Step-Growth Polymers for High-Performance Materials - American

Chapter 13

Synthesis and Properties of a Novel Series of Poly(arylene ether ketone)s Containing Unsymmetric Benzonaphthone Units 1

J. E. Douglas and Z. Y. Wang Downloaded by CORNELL UNIV on July 26, 2016 | http://pubs.acs.org Publication Date: May 5, 1996 | doi: 10.1021/bk-1996-0624.ch013

Department of Chemistry, Ottawa-Carleton Chemistry Institute, Carleton University, 1125 Colonel By Drive, Ottawa K1S 5B6, Canada

The design and synthesis of four unsymmetric 4,4'-dihalobenzo-1'naphthone monomers and their polymerizations with various bisphenols, 4,4'-isopropylidenediphenol (BPA), 4,4'hexafluoroisopropylidenediphenol (6F-BPA), 9,9-bis(4hydroxyphenyl)fluorene (FBP) and 1,4-hydroquinone (HQ), are reported. The enhanced reactivity of the naphthoyl group, as measured by its ability to activate chlorides towards displacement with phenoxides in S Ar-type polycondensation is clearly demonstrated. Copolymerizations of the dichloride and difluoride monomers in varying ratios were done with B P A . Model reactions were carried out and showed that chlorine on the benzoyl unit of the monomer exchanges more quickly with fluoride ion than chlorine on the naphthoyl moiety. The rate of this halogen exchange was found to be of little significance on the polyetherification time scale. An end-capped polymer with B P A was made and had an absolute number average molecular weight (Mn) of 58,300, corresponding to a monomer repeat length (n) of 127. Proton N M R shows the presence of three sequential isomers of this polymer series. The effects of N-methyl-2-pyrrolidinone and tetramethylene sulfone as solvents were also studied. The glass transition temperatures (Tgs) increased by 20-45 °C, relative to the Tgs of poly(arylene ether ketone)s containing a benzophenone unit. Decomposition temperatures for 5% weight loss as assessed by thermogravimetric analysis for all polymers were above 497 °C in air. Young's moduli ranged from 1.99 to 3.25 GPa. N

Poly(aryl ether ketone)s (PAEKs) represent a class of engineering thermoplastics which possess properties (e.g. mechanical strength and durability) that are superior 1

Corresponding author 0097-6156/96/0624-0226$12.00/0 © 1996 American Chemical Society Hedrick and Labadie; Step-Growth Polymers for High-Performance Materials ACS Symposium Series; American Chemical Society: Washington, DC, 1996.

13. DOUGLAS & WANG

PAEKs with Unsymmetric Benzonaphthone Units

to those of most commodity plastics. They compete with metals, ceramics and glass in a variety of applications. PAEKs are principally made by nucleophilic displacement polycondensation of bisphenoxides and activated dihaloarylketones (7,2). For example, P E E K is made by polymerization of 1,4-hydroquinone (HQ) with 4,4'-difluorobenzophenone (3). It is generally believed that these polycondensations proceed through a S Ar mechanism involving an intermediate Meisenheimer complex (4). There are many factors which govern the success of these reactions. Some of these include solvent, temperature, the reactivity and chemical specificity of the pair of monomers used. It is well known that the rates of S A r reactions are greater for difluoroarylketones than their chloride analogues (4). Consequently, it is generally accepted that difluoroarylketones are activated toward nucleophilic displacement and can form high molecular weight polymers with little difficulty (5-10). However, the displacement of chlorine from dichloroarylketones with bisphenoxides to form high molecular weight PAEKs is more difficult (5-10). The latter are believed to undergo a competitive reductive dehalogenation reaction via a SRNI SET mechanism which accounts for the formation of low weight PAEKs (6,8,9). Exceptions include the use of (a) a diketo monomer having a 1:1 ketone/chlorine ratio as opposed to one with a 1:2 ketone/chlorine ratio (5,70), (b) a small amount of potassium fluoride in the presence of a phase transfer catalyst (77), (c) 'reactive' bisphenols such as 9,9-bis(4-hydroxyphenyl)fluorene (HPF) (10), and (d) 'reactive' dichloroheteroarylketones such as bis(5-chlorothienyl-2)ketone (72). According to the hard-soft-acid-base theory, certain bisphenols (as bases) have stronger attractions to particular dihaloarylketones (as acids) (75,74). Thus, the pairing up of bisphenols with appropriate dihaloarylketones becomes an important factor in achieving high molecular weight PAEKs (5). For the past decade, there has been much research done in an effort to improve the thermal stability and mechanical strength of high performance thermoplastics. For a polymer to be considered 'thermally stable' or 'heat resistant', it should not decompose below 400 °C and should retain its useful properties close to its decomposition temperature (Td) over a long period of time (75). A common strategy to improve the thermal stability has been to increase the number of aromatic units in the repeat unit of the polymer backbone. Unfortunately, much of the progress made in enhancing thermal stabilities has come at a cost of poor processibility and solubility of the polymer. It has become the focus of scientists to develop new materials with improved solubilities and processibility, as well as high thermal and mechanical strengths. In the late 80's, Hergenrother developed a P A E K containing a 2,6dibenzoylnaphthalene unit with a Tg of 185 °C (10). In an effort to improve solubility, Ritter reported the synthesis of 1,5-naphthylene-based PAEKs with long alkoxy chains which resulted in poor thermal stability (76). Endo et. al. recently introduced the methyl groups at the 2,6-positions of a 1,5-naphthylene unit in P A E K to improve solubility and the Tg (222 ° Q (77). We have recently designed and synthesized four unsymmetric dihalobenzo-l'-naphthone monomers l a - d containing chlorine and fluorine (Figure 1) (18,19). The structures of these monomers offer a unique unsymmetry previously rarely seen in P A E K history. It became possible now to study the effect the unsymmetric benzonaphthone unit would have on sequential ordering as well as thermal and mechanical properties. N

N

Downloaded by CORNELL UNIV on July 26, 2016 | http://pubs.acs.org Publication Date: May 5, 1996 | doi: 10.1021/bk-1996-0624.ch013

227

Hedrick and Labadie; Step-Growth Polymers for High-Performance Materials ACS Symposium Series; American Chemical Society: Washington, DC, 1996.

228

STEP-GROWTH POLYMERS FOR HIGH-PERFORMANCE MATERIALS

Preliminary results have demonstrated that all four monomers la-d can be polymerized effectively with many bisphenols to form high molecular weight P A E K s 2-5 (Figure 1) (18,19). As part of an ongoing systematic investigation of the effects of structural symmetry and the substitution pattern of the arylene core in PAEKs on the polymer properties, the detailed synthesis and properties of a series of P A E K s derived from la-d and bisphenols are described herein.


Polycondensation In the process of studying this series of monomers, it was found that both la and l b could make high molecular weight polymers with B P A , whereas lc and Id could not (Table I). Reverse precipitation was performed in most cases, except entries 3 and 4 in Table I and entry 4 in Table Π. This technique will narrow the polydispersity index and increase the apparent molecular weight (by GPC). But the effect to the solution viscosity will be minimal. Both lc and Id contain the 4chlorobenzoyl moiety which has been reportedly difficult to polymerize with B P A (10). Whereas la and lb contain the undoubtedly reactive 4-fluorobenzoyl moiety and the chloronaphthoyl group. The naphthyl ring appears to promote chlorine displacement in polyetherifications with bisphenoxides relative to the phenyl ring (18,19) This can be attributed to the increased conjugation and stability imparted to the Meisenheimer complex by the naphthyl ring. Hiickel molecular orbital (HMO) calculations also suggest that the chloronaphthyl ring be more reactive than the chlorophenyl unit towards nucleophilic displacement (20).

Table I. Polymerizations of Dihalides la-d with Bisphenols (19) Entry Polymer Dihalide Bisphenol Mw xW

Mn xlO'

MwIMn

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

5.70 4.12 1.88 2.23 2.26 2.30 2.66 2.25 9.10 4.95 1.96 6.26 10.0 9.89 5.15 3.72

2.80 2.64 1.95 1.76 3.19 2.63 2.53 2.68 1.86 2.35 3.05 1.98 1.88 2.05 2.30 3.59

4

2 2 2 2 3 3 3 3 4 4 4 4 5 5 5 5

la lb lc Id la lb lc Id la lb lc Id la lb lc Id

BPA BPA BPA BPA HQ HQ HQ HQ 6F-BPA 6F-BPA 6F-BPA 6F-BPA FBP FBP FBP FBP

16.0 10.9 3.67 3.98 7.20 6.05 6.73 6.03 16.9 11.6 6.00 12.4 18.8 20.2 11.9 13.4

4

%* (dL/g)


0.90 0.58 0.28 0.27 0.61 0.60 0.56 0.55 0.84 0.73 0.43 0.65 0.76 0.86 0.55 0.66

13.

DOUGLAS & WANG


Copolymerizations of l a and Id in molar ratios of 1:1, 1:2, 1:4 and 1:9 with B P A were then performed (Table Π). Reasonably high molecular weights were achieved with ratios of la to Id as low as 1 to 4 (Entry 3, Table Π), in comparison with polymerization of Id and B P A (Entry 4, Table T). In light of these results, a halogen exchange reaction between the chlorine on the phenyl part with in-situ generate*! fluoride ion during polycondensation seemed possible. Therefore, two model reactions were performed to investigate this phenomenon.

Table II. Copolymerization of monomers la and Id with BPA Entry

Molar Ratio Mw laid xlOr

Mn xlO-

Mw/Mn

1:1 1:2 1:4 1:9

5.40 2.89 2.68 2.16

1.96 2.14 1.86 2.14


4

1 2 3 4

10.6 6.18 4.97 4.62

(dUg)

4

0.55 0.44 0.37 0.29

In the first model reaction, Id was subjected to the same conditions used in all previous polymerizations (210 °C, T M S O ^ h C l , and Κ £ 0 ) without B P A but with K F to promote the halogen exchange of chlorine with fluorine (Figure 2). It was found that lb formed faster and in a greater yield than lc. This demonstrated that the Cl-F exchange occurs more rapidly on the phenyl ring than on the naphthyl ring. A halogen exchange of this kind would facilitate polymerization. A second model reaction was done in which fluoride ion was generated in situ by reacting two equivalents of phenol with l a (Figure 3). Monomer Id was then added to the reaction mixture to see if any Cl-F exchange occurred. Using the in-situ generated fluoride ion was believed to be closer to the actual polymerization environment than the addition of K F salt It was discovered that l b was formed in greater quantity than lc but at a much slower rate than in the first model reaction. Although being confirmed, this slow halogen exchange perhaps plays a minor role in the actual polymerization mechanism. An end-capping experiment was carried out with a 1% excess of difluoride l a and 2% of 3,5-di-terf -butylphenol relative to BPA. End-capping controls the molecular weight and allows one to calculate an exact molecular weight as opposed to a relative one as given by GPC. From the high resolution *H N M R , the relative integration values of the peaks at 1.6 ppm (the methyl group of BPA) and 1.3 ppm (tert -butyl group) was calculated and the number of repeat unit (n) was found to be 127 (Figure 4). Accordingly, the absolute number-average molecular weight (Mn) was calculated to be 58,300, larger than that obtained by G P C (Mn = 47,300). Therefore, the exact molecular weights of these polymers should be greater than the apparent ones determined by GPC. Inherent viscosity for this end-capped polymer 6 was found to be 0.47 dL/g. 3


229



230

Figure 2. Model Cl-F exchange reaction using K F .


DOUGLAS & WANG


2PhOH

2F"

F

K C0 TMS0 210 °C 2

3

2

ld TMS0 210 °C


la

2

lb:X = C l , Y = F l c X = F; Y = C1

ld

ε

lb

ο c ο

»

le

Time (h)

Figure 3. In-situ Cl-F exchange model reaction.

CH,

6

Figure 4. *Η N M R of end-capped poly(arylene ether ketone ) 6.


232


Solvent Effects Two solvent systems were investigated in this study. The first one involved N M P with toluene as an azeotroping solvent in a 20% solid content (Table ΙΠ). It was possible to make high molecular weight polymers from l a with both H Q and B P A . But difficulties arose when trying to polymerize l b with B P A (Entry 3). A modest molecular weight of 3.64 x l O O u = 0.36 dL/g) was achieved in N M P . A dark green color was also observed in the reaction mixture. Strukelj et. al. studied the solvent effects in the preparation of poly(aryl ether benzils)s and suggested that this green color stems from impurities in the commercially available N M P (21). Decomposition products of N M P or reactions of reactive species with N M P , also seem to have a dramatic effect on molecular weight and appear to degrade the polymer after molecular weight build-up. Percée et. al. also observed that reductive dehalogenation of diaryl halides can occur in N M P (6). In an effort to avoid these problems and increase molecular weight, a second solvent system, T M S 0 and chlorobenzene, was used. A better result was obtained for polymerization of l b and B P A (Mw = 10.86 χ 10 ; T U = 0.58 dL/g) at 210 °C in a 35% solid content when using this alternative solvent system.


4

2

4

Table III. Polymerization of l a and l b with B P A and H Q in N M P Entry Monomer Bisphenol Temp. Mw xlO CO

Mn xlO

MwIMn *7«A (dIVg)

1 2 3 4

6.68 3.89 2.14 3.79

2.06 1.96 1.70 2.13

4

la la lb lb

BPA HQ BPA HQ

180 180 180 180

13.8 7.63 3.64 8.09

4

0.73 0.57 0.36 0.54

The unsymmetry of the microstructure of this polymer series stems from the unsymmetric nature of the dihalobenzonaphthone monomers la-d, since all four bisphenols used in this study are symmetrical. There are three possible diads in this series: (a) head to tail, (b) head to head, and (c) tail to tail (Figure 5). Evidence of these sequential isomers comes clearly from the *H N M R , as three singlets can be seen at 1.6 ppm for the end-capped polymer 6 (Figure 4). Although the relative abundance of three isomers can be quantitated (ca. 1:2:1), the peaks can not be assigned to any specific diads. Thermal and Mechanical Properties In all cases, insertion of the naphthyl ring into the PEEK-like polymer series increases the Tgs by 20-45 °C. Polymer 3 experiences the greatest increase in Tg (45 °C) over PEEK'S value of 143 °C. But none of these P A E K s showed any sign of crystalline behavior according to differential scanning calorimetry (DSC).



13.

DOUGLAS & WANG


Figure 5. Structures of three diads for PAEKs derived from unsymmetric dihalide 1.

Although polymer 3 is very similar to P E E K in their primary structures, the bulky naphthyl ring and the random sequential order may prohibit the former from effective packing for crystallization. The decomposition temperatures (Td) ranged from 497 to 519 °C in static air for polymers 2-5 (Table IV), as assessed by thermogravimetry. All values obtained from thermomechanical analysis (TMA) were done in the tensile stress-strain mode. Young's moduli for all polymers 2-5 fall within the same order of magnitude (1.99 - 3.25 GPa, Table IV), which are typical for engineering PAEKs. At elevated temperatures, films of these polymers maintain good mechanical properties in the gigapascal range up to 180 °C. Maximum tan δ values were in the range of 179 °C to 253 °C, which agree well with the Tg values obtained from DSC.

Table I V . Thermal and mechanical properties of polymers 2-5 PAEK

2 3 4 5

Td (° Q " (air)

Tg(°Q DSC TMA

497 506 517 519

189 188 199 272

b

Young's Modulus ( E \ GPa)

179 183 185 253

1.99 2.39 2.59 3.25

a Decomposition temperature taken at 5% weight loss, b Taken as the max. tan δ value in static air.


233

234


Experimental


Materials. Tetramethylene sulfone (TMSO^ (99%), N-methyl-2-pyrrolidinone (NMP) (99%), Ν,Ν-dimethylacetamide (DMAc) (99%), toluene, chlorobenzene and 3,5-di-terr-butylphenol were purchased form Aldrich Chemical Co. and used without further purification. Anhydrous potassium carbonate was ground in a crucible before use. 1,4-Hydroquinone (HQ) was recrystallized from ethanol. 4,4'Isopropylidenediphenol (BPA), 4,4'-hexafluoroisopropylidenediphenol (6F-BPA) and 9,9-bis(4-hydroxyphenyl)fluorene (FBP) were recrystallized from toluene. Measurements. Melting points were measured on a Fisher-Johns Melting point apparatus. Mass spectra were taken from a VG7070E Mass Spectrometer. Apparent molecular weights were determined by gel permeation chromatography (GPC) using a PL-Gel column (5μ particle size) and chloroform as the eluting solvent. Molecular weights were based on calibrations with polystyrene standards and a U V detector was set at 254-nm wavelength. Inherent vicosities were measured using 0.5 g/dL chloroform solutions at 25.0 °C in a calibrated Ubbelohde dilution viscometer. *H and C N M R spectra were obtained on a Bruker-400 instrument using deuterated chloroform. F N M R was measured on a Varian XL-300 using deuterated DMSO as a solvent and CC1 F as a reference. IR spectra were measured on a Perkin Elmer Series 1600 FTIR and Bomem-FTIR Michelson Series instrument. Thermal stabilities of the polymer samples were determined using a Seiko 220 TG/DTA analyzer run from ambient temperature to 1000 °C at 10 °C/min. Tests were done in nitrogen flushed at 200 mL/min. Decomposition temperatures (Td) were taken at 5% weight loss. The glass transition temperatures (Tg) were determined using a Seiko 220C DSC used in normal DSC mode, with a heating rate of 10 °C/min from ambient temperature to 35°C below Td. Three consecutive runs were performed for each polymer (with normal cooling in between scans), and Tg was taken from the third scan as the midpoint of the change in slope of the baseline. The tensile mechanical properties of the polymer films were obtained using a Seiko 120C TMA/SS analyzer operated in stress-strain mode at a heating rate of 3 °C/nun to 40 °C above the Tg. 1 3

1 9

3

Monomer Synthesis. 1-Chloro and 1-fluoronaphthalene readily undergo the Friedel-Crafts reaction with the corresponding 4-halobenzoyl chlorides to form die four monomers la-d. The following is a typical procedure for the synthesis of these monomers: To a 100 mL, three-necked, round-bottomed flask containing a magnetic stirring bar flame dried under nitrogen flow were added 4-fluorobenzoyl chloride (5.060 g, 31.83 mmol), 1-fluoronaphthalene (5.120 g, 31.83 mmol) and dry C H ^ (30 mL). The reaction flask was then cooled in an ice bath (5 °C) before anhydrous A1C1 (35.10 g, 38.50 mmol) was added slowly. The solution turned yellow then a dark red/brown color. After an hour the solution was quenched with iced water and turned yellow. The organic layer was washed with aqueous HC1 (5%), aqueous NaOH (5%), brine (23%) and water. The organic layers were combined and dried over anhydrous M g S 0 . The solvent was removed under reduced pressure to give la as white crystals (crude yield 69%; 55 % yield after recrystallization from; mp 84-86 °C). IR (KBr) 1657.3 c m (C=0); M S (EI, m/e, 3

4

1


13.

DOUGLAS & WANG

PAEKs with Unsymmetric Benzonaphthone Units +

relative intensity %) 173 ( M - PhF, 100), 268 (M"\ 87.6), 123 (COPhF\ 68.9), 145 ( M * - COPhF, 63.3), 95 (PhF*, 54.4); Ή N M R (400 MHz) δ 8.16 (d, 1 H), 8.21 (d, 1 H), 7.85-7.91 (m, 2 H), 7.54-7.64 (m, 3 H), 7.12-7.21 (m, 3 H); F N M R (282.2 MHz) δ -104.93 (Ph-F), -117.22 (Naph-F). l b : white cubic crystals, 70% crude yield, 63% yield after recrystallization fromhexane/cyclohexane; mp 117-118 °Q IR (KBr) 1656.4 c m (C=0); MS (EI, m/e, relative intensity %) 123 (COPhF, 100), 284 ( M \ 92.0), 189 (M+ - PhF, 76.3), 95 (PhF*, 66.6), 161 ( M - COPhF, 41.7); Ή N M R (400 Mhz) δ 8.39 (d, 1H), 8.05 (d, 1 H), 7.85-7.94 (m, 2 H), 7.63 (d, 1 H), 7.54-7.68 (m, 2 H), 7.47 (d, 1 H), 7.10-7.16 (m, 2 H) ); F N M R (282.2 MHz) δ -104.32. l c : white fluffy needles (63% yield after recystallization from EtOH); mp 84 °C); IR (KBr) 1644.2 c m (C=0); MS (EI, m/e, relative intensity %) 173 ( M PhCl, 100), 284 ( M , 55.7), 145 ( M - COPhCl, 55.3), 249 ( M - CI, 31.9), 139 (COPhCl*, 36.9); H N M R (400 MHz) δ 8.19 (m, 2 H), 7.79 (d, 2 H ) , 7.61 (m, 2 H), 7.55 (d, 1 H), 7.45 (d, 2 H), 7.17 (d, 1 H); F N M R (282.2 MHz) δ -116.79. Id: white prismatic needles (45% crude yield, initially recrystallized in cyclohexane to remove orange impurities, then washed in methanol and finally recrystallized in EtOH with a yield of 14%); IR (KBr) 1644.6 c m (C=0); MS (EI, m/e, relative intensity %) 189 ( M - PhCl, 100), 139 (COPhCl , 73.2), 300 ( M , 67.7), 265 ( M - CI, 54.3), 161 (M* - COPhCl, 52.0); Ή N M R (400 MHz) δ 8.39 (d, 1 H), 8.07 (d, 1 H), 7.79 (d, 2 H), 7.55-7.69 (m, 2 H) 7.63 (d, 1 H ) , 7.47 (d, 1 H), 7.44 (d, 2 H). 19

1

+

19

1

+


+

+

+

l

19

1

+

+

+

+

Polymerization. General procedures for both solvent systems used in this study are described below. NMP/Toluene. A 50 mL, three necked round bottom flask equipped with a Dean-Stark trap connected with condenser and a nitrogen purge line was flame dried. Monomer l a (1.070 g, 4.000 mmol), B P A (0.910 g, 4.000 mmol) and K C 0 (1.110 g, 8.000 mmol) were added to the flask with N M P (10 mL) and toluene (20 mL). The mixture was purged with nitrogen and stirred for 20 min, then heated slowly to 120-130 ° C The water and toluene were co-distilled while deoxygenated toluene was introduced. The solution turned yellow initially then darker orange. After 2-3 h, the temperature was increased to 180 °C. The solution turned green and became viscous after one hour at higher temperature. The reaction was monitored by G P C and stopped after 2 h. After letting it cool, it was diluted with N M P (9 mL), then added dropwise into methanol containing a few drops of concentrated HC1. A l l polymers were purified by dissolving in chloroform, filtering through Celite to remove any salts and precipitating into methanol again. The low molecular weight fractions were removed in all cases by reverse precipitation in this solvent system. This technique involved adding methanol dropwise into a solution made with chloroform (50 mL) and the polymer. This coagulated to form a gummy residue and a white cloudy solution consisting of the lower molecular weight fractions. The cloudy solution was then decanted and the gummy residue was dissolved in chlorofom (5-10 mL) and precipitated finally into methanol (150 mL). T M S 0 / C h l o r o b e n z e n e . A 50 mL, three-necked, round-bottomed flask equipped with a Dean-Stark trap connected with a condenser and a nitrogen purge 2

3

2


235

236


line was flame dried. A solution of dihalide monomer (3.000 mmol), B P A (3.000 mmol), potassium carbonate (0.749 g, 5.400 mmol), T M S 0 (4 mL) and chlorobenzene (4 mL) was heated to 210 °C in an oil bath in 30-40 min. Water formed during the reaction was removed as an azeotrope with chlorobenzene. The oil bath temperature was maintained at 210 °C for 2-4 h depending on the progress of the polymerization. The reaction was followed by G P C and the reaction was stopped when the molecular weight was seen to decrease after an initial increase. The polymer was then precipitated directly into methanol and collected by filtration. All polymers were purified by dissolving in CHC1 , filtering through Celite to remove any salts and precipitating into methanol. Reverse precipitation, as described in the above procedure, was performed in all cases except entries 3 and 4, Table I. In these two cases, it was believed that the polymer's molecular weights (as measured by GPC) were too low and therefore too much of the polymer would be lost in reverse precipitation. 2


3

Copolymerization. Four copolymerizations were done in varying molar ratios of difluoro (la) to dichloro (lb) monomer (ie 1:1, 1:2, 1:4, and 1:9) with BPA on a 3 mmol scale. A typical procedure for the copolymerization is as follows: A 50 mL, three-necked, round-bottomed flask equipped with a Dean-Stark trap connected with a condenser and nitrogen purge line was flame dried. A mixture of la (0.402 g. 1.500 mmol), l d (0.450 g, 1.5 mmol), I ^ C C ^ (0.746 g, 5.400 mmol), BPA (0.685 g, 3.000 mmol), T M S 0 (4 mL) and chlorobenzene (4 mL) was heated to 210 °C in an oil bath in 40 min. Water formed during the reaction was removed as an azeotrope with chlorobenzene. The oil bath temperature was maintained at 210 °C for 2 h. Two mL of T M S 0 were added to the system when stirring became difficult. The progress of the polymerization was followed by G P C and the reaction was stopped when the molecular weight was seen to decrease after an initial increase. The reaction mixture was then poured into methanol to precipitate die polymer which was collected by filtration, redissolved in solvent and filtered through Celite to remove any salts and precipitated into methanol. With the exception of entry 4, Table Π, all copolymers were reverse precipitated like in the above procedures for the same reasons. Model Reaction 1. A 50 mL, three-necked, round bottomed flask was set up with a Dean-Stark trap, condenser and nitrogen purge line as before, l d (0.990 g, 3.000 mmol), Κ ^ 0 (0.749 g, 5.400 mmol), T M S 0 (4 mL) and chlorobenzene (3 mL) were added to the system. This was then heated to 210 °C in 40 min and stirred. Standards of the four possible halogen exchange products (la, l b , lc and ld) had been made previously. The progress of the reaction was monitored by H P L C and retention times were used to identify peaks. Relative abundance was determined using the peak area of the four monomers. This did not include the area of the unidentified compound at a lower retention time which emerged during the course of the reaction, small at first, larger at die end. This was believed to be either a decomposition product of T M S 0 or a reductive dehalogenation product. Model Reaction 2. A 50 mL, three-necked, round bottomed flask with Dean-Stark trap, condenser and nitrogen purge line was flame dried as before, l a (0.429 g, 1.500 mmol), phenol (0.282 g, 3.00 mmol), Κ ^ 0 (0.749 g, 5.400 mmol), T M S 0 (4 mL) and chlorobenzene (3 mL) were added to the system and 2

2

3

2

2

3

2


13. DOUGLAS & WANG


heated to 210 °C. After l h of heating, l d (0.450 g, 1.500 mmol) was added. The reaction was again monitored by HPLC. End C a p p i n g . A Dean-Stark trap with a condenser and 50 mL, roundbottomed flask was set up as before and flame dried, l a (2.144 g, 8.000 mmol), B P A (1.806 g, 7.920 mmol), K C 0 (2.208 g, 16.00 mmol) and 3,5-di-*m butylphenol (0.055 g, 0.160 mmol), T M S 0 (10 mL) and chlorobenzene (3 mL) were added to the reaction flask. The temperature was maintained at 170 XI for 1.5 h to azeotrope off water. Afterwards, the reaction was increased to 210 °C for 30 min. More T M S 0 (6 mL) was added to allow stirring to continue. The reaction was stopped 30 min later and worked up as before with reverse precipitation. The polymer 6 was purified by reverse precipitation, ηω, = 0.47 dL/g; IR (film) 1653 c m (C=0); Ή N M R 8.38 (m, 1 H), 8.19 (m, 1 H), 7.82 (d, 2 H), 7.53 (m, 2 H), 7.47 (d,l H), 7.25 (m, 4 H), 7.03 (d, 2 H), 6.96 (d, 4 H), 6.80 (d, 1 H ) , 1.69 (t, 6.91H), 1.30 (d, 0.33 H). 2

3

2

2


1

Conclusion A series of poly(arylene ether ketone)s having different sequential diad structures derived from unsymmetric 4,4'-dihalobenzo-r-naphthone and bisphenols arc readily soluble in chloroform, 1,1,2,2-tetrachloroethane, and N M P . They appear to amorphous and show relative higher Tgs than the analogues derived from 4,4'dihalobenzophenone and bisphenols, as assessed by DSC. The chloronaphthoyl group was found to be more reactive than the chlorophenyl group in the S Ar polycondensation. Although model reactions show a Cl-F exchange reaction under the polymerization conditions, its contribution to the increase in molecular weight of the polymer is minimal. N

Acknowledgments. We thank the Natural Sciences and Engineering Research Council of Canada for financial support. Literature Cited 1. Parodi, F. in Comprehensive Polymer Science; Allen, G.; Bevington, J. C., Eds; Pergamon Press: Oxford, 1989; Vol. 5, p 561. 2. Saunders, K. J. Organic Polymer Chemistry; Chapman and Hall: New York, 1988; p 284. 3. ICI Americas, Inc. Wilmingtion, DE 19897, USA. 4. March, J. Advanced Organic Chemistry; 4th Ed., John Wiley and Sons, Inc.: Toronto, 1992; pp 641-653. 5. Percec, V.; Grigoras, M.; Clough, R. S.; Fanjul, J. J. Poly. Sci.: Part A: Poly .Chem.. 1995, 33, 331. 6. Percec, V.; Clough, R. S.; Rinaldi, P. L.; Litman, V. E. Macromolecules, 1994, 27, 1535. 7. Percec, V.; Clough, R. S.; Fanjul, J.; Grigoras, M. Polym. Prepr., 1993, 34(1), 162. 8. Percec, V.; Clough, R. S.; Rinaldi, P. L.; Litman, V. E.; Macromolecules, 1991, 24, 5889. 9. Percec. V.; Clough, R. S.; Rinaldi, P. L.; Litman, V.E. Polym. Prepr., 1991, 32(1), 353.


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10. Hergenrother, P. M.; Jensen, B. J.; Havens, S. J. Polymer, 1988, 29, 358. 11. Hoffman, U.; Helmer-Metzmann, F.; Klapper, M.; Müllen, K. Macromolecules, 1994, 27, 3574. 12. DeSimone, J. M.; Sheares, V. V. Macromolecules, 1992, 25, 4235. 13. Pearson, R. G.; Songstand, J. J. Am. Chem. Soc. 1967, 89, 1827. 14. Ho, T. L. Chem. Rev. 1975, 75, 1. 15. Stevens. M. P., Polymer Chemistry- An Introduction; 2nd Edition, Oxford University Press: NY, NY, 1990. 16. Ritter, H.; Thorwirth, R. Makromol. Chem.. 1993, 194, 1469. 17. Endo, T.; Takata, T.; Ohno, M. Macromolecules, 1993, 27, 3447. 18. Douglas, J. E.; Wang, Ζ. Y. Polym. Prepr., 1995, 36(1), 753. 19. Douglas, J. E.; Wang, Ζ. Y. Macromolecules, 1995, 28, 5970. 20. Hückel molecular orbital program is available from the Molecular Modeling System, Cambridge Scientific Computing Inc., 875 Massachusetts Ave., Suite 61, Cambridge, MA. The greater the net charge at the carbon where the halogen is bonded, the more reactive it is with a phenoxide in nucleophilic displacement polycondensation. 4,4'-Dichlorobenzophenone has a net charge of 0.025 at C-4 and generally cannot polymerize to high molecular weight, whereas 4,4'-difluorobenzophenone can (net charge = 0.050 at C-4). Calculations for monomers 1b and 1d showed that the carbon on the naphthylringto which chlorine is attached has a net charge of 0.044 and 0.045, respectively. These calculations, although not always accurate, indicate the increased aptitude the naphthyl ring has to displace chlorine over the phenyl ring. 21. Strukelj, M.; Hedrick, J.; Hedrick, J.; Tweig, R. Macromolecules, 1994, 27, 6277. RECEIVED December 4, 1995


Step-Growth Polymers for High-Performance Materials - American

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