Mono-terminated oligomers. Series of mono-terminated oligomers as liquid rubbers have been prepared via the CM reaction with commercial rubbers as raw materials, for designing new polymer architects or various applications. Gutierrez and Tlenkopatchev reported the metathesis transformations of natural products. They synthesized the terpene-terminated oligomers with yields of 80-90% from the bio-based β-pinene and NR via a solvent-free CM reaction with the G2 catalyst (Scheme 14).53 The products with molecular weight in a wide range could be obtained by adjusting the β-pinene/NR ratio. And a model reaction was used to confirm the CM reaction between NR and β-pinene, using (Z)-3-methyl-2-pentene and beta-pinene. The groups also reported the degradation of NR via CM reaction with mandarin oil (74% d-limonene, 15.6% γ-terpinene and 4.2% α-pinene) or d-limonene as both CTAs and green solvent.54 The molecular weight of the oligomers were around 102 with yields of 80%, at 50 °C for 24 hours, with NR/G2 ratio of 250.


20

Page 21 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


11%

m

42% m

n

17% m

Scheme 14. CM degradation of NR using β-pinene as CTA.

Jiang et al reported the CM degradation of PB using the G2 catalyst, in a 2.0% (m/v) solution of 1,2-dichloroethane at 30 °C (Scheme 15).55 The functionalized telechelic PB oligomers with the designed Mn and PDI in a wide range could be obtained by altering CTA, controlling the PB/CTA and PB/catalyst ratios as well as the reaction time. The Mn of the CM products would be on order of a few hundred with narrow PDI (< 1.50) with mono-olefins as CTAs. The results indicated that the number of the butadiene repeating unit in the telechelic oligomers could be as low as two or even only one. 77%

m

4

4

15%

m

n

4

m

none 4

Scheme 15. CM degradation of PB and compositions and yields of oligomers calculated via GCMS analyses.

Zou et al reported the CM degradation and functionalization of SBR with allyl hexanoate, allyl chloroacetate, 5-hexenyl acetate and trifluoroethyl methacrylate as CTAs using the G2 catalyst in


21


Page 22 of 48

1,2-dichloroethane at 30 °C.56 The catalyst concentration, CTA concentration and reaction time were found to be major factors influencing the molecular weights and polydispersity of the targeted telechelic SBR oligomers. Well-defined oligomers with molecular weights ranging from 700 to 36600 and PDI of 1.17-4.79 were realized. And the Tg of the SBR oligomers decreased with longer reaction time. It was also found that the fluoro-substituted olefins, such as trifluoroethyl methacrylate, can hardly attach to the SBR chain in comparison with other CTAs.

Hydrogenated rubbers with reduced molecular weights. Hydrogenation is an efficient strategy to significantly improve the physical, chemical, thermal and mechanical properties of the diene-based rubbers, or efficiently prepare polymers which are costly or difficult to obtain via the normal polymerization techniques.57,58 After the in-situ hydrogenation of PB synthesized by the ROMP of 1,5-cyclooctadiene in one pot with a hydrogenation degree (HD%) of > 90% at 50 °C under 30 psi H2,59 Fogg’ group explored the transformation of the G1 catalyst into dihydride, dihydrogen and hydride species,60 and the tandem ROMP-hydrogenation reaction under mild condition, in which the metathesis or hydrogenation catalysis could be switched with methanol and base such as triethylamine.61 Based on the ligand manipulation in the metathesis catalysts, they found that the hydrogenation of ROMP polymers could be realized under 1 atm hydrogen.62 Afterward, they reported the tandem ROMP-hydrogenation with G3 catalyst for the synthesis of functionalized PNB, combining high ROMP activity, controlled polymerization, and high hydrogenation activity.63 Cobo et al reported a Os-based complex, OsHCl(CO)(PiPr3)2, for the tandem ROMP– hydrogenation of NBE and its derivatives.64 In their works, PNB could be completely


22

Page 23 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


hydrogenated at 40 °C and 3 atm of H2 in 48 h, while the complete hydrogenation of poly(norbornadiene) was achieved at 75 °C with the same H2 pressure and reaction time. On the other hand, the olefin metathesis catalysts have been successfully used for the selectively catalytic hydrogenation of the ready-synthesized diene-based rubbers. Owing to the CM reaction between the C=C bonds in the unsaturated diene-based rubbers during the hydrogenation, saturated rubbers with reduced molecular weights were obtained. Kongparakul et al reported the metathesis hydrogenation of the metathesized NR latex using the G2 catalyst with [Ru] = 234 M; [C=C] = 100 mM; PH2 = 40.8 bar and T = 90 °C, with HD% > 97% under mild conditions and without any organic solvent.65,66 The slight change in the molecular weight of NR under nitrogen atmosphere implied that only CM occurred during the reaction. However, it drastically decreased under hydrogen atmosphere, and the decreasing of molecular weight is beneficial to the hydrogenation of the C=C bonds in NR, owing to its lower solution viscosity. Since both metathesis and hydrogenation were performed in a single system, the relative selectivity for the two reactions was a key factor for the overall catalytic process. CTA led to the polymer chain-breaking reactions, resulting in the reduction of the polymer molecular weight. Ai et al reported the selectively catalytic hydrogenation of nitrile-butadiene rubber (NBR) with the G2 catalyst in various solutions, with a highest HD% of 75%.67 It was found that more catalyst, lower H2 pressure, higher reaction temperature, and longer reaction time were favorable to the degradation of the polymer. Notably, the proposed approach could be used to reduce the Mooney viscosity of H-NBR, which strongly restricts their processability. Furthermore, the liquid H-NBR sample (molecular weight less than 104) was obtained with high catalyst dosage. Because the CM and hydrogenation are competitive reaction with each other occur in one pot, the molecular weight and HD% of the products could not be controlled. The authors established a


23


Page 24 of 48

two-step strategy to prepare the hydrogenated nitrile-butadiene rubber (H-NBR) products with controllable molecular weight from the commercial NBR product, via CM polymer chainbreaking and heterogeneous catalytic hydrogenation.68 The molecular weight of the H-NBR products (including liquid H-NBR) could be controlled by adjusting the G2 catalyst amount, with high HD% near 100%.

Others. CM reaction has also been used to design novel functional rubber materials and additives. Otsuka’s group reported a strategy for synthesis of natural/synthetic hybrid materials, via the controlled scrambling reactions of olefin-containing polyurethane and diene-based rubbers (PIB or naturally occurring PI) by step or chain polymerization via the macromolecular CM using the G2 catalyst.69 The scrambled copolymers were obtained with different thermal and mechanical properties depending on the reaction conditions, such as reaction time and solvent. Crosslinked polymers have important potentials owing to their unique properties in comparison with the un-crosslinked ones. However, the shortcomings such as poor processability limit their applications. Guan and his coworkers developed a simple and efficient strategy to synthesize adaptive crosslinked polymers via CM reaction with very low amount of the G2 catalyst, by combining the mechanical property of the crosslinked polymers and the processability of the uncrosslinked one, which could restore the permanent elastomeric properties of the crosslinked rubbers after processing.70 The group also demonstrated the application of the CM reaction in healing polymers via dynamic exchange of strong C=C bonds.71 With very low amount of the G2 catalyst, the crosslinked PB effectively self-healed under moderate pressures. Martinez and Hillmyer designed novel thermoset elastomers via the ROMP copolymerization of 3-hexyl-cis-cyclooctene and cis-cyclooctene with the G2 catalyst, with maleic acid as a CTA to control the molecular weight, branching degree and crystallinity of the resultant carboxy-


24

Page 25 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


telechelic polyalkenamers, followed a hydrogenation process.72 The telechelic polyolefins after the hydrogenation showed high thermal resistance, low Tg (< −57 °C) and low viscosity before crosslinking. Such features are favorable to the controlled curing with polyfunctional aziridines to produce thermoset elastomers. Tuba et al reported the synthesis of silica filler compatible recyclable polypentenamer copolymers via equilibrium ROMP of cyclopentene and 4-(triethoxy)siloxy cyclopentene, based on the synthesis of polyolefins utilizing the G2 or HG2 catalyst via equilibrium ROMP of cyclopentenes and their silylated derivatives.73 The polypentenamer tire additives were synthesized high yields (>80%) at 0 °C and readily depolymerized at 40 °C and/or under diluted conditions using the same catalyst, and even in neat at room temperature and at very low monomer/catalyst ratio. Zheng’s group reported the synthesis of a series of polyhedral oligomeric silsesquioxanes (POSS)-terminated polycyclooctadiene (PCOD) telechelics via ROMP with the following two steps: i) synthesis of 1,4-diPOSS-but-2-ene via copper-catalyzed Huisgen cycloaddition reaction; and ii) ROMP of cyclooctadiene with the G2 catalyst with 1,4-diPOSS-but-2-ene as a CTA.74 The POSS-terminated PCOD telechelics with variable lengths of PCOD were prepared by adjusting the CTA/cyclooctadiene ratios. All the POSS-terminated PCOD telechelics in bulks were microphase-separated aggregates of 20-50 nm via the POSS-POSS interactions. Furthermore, the POSS molecules can act as the heterogeneous nucleating agent for the crystallization of PCOD, and the enrichment of POSS units on the material surface could enhance the surface hydrophobicity and reduce surface free energy. Yang et al designed novel thermoplastic elastomers (TPEs) with poly[exo-1,4,4a,9,9a,10hexahydro-9,10(1',2')-benzeno-1,4-methanoanthracene] (PHBM) as the hard block and the polymer of NBE derivative as the soft block via living ROMP using the G3 catalyst and


25


Page 26 of 48

sequential addition of monomers.75 The integration of the interplayed physical crosslinking (hard block) and the dynamic interaction (soft block) rendered the self-assembled network excellent mechanical property and self-healing capability, with recovery of tensile strength (near 100%) and strain at break (about 85%) with a PHBM weight ratio of 5%.

MODELING AND SIMULATION Compared with the great progress in the experimental works on the ROMP and CM reactions, the works on their modeling and simulation are still inadequate, which could be used to understand the reaction mechanism and elucidate the products. In the ROMP system, cyclic oligomers are usually formed by a “back-biting” reaction, thermodynamically controlled by the ring-chain equilibrium.76,77 Chen et al developed a computational method to accurately predict the critical concentration and equilibrium ring-chain distribution in the ROMP of cycloolefins, based on the JS-RIS model and a Monte Carlo configurational search with the ring strain as an enthalpic term.78 The calculation results was in good agreement with experiment, so the product distribution could be completely predicted under a certain ROMP condition. Tlenkopatchev and his coworkers reported the molecular modeling of the distributions of cyclic and linear products in the ring-opening cross-metathesis of cis,cis-1,5-dimethyl-cycloocta1,5-diene, cis,cis-1,6-dimethyl-cycloocta-1,5-diene and cis,cis-cycloocta-1,5-diene with ethylene at 298.15 K using the B3LYP/6-31G(d,p) level of theory.79,80 It was revealed that the ring-chain equilibrium constants were dependent on the nature of cyclic diene, in agreement with the reported experimental data by others. The computational modeling of ring-chain equilibria for the ring-opening cross-metathesis of cyclohexene with 1,2-dicarbomethoxy-ethylene, 1,4dicarbomethoxy-but-2-ene (DCB) and ethylene demonstrated that the cyclohexene and ringopened products tended to the thermodynamically stable six-membered ring, and the carbonyl-


26

Page 27 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


containing olefins could drive the cross-metathesis with cis,cis-cycloocta-1,5-diene to the ringopened products.81 Since the early 1970s Hummel started to research the computer simulation of metathesis reactions in order to elucidate the rubber structures.82,83 Following with the analysis of the degraded products84 and understanding the degradation mechanism,85 the polymer degradation CM reaction has been widely investigated. Gutierras et al reported the molecular modeling of the products in the ethenolysis of 1,4-PIP at 25 °C using the B3LYP/6-31G(d,p) level of theory.86 The results revealed a complete shift of the chain–ring and chain–chain equilibria toward 2methyl-1,5-hexadiene. The concentration of 2-methyl-1,5-hexadiene equilibrated with α,ω-vinylterminated oligomers was of 90 mol%, while the cyclic oligomers equilibrated with linear molecules was less. The 1,5-hexadiene concentration equilibrated with butadiene was 46% in the ethenolysis of 1,4-PB. Such results were revealed by experimental investigation. Tlenkopatchev et al carried out the systematic simulating of the rubber CM degradation, such as the distribution of cyclic oligomers via intramolecular CM degradation of cis-PB and NR, and those via intermolecular CM degradation of cis-PB. It was found that the chain-ring equilibrium shifted towards the all-trans cyclic isomers for cis-PB, in which the transformation of larger rings into 3-6 butadiene units-contained cyclic products was favorable to the cyclic butadiene tetramers and pentamers as main products,87 while the chain–ring and chain-chain equilibria shifted toward 1,5-hexadiene in the intermolecular CM degradation of cis-PB with ethylene as CTA at 298.15 K, with negligible cyclic oligomers. The equilibrium constant between 1,5-hexadiene and α,ω-vinylterminated butadiene oligomers was found to depend on the cis/trans isomer ratio. The 1,5hexadiene concentration equilibrated with cis-butadiene oligomers was 86 mol%, with the concentration of the trans-butadiene oligomers of 50 mol-% of 1,5-hexadiene.88 As for the intramolecular CM degradation of NR, the 2-4 isoprene units-contained cyclic oligomers were


27


Page 28 of 48

produced with the all-trans cyclic isoprene trimer as the main product due to the ring-ring equilibrium. And the transformation of larger rings into trans,trans,trans-1,5,9-trimethyl-1,5,9cyclododecatriene was favored thermodynamically.89

APPLICATIONS S Besides the abovementioned production strategies for the specialty rubbers via olefin metathesis reaction of diene-based rubbers or waste tyres in which the degradation of rubbers was involved, the degradation of diene-based rubbers or waste tyres is very important for the analysis of rubbers (whether crosslinked or not) and the recycle of waste rubbers (including tyres). For analysis. It is quite difficult to analyze the composition of the crosslinked rubber. Kiattanavith and Hummel established a strategy for the quantitative determination of the filler amount (carbon black) in the vulcanized NR rubber by CM degradation using a WCl6(C2H5)3Al2Cl3 catalyst with 1-octene as CTA at 20°C.90,91 After the CM degradation, the filler was separated and weighed. The results showed that the filler amount could be quantitatively determined in the vulcanized NR rubber with low crosslinking degrees. Leimgruber et al explored the possibilities of CM to degrade the crosslinked rubber network without destroying the adhesion layer.92 Different types of rubber, NR, NBR, and SBR, can be degraded into soluble fragments by using the G2 catalyst and 1-octene as a CTA at 110°C for 1 h. Then the uncovered adhesion layers could be subsequently analyzed with common analytical methods such as optical microscopy, focusvariation microscopy, and scanning electron microscopy. It was found that the CM reaction was not only drastically improved by 1-octene but also accelerated, as the overall degradation time could be reduced by approximately 50–70%. As the authors claimed, the reason for this higher reactivity and faster degradation of rubber in the presence of 1-octene probably comes from the fact that the crosslinked rubber network is not


28

Page 29 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


easily accessible due to steric as well as diffusion effects. At the beginning of the CM reaction, the catalyst reacts with the C=C double bounds in the crosslinked rubber. The C–C bond of the polymer was cleaved as a result, due to the rearrangement of the C=C double bonds. In doing so, the metal center remained bound to the rubber, a rubber particle, or a rubber polymer. However in these stages, it is hardly available for the CM because of its steric hindrance as the next C=C double bond has to be coordinated. 1-Octene is able to diffuse easily to the steric-hindered metal center and can participate in the CM reaction. Now, the catalyst could be ‘‘recycled’’ for the CM degradation of rubber network. Carboxyl content plays an important role in the performance of the carboxylated nitrile butadiene rubber (XNBR). However, it is difficult to be determined due to the poor solubility of XNBR owing to its high molecular weight. Ai et al developed a facile method to do it by CM degradation the XNBR sample using the G1 catalyst.93 Acrylonitrile (AN) was used as CTA, not only enhancing the polarity of the solvent for dissolving the XNBR sample in the CM degradation, but also introducing more cyano groups into the degraded products, in order to improve their solubility in strong polar solvents. After the CM degradation with 2% AN and 0.2% G1 catalyst at 60 °C for 30 min, the Mn of the product decreased to 0.26×104 with PDI of 3.83. Such product was easy to be dissolved completely with lower viscosity within 20 min, which needs 5 h in the direct titration (Zeon R-144A-95) method, favoring the fast titrimetric analysis.

For recycling. Due to the large production of polymers, the chemical recycling of polymer waste, which would offer a sustainable polymer reusing technology, is of major importance. This process consists of the conversion of polymer waste into monomers or reactive functional


29


Page 30 of 48

polymers or oligomers for a further use in the development of new high value polymers.94 Now, the most widely used strategies for the rubber wastes are energy recovery and recycling. Fortunately, the end-of-life management of the rubber wastes may be improved with the recent developments in organic and polymer chemistry.95 In the classical recycling methods, more or less linkage was broken off, via CM reaction96,97 or selective oxidolysis98,99 of the skeleton C=C bonds, which would damage the elastomeric property of the recycled products. The telechelic recycled products with functional terminated groups (such as vinyl or hydroxyl) could be used as raw materials for the synthesis of polyolefin rubbers, polyurethane elastomers100 or (polyApolybutadiene-polyA) triblock copolymers.101 And the dynamic bridges have been designed to make the resultant rubber recyclable and even self-healing in some cases.102 Sels et al reported the preparation of large macrocyclic oligo(butadiene)s (C16-C44) with high yield from commercial 1,4-PB (Scheme 16), in which the high molecular weight 1,4-PB with a low 1,2-vinyl content limited the formation of linear fragments.103 The results showed that the distribution of the cyclic products was largely depended on the ligand structure of the Ru catalysts. To be specific, the G2 catalyst favored the formation of t,t,t-cyclododecatriene, while the G1 catalyst selectively produced the macrocyclic oligo(butadiene) fraction with yield of 90%.

n

m

x

Scheme 16. Formation of macrocycles and cyclopentene/cyclohexene derivatives from vinylcontaining 1,4-PB.


30

Page 31 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Sulfur-crosslinked cis-1,4-PB samples were metathetically degraded with 4-octene as CTA under dry-nitrogen atmosphere at 60°C for 48 h.104 It was found that the WCl6/Sn(CH3)4 catalyst possessed much higher catalytic activity, compared with the W(CO)6/hv/CCl4 catalyst. The symmetrical 4-octene eliminated the possible metathesis products from the low molecular olefin itself (Scheme 17), and the high S content led to the low contents of the main products (C12 (p = 1) and C15 (p = 2))

n

+ C3H7 CH CH C3H7

C3H7 CH CH CH2 CH2 CH pCH C3H7 p = 1, 2, 3, ...

Scheme 17. Degradation of sulfur-crosslinked 1,4-PB with 4-octene.

Watson and Wagener reported the first work on the solid-state depolymerization of an unsaturated polymer, by simple mixing of the polymer with the G1 catalyst without any solvent.105 The molecular weight of PB decreased of 2 orders of magnitude, from (2-3) × 106 to 7.2 × 103, after 48 h at room temperature in an inert atmosphere with 0.25 mol% of catalyst. Based on the experimental results, the authors dictated the degradation equilibrium by three processes: (i) conversion of polymer to cycles, (ii) incorporation of the G1 catalyst within the polymer as a chain limiter, and (iii) conversion of 1,4-1,2-1,4 triads as chain limiters, namely, intramolecular chain limitation. Wolf and Plenio synthesized small oligoisoprenes via the ethenolysis of NR with (NHC)(NHCewg)RuCl2(=CRR’) catalyst of 0.1 mol% per C=C in NR (Scheme 18).106 Ethenolysis has currently been known as a green and controlled tool to cleave the unsaturated hydrocarbon chains or produce shorter terminal olefins in a manner.107


31


Page 32 of 48

ethene n

[Ru] m

oligoisoprenes m = 0, 1, 2, 3, 4, 5, ...

Scheme 18. Ethenolysis of natural rubber and the structures of the isolated oligoisoprenes.

Ouardad and Peruch reported the CM degradation of trans-1,4-PI using the G1, G2 and HG2 catalysts with ethylene or 1-octene as CTA in toluene at 60 °C.108 The G1 catalyst led to low degradation, due to the catalyst decomposition and/or inter-chain CM reactions, while complete CM degradation was achieved with the G2 catalyst in 15 min, with Mw of the products of 1530. However, it was difficult to synthesize well-defined PI with desired molecular weight with the Grubbs catalysts. Contrarily, the HG2 catalyst was more efficient to control the CM degradation of trans-1,4-PI. And the pure trans-1,4-PI could be afforded via the regioselective degradation with molecular weight in 10000-50000. However, PI of lower molar masses (Mn < 10000) contained some cis units, due to the isomerization reaction. Nowadays, it is a serious environmental problem for the recycling and recovery of the postconsumer tyres, due to their very complex structure and composition. Olefin metathesis reaction has been reported recently as a great progress in sustainable management of waste tyres, beside the pyrolysis to produce valuable oil, char and gas products,109 or incorporation into polymeric matrices110 and cement concrete.111 Mouawia et al reported an efficient and controlled CM degradation of NR using the G2 catalyst in hydrophobic ionic liquid (N,N-dioctylimidazolium bromide (C8C8ImBr)).112 Acetoxy telechelic PI (Mn of 45 000-62 000) with low Ru contamination and high yield was obtained with less ionic liquid at low temperature for a short time. The degradation rate could be controlled with the PI concentration. Most importantly, the


32

Page 33 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


proposed method has been successfully used for the metathetic degradation of waste tires, although with low yield. Besides the above application, the CM degradation has been also recognized as a powerful technique for the reactor clean-up in the industrial practice, which could degrade the crosslinked by-products containing C=C double bonds into soluble pieces.

CONCLUSIONS AND PROSPECTS In summary, significant progress has been achieved for the olefin metathesis reaction in the rubber chemistry and industry with commercial products or waste rubbers as raw materials, both in molecular modeling, experimental investigations and industrial applications, especially for the production of specialty rubbers and the recycling of the waste rubbers. However, there still remains challenge in such fields for more efficient and green applications. For the hydrogenation of diene-based rubbers, the recovery and reuse of the catalysts should be improved, due to their high-cost, waste, and even the damaged performance of the hydrogenated products, besides the controllable HD% and molecular weight of the hydrogenated products. Although the homogeneous catalysts could be recovered with ppm level remained in the products, the solid supported olefin metathesis catalysts as heterogeneous ones should be the promising method. On the other hand, novel efficient catalysts should be discovered to avoid or eliminate the gelation in the CM reaction. For the production of low-molecular-weight functional oligomers and the recycling of the waste rubbers, the yield of desired products should be improved with the help of novel efficient catalyst system. In a word, the development in high efficiency catalyst should be the key issue in the future excellent applications of the olefin metathesis reaction in the rubber chemistry and industry, or


33


Page 34 of 48

extending to the whole polymer science and engineering field. On the other hand, more experimental studies have been reported, but the work on the mechanism, molecular modeling and prediction was deficient. It should be strengthened with the development in computing method, in order to provide guidance for the catalyst design and product control, especially for the green recycle of waste rubbers such as waste tyres.

AUTHOR INFORMATION * Corresponding Author Tel./Fax: 86 0931 8912582. E-mail: [email protected]. Notes The authors declare no competing financial interest.

REFERENCES (1) Grubbs, R.H. Olefin-metathesis Catalysts for the Preparation of Molecules and Materials. Angew. Chem. Int. Ed. 2006, 45, 3760–3765. (2) Queval, P.; Jahier, C.; Basle, O.; Mauduit, M. Cationic Ruthenium Complexes in Olefin Metathesis. Curr. Org. Chem. 2013, 17, 2560–2574. (3) Szymanska-Buzar, T. Carbonyl Complexes of Molybdenum and their Catalytic Activity. Curr. Org. Chem. 2012, 16, 3–15. (4) Furstner, A. Olefin Metathesis and Beyond. Angew. Chem. Int. Ed. 2000, 39, 3012–3043. (5) Hoveyda, A. H.; Zhugralin, A. R. The Remarkable Metal-catalysed Olefin Metathesis Reaction. Nature 2007, 450, 243–251.


34

Page 35 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(6) HeArisson, J.-L.; Chauvin, Y.; Catalyse de Transformation des Oléfines par les Complexes du Tungstène. II. Télomérisation des Oléfines Cycliques en Présence D'oléfines Acycliques. Makromol. Chem. 1970, 141, 161–176. (7) Schuster, M.; Blechert, S. Olefin Metathesis in Organic Chemistry. Angew. Chem. Int. Ed. 1997, 36, 2036–2056. (8) Behr, A.; Vorholt, A.J.; Ostrowski, K.A.; Seidensticker, T. Towards Resource Efficient Chemistry: Tandem Reactions with Renewable. Green Chem. 2014, 16, 982–1006. (9) Chikkali, S.; Mecking, S. Refining of Plant Oils to Chemicals by Olefin Metathesis. Angew. Chem. Int. Ed. 2012, 51, 5802–5808. (10)

Schrock, R.R. Synthesis of Stereoregular Polymers through Ring-Opening Metathesis

Polymerization. Acc. Chem. Res. 2014, 47, 2457–2466. (11)

Dong, Y.F.; Matson, J.B.; Edgar, K.J. Olefin Cross-Metathesis in Polymer and

Polysaccharide Chemistry: A Review. Biomacromolecules 2017, 18, 1661–1676. (12)

Sinclair, F.; Alkattan, M.; Prunet, J.; Shaver, M. P. Olefin Cross Metathesis and Ring-

closing Metathesis in Polymer Chemistry. Polym. Chem. 2017, 8, 3385–3398. (13)

Leimgruber, S.; Trimmel, G. Olefin Metathesis Meets Rubber Chemistry and Technology.

Monatsh. Chem. 2015, 146, 1081–1097. (14)

Kobayashi, S. Ring-Opening Metathesis Polymerization in Encyclopedia of Polymeric

Nanomaterials, Ed. by Kobayashi, S.; Mullen, K. Springer Berlin Heidelberg, 2014, pp. 1– 12. (15)

Ivin, K.J.; Laverty, D.T.; O’Donnell, J.H.; Rooney, J.J.; Stewart, C.D. Cis-trans Double

Bond Distribution in Poly(1,3-cyclopentylenevinylene): Dependence on Metathesis Catalyst, Cocatalyst, and Additives. Makromol. Chem. 1979, 180, 1989–2000.


35


(16)

Page 36 of 48

Singh, R.; Czekelius, C.; Schrock, R. R. Living Ring-Opening Metathesis Polymerization

of Cyclopropenes. Macromolecules 2006, 39, 1316–1317. (17)

Wu, Z.; Grubbs, R.H. Synthesis of Perfect Rubber Using Ring-opening Metathesis

Polymerization of 1-Methylcyclobutene. J. Mol. Cat. 1994, 90, 39–42. (18)

Keitz, B.K.; Fedorov, A.; Grubbs, R.H. Cis-Selective Ring-Opening Metathesis

Polymerization with Ruthenium Catalysts. J. Am. Chem. Soc. 2012, 134, 2040–2043. (19)

Gonsales, S. A.; Kubo, T.; Flint, M. K.; Abboud, K.A.; Sumerlin, B.S.; Veige, A.S.

Highly Tactic Cyclic Polynorbornene: Stereoselective Ring Expansion Metathesis Polymerization of Norbornene Catalyzed by a New Tethered Tungsten-Alkylidene Catalyst. J. Am. Chem. Soc. 2016, 138, 4996–4999. (20)

Nadif, S.S.; Kubo, T.; Gonsales, S.A.; Ramani, S.V.; Ghiviriga, I.; Sumerlin, B.S.; Veige,

A.S. Introducing “Ynene” Metathesis: Ring-Expansion Metathesis Polymerization Leads to Highly Cis and Syndiotactic Cyclic Polymers of Norbornene. J. Am. Chem. Soc. 2016, 138, 6408–6411. (21)

Rosebrugh, L.E.; Marx, V.M.; Keitz, B.K.; Grubbs, R.H. Synthesis of Highly Cis,

Syndiotactic Polymers via Ring-Opening Metathesis Polymerization Using Ruthenium Metathesis Catalysts. J. Am. Chem. Soc. 2013, 135, 10032–10035. (22)

Tanahashi, H.; Tsurugi, H.; Mashima, K. Synthesis of Alkyl and Alkylidene Complexes

of Tungsten Bearing Imido and Redox-Active α-Diimine or o-Iminoquinone Ligands and Their Application as Catalysts for Ring-Opening Metathesis Polymerization of Norbornene. Organometallics 2015, 34, 731–741. (23)

Hou, X. H.; Nomura, K. (Arylimido)vanadium(V)−Alkylidene Complexes Containing

Fluorinated Aryloxo and Alkoxo Ligands for Fast Living Ring-Opening Metathesis


36

Page 37 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Polymerization (ROMP) and Highly Cis-Specific ROMP. J. Am. Chem. Soc. 2015, 137, 4662–4665. (24)

Hou, X. H.; Nomura, K. Ring-Opening Metathesis Polymerization of Cyclic Olefins by

(Arylimido)vanadium(V)-Alkylidenes: Highly Active, Thermally Robust Cis Specific Polymerization. J. Am. Chem. Soc. 2016, 138, 11840–11849. (25)

VenkatRamani, S.; Roland, C.D.; Zhang, J.G.; Ghiviriga, I.; Abboud, K.A.; Veige, A.S.

Trianionic Pincer Complexes of Niobium and Tantalum as Precatalysts for ROMP of Norbornene. Organometallics 2015, 34, 731–741. (26)

Lienert, C.; Frey, W.; Buchmeiser, M.R. Stereoselective Ring-Opening Metathesis

Polymerization with Molybdenum Imido Alkylidenes Containing O ‑ Chelating N ‑ Heterocyclic Carbenes: Influence of Syn/Anti Interconversion and Polymerization Rates on Polymer Structure. Macromolecules 2017, 50, 5701−5710. (27)

Nomura, K.; Hou, X. H. Synthesis of Vanadium–alkylidene Complexes and Their Use as

Catalysts for Ring Opening Metathesis Polymerization. Dalton Trans. 2017, 46, 12-24. (28)

Autenrieth, B.; Schrock, R.R. Stereospecific Ring-Opening Metathesis Polymerization

(ROMP) of Norbornene and Tetracyclododecene by Mo and W Initiators. Macromolecules 2015, 48, 2493−2503. (29)

Ogawa, K.A.; Goetz, A.E.; Boydston, A.J. Metal-Free Ring-Opening Metathesis

Polymerization. J. Am. Chem. Soc. 2015, 137, 1400–1403. (30)

Mikus, M.S.; Torker, S.; Hoveyda, A.H. Controllable ROMP Tacticity by Harnessing the

Fluxionality of Stereogenic-at-Ruthenium Complexes. Angew. Chem. Int. Ed. 2016, 55, 4997–5002.


37


(31)

Page 38 of 48

Hillmyer, M.A.; Nguyen, S.T.; Grubbs, R.H. Utility of Metathesis Catalyst for the

Preparation of End-functionalized Polybutadiene. Macromolecules 1997, 30, 718–721. (32)

Thomas, R.M.; Grubbs, R.H. Synthesis of Telechelic Polyisoprene via Ring-opening

Metathesis Polymerization in the Presence of Chain Transfer Agent. Macromolecules 2010, 43, 3705–3709. (33)

Radlauer, M.R.; Matta, M.E.; Hillmyer, M.A. Regioselective Cross Metathesis for Block

and Heterotelechelic Polymer Synthesis. Polym. Chem. 2016, 7, 6269–6278. (34)

Nomura, K.; Hou, X.H. Cis-Specific Chain Transfer Ring-Opening Metathesis

Polymerization Using a Vanadium(V) Alkylidene Catalyst for Efficient Synthesis of EndFunctionalized Polymers. Organometallics 2015, 34, 4103–4106. (35)

Michel, X.; Fouquay, S.; Michaud, G.; Simon, F.; Brusson, J.-M.; Roquefort, P.; Aubry,

T.; Carpentier, J.-F.; Guillaume, S.M. Tuning the Properties of α,ω-Bis(trialkoxysilyl) Telechelic Copolyolefins from Ruthenium-catalyzed Chain-transfer Ring-opening Metathesis Polymerization (ROMP). Polym. Chem. 2017, 8, 1177–1187. (36)

Yang, B.; Abel, B.A.; McCormick, C.L.; Storey, R.F. Synthesis of Polyisobutylene

Bottlebrush Polymers via Ring-Opening Metathesis Polymerization. Macromolecules 2017, 50, 7458–7467. (37)

Lambeth, R.H.; Federson, S.J.; Baranoski, M.; Rawlett, A.M. Methods for Removal of

Residual Catalyst from Polymers Prepared by Ring Opening Metathesis Polymerization. J. Polym. Sci.: Polym. Chem. 2010, 48, 5752–5757. (38)

Al-hashimi, M.; Abu Baker, M.D.; Elsaid, K.; Berbreiter, D.E.; Bazzi, H.S. Ring-opening

Metathesis Polymerization Using Polyisobutylene Supported Grubbs Second Generation Catalyst. RSC Adv. 2014, 4, 43766–43771.


38

Page 39 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(39)

Balcar, H.; Bek, D.; Sedlacek, J.; Dedecek, J.; Bastl, Z.; Lamac, M. RuCl2(p-

cymene)(PCy3) Immobilized on Mesoporous Molecular Sieves as Catalyst for ROMP of Norbornene and its Derivatives. J. Mol. Cat.: Chem. 2010, 332, 19–24. (40)

Larabi, C.; Szeto, K.C.; Bouhoute, Y.; Charlin, M.O.; Merle, N.; de Mallmann, A.;

Gauvin, R.M.; Delevoye, L.; Taoufik, M. Solvent-Free Ring-Opening Metathesis Polymerization of Norbornene over Silica-Supported Tungsten–Oxo Perhydrocarbyl Catalysts. Macromol. Rapid Commun. 2016, 37, 1832–1836. (41)

Costabile, C.; Grisi, F.; Siniscalchi, G.; Longo, P.; Samo, M.; Sannino, D.; Leone, C.;

Ciambelli, P. Study of the Activity of Grubbs Catalyst-Functionalized Multiwalled Carbon Nanotubes in the Ring Opening Metathesis Polymerization. J. Nanosci. Nanotechnol. 2011, 11, 10053–10062. (42)

Elbert, J.; Mersini, J.; Vilbrandt, N.; Lederle, C.; Kraska, M.; Gallei, M.; Stuhn, B.;

Plenio, H.; Rehahn, M. Reversible Activity Modulation of Surface-Attached Grubbs Second Generation Type Catalysts Using Redox-Responsive Polymers. Macromolecules 2013, 46, 4255–4267. (43)

Connon, S.J.; Blechert, S. Recent Developments in Olefin Cross-Metathesis. Anew. Chem.

Int. Ed. 2003, 42, 1900–1923. (44)

Solanky, S.S.; Campistron, I.; Laguerre, A.; Pilard, J.-F. Metathetic Selective Degradation

of Polyisoprene: Low-molecular-weight Telechelic Oligomer Obtained from both Synthetic and Natural Rubber. Macromol. Chem. Phys. 2005, 206, 1057–1063. (45)

Lucas, F.; Peruch, F.; Carlotti, S.; Deffieux, A.; Leblanc, A.; Boisson, C. Synthesis of

Dihydroxy Poly(ethylene-co-butadiene) via Metathetical Depolymerization: Kinetic and Mechanistic Aspects. Polymer 2008, 49, 4935–4941.


39


(46)

Page 40 of 48

Saetung, N.; Campistron, I.; Pascual, S.; Pilard, J.F.; Fontaine, L. One-pot synthesis of

Natural Rubber-based Telechelic cis-1,4-Polyisoprenes and Their Use to Prepare Block Copolymers by RAFT Polymerization. Macromolecules 2011, 44, 784–794. (47)

Sadaka, F.; Campistron, I.; Laguerre, A.; Pilard, J.-F. Telechelic Oligomers Obtained by

Metathetic Degradation of both Polyisoprene and Styrene–butadiene Rubbers. Applications for Recycling Waste Tyre Rubber. Polym. Degrad. Stab. 2013, 98, 736–742. (48)

Patil, V.B.; Saliu, K.O.; Jenkins, R.M.; Carahan, E.M.; Kramer, E.J.; Fredrickson, G.H.;

Bazan, G.C. Efficient Synthesis of α,ω-Divinyl-functionalized Polyolefins. Macromol. Chem. Phys. 2014, 215, 1140–1145. (49)

Zou, T.T.; Jiang, B.; Lin, S.H.; Pan, Q.M. Metathetic Degradation of Polybutadiene and

Formation of Telechelic Oligomers via Cross Metathesis. Acta Polym. Sin. 2016, 1374–1382. (50)

Mouawia, A.; Nourry, A.; Gaumont, A.C.; Pilard, J.F.; Dea, I. Controlled Metathetic

Depolymerization of Natural Rubber in Ionic Liquids: From Waste Tires to Telechelic Polyisoprene Oligomers. ACS Sustainable Chem. Eng. 2017, 5, 696–701. (51)

Smith, R.F.; Boothroyd, S.C.; Thompson, R.L.; Khosravi, E. A Facile Route for Rubber

Breakdown via Cross Metathesis Reactions. Green Chem. 2016, 18, 3448–3455. (52)

Michel, X.L.; Fouquay, S.; Michaud, G.; Simon, F.; Brusson, J.-M.; Carpentier, J.-F.;

Guillaume, S.M. Simple Access to Alkoxysilyl Telechelic Polyolefins from Rutheniumcatalyzed Cross-metathesis Depolymerization of Polydienes. Eur. Polym. J. 2017, 96, 403– 413. (53)

Gutierrez, S.; Tlenkopatchev, M.A. Metathesis of Renewable Products: Degradation of

Natural Rubber via Cross-metathesis with b-Pinene using Ru-alkylidene Catalysts. Polym. Bull. 2011, 66, 1029–1038.


40

Page 41 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(54)

Martinez, A.; Gutierrez, S.; Tlenkopatchev, Metathesis Transformations of Natural

Products: Cross-metathesis of Natural Rubber and Mandarin Oil by Ru-alkylidene Catalysts. Molecules 2012, 17, 6001–6010. (55)

Jiang, B.; Wei, T.; Zou, T.T.; Rempel, G.L.; Pan, Q.M. A Novel Approval for

Degradation of Polybutadiene and Synthesis of Diene-based Telechelic Oligomers via Olefin Cross Metathesis. Macromol. React. Eng. 2015, 9, 480–489. (56)

Zou, T.T.; Jiang, B.; Lin, S.H.; Pan, Q.M. Metathetic Degradation of Styrene-butadiene

Rubber via Ru-alkylidene Complex Catalyzed Reaction. Polym.-Korea 2016, 40, 663–670. (57)

Wang, H.; Yang, L.J.; Rempel, G.L. Homogeneous Hydrogenation Art of Nitrile

Butadiene Rubber: A Review. Polym. Rev. 2013, 53, 192–239. (58)

Wang, H.; Rempel, G.L. Aqueous-phase Catalytic Hydrogenation of Unsaturated

Polymers. Cat. Today 2015, 247, 117–123. (59)

Dias, E.L.; Grubbs, R.H. Synthesis and Investigation of Homo- and Heterobimetallic

Ruthenium Olefin Metathesis Catalysts Exhibiting Increased Activities. Organometallics 1998, 17, 2758–2767. (60)

Drouin, S.D.; Yap, G.P.A.; Fogg, D.E. Hydrogenolysis of a Ruthenium Carbene Complex to

Yield

Dihydride-Dihydrogen

Tautomers:

Mechanistic

Implications

for

Tandem

ROMP-

Hydrogenation Catalysis. Inorg. Chem. 2000, 39, 5412–5414.

(61)

Drouin, S.D.; Zamanian, F.; Fogg, D.E. Multiple Tandem Catalysis: Facile Cycling

between Hydrogenation and Metathesis Chemistry. Organometallics 2001, 20, 5495–5497. (62)

Fogg, D.E.; Amoroso, D.; Drouin, S.D.; Snelgrove, J.; Conrad, J.; Zamananian, F. Ligand

Manipulation and Design for Ruthenium Metathesis and Tandem Metathesis-hydrogenation Catalysis. J. Mol. Cat. A: Chem. 2002, 190, 177–184.


41


(63)

Page 42 of 48

Camm, K.D.; Castro, N.M.; Liu, Y.W.; Czechura, P.; Snelgrove, J.L.; Fogg, D.E.

Tandem ROMP-Hydrogenation with a Third-Generation Grubbs Catalyst. J. Am. Chem. Soc. 2007, 129, 4168–4169. (64)

Cobo, N.; Esterulas, M.A.; Gonzalez, F.; Herrero, J.; Lopez, A.M.; Lucio, P.; Olivan, M.

OsHCl(CO)(PiPr3)2 as Catalyst for Ring-opening Metathesis Polymerization (ROMP) and Tandem ROMP–hydrogenation of Norbornene and 2,5-Norbornadiene. J. Cat. 2004, 223, 319–327. (65)

Kongparakul, S.; Ng, F.T.T.; Rempel, G.L. Metathesis Hydrogenation of Natural Rubber

Latex. Appl. Cat. A Gen. 2011, 405, 129–136. (66)

Kongparakul, S.; Ng, F.T.T.; Rempel, G.L. Green Process for Natural Rubber Latex

Hydrogenation via Metathesis. Top. Cat. 2012, 55, 524–529. (67)

Ai, C.J.; Gong, G.B.; Zhao, X.T.; Liu, P. Selectively Catalytic Hydrogenation of Nitrile-

butadiene Rubber Using Grubbs II Catalyst. Macromol. Res. 2017, 25, 461–465. (68)

Ai, C.J.; Li, J.G.; Gong, G.B.; Zhao, X.T.; Liu, P. Preparation of Hydrogenated Nitrile-

butadiene Rubber (H-NBR) with Controllable Molecular Weight with Heterogeneous Catalytic Hydrogenation after Degradation via Olefin Cross Metathesis. React. Funct. Polym. 2018, DOI: 10.1016/j.reactfunctpolym.2017.12.016. (69)

Ohishi, T.; Suyama, K.; Kamimura, S.; Sakada, M.; Imato, K.; Kawahara, S.; Takahara,

A.; Otsuka, H. Metathesis-driven Scrambling Reactions between Polybutadiene or Naturally Occurring Polyisoprene and Olefin-containing Polyurethane. Polymer 2015, 78, 145–153. (70)

Lu, Y.X.; Tournilhac, F.; Leibler, L.; Guan, Z.B. Making Insoluble Polymer Networks

Malleable via Olefin Metathesis. J. Am Chem. Soc. 2012, 134, 8424–8427.


42

Page 43 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(71)

Lu, Y.X.; Guan, Z.H. Olefin Metathesis for Effective Polymer Healing via Dynamic

Exchange of Strong Carbon–Carbon Double Bonds. J. Am Chem. Soc. 2012, 134, 14226– 14231. (72)

Martinez, H.; Hillmyer, M.A. Carboxy-Telechelic Polyolefins in Cross-Linked

Elastomers. Macromolecules 2014, 47, 479–785. (73)

Tuba, R.; Balogh, J.; Hlil, A.; Barlog, M.; Al-Hashimi, N.; Bazzi, H.S. Synthesis of

Recyclable Tire Additives via Equilibrium Ring-Opening Metathesis Polymerization. ACS Sustainable Chem. Eng. 2016, 4, 6090–6094. (74)

Li, L.; Zhang, C.Y.; Zheng, S.X. Synthesis of POSS-terminated Polycyclooctadiene

Telechelics via Ring-opening Metathesis Polymerization. J. Polym. Sci. A: Polym. Chem. 2017, 55, 223–233. (75)

Yang, J.X.; Long, Y.Y.; Pan, L.; Men, Y.F.; Li, Y.S. Spontaneously Healable

Thermoplastic Elastomers Achieved through One-Pot Living Ring-Opening Metathesis Copolymerization of Well-Designed Bulky Monomers. ACS Appl. Mater. Interfaces 2016, 8, 12445–12455. (76)

Hocker, H. The Metathesis Reaction of Cycloolefins and Heterocyclic Olefins:

Thermodynamics and Mechanistic Aspects. Macromol. Chem. Phys. 1985, 12, 143–152. (77)

Hocker, H. Ring Opening Polymerization of Cycloolefins by Means of Metathesis

Catalyst: Kinetic and Thermodynamic Effects on the Product Distribution. Macromol. Symp. 1986, 6, 47–52. (78)

Chen, Z.-R.; Claverite, J.P.; Grubbs, R.H.; Kornfield, J.A.

LModeling Ring-Chain

Equilibria in Ring-Opening Polymerization of Cycloolefins. Macromolecules 1995, 24, 2147–2154.


43


(79)

Page 44 of 48

Tlenkopatchev, M.A.; Vargas, S.M.; Fomine, S. Molecular Modeling of Ring-Opening

Cross Metathesis. Distributions of Products for the Ethenolysis of cis,cis-Cycloocta-1,5-diene and cis,cis-1,5-Dimethyl-Cycloocta-1,5-Diene. Tetrahedron 2002, 58, 4817–4824. (80)

Gutierras, S.; Vargas, S.M.; Tlenkopatchev, M.A. Molecular Modeling of Ring-Chain

Equilibria for the Ring-Opening Cross-Metathesis of cis,cis-1,5-Dimethyl-Cycloocta-1,5Diene with Ethylene at T = 298:15 K. J. Chem. Thermodynamics 2004, 36, 29–36. (81)

Gutierras, S.; Fulgencio, A.; Tlenkopatchev, M.A. Density Functional Theory Study of

Ring-Chain Equilibria for the Cross-Metathesis of Cyclohexene and cis,cis-Cycloocta-1,5Diene with Functionalized Olefins. J. Chem. Thermodynamics 2006, 38, 383–387. (82)

Stukalin, E.B.; Cai, L.H.; Kumar, N.A.; Leibler, L.; Rubinstein, M. Self-healing of

Unentangled Polymer Networks with Reversible Bonds. Macromolecules 2013, 46, 7525– 7541. (83)

Lorber, F.; Hummel, K. Ein Kinetischer Effekt bei der Metathese-reaktion von

Ungesättigten Polymeren mit Niedermolekularen Olefinen. Makromol. Chem. 1973, 177, 257–260. (84)

Martl, M.G.; Zuegg, J.; Hummel, K. Improved Computer Simulation of Metathesis

Reactions. J. Mol. Cat. 1991, 65, 127–138. (85)

Hummel, K. Polymer Degradation by Olefin Metathesis. Pure Appl. Chem. 1982, 54,

351–364. (86)

Hummel, K.; Stelzer, F.; Heiling, P.; Wedam, O. A.; Griesser, H. Some New Aspects of

Polymer Degradation by Olefin Metathesis. J. Mol. Cat. 1980, 8, 253–260. (87)

Gutierras, S.; Vargas, S.M.; Tlenkopatchev, M.A. Computational Study of Metathesis

Degradation of Rubber. Distributions of Products for the Ethenolysis of 1,4-Polyisoprene. Polym. Degrad. Stab. 2004, 83, 149–156.


44

Page 45 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(88)

Tlenkopatchev, M.A.; Bercenas, A.; Fomine, S. Computational Study of Metathesis

Degradation of Rubber, 1. Distribution of Cyclic Oligomers via Intramolecular Metathesis Degradation of cis-Polybutadiene. Macromol. Theory Simul. 1999, 8, 581–585. (89)

Tlenkopatchev, M.A.; Bercenas, A.; Fomine, S. Computational Study of Metathesis

Degradation of Rubber, 3. Distribution of Cyclic and Linear Oligomers via Intermolecular Degradation of cis-Poly(butadiene). Macromol. Theory Simul. 2001, 10, 729–735. (90)

Kiattanavith, N.; Hummel, K. Determination of Carbon Black Filler in Natural Rubber

Vulcanizates by Olefin Metathesis Degradation. Polym. Degrad. Stab. 1993, 41, 1–3. (91)

Hummel, K.; Kiattanavith, N.; Bernard, E. Determination of Carbon Black Fillers in

Vulcanizates of Natural Rubber by Metathesis Degradation. Macromol. Mater. Eng. 1993, 207, 137–143. (92)

Leimgruber, S.; Kern, W.; Hochenauer, R.; Melmer, M.; Holzner, A.; Trimmel, G.

Rubber-brass Adhesion Layer Analysis Using the Olefin-metathesis Method. Rubb. Chem. Technol. 2015, 88, 219–233. (93)

Ai, C.J.; Gong, G.B.; Zhao, X.T.; Liu, P. Determination of Carboxyl Content in

Carboxylated Nitrile Butadiene Rubber (XNBR) After Degradation via Olefin Cross Metathesis. Polym. Test. 2017, 60, 250–252. (94)

Fainleib, A.; Pires, R.V.; Lucas, E.F.; Soares, B.G. Degradation of Non-vulcanized

Natural Rubber - Renewable Resource for Fine Chemicals Used in Polymer Synthesis. Polimeros 2013, 23, 441–450. (95)

Imbemon, L.; Norvez, S. From Landfilling to Vitrimer Chemistry in Rubber Life Cycle.

Eur. Polym. J. 2016, 82, 347–376. (96)

Stelzer, F.; Hobisch, G.; Pong Ratz, T.; Hummel, K. Metathesis Degradation of

Acrylonitrile/Butadiene Copolymers. J. Mol. Cat. 1988, 46, 423–431.


45


(97)

Page 46 of 48

Hummel, K. Degradation of Unsaturated Polymers by Olefin Metathesis. J. Macromol.

Sci: Part A-Pure Appl. Chem. 1993, A30, 621–632. (98)

Zhou, Q.Z.; Jie, S.Y.; Li, B.G. Facile Synthesis of Novel HTPBs and EHTPBs with High

cis-1,4 Content and Extremely Low Glass Transition Temperature. Polymer 2015, 67, 208– 215. (99)

Zhou, Q.Z.; Jie, S.Y.; Li, B.G. Preparation of Hydroxyl-Terminated Polybutadiene with

High Cis-1,4 Content. Ind. Eng. Chem. Res. 2014, 53, 17884–17893. (100) Cao, Z.; Jie, S.Y.; Li, B.G. Preparation and Properties of Epoxided Hydroxyl-terminated Polybutadiene Based Polyurethane Elastomers. Acta Polym. Sin. 2017, 8, 1350–1357. (101) Sundararajan, G.; Vasudevan, V.; Reddy, K.A. Synthesis of Triblock Copolymers— (polyA-polybutadiene-polyA)—via Metathesis Polymerization. J. Polym. Sci. A: Polym. Chem. 1998, 36, 2601–2610. (102) Tlenkopatchev, M.A.; Bercenas, A.; Fomine, S. Computional Study of Metathesis Degradation of Rubber, 2. Distribution of Cyclic Oligomers via Intramolecular Metathesis Degradation of Natural Rubber. Macromol. Theory Simul. 2001, 10, 441–446. (103) Dewaele, A.; Renders, T.; Yu, B.Y.; Verpoort, F.; Sels, B.F. Depolymerization of 1,4Polybutadiene by Metathesis: High Yield of Large Macrocyclic Oligo(butadiene)s by Ligand Selectivity Control. Cat. Sci. Technol. 2016, 6, 7708–7717. (104) Zumreoglu-Karan, B.; Bozkurt, C.; Imamoglu, Y. Degradation of Sulfur-crosslinked cis1,4 Polybutadiene by Metathesis Catalysts. Polym. J. 1992, 24, 25–29. (105) Watson, M.D.; Wagener, K B. Solvent-Free Olefin Metathesis Depolymerization of 1,4Polybutadiene. Macromolecules 2000, 33, 1494–1496. (106) Wolf, S.; Plenio, H. On the Ethenolysis of Natural Rubber and Squalene. Green Chem. 2011, 13, 2008–2012.


46

Page 47 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(107) Bidange, J.; Fischmeister, C.; Bruneau, C. Ethenolysis: A Green Catalytic Tool to Cleave Carbon–Carbon Double Bonds. Chem. Eur. J. 2016, 22, 12226–12244. (108) Ouardad, S.; Peruch, F. Metathetic Degradation of Trans-1,4-polyisoprene with Ruthenium Catalysts. Polym. Degrad. Stab. 2014, 99, 249–253. (109) Williams, P.T. Pyrolysis of Waste Tyres: A Review. Waste Manag. 2013, 33, 1714–1728. (110) Ramarad, S.; Khalid, M.; Ratnam, C.T.; Chuah, A.L.; Rashmi, W. Waste tire Rubber in Polymer Blends: A Review on the Evolution, Properties and Future. Prog. Polym. Sci. 2015, 72, 100–140. (111) Thomas, B.S.; Gupta, R.C. A Comprehensive Review on the Applications of Waste tire Rubber in Cement Concrete. Renew. Sustainable Energy Rev. 2016, 54, 1323–1333. (112) Mouawia, A.; Nourry, A.; Gaumont, A.-C.; Pilard, J.-F.; Dez, I. Controlled Metathetic Depolymerization of Natural Rubber in Ionic Liquids: From Waste Tires to Telechelic Polyisoprene Oligomers. ACS Sustainable Chem. Eng. 2017, 5, 696–700.


47


Page 48 of 48

TOC

ROMP

CM

Olefin Metathesis in Rubber Chemistry and Industry Modeling and Simulation

Applications


48

Olefin Metathesis Reaction in Rubber Chemistry and Industry and

Recommend Documents