Synthesis of Fully Biobased Polyesters from Plant Oil - ACS Publications

Subscriber access provided by UNIVERSITY OF ADELAIDE LIBRARIES

Article

Synthesis of Fully Bio-based Polyesters from Plant Oil Liejiang Jin, Keyu Geng, Muhammad Arshad, Reza Ahmadi, and Aman Ullah ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b01668 • Publication Date (Web): 14 Sep 2017 Downloaded from http://pubs.acs.org on September 15, 2017

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 free 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 accessible to all readers and 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.

ACS Sustainable Chemistry & Engineering 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 28

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

ACS Sustainable Chemistry & Engineering

1

Synthesis of Fully Bio-based Polyesters from Plant Oil

2

Liejiang Jin†, Keyu Geng†‡, Muhammad Arshad†, Reza Ahmadi†, Aman Ullah†*

3

†Department of Agricultural, Food and Nutritional Science, 4-10 Agric/For Centre, University of

4

Alberta, Edmonton, Alberta, Canada T6G 2P5

5

‡Department of Polymer Science and Engineering, Zhejiang University, Zhe Da Road 38,

6

Hangzhou 310027, China

7

*Corresponding author: Dr. Ullah, Email: [email protected]

8

Tel: +1 (780) 492-4845,

Fax: +1(780) 492-4265

9 10 11 12 13 14 15 16 17 18 19 20 21 22 1

ACS Paragon Plus Environment


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

1

Abstract

2

Self-metathesis of fatty acid methyl esters (FAMEs) from natural oils and commercial oleic acid

3

was carried out using microwave reactor in solvent free conditions. Self-metathesis products

4

were further identified and quantified by gas chromatography-mass spectroscopy (GC-MS) and

5

gas chromatography-flame ionization detector (GC-FID). Conversion of ~50% was achieved

6

within short span (~2 min) in the presence of 0.05 mol% Hoveyda-Grubbs 2nd generation catalyst

7

(HG2) giving an equilibrium mixture of alkenes, α,ω-diester and FAMEs. Highly pure

8

dimethyl-9-octadecene-1,18-dioate (diester) was separated and the desired quantity of it was

9

reduced to 9-octadecene-1,18-diol (diol). Condensation polymerization of diester and diol as

10

monomers was performed using conventional heating, microwave irradiation and microwaves

11

coupled with conventional heating. Characterization and analysis of synthesized biopolyesters

12

were carried out using different techniques including nuclear magnetic resonance (NMR),

13

Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), gel

14

permeation chromatography (GPC), thermal gravimetric analysis (TGA), dynamic mechanical

15

analysis (DMA) and tensile tests. Polyesters with highest molecular weight of 337KDa, ~50 oC

16

melting point, degradation temperature of about 400 oC, and the maximum strength of ~5.5MPa

17

were obtained. These materials have great future potential to be used in different applications as

18

a substitute of non-renewable polyesters.

19

Keywords: plant oil, self-metathesis, microwave irradiation, aliphatic polyester, renewable

20

resources

21

Introduction

22

Fossil feedstocks, which are abundant and cheap, have been supplying the vast majority of raw

23

materials for polymer production over the last few decades. However, fossil oil as non-renewable

24

resource is gradually depleting and its exploitation and combustion have negative impacts on

25

environment and ecosystem1. As an alternative to avoid these disadvantages, renewable 2


Page 2 of 28

Page 3 of 28

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


1

resources which meet the requirements of environment protection and sustainable development

2

are now being considered as building blocks for the preparation of polymeric materials and are

3

attracting a growing interest from academia and industry.

4

The largely available and easily accessible renewable resources are taken into consideration,

5

such as plant oils. In Canada, millions of tons of plant oils are being produced every year, as

6

renewable feedstocks which can be used for production of fine chemicals and polymers. Plant

7

oils, including canola oil have abundant unsaturated hydrocarbon chains. They are generally

8

converted to fatty acids (FAs) or fatty acid methyl esters (FAMEs) for the simplicity of

9

modification. Many reactions have been developed to modify FAs and FAMEs into α,

10

ω-functionalized compounds as valuable monomers of polyesters, polycarbonates and

11

polyamides. For instance, alkoxycarbonylation2-3 is effective to convert unsaturated FAMEs to

12

compounds with esters on both ends. Other reactions, such as ozonolysis4-5 and thiol-ene click

13

reaction6-7 have also been used to provide additional carboxyl acid, ester or amine groups to fatty

14

acids.

15

Moreover, olefin self-metathesis 8, a type of reaction which allows the exchange of substituents

16

on olefinic double bonds, is also a powerful tool for the preparation of bifunctional monomers.

17

The olefin metathesis due to its operational simplicity, mild reaction conditions, and environment

18

friendliness is considered an attractive technique for synthetic transformations. The

19

self-metathesis of unsaturated FAMEs was initially investigated by Boelhouwer’s group. Using

20

WCl6 and Me4Sn as catalytic system in chlorobenzene solution, methyl oleate and methyl

21

elaidate were transformed to desired alkene and diesters with ~50% conversion in 24 hours9.

22

Solvent free self-metathesis was successfully carried out in a later stage and then commonly used.

23

For instance, Mecking et al. obtained C20 diester with 33% yield from self-metathesis of

24

10-undecenoic acid at 48 oC within 4 hours10. Recently, Meier et al. reported higher conversion

25

98% of FAMEs from linseed and chia seed oil at 100 °C for 24h in the presence of 0.15 mol% 3



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

1

Grubbs 1st generation catalyst and 0.30 mol% 1,4-benzoquinone (BQ) as olefin isomerisation

2

suppressant. However, for relatively larger scale batch of methyl linolenate ~ 30 grams, longer

3

reaction time of 36 hours and higher catalyst loading of 0.45 mol % (three different batches of

4

0.15 mol%) were required11. With the advantages of low catalyst loading, solvent free and

5

moderate conditions, olefin self-metathesis has extraordinary performance to build α,

6

ω-functionalized acids or esters from plant oils but catalyst deactivation due to longer reaction

7

times still remains a challenge.

8

Microwaves, having wavelengths between infrared and radio waves, have been widely used as

9

an unconventional technique for the acceleration of various organic reactions from late 20th

10

century12-13. A few studies on olefin metathesis under microwave irradiation have been reported,

11

particularly microwave-assisted ring-closing self-metathesis14-15 of several α,ω-dienes and

12

cross-metathesis16-17 of α-olefins. Reaction time was cut down to a few minutes or even seconds

13

from number of hours usually required by conventional heating method without affecting the

14

yield (>70%). However, microwave-enhanced olefin metathesis of natural resources has rarely

15

been investigated. To the best of our knowledge, there are no reports on the microwave-assisted

16

self-metathesis of plant oils such as canola and soybean oil. In addition to olefin metathesis,

17

research work regarding polycondensation of fossil fuel based monomers using microwave

18

technology has also attracted attention all over the world18-19. Takeuchi et al. obtained

19

poly(butylene succinate) (PBS) with weight average molecular weight (Mw) of 23,500 g/mol

20

using microwave technology in a short time period (~20 min)20.

21

Recently, our group has reported cross-metathesis (ethenolysis and alkenolysis) of canola oil

22

methyl esters using microwaves under solvent free conditions21. In this study, for the first time

23

we are reporting microwave-assisted self-metathesis of FAMEs from plant oils for the

24

production of diester. The desired quantity of this diester was reduced to diol, and both of these

25

monomers (diester and diol) were used for the synthesis of biopolyesters. Though a few 4


Page 4 of 28

Page 5 of 28

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


1

examples of conventional polycondensation of plant oil derived diesters and diols have been

2

successfully carried out2-3, 10. To the best of our knowledge, microwave-induced polymerization

3

of these monomers has never been reported. The current study also includes the comparison of

4

conventional and microwave-enhanced polycondensation of plant oil derived diester and diol

5

under optimized conditions.

6

Result and Discussion

7

Olefin Metathesis of FAMEs

8

Plant oil methyl esters (POMEs) are generally mixtures of several FAMEs with different chain

9

lengths and unsaturation. Some of common FAME types are depicted in figure 1, containing

10

saturated, monounsaturated and polyunsaturated hydrocarbon chains.

11 12

Figure 1. Fatty acid methyl esters from different plant sources.

13

The self-metathesis of polyunsaturated POMEs produce several cyclo-olefins and short-chain

14

olefins which are volatile, including cyclohexa-1,4-diene and hex-3-ene11. Therefore, to

15

minimize product complexity by self-metathesis, the natural oil sources predominantly having

16

oleic acid (c18:1) were selected for this study using self-metathesis under microwave conditions.

17

For this purpose, firstly the fatty acids from oils were converted to monomeric methyl esters for

18

the simplicity of quantification and elimination of acidic group to quench its ability potentially

19

involved for the deactivation of catalyst. The compositions of POMEs were identified by GC-MS

20

and quantified by GC-FID, as shown in table 1. Polyunsaturated FAMEs (c18:2/c18:3) from all 5



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 6 of 28

1

three sources are less than 17%, while the monounsaturated FAMEs (c16:1/c18:1) are

2

predominant compounds (> 75%).

3

Table 1. Composition of different POMEs FAMEs*

c14:0

c16:0

c18:0

c16:1c

c18:1c

c18:2c

c18:3c

A

-

6.7%

-

-

77.0%

13.3%

3.0%

B

-

7.4%

5.6%

-

82.5%

4.4%

-

C

3.4%

5.8%

-

5.8%

79.2%

5.8%

-

4 5

(*A: canola oil methyl ester, B: high oleic soybean oil methyl ester,

6

Hoveyda Grubbs 2nd generation catalyst (HG2) was particularly employed in this study for its

7

high tolerance to polar and protic environments. The self-metathesis of pure methyl oleate using

8

conventional heating has suggested that increase in reaction temperature leads to a drop of

9

observed conversion.22 . Therefore, medium temperature of 50oC was selected in this work.

C: methyl oleate technical grade) determined by GC-FID.

O O O O O O

self-metathesis

H3C(H2C)7 (a)

(CH2)4CH3

H3C(H2C)7

H3C(H2C)7 (b)

(c)

(CH2)7CH3

O (d)

O (e)

O O (f)

O

O O

O

10

(g)

11

Scheme 1. Self-metathesis of canola oil methyl esters.

O

6


O

Page 7 of 28

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


1

A good conversion rate for self-metathesis of canola oil methyl esters was observed with in very

2

short reaction time (2 min), while the product structures were deduced/characterized by their

3

elution time, peak areas and MS spectra (figure 2). The unsaturated methyl esters in canola oil

4

and their products after self-metathesis are depicted in scheme 1. The products have been

5

classified into three types: olefins with internal double bonds (a, b, c); unsaturated FAMEs (d, e,

6

f); and unsaturated diester (g). Both cis- and trans- isomers were identified for compounds e, f

7

and g from GC-MS. Commonly the cis- compound has larger dipole moment and higher polarity,

8

so trans- isomers are suggested to be eluted ahead of cis-isomers based on the separation

9

principles of GC. This point of view was confirmed by comparing the elution time of c18:1t

10

(trans) in the spectrum of metathesis products and c18:1c (cis) in FAMEs (figure 2).

11

Generally, during self-metathesis using conventional heating, the diesters with shorter or longer

12

chain lengths may be generated due to olefin isomerization23, leading to difficulty in separation

13

of diester products. In this study, only peaks of C18 diester were identified. The absence of C17

14

or C19 diesters peaks in GC-MS spectrum strongly suggests that olefin isomerization did not

15

take place during microwave reaction.

7



3x105 (1) COME (2) SM-Products

f(c18:1t)

Abundance

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 8 of 28

2x105

c

e(trans) c16:0

1x10

5

a e(cis)

g(trans)

b d

f(c18:1c)

c16:0

g(cis)

c18:1c18:2 c18:3

(2) (1)

0 20

30

40

50

60

70

80

90

Retention time (min)

1 2 3

Figure 2. GC-MS spectrum of canola oil methyl esters (COME) and self-metathesis (SM) products.

4

However, the existence of c18:1t (f) indicated that the reactants were not fully converted due to

5

equilibrium state of alkene self-metathesis. Conversion rate of ~50% was widely observed from

6

publications. For instance, Thomas A. FoGlia observed exactly 50% conversion rate from

7

olefin-metathesis of methyl oleate using Re2O3·Al2O3·Me4Sn catalyst24. Roland Winde reported

8

conversion rate of 49.6% for methyl oleate self-metathesis using a phoban-indenylidene

9

ruthenium catalyst25.

10

Herein, to investigate the chemical equilibrium state directly, the real conversion (Conv(R)) was

11

defined as the ratio of olefins and diesters amount to total amount of products26. To simplify the

12

conversion rate calculation, three assumptions were established: (1) The mass response factors

13

(MRF) of double-bond isomers were considered the same; (2) MRF of analogical compounds

14

(for olefins, FAMEs and diesters, respectively) were assumed the same; (3) the amount of

15

generated olefins equals to that of diesters. By considering all these factors, MRFs of

16

representative FAME (methyl oleate) and diester (dimethyl-9-octadecene-1,18-dioate isomers) 8


Page 9 of 28

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


1

were obtained after calibration, as presented in Figure S6 & S7. Conv(R) was determined using

2

the following formula (1), where "c" represent concentration for each components. ConvR% =

3

=

× 100

--------- (1)

4

In case of canola oil methyl ester, 50.6% Conv(R) was observed (table 2). The reliability of

5

calculation was reconfirmed via yield calculation from an amplified reaction. 14.5g of

6

dimethyl-9-octadecene-1,18-dioate (Conv(R) ≈ 43%) was separated after the self-metathesis

7

reaction of 63g FAMEs. Considering percentage of saturated FAMEs and loss of products during

8

purification, the actual Conv(R) was supposed to be more close to the result calculated based on

9

GC-FID.

10

Though the calculated conversions were in line with the reported results, it was still unknown

11

whether the reaction was in equilibrium state under microwave irradiation or not. To figure out

12

the equilibrium point of microwave-assisted self-metathesis, aliquots were taken out for GC-FID

13

analysis at different time intervals (2, 6, 10, 20, 30 and 60 minutes). The conversion of FAMEs

14

into olefins and diesters was found to be around 50% after the chemical equilibrium was

15

achieved. Moreover, figure S8 also represent that olefin metathesis was completed within 2

16

minutes by microwave heating as compared to conventional heating which requires number of

17

hours. In this way, a rapid and efficient method has been established using microwaves.

18

Further, FAME mixtures from two other sources were investigated for microwave-induced

19

self-metathesis. Technical grade methyl oleate and high oleic soybean oil methyl esters were

20

successfully converted into diester. For methyl oleate, around 50% Conv(R) was achieved (table

21

2, entry 3), which is similar to the previously reported data on self-metathesis of methyl oleate.

22

However, only 39.2% conversion was observed in case of high oleic soybean oil methyl esters

23

self-metathesis (table 2, entry 2). Residual glycerol in FAMEs might be a conceivable reason for

24

lower conversion, as catalyst get deactivated after forming a Grubbs hydride complex with 9



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 10 of 28

1

alcohol27. As, we have observed that crude FAMEs with residual glycerol have not displayed any

2

conversion even after 20 min under microwave radiation.

3

Table 2. The conversion of FAMEs by self-metathesis Entry

FAMEsa

Reaction Time(mins)b

Conv(R)%

1

A

2

50.6

2

B

2

39.2

3

C

2

51.3

4 5

a

6

Effect of Catalyst Loading on Conversions

7

The effect of catalyst concentration on conversion rate of FAMEs (methyl oleate) for their self

8

metathesis was also investigated using different catalyst loadings of HG2 (0.05 to 0.005 mol%).

9

HG2 loading was gradually reduced from 0.05 mol% to 0.005 mol% (table 3). Once the HG2

10

loading was decreased to 0.01 mol%, the required reaction time was prolonged from 2 to 6

11

minutes to achieve similar conversion (~50.8%) as given in table 3 and entry 3. Further lowering

12

of HG2 concentration to 0.005 mol% led to a sharp drop of conversion rate to 8.5% (table 3,

13

entry 4). Even with extended reaction time, the conversion was not improved. We hypothesized

14

that very low concentration of HG2 has completely been degraded/deactivated before the

15

completion of reaction. Therefore, catalyst loading of 0.01 mol% was considered as a preferred

16

concentration for self-metathesis.

17

18

A: canola oil methyl ester, B: high oleic soybean oil methyl ester, C: methyl oleate technical grade.

b

Conditions: 50 oC under microwave radiations at 0.05 mol% HG2 loading.

Table 3. The conv(R) of FAMEs (methyl oleate) after self-metathesis.

a

Entry

HG2 Loading (%)

Reaction Time(min)a

Conv(R)%

1

0.05

2

51.3

2

0.01

2

40.9

3

0.01

6

50.8

4

0.005

2

8.5

Conditions: 50oC under microwave radiations.

10


Page 11 of 28

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


1

Preparation and Characterization of Polyesters

2

Polyesters were prepared by polycondensation of diester (Dimethyl-9-octadecene-1,18-dioate)

3

and diol (9-octadecene-1,18-diol) in the presence of SnCl2 or Ti(OBu)4 as catalyst at suitable

4

temperature as shown in scheme 2. Whereas, diol was obtained by reducing diester with lithium

5

aluminum hydride (LiAlH4, see supp. info.). The preparation of polyester was carried out using

6

three different approaches; (a) by conventional heating, (b) by microwave and (c) by coupling

7

microwave and conventional heating.

8 9

Scheme 2: Polycondensation of diester (Dimethyl-9-octadecene-1,18-dioate) and diol

10

(9-octadecene-1,18-diol) in the presence of catalyst (SnCl2 or Ti(OBu)4)

11

Polycondensation by Conventional Heating

12

Firstly, the polycondensation of diester and diol was carried out at 200°C by conventional

13

heating using two different catalysts (SnCl2 and Ti(OBu)4) for different time intervals to explore

14

optimum conditions for polyester preparation as shown in table 4 and S1. Polyesters obtained in

15

the presence of both catalysts for different time intervals are of almost similar molecular weight

16

having their melting temperatures (Tm) in the range of 50-51 oC.

17

11



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

1

Page 12 of 28

Table 4. Polycondensation of diester and diol by conventional heating Entry

Catalyst

Time (h)

Tm (oC)

∆Hm (J/g)

1

2% SnCl2

8

51.6

85.4

2

2% SnCl2

16

50.0

78.8

2

Melting temperatures and melting enthalpy (∆Hm) of polyesters obtained by conventional

3

heating were determined by DSC as shown in table 4 and S1. A very slight difference in the Tm

4

and ∆Hm values of polyesters was observed, which means there is no significant effect of catalyst

5

nature and reaction time interval. However, the melting point of polyesters prepared with

6

unsaturated long-chain monomers is lower than the saturated aliphatic polyesters. Mecking and

7

his colleagues have prepared saturated long-chain C19 3 and C20

8

both of these have 103 oC melting temperature, while the ∆Hm of those saturated polyesters were

9

144 J/g and 178 J/g respectively which are much higher than our synthesized polyesters. The

10

reported high ∆Hm values indicate that these saturated polyesters possess higher degree of

11

crystallization. While in our case, ∆Hm is only 78-88 J/g (table 4 and table S1), which could be

12

attributed to unsaturation of polyesters restricting the free motion of hydrocarbon chains.

13

Therefore, the arrangement of unsaturated long-chain in microstructure is less organized than

14

saturated polyester, which leads to lower degree of crystallization and melting point.

15

Microwave Assisted Polycondensation

16

Microwave-induced polycondensation of diester/diol was carried out in a CEM discover

17

microwave reactor, using open vessel mode under high vacuum (~0.1 bar). Initially, trials using

18

2% Ti(OBu)4 were attempted and only after few seconds of microwave irradiation, blue plasma

19

occurred. The starting materials were charred and glassware was cracked immediately (figure

20

S9a). Initially, it was assumed that under high pressure the microwave energy was mostly

21

absorbed by the polymer debris attached on the vessel wall causing a rapid temperature rise of

22

glassware18. Therefore, the vacuity was reduced (0.7 bar) to decrease polymerization rate and 12


10

polyesters and reported that

Page 13 of 28

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


1

avoid energy accumulation. Unfortunately, experiment using Ti(OBu)4 as catalyst failed again

2

with the occurrence of plasma. This was probably due to titanium causing sparking leading to

3

occurrence of plasma. Then SnCl2 was tried as catalyst under ~0.7 bar vacuum and it worked

4

well for polymer preparation without occurrence of any plasma.

5 6

Table 5. Polycondensation of diester/diol using 2% SnCl2 under microwave irradiations at 200°C. Entry

Atmosphere

Time (min)

Tm(oC)

∆Hm(J/g)

1

N2

15

50.9

111.4

2

N2

60

50.6

97.2

60

51.0

108.6

3 *

*

0.7 bar vacuum

7 8

pressure to 0.7 bar.

9

So further microwave assisted reactions were studied using SnCl2 under nitrogen atmosphere and

10

in the absence of inert nitrogen at 0.7 bar vacuum (table 5). The formation of polymer was

11

accomplished within 15 minutes in both cases (figure S9b) compared to polymerization by

12

conventional heating which took longer reaction times. While melting point of polyesters from

13

microwave induced method was also observed in the range of 50-51oC (figure 3, table 5).

14

Slightly lower molecular weight polyester was obtained by microwave heating in comparison to

15

those obtained by conventional heating (figure S10)

16

The molecular masses, strength and stiffness of polyesters prepared by conventional heating and

17

by microwave irradiation were found to be different. It was observed that the polyesters by

18

microwave-assisted method have lower strength and stiffness as compare to those obtained by

19

conventional heating, which could be attributed to entrapped residual methanol, difference in the

20

ratio of monomers used and lower molar mass of polyesters. It was difficult to prepare the film

21

of this polyester for mechanical study, therefore, a coupled method was established, where both

22

microwave and conventional heating were used for polycondensation.

The reaction was performed under nitrogen atmosphere for 15 minutes on a microwave before reducing the

13



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 14 of 28

1

Polycondensation by Coupling Microwave and Conventional Heating

2

In coupled method, initially polycondensation reaction was performed for 15 minute on a

3

microwave reactor at under nitrogen atmosphere. After that, the reaction was continued at

4

reduced pressure (0.7 bar) for particular time intervals (table 6). These microwave assisted

5

polyesters were further heated to 200°C on a hot plate using high vacuum (~0.1 bar). The heat

6

source was removed after 2.5 hours to obtain much stronger and hard polyester with molecular

7

weight approximately equal to the polyester from conventional heating (figure S10). By using

8

this coupled method, the polyester was obtained with molecular weight close to that prepared by

9

conventional heating, where total reaction time was cut down to half compared to

10

polycondensation reaction by conventional heating. Table 6. Polycondensation of diester/diol with 2% SnCl2 (0.7 bar) under microwave conditions

11

*

Entry

T(oC)

1

200

2

*

Tm(oC)

∆Hm(J/g)

15

51.2

100.0

200

30

51.4

96.5

3

200

60

50.1

94.2

4

200

90

51.1

94.6

5

220

15

50.8

103.9

6

220

30

50.9

97.0

7

220

60

50.4

106.5

Time (min)

12 13

pressure to 0.7 bar.

14

Almost all of polyesters prepared by different heating methods displayed glass transitions

15

temperatures at 0 °C or below 0 °C. The polyester synthesized with heating method had Tg of

16

0°C while the polyesters synthesized by microwaves and coupled method using microwaves and

17

conventional heating displayed Tg of ~ -26°C and -1°C respectively. The polyesters also showed

18

similar melting temperatures (Tm) ranging from 50-51°C as have been determined by DSC given

19

in figure 3. The enthalpy (∆Hm) of all synthesized polyesters was also determined from DSC.

20

Higher value of melting enthalpy (∆Hm) for microwave based polyesters was observed as

Each reaction was performed under nitrogen atmosphere for 15 minutes on a microwave before reducing the

14


Page 15 of 28

1

compared to those obtained by heating method. As we discussed above, ∆Hm is a valuable index

2

of degree of crystallization. Commonly, for polymers with same compositions and structures, the

3

increase of molecular length will result in more difficulty of crystallization. Though quantitative

4

relation between Mw and ∆Hm cannot be determined, it is generally considered that ∆Hm will

5

decrease with the rise of molecular weight.

0.5

second heating

Exo up

0.0 Heat flow (J/g)

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


-0.5 -1.0 -1.5 Ht MW+Ht MW

-2.0 -2.5 -20

0

20

40

60

80 100 120 140 160

Temperature (oC)

6 7 8

Figure 3. DSC curves of polyesters from heating (Ht), microwave irradiation (MW) and coupled methods (MW+Ht). Curves have been offset for clarity.

9

Using ∆Hm as a reference of molecular weight, microwave conditions were optimized by

10

adjusting reaction temperature and time (table 6). At 200°C, ∆Hm decreased continuously with

11

increase of reaction time and remained constant afterwards. However, when the temperature was

12

increased to 220°C, a rise in ∆Hm was observed from 30 to 60 minutes, which might have

13

resulted from polymer degradation (table 6). Thermal degradation of polymer under microwave

14

conditions have been reported by few groups20, 28-29. Hence, high temperature and long reaction

15

times

16

polymerization.

under

microwave

irradiations

are

not

recommended

15


for

microwave-assisted


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 16 of 28

1

The prepared polyesters and monomers were characterized and evaluated with different

2

analytical techniques such as ATR-FTIR, 1H-NMR, GPC, TGA, DSC, DMA and tensile testing.

3

In addition, for polycondensation, the purity level and the ratio of each component are critical

4

factors which directly influence the molecular weight of eventual polymer. Prior to

5

polymerization, the purity and structure of dimethyl-9-octadecene-1,18-dioate (diester) and

6

corresponding diol (9-octadecene-1,18-diol) was confirmed by GC-MS, HRMS and nuclear

7

magnetic resonance spectroscopy (NMR), using both 1H and

8

S1-S4). NMR and FTIR of different polyesters presented similar profiles therefore the NMR and

9

FTIR spectra of polyester (entry 2, table 4) were plotted representatively. The 1H-NMR spectrum

10

of polyester is given in figure 4. All significant peaks associated with different protons have been

11

clearly labeled in the structure of polyester given in figure 4. In addition to these significant

12

peaks, two small peaks at chemical shifts of 3.66 ppm (singlet) and 3.62 ppm (triplet) shown in

13

the expanded region of figure 4 corresponds to terminal hydroxyl and methoxy protons of the

14

polyester. The presence of all these significant peaks and the absence of the hydroxyl and diester

15

methoxy protons of monomers indicated the successful preparation of polyesters.

16

results also support the formation of polyester as shown in figure S5 (supp. info.).

16


13

C-NMR analysis (see figure

13

C-NMR

Page 17 of 28

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


1 2

Figure 4. 1H NMR spectrum (400MHz, C2D2Cl4) of polyester.

3

Moreover, ATR-FTIR analysis of diol, diester and polyesters were also performed to further

4

confirm their structure as shown in figure 5. The characteristic absorption bands at 1735 cm-1

5

(-C=O) and 1170 cm-1 (-C-O-C-) of diester have been completely disappeared in the spectrum of

6

diol, which was obtained by reducing diester. In addition to that, the presence of new band at

7

3350 cm-1 affiliated to hydroxyl group indicates the complete conversion of diester into diol. The

8

absence of characteristic hydroxyl band and the presence of absorption bands associated to

9

carbonyl and ether functional groups with higher intensity in the polyester spectrum confirms the

10

successful polycondensation of diester and diol.

17



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 18 of 28

(1)

(2) -OH

(3) C=O (1) diester (2) diol (3) polyester

C-O-C

3500 3000 2500 2000 1500 1000

500

-1

1

wavenumbers (cm )

2 3

Figure 5. ATR-FTIR spectra of (1) dimethyl-9-nonadecene-1,18-dioate, (2) 9-octadecene-1,18-diol, (3) poly(1,18-9-nonadecendiyl-1,18-9-nonadecenedioate).

4

Polyesters displayed very high molecular weight (Mw), when analysed with the help of gel

5

permeation chromatography (GPC) as shown in figure S10 (supp. info.). The polyester prepared

6

by conventional heating displayed slightly higher molecular weight (Mw = 337 KDa, Mw/Mn =

7

7.3) as compared to the polyester obtained by microwave heating (Mw = 275 KDa, Mw/Mn = 8.8)

8

and by coupling microwave and conventional heating (Mw = 315 KDa, Mw/Mn = 9.5). Due to

9

uncontrolled polymerization process, a high polydispersity index (Mw/Mn ) values were observed

10

in all polyesters obtained by different methods.

11

Furthermore, the thermal degradation behavior of diester, diol and selected polyester (entry 2,

12

table 4) was investigated by thermogravimetric analysis (TGA). Polyesters obtained from

13

heating, microwave or coupled method displayed similar TGA curves, therefore, only the curves

14

of polyester from heating method was plotted. Diester and diol displayed initial weight loss at

15

very low temperature (~160°C) as they exist as an individual molecule having less thermal

16

stability and intermolecular forces. It is obvious from figure 6 that compare to diester, diol has 18


Page 19 of 28

1

less thermal stability as its volatilization/decomposition took place in the temperature range of

2

160-265°C, while the volatilization/decomposition of diester was observed in temperature range

3

of 160-285°C. This difference in their stability/ weight change behavior can be attributed to their

4

divergent intermolecular interaction as they carry dissimilar functional groups. While the

5

polyester obtained after condensation of diol and diester demonstrated higher thermal stability

6

showing initial weight loss starting at 375°C. The polyester remains under continuous

7

degradation up to 485°C with final weight loss of 100%. The higher thermal stability of polyester

8

and its degradation at higher temperature corresponds to high molecular weight and strength of

9

polyester. 100 diester diol polyester

80

Weight (%)

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


60 40 20 0 100

200

300

400

500

600

o

10

Temperature ( C)

11 12

Figure 6. Thermogravimetric analysis (weight % versus temperature) curves of diester, diol and polyester.

13

Mechanical properties of polyesters were studied by preparing films of the powdered materials

14

(hot pressed) using a Carver Press. The polyester obtained by microwave heating was not strong

15

enough to form a film. Therefore, the mechanical and tensile testing results of polyesters 19



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 20 of 28

1

obtained by conventional heating and coupled heating method are reported in supporting

2

information (figure S11, S12 & S13). The polyester obtained by coupled heating method (MW +

3

Ht) demonstrated 2.3 MPa break stress, which is almost half of the maximum break stress (5.5

4

MPa) achieved with polyesters prepared by conventional heating (figure S13). However, the

5

elongation at break of polyester from coupled heating method is up to 11%, which is almost

6

double compared to the polyester obtained by conventional heating method. The higher break

7

stress and less elongation at break (strain) value for polyester obtained by heating method could

8

be attributed to its higher molecular weight making it more strong and rigid as compared to the

9

polyesters from coupled heating method.

10

Dynamic mechanical studies of polyesters were conducted in two different temperature ranges

11

due to dissimilar behavior of polyesters as shown in figure S12. Because of higher rigidity of

12

polyester from heating method, it broke quickly below -50°C, so temperature range for its

13

measurement was set from -50 to 60°C. A slight difference was observed in the storage modulus

14

of both types of polyesters. With the rise of temperature, storage modulus of both polyesters

15

decreases gradually and then above 50°C their storage modulus went down rapidly to zero.

16

Overall polyester from heating method displayed bit higher storage modulus as compare to the

17

one obtained by coupled method.

18

A high decomposition temperature and medium strength was observed for the polyester we

19

synthesized. Nevertheless, the melting point of our synthesized polyester was lower compared to

20

fossil fuel derived synthetic polyesters such as polyethylene terephthalate which has a melting

21

temperature of ~250 oC. The low melting point of this synthesized biopolyester may limit its

22

high temperature applications in its current state. Nevertheless, applications at low temperature,

23

such as packaging could be expected from the biopolyester. For high temperature applications,

24

further crosslinking of -C=C- double bonds is likely to enhance the strength and thermal 20


Page 21 of 28

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


1

properties of polyester enormously, which could benefits potential applications in wider

2

temperature range.

3

Conclusion

4

Fully renewable plant oil based polyesters were successfully prepared using conventional and

5

microwave heating from monomers obtained by self-metathesis of FAMEs. Self-metathesis of

6

FAMEs from different sources was completed within 2 min, providing ~50% conversion using

7

microwave technique. The products of self-metathesis were identified and quantified by GC-MS

8

and GC-FID analysis. Similar conversion was achieved within 6 minutes, when HG2 catalyst

9

loading was decreased from 0.05 mol% to 0.01 mol%. Diester was separated from

10

self-metathesis products of FAMEs. Diol with high purity and yield was obtained via reduction

11

of diester. Polycondensation of diester and diol was carried out using conventional heating,

12

microwave irradiation and by coupling microwave and conventional heating. In all cases, the

13

polyesters were prepared successfully, but with slightly different molecular weights. The

14

polyesters were characterized by various analytical techniques including NMR, FTIR, GPC,

15

DSC, TGA, DMA and tensile testing. The polyesters obtained by coupled method (microwave

16

and conventional heating, Mw = 315 KDa) and by conventional heating (Mw = 337 KDa) were of

17

enough strength for film preparation to be used for mechanical study as compared to the

18

polyester obtained entirely by microwave irradiation (Mw = 275 KDa). Higher elongation at

19

break (11%) and lower storage modulus was observed for polyesters using coupled method,

20

while lower elongation at break (6.5%) and higher storage modulus was achieved for polyester

21

by conventional method. By using microwave irradiation, polyesters were obtained in 15

22

minutes, while the coupled microwave and conventional heating method afforded polyester with

23

good strength in 4 hours, which could only be achieved within 8 hours by conventional heating.

21



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 22 of 28

1

Experiment Section

2

Materials

3

High oleic soybean and canola oil samples were kindly provided by Bung Canada. Oleic acid

4

(technical grade) was supplied by Anachemie. Hoveyda-Grubbs catalyst 2nd generation, lithium

5

aluminum hydride, tin(II) chloride, titanium butoxide, silica gel (technical grade, 63-200µm),

6

1,1,2,2-tetrachloroethane-d2, chloroform-d were purchased from Sigma Aldrich. Thin layer

7

chromatography plates (TLC silica gel 60 F254) were from Merck Group.

8

Organic solvents, including tetrahydrofuran (THF) was dried by stirring over CaH2 for three days

9

and then filtered in nitrogen atmosphere., dichloromethane (DCM), methanol, acetone, ethyl

10

acetate and inorganic materials, such as potassium hydroxide, sodium sulfate, sodium hydroxide,

11

sodium sulphate were purchased from Sigma Aldrich. Hexane solvent was purchased from

12

Caledon chemicals. Unless specified, these chemicals were used as received.

13

General Consideration

14

Attenuated Total Reflectance- Fourier Transform Infrared (ATR-FTIR). Spectroscopic analyses

15

were performed on a Nicolet 8700 spectrometer (Madison, WI, USA). For FTIR analysis, the

16

solid or liquid samples were placed directly onto the surface of the ATR crystal and analyzed.

17

Nuclear Magnetic Resonance (NMR). 1H NMR and 13C NMR analyses were carried out at room

18

temperature on Varian INOVA instrument at 400 MHz and 100 MHz frequencies respectively.

19

Gas Chromatography – Flame Ionization Detector (GC-FID). Perkin Elmer GC Clarus 500

20

instrument equipped with fused silica capillary column SP2560 (100 m × 0.25 mm × 0.2 µm film

21

thickness), detector 5975B inert XL MSD and

22

and quantify fatty acid methyl esters (FAMEs) and products from olefin metathesis. Temperature

23

of 280 oC was set for detector and 240 oC for injector. Hydrogen and air gases were used as flow

24

phases at a rate of 450 mL/min and 45 mL/min respectively. A 2 µL sample was injected and

25

20:1 ratio of split mode was selected. Oven temperature was held at 45 oC for 4 min and then

flame ionization detector (FID) was used to identify

22


Page 23 of 28

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


1

increased to 175 oC at a rate of 13 oC/min. After holding for 27 min, it was eventually increased

2

to 215 oC at heating rate of 4 oC/min and maintained for 35min.

3

Gas Chromatography-Mass Spectrometry (GC-MS). GC-MS analysis were conducted on Agilent

4

6890N (USA) equipment. The used column and other conditions were set the same as GC-FID.

5

The molecular structures were identified by mass spectroscopy with scanning range of 50-600

6

amu at a rate of 2.66/second. While the microwave assisted reactions were carried out in an open

7

vessel mode microwave reactor (CEM Discover Labmate) equipped with infrared temperature

8

sensor (Maximum pressure = 250 psi, maximum power = 200 W).

9

Differential Scanning Calorimetry (DSC) Measurement. DSC measurements were performed on a

10

TA Instrument (2920 Modulated DSC, USA) in nitrogen atmosphere. Samples (4.0-7.0 mg) were

11

sealed in a pan and were placed into a DSC cell. The thermograms were recorded by heating the

12

samples up to 150oC at a rate of 3 oC/min after equilibrating at -30 oC. DSC data from 2nd heating

13

cycle of samples was reported to eliminate the thermal history of the materials.

14

Thermogravimetric Analysis(TGA). TGA was performed on a Q50 TGA instrument in the

15

presence of nitrogen flow at a rate of 60 ml/min. Samples with 5.0-20.0 mg was taken in a pan

16

and placed in a furnace for analysis. The weight loss/thermal behavior of the samples was

17

recorded by heating the samples up to 600oC at heating rate of 10oC/min.

18

Gel Permeation Chromatography (GPC). The average molecular weights (Mw) of prepared

19

polyesters were determined by Gel permeation chromatography. Styragel HR 4E column (4.6

20

mm × 300 mm) and 2000 ELSD detector were equipped with GPC instrument. The samples with

21

concentration of 0.5 mg mL−1 in THF were used, where THF was used as an eluent with flow

22

rate of 0.5 mL min−1. A series of polystyrene standards was used to calibrate the instrument.

23

Film Preparation. For polyesters film preparation, the polyesters (~1.5g) were crushed in a

24

mortar and then taken on steel plates for compression molding. Carver press was used to press 23



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 24 of 28

1

the samples, where a temperature of 80oC and a pressure of 100 psi were applied for ~8 min. The

2

prepared polyester films were cut into a desired size before their mechanical study.

3

Tensile Testing. The mechanical properties of polyester films were studied by a universal testing

4

machine (autograph AGSX Shimadzu) at room temperature. Both ends of the film were fixed to

5

50N load cell. The film was stretched at a rate of 0.90mm/s until ruptured.

6

Dynamic Mechanical Analysis (DMA). The viscoelastic properties of polyester films were

7

measured using a TA Instrument (DMA Q800). At an oscillatory frequency of 1 Hz with applied

8

deformation of 0.2% during heating, the measurement was carried out in a tensile mode where

9

temperature was programmed from -90 oC to 60 oC at a rate of 2 oC/min.

10

Microwave Assisted Self-metathesis of Different Methyl Esters. Fatty acid methyl esters

11

(FAMEs) derived from oils (2 g) were placed into a 10 mL microwave tube equipped with a

12

stirring bar. HG2 (0.05 mol%) catalyst was weighed and added into the reaction vessel in an

13

inert atmosphere using glove box. A line of nitrogen flow was provided into reaction vial and the

14

reaction was performed on a microwave reactor at a set temperature for required time period.

15

Product mixtures were passed through small column of silica gel to remove the catalyst. A

16

sample with concentration of 0.5 mg/ml in dichloromethane was prepared and run for GC-MS

17

and GC-FID analysis to characterize and quantify the products. The required product component

18

dimethyl-9-octadecene-1,18-dioate (diester) was separated/purified with silica gel column

19

chromatography using 2% ethyl acetate in hexane as an eluent.

20

Polycondensation by Conventional Heating. Equal amounts of diester (0.5 mmol) and diol (0.5

21

mmol) were taken into a 10 mL glass tube and then 2.0 mol% catalyst either SnCl2 or Ti(OBu)4

22

was added. Initially, at reduced pressure (~0.7 bar) the reaction was run at 100 oC and then its

23

temperature was raised gradually from 100oC to 200oC at a heating rate of 10 oC/20 min. The

24


Page 25 of 28

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


1

reaction was stopped after 16 hours and the polyesters obtained in yellow colored solid was

2

washed with THF and dried prior to any analysis.

3

Microwave Assisted Polycondensation. Equimolar ratio of diester and diol was taken in a 10

4

ml microwave glass vial and after adding the desired amount of catalyst, the reaction vial was

5

placed in cavity of microwave reactor. The microwave assisted reaction was performed at 200 oC

6

under nitrogen atmosphere for 15 minutes and then at reduced pressure (0.7 bar) for certain time

7

period (table 5). The prepared polyester was washed with THF and dried before proceeding for

8

different analysis.

9

Polycondensation by Coupling Microwave with Conventional Heating. In coupled method,

10

firstly polycondensation of diester and diol was carried out using similar method as mentioned

11

above in microwave assisted synthesis. These microwave assisted polyesters were further heated

12

to 200°C on a hot plate using vacuum (~0.1 bar). The heat source was removed after 2.5 hours.

13

The obtained polyesters were thoroughly washed with THF and dried before proceeding for

14

various analyses.

15

Supporting Information. Contains methodology for preparation of methyl oleate, diol, canola

16

and soybean oil methyl esters, HRMS and 1H NMR of diester and diol, 13C NMR of diester, diol

17

and polyester, GC-MS and GC-FID data of self-metathesis reactions, table for polyesters

18

prepared by cconventional heating using Ti(OBu)4 as catalyst, polyesters film images and their

19

GPC, DMA and mechanical testing results.

20

Acknowledgements. Authors gratefully acknowledge the financial support for current work by

21

The Alberta Innovates Bio Solutions (AI Bio). The plant oils were kindly provided by Bunge

22

Canada, Dupont Pioneer and Soy 2020.

25



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

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

Page 26 of 28

References: 1. Bilgen, S., Structure and environmental impact of global energy consumption. Renew. Sustainable Energy Rev. 2014, 38, 890-902. doi: 10.1016/j.rser.2014.07.004 2. Roesle, P.; Stempfle, F.; Hess, S. K.; Zimmerer, J.; Río Bártulos, C.; Lepetit, B.; Eckert, A.; Kroth, P. G.; Mecking, S., Synthetic polyester from algae oil. Angew. Chem. Int. Ed. 2014, 53 (26), 6800-6804.doi: 10.1002/anie.201403991. 3. Quinzler, D.; Mecking, S., Linear semicrystalline polyesters from fatty acids by complete feedstock molecule utilization. Angew. Chem. Int. Ed. 2010, 49 (25), 4306-4308. doi: 10.1002/ange.201001510. 4. Meier, M. A.; Metzger, J. O.; Schubert, U. S., Plant oil renewable resources as green alternatives in polymer science. Chem. Soc. Rev. 2007, 36 (11), 1788-1802. doi: 10.1039/b703294c. 5. Santacesaria, E.; Sorrentino, A.; Rainone, F.; Di Serio, M.; Speranza, F., Oxidative cleavage of the double bond of monoenic fatty chains in two steps: a new promising route to azelaic acid and other industrial products. Ind. Eng. Chem. Res. 2000, 39 (8), 2766-2771. doi: 10.1021/ie990920u. 6. Türünç, O.; Meier, M. A., The thiol‐ene (click) reaction for the synthesis of plant oil derived polymers. Eur. J. Lipid Sci. Technol. 2013, 115 (1), 41-54. doi: 10.1002/ejlt.201200148. 7. Türünç, O.; Meier, M. A., Fatty Acid Derived Monomers and Related Polymers Via Thiol‐ ene (Click) Additions. Macromol. Rapid Commun. 2010, 31 (20), 1822-1826. doi: 10.1002/marc.201000291. 8. Rybak, A.; Fokou, P. A.; Meier, M. A., Metathesis as a versatile tool in oleochemistry. Eur. J. Lipid Sci. Technol. 2008, 110 (9), 797-804. doi: 10.1002/ejlt.200800027. 9. Van Dam, P.; Mittelmeijer, M.; Boelhouwer, C., Metathesis of unsaturated fatty acid esters by a homogeneous tungsten hexachloride–tetramethyltin catalyst. J. Chem. Soc., Chem. Commun. 1972, (22), 1221-1222. doi: 10.1039/C39720001221. 10. Trzaskowski, J.; Quinzler, D.; Bährle, C.; Mecking, S., Aliphatic Long‐Chain C20 Polyesters from Olefin Metathesis. Macromol. Rapid Commun. 2011, 32 (17), 1352-1356. doi: 10.1002/marc.201100319. 11. Mutlu, H.; Hofsäß, R.; Montenegro, R. E.; Meier, M. A., Self-metathesis of fatty acid methyl esters: full conversion by choosing the appropriate plant oil. RSC Adv. 2013, 3 (15), 4927-4934. doi: 10.1039/c3ra40330k. 12. Gedye, R.; Smith, F.; Westaway, K.; Ali, H.; Baldisera, L.; Laberge, L.; Rousell, J., The use of microwave ovens for rapid organic synthesis. Tetrahedron Lett. 1986, 27 (3), 279-282. doi: 10.1016/S0040-4039(00)83996-9.

26


Page 27 of 28

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

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


13. Lidström, P.; Tierney, J.; Wathey, B.; Westman, J., Microwave assisted organic synthesis—a review. Tetrahedron 2001, 57 (45), 9225-9283. doi: 10.1016/S0040-4020(01)00906-1. 14. Thanh, G. V.; Loupy, A., Microwave-assisted ruthenium-catalyzed olefin metathesis under solvent-free conditions. Tetrahedron Lett. 2003, 44 (51), 9091-9094. doi: 10.1002/chin.200413050. 15. Appukkuttan, P.; Dehaen, W.; Van der Eycken, E., Microwave-Enhanced Synthesis of N-Shifted Buflavine Analogues via a Suzuki− Ring-Closing Metathesis Protocol. Org. Lett. 2005, 7 (13), 2723-2726. doi: 10.1021/ol050806+. 16. Morris, T.; Sandham, D.; Caddick, S., A microwave enhanced cross-metathesis approach to peptidomimetics. Org. Biomol. Chem. 2007, 5 (7), 1025-1027. doi: 10.1039/b700804j. 17. Bargiggia, F. C.; Murray, W. V., Cross-metathesis assisted by microwave irradiation. J. Org. Chem. 2005, 70 (23), 9636-9639. doi: 10.1021/jo0514624. 18. Nagahata, R.; Sano, D.; Suzuki, H.; Takeuchi, K., Microwave‐Assisted Single‐Step Synthesis of Poly (lactic acid) by Direct Polycondensation of Lactic Acid. Macromol. Rapid Commun. 2007, 28 (4), 437-442. doi: 10.1002/marc.200600715. 19. Cao, H. L.; Wang, P.; Yuan, W. B., Microwave‐Assisted Synthesis of Poly (L‐lactic acid) via Direct Melt Polycondensation Using Solid Super‐Acids. Macromol. Chem. Phys. 2009, 210 (23), 2058-2062. doi: 10.1002/macp.200900231. 20. Velmathi, S.; Nagahata, R.; Sugiyama, J. I.; Takeuchi, K., A Rapid Eco‐Friendly Synthesis of Poly (butylene succinate) by a Direct Polyesterification under Microwave Irradiation. Macromol. Rapid Commun. 2005, 26 (14), 1163-1167. doi: 10.1002/marc.200500176. 21. Ullah, A.; Arshad, M., Remarkably Efficient Microvawe‐Assisted Cross‐Metathesis of Lipids in Solvent Free Conditions. ChemSusChem. 2017, 10 (10), 2167-2174. doi: 10.1002/cssc.201601824. 22. Doll, K. M., Increased functionality of methyl oleate using alkene metathesis. Int. J. Sustain. Eng. 2014, 7 (4), 322-329. doi: 10.1080/19397038.2013.852269. 23. Lehman, S. E.; Schwendeman, J. E.; O'Donnell, P. M.; Wagener, K. B., Olefin isomerization promoted by olefin metathesis catalysts. Inorg. Chim. Acta 2003, 345, 190-198. doi: 10.1016/S0020-1693(02)01307-5. 24. Kohashi, H.; Foglia, T. A., Metathesis of methyl oleate with a homogeneous and a heterogeneous catalyst. J. Am. Oil Chem. Soc. 1985, 62 (3), 549-554. doi: 10.1007/BF02542330. 25. Forman, G. S.; Bellabarba, R. M.; Tooze, R. P.; Slawin, A. M.; Karch, R.; Winde, R., Metathesis of renewable unsaturated fatty acid esters catalysed by a phoban-indenylidene ruthenium catalyst. J. Organomet. Chem. 2006, 691 (24), 5513-5516. doi: 10.1016/j.jorganchem.2006.06.021.

27



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

1 2 3 4 5 6 7 8 9 10 11 12

26. Ngo, H. L.; Jones, K.; Foglia, T. A., Metathesis of unsaturated fatty acids: Synthesis of long-chain unsaturated-α,ω-dicarboxylic acids. J. Am. Oil Chem. Soc. 2006, 83 (7), 629-634. doi:10.1007/s11746-006-1249-0. 27. Beach, N. J.; Lummiss, J. A.; Bates, J. M.; Fogg, D. E., Reactions of Grubbs Catalysts with Excess Methoxide: Formation of Novel Methoxyhydride Complexes. Organometallics 2012, 31 (6), 2349-2356. doi: 10.1021/om201288p. 28. Kéki, S.; Bodnár, I.; Borda, J.; Deák, G.; Zsuga, M., Melt polycondensation of D, L-lactic acid: MALDI-TOF MS investigation of the ring-chain equilibrium. J. Phys. Chem. B 2001, 105 (14), 2833-2836. doi: 10.1021/jp003581n. 29. Brunel, R.; Marestin, C.; Martin, V.; Mercier, R.; Schiets, F., Assisted microwave synthesis of high molecular weight Poly (ArylEtherKetone)s. High Perform. Polym. 2008, 20 (2), 185-207. doi: 10.1177/0954008307079617.

13 14 15 16

Page 28 of 28

For Table of Contents Use Only

17

Synopsis:

18

The current study describes rapid synthesis of unsaturated α, ω-bifunctional aliphatic monomers

19

(diester & diol) from plant oils using microwave-assisted self-metathesis and fully biobased

20

polyesters thereof using polycondensation process.

21

28


Synthesis of Fully Biobased Polyesters from Plant Oil - ACS Publications

Recommend Documents