Synthesis of ether‐linked bisoxazolines and their use in step‐growth polymerization reactions with phenolics

Six new ether‐linked bisoxazolines have been synthesized via reaction of p‐hydroxyphenyl‐2‐oxazoline with dihalides. These bisoxazolines may be used as chain extenders or crosslinkers for resins, monomers or polymers containing various acidic groups, including phenolics, via step‐growth (1 : 1) reactions. As an illustration, a phenol‐formaldehyde polycondensate (Alnovol) and an enzyme oligomerized bisphenol A resin, as well as poly (p‐hydroxystyrene), was chain extended and crosslinked to produce thermosets with high glass transition temperatures. The new bisoxazolines were also polymerized with diphenol compounds, such as diphone D and bisphenol P to generate linear or branched oligomers and polymers. Differential scanning calorimetry was used to evaluate the potential for polymerization and crosslinking reactions. Preliminary results showed that the new, ether‐linked bisoxazolines have potential for formulating high performance thermosets. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis and properties of poly(arylene ether phenyl-s-triazine)s

A series of new poly(arylene ether phenyl-s-triazine)s was prepared by the nucleophilic aromatic substitution polymerization of the potassium salt of bisphenols with 2,4-bis (halophenyl)-6-phenyl-s-triazine in N-methyl-2-pyrrolidone at elevated temperature. The polymers with inherent viscosities exceeding 0.5 were obtained after polymerization for 1 h using 2,4-bis(fluorophenyl)-6-phenyl-s-triazine as a monomer. The glass transition temperatures of the resulting polymers ranged from 200 to 260°C depending on the bisphenol used in the polymer synthesis. The poly(arylene ether phenyl-s-triazine)s demonstrated excellent thermal stabilities in excess of 490°C (5% weight loss in air). The isothermal TGA measurements (400°C under air or nitrogen atmosphere) revealed that the 4,4'-biphenol- and hydroquinone-based poly(arylene ether phenyl-s-triazine)s belong to the most superior class of heat resistant polymers, such as polyimide Kapton?. The mechanical properties of these polymers are also described. © 1994 John Wiley & Sons, Inc.     

Poly(aryl ethers) by nucleophilic aromatic substitution. I. Synthesis and properties

A series of new aromatic polyethers have been prepared by solution condensation polymerization. The synthesis involves the condensation of a dialkali metal salt of a dihydric phenol with an “activated” or negatively substituted aromatic dihalide in an anhydrous dipolar aprotic solvent at elevated temperatures. The reaction is rapid, free of side reactions, and yields polymers of excellent color. Bakelite polysulfone can be prepared in this manner by reaction of the disodium salt of bisphenol A with 4,4′-dichlorodiphenyl sulfone in dimethyl sulfoxide (DMSO). Only dipolar aprotic solvents are useful for conducting the polymerization. Of these, DMSO and Sulfolane (tetrahydrothiophene 1,1-dioxide) are the most effective. Water or other competing nucleophiles must be absent if high molecular weight is to be obtained. Besides providing the necessary solubility, this highly polar solvent is believed to be essential in providing the rapid polymerization rates observed. The rates are further found to depend on the basicity of the bisphenol salt and upon the electron-withdrawing power of the activating group in the dihalide. As is usual for this type of reaction, the difluorides are found to be more reactive than the corresponding dichlorides. Most of the polyethers are amorphous, rigid, tough thermoplastics with high second-order transitions (T_g). Thermal stability and electrical properties are noteworthy. These and other properties are described for polysulfone, and glass transitions are given for a selected list of the other polyethers.     

Polymerization of aromatic hydrocarbons with sulfur

The polymerization reactions of elemental sulfur with the polynuclear aromatic hydrocarbons pyrene and chrysene were studied. Heating the hydrocarbons with sulfur produces a series of sulfur-containing oligomers in which the aromatic ring systems remain intact. Polymerization is effected through the dehydrogenative action of sulfur and leads to thermally stable five- or six-membered heterocyclic ring systems. The major loss of sulfur during subsequent heat treatment occurs only at carbonization temperatures above 1000°C.     

Synthesis and properties of poly(arylene ether imide ketone)s

Poly(arylene ether ketone)s containing imide units were prepared by the aromatic nucleophilic displacement reaction of the potassium salts of bisphenols with bis(4-fluorobenzoyl)phthalimides in N-methyl-2-pyrrolidone at elevated temperature. The polymers having inherent viscosities of 0.34–0.77 dL/g were obtained in 2 h. The polymers exhibited glass transition temperatures ranging from 216 to 268°C and decomposition temperatures (5% weight loss under air atmosphere) ranging from 450–570°C mainly depending on the bisphenols used in the polymer synthesis. The isothermal TGA measurements (400°C under air or nitrogen atmosphere) revealed that the 4,4'-biphenol- and hydroquinone-based poly(arylene ether ketone imide)s belong to a superior class of heat resistant polymers. The mechanical properties of these polymers are also described. © 1994 John Wiley & Sons, Inc.     

Aliphatic–aromatic copolyesters derived from 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol

With the massive changes taking place in the world today, the development of new thermally and mechanically stable polymeric materials is of utmost importance. This article focuses on the synthesis and thermal characterization of a new series of copolyesters that incorporate both aromatic as well as aliphatic diols. This is of interest because most polymer materials that exhibit high thermal and/or mechanical properties contain aromatic monomer units only. These aromatic units usually contribute to either the thermal or mechanical properties but typically not both. An example of this is bisphenol A polycarbonate, which has high mechanical properties but only moderate thermal properties when compared, for example, to polyimides. In recent years there has been an interest in copolyesters that contain 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol (CBDO). This aliphatic monomer imparts some very unique thermal as well as mechanical properties. This article will report the thermal properties of a new series of CBDO‐based copolyesters. These polymers include CBDO, a series of bisphenols, and terephthaloyl chloride. The series of bisphenols discussed here include bisphenol A, AF, F, and HPF. These polymers display glass transition temperatures near 200 °C and decomposition temperatures from 390–420 °C (Argon) and from 385–410 °C (Air). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3473–3478, 2004     

Proton-transfer polyaddition reactions in syntheses of linear,branched, and functionalized poly(p-divinyl aromatics). I. Synthesis,kinetics, and mechanism of formation of linear unsaturated poly[bis(p-vinylphenyl) ether]

A peculiar step-growth (cationic) polymerization of bis(p-vinylphenyl) ether (BVPE) in nonpolar or slightly polar aromatic solvents in the temperature range from 70 to 150°C in the presence of 2.5–5.0 mmol/L of p-toluenesulfonic acid has been studied. Optimum polymerization conditions were found. New linear unsaturated polymers of BVPE with terminal vinyl groups and weight-average molecular weight from 1500 to 10,000 were obtained. The structure and the formation mechanism of these oligomers and polymers were established, and the accompanying side reactions were considered. The rate constants were measured for eight temperatures, and the activation energy was found to be −42 kJ/mol. The optimum polymerization temperature was about 80°C. © 1996 John Wiley & Sons, Inc.     

Displacement polymerization. III. Synthesis and characterization of polyazoxyarylethers

A new class of polyazoxyarylethers was prepared by nucleophilic displacement polymerization using an activated dichlorocompound and a bisphenol dianion in anhydrous aprotic solvent. Model reactions were studied with 3,3′- and 4,4′-dichloroazoxybenzene and various phenol and thiophenol salts to find out the reaction conditions for polycondensation. IR, ¹H NMR, and elemental analyses were used to establish the structure of the model compounds and the polymers. Thermal analysis indicated that the oxy derivative is less prone to thermo-oxidative degradation than the corresponding thio derivative of polyazoxyarylether. The polymers are crystalline and soluble in halogenated hydrocarbons and polar solvents.     

Anionic polymerization of acrylates. III. Polymerization of 2-ethylhexyl acrylate initiated by lithium-tert-butoxide

The polymerization of 2-ethylhexyl acrylate (EtHA) initiated with lithium-tert-butoxide (t-BuOLi) in tetrahydrofuran (THF) and in the temperature range between ?60 and 20°C was investigated. The reaction rate is distinctly temperature-dependent and at ?60°C is already very low, similarly to the polymerization of methacrylates. Molecular weights of the polymers thus formed, particularly at higher temperatures, are inversely proportional to conversion of the monomer due to the slow initiation reaction. This is documented by the low consumption of alkoxide even at long reaction times, which also depends on the reaction temperature. At higher temperatures the polymerization stops spontaneously, due to the greater extent of autotermination reactions. The weak initiating efficiency of the alkoxide decreases still more with decreasing concentration of the monomer during the polymerization, as confirmed by the concentration dependence of the reaction rate in toluene at ?20°C. The results suggest a negligible initiating effect of alkoxides in complex bases, particularly at lower polymerization temperatures. © 1992 John Wiley & Sons, Inc.     

Study of the reaction mechanism of the copper chelate with DGEBA using DSC

The reaction mechanism of metal-containing and complex compound with epoxy oligomer of diglycidyl ether of bisphenol A (DGEBA) was studied using dynamic DSC technique. It is shown that cure reaction of the epoxy oligomers with copper acetate proceeds at two stages: through coordination of cation with the epoxy group, and through ionic polymerization at high temperatures. Mechanism of curing of DGEBA with copper chelate depends on equilibrium process of dissociation of the chelate which, in turn, depends not only on temperature of curing but also on concentration of the hardener. At the dissociation temperature of the hardener, polymerization proceeds according to ionic mechanism. Hardening of the epoxy oligomers due to interaction of epoxy groups with unconnected amine groups predominate at higher temperatures or at higher concentrations of the hardener. At low temperatures and small concentrations of the hardener, polymerization proceeds according to catalytic ionic mechanism. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of styrene oligomers on syndiospecific polymerization of styrene

Styrene oligomers, preferentially consisting of styrene dimers and trimers, are formed by a free radical mechanism at the thermal polymerization of stabilizer-free styrene during storage and at higher polymerization temperatures. The identity of several dimer and trimer fractions formed in such a free radical polymerization, their influence on a coordinative polymerization reaction, the syndiospecific polymerization of styrene, as well as their effect on the properties of the resulting polymers has been investigated.Styrene dimers and styrene trimers reduce the polymerization activity of the transition metal catalyst significantly, especially at low amounts of oligomers added to the styrene. This behavior is discussed with respect to a proposed mechanism involving complexation of the active transition metal species with the specific oligomer instead of the styrene monomer, resulting in increased steric hindrance towards insertion of a styrene molecule to the active site.Both oligomers reduce the molecular weight of the syndiotactic polystyrene, by acting as chain-transfer agents. The constancy of the polydispersity over the whole concentration range of added dimer or trimer indicates that the uniformity of the active sites of the coordinative polymerization is not significantly influenced by the presence of the oligomers.The thermal properties of the polymers demonstrate that the oligomers do not affect the high syndiospecificity of the active catalytic sites, whereas the increase in crystallization temperature with increasing amounts of styrene dimer or trimer is comparable to effects observed by the addition of crystallization nucleators to semicrystalline polymers.     

Poly(urethane‐co‐benzoxazine)s via reaction of phenol terminated urethane prepolymers and benzoxazine monomer and investigation of their properties

In the present work, a new method was developed for the combination of polyurethanes (PUs) and polybenzoxazine (PBz) to obtain novel thermoset poly(urethane‐co‐benzoxazine)s with good thermal, mechanical, and electrical properties as well as low temperature curing profile. Knowing the catalytic effect of compounds possessing free phenolic groups on ring opening polymerization of benzoxazine monomers, preparation of phenol terminated urethane oligomers (PTPU) as the macroinitiator for a benzoxazine monomer (Ba) was considered. Firstly, NCO‐terminated urethane prepolymers were prepared from the reaction of poly(tetramethyleneether glycol), and 2,4‐tolylene diisocyanate, and then end functionalized with bisphenol‐A under proper condition. DSC, DMTA, and gel content measurements were applied to find optimum ring opening polymerization condition (170°C for 1 hr and 200°C for 15 min). Various kinds of thermoset polymers were prepared by the reaction of PTPU at different molecular weights with variable contents of Ba. All of monomeric and polymeric materials were characterized by conventional spectroscopic methods and their thermal, mechanical, viscoelastic, and electrical properties were measured and properties were correlated to their structure. Due to the interesting properties of these new materials, the possibility of using them as electrical insulators with higher service temperature in comparison to common PUs were examined and their potential applicability was confirmed. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and characterization of carborane-containing poly(hydroxy ethers) with excellent thermal stability

o-Carborane-containing poly(hydroxy ethers)(P1, P2 and P3) were synthesized via "advancement reaction" of o-carborane-containing bisphenol(4) and diglycidyl ether of bisphenols(DGEBA and 1). FTIR and ~(1) H-, ~(13)C-, and ~(11) B-NMR were utilized to characterize the obtained polymers. TGA test was conducted under nitrogen and air. It is found that the shielding effect of carborane moiety on its adjacent aromatic structures contributes to high initial decomposition temperatures, while oxygen in air has an adverse effect on the initial decomposition temperature. The oxygen can combine with polymer chain to form peroxide and hydroperoxide groups, which are more reactive during the degradation process. Besides, o-carborane-containing poly(hydroxy ethers) have high char yield at elevated temperatures. The boron atom combines with oxygen from the polymer structure or/and from air, thus to form a three-dimensional network linked with B―O―B and B―C bonds, and retain the polymer weight to a large extent.     

Polymerization of epoxide with hydroxylamides as thermally latent initiators

A new class of thermally latent initiators for the ring‐opening polymerization of epoxides has been developed. The latent initiators developed herein were the hydroxylamides 1a , 1b , and 1c , which were synthesized from phthalide, 3‐isochromanone, and cis‐cyclohexahydrophthalide, respectively, by their ring‐opening reactions with pyrrolidine. These hydroxylamides were designed so that their hydroxyl groups could attack the amide moiety intramolecularly upon heating, leading to ring closure and formation of the corresponding lactones while releasing pyrrolidine, the initiator for the anionic ring‐opening polymerization of an epoxide. The temperatures at which this thermal dissociation occurred were strongly dependent on the hydroxylamide molecular structure. When using the hydroxylamides as thermally latent initiators, the polymerizations of bisphenol‐A diglycidyl ether were investigated at various temperatures. This investigation clarified that the threshold temperature, that is, the temperature at which polymerization was initiated, increased in the order of 1a , 1b , and then 1c . © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2611–2617     

The degradation mechanism using TG-MS technique of some aromatic polyethers containing flexible spacers

The paper presents a thermogravimetric study of some aromatic poly- and copolyethers, using mass spectrometry technique combined with thermogravimetric analysis. The polymers were synthesized by phase transfer catalysis technique, using bis(2-chloroethyl)-ether or 1,6-dichlorohexane as flexible spacers and various bisphenols (4,4'-dihydroxydiphenyl, 4,4'-dihydroxyazobenzene and bisphenol A). The presence of azobenzenic moieties in the chain induces a liquid crystalline behavior, but, due to the high values of the transition temperature, some precautions during the thermal characterisation are necessary. In the case of azobenzenic samples, the degradation reactions begin, as a function of the chemical structure, around 230-250°C. A degradation mechanism based on chain transfer reactions was proposed. The chain flexibility influences the thermal degradation mechanism, in the case of rigid polymers the chain transfer reactions being less probable. For the flexible chains, the thermal stability is not essentially influenced by the copolymerisation ratio between the two aromatic bisphenols. This revised version was published online in July 2006 with corrections to the Cover Date.     

Aromatic-aliphatic copolyesters—II. Various polycondensation processes

Aromatic aliphatic copolyesters, using hydroquinone, resorcinol, 4,4′-dihydroxybiphenyl (DHBP) 2,2 bis(4-hydroxyphenyl)propane and 4,4′-dihydroxydiphenyl sulphone (DHDPS) as bisphenols and ethylene glycol as diol, have been synthesized by interfacial, low temperature and high temperature solution condensation. Relative reactivities of these bisphenols and ethylene glycol have been evaluated by various polycondensation methods at a fixed ratio of bisphenol/glycol. Decrease in the extent of polymerization and viscosity was observed by incorporation of aliphatic diol. Viscosity was also influenced by the chemical structure of the bisphenol.     

Thermally reversible linking of halide-containing polymers by potassium dicyclopentadienedicarboxylate

A novel crosslinker for thermally reversible covalent (TRC) linking of halide-containing polymers is suggested. Chlorine-containing polymers such as chloromethylstyrene copolymers, chlorinated polypropylene, polyvinylchloride, chlorinated polyisoprene, and polyepichlorohydrin were crosslinked with potassium dicyclopentadienedicarboxylate (KDCPDCA). The crosslinker was prepared by reacting potassium ethoxide with dicyclopentadienedicarboxylic acid. Because of the low solubility of KDCPDCA in organic solvents, a phase transfer catalyst, benzyltrimethyl-ammonium bromide, was employed for the crosslinking reaction. The crosslinking reaction occurred at a higher rate in a polar solvent, such as dimethylformamide, than in a nonpolar one, such as toluene, and was affected by the nature of the chlorine-containing polymer. Some of the polymers crosslinked even at room temperature. The chain-extending reaction between KDCPDCA and a α,ω-dihalide compound such as α,α′-dichloro-p-xylene, 1,4-dichlorobutane, or 1,4-dibromobutane also was carried out to obtain linear oligomers. The IR spectra indicated that the crosslinking and chain-extending reactions were based on the esterification between the halide carbon bonds of the polymer and the COOK groups of KDCPDCA. The flowability at 195 °C and solubility on heating in a dichlorobenzen-maleic compound mixture of the crosslinked polymers indicated that the TRC crosslinking occurred via the reversible Diels–Alder cyclopentadiene/dicyclopentadiene conversion as long as the polymer was thermally stable and did not contain olefinic CC bonds. The TRC linking also was confirmed by the rapid decrease of the specific viscosity of the obtained linear oligomers on heating. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4390–4401, 1999     

Synthesis of α,ω-arylamine functionalized poly(dimethylsiloxane)s

This research has focused on the development of telechelic, aromatic amine functional, poly(dimethylsiloxane) oligomers without any aliphatic components in the polymer backbone. The intent is to produce flexible oligomers with enhanced thermal stability for incorporation into materials which will be processed at elevated temperatures. The poly(dimethylsiloxane)s have been synthesized using living polymerization of hexamethylcyclotrisiloxane with protected aniline derivatives as initiators and termination reagents for the reactions. Low molecular weight oligomers prepared using the living polymerization method can be easily converted to a range of higher, controlled molecular weight materials in redistribution reactions. A basic tetramethylammonium siloxanolate catalyst in conjunction with octamethylcyclotetrasiloxane has been used for the equilibration procedure. © 1993 John Wiley & Sons, Inc.     

All‐aromatic liquid crystalline thermosets with high glass transition temperatures

We have synthesized and characterized a new family of low melting all‐aromatic ester‐based liquid crystal oligomers end‐capped with reactive phenylethynyl end groups. In a consecutive, high‐temperature step, the reactive end groups were thermally activated and polymerization was initiated. This reactive oligomer approach allows us to synthesize liquid crystal thermosets with outstanding mechanical and thermal properties, which are superior to well‐known high‐performance polymers such as PPS and PEEK. We have modified an intractable LC formulation based on hydroquinone and terephthalic acid, with M_n = 1000, 5000, and 9000 g mol^?1, and varied the backbone composition using isophthalic acid, resorcinol, 4‐hydroxy‐benzoic acid, 6‐hydroxy‐2‐naphthoic acid, and chlorohydroquinone. All fully cured polymers showed glass transition temperatures in the range of 164–275 °C, and high storage moduli at room temperature (～ 5 GPa) and elevated temperature (～ 2 GPa at 200 °C). All oligomers display nematic mesophases and in most cases, the nematic order is maintained after cure. Rheology experiments showed that the phenylethynyl end group undergoes predominantly chain extension below 340 °C and crosslinking above this temperature. Highly aligned fibers could be spun from the nematic melt, and we found that the order parameter 〈P₂〉 was not affected by the chain extension and crosslink chemistry. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1368–1380, 2009     

Effect of supercritical carbon dioxide on the diffusion coefficient of phenol in poly(bisphenol A carbonate)

For some polymers, the rate of solid‐state polymerization (SSP) is higher with supercritical carbon dioxide (scCO₂) as the sweep gas than with atmospheric N₂. One explanation for this higher rate is that the diffusion coefficient of the condensate molecule is higher in the CO₂‐swollen polymer. To investigate this hypothesis, we measured the diffusion coefficient of phenol in poly(bisphenol A carbonate) (BPA‐PC) by carrying out SSP of this polymer under diffusion‐limited conditions. Under these conditions, the diffusion coefficient of the condensate molecule could be calculated from the profile of the molecular weight versus time. The phenol diffusivity was determined between 135 and 180 °C in the presence of N₂ at about 1 bar and in the presence of scCO₂ at about 138, 207, and 345 bar. The diffusion coefficient of phenol was up to 200% higher in scCO₂ than in N₂, depending on the temperature and CO₂ pressure. With both N₂ and scCO₂, the activation energy for phenol diffusion in BPA‐PC was larger than the activation energy for the reaction between hydroxyl and phenyl end groups that occurred during SSP of BPA‐PC. As a result, the overall SSP reaction shifted from diffusion control at low temperatures toward chemical‐reaction control at high temperatures. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1143–1156, 2003