Syntheses of copolymers containing pendant cyclic iminoethers and crosslinking reactions of these copolymers with dithiols and dicarboxylic acids

Copolymers containing pendant cyclic iminoethers were prepared by radical copolymerizations of 2-vinyl-2-oxazoline (VOZO), 5-methyl-2-vinyl-2-oxazoline (MVOZO), 4,4-dimethyl-2-vinyl-2-oxazoline (DMVOZO), 4,4-dimethyl-2-vinyl-5,6-dihydro-4H-1,3-oxazine (DMVOZI), and 4,4,6-trimethyl-2-vinyl-5,6-dihydro-4H-1,3-oxazine (TMVOZI) with styrene, methyl methacrylate (MMA), and ethyl acrylate (EA) using AIBN as an initiator. In addition, the monomer reactivity ratios of VOZO, MVOZO, DMVOZO, and DMVOZI with styrene and MMA were determined. The crosslinking reactions of these copolymers with polyfunctional thiols such as 6-(N,N-dibutyl)amino-1,3,5-triazine-2,4-dithiol (DBDT), 4,4′-oxydi(benzenedithiol) (OBDT), and pentaerythritol tetrathioglycolate (PETT), and dicarboxylic acids such as succinic acid, adipic acid, and sebacic acid were carried out at several reaction temperatures. From these results, it was found that the order of reactivity of pendant cyclic iminoethers to the thiols was VOZO > DMVOZO ≥ DMVOZI > MVOZO > TMVOZI, and that of the cyclic iminoethers to the carboxylic acids was VOZO > MVOZO ≥ DMVOZI > TMVOZI ≥ DMVOZO. Furthermore, the order of reactivity of the thiols to the cyclic iminoethers was DBDT > OBDT > PETT, and that of the dicarboxylic acids to the cyclic iminoethers was succinic acid > adipic acid > sebacic acid.     

The formation of polyethylene terephthalate in the presence of dicarboxylic acids

The process of polyethylene terephthalate (PET) formation in the presence of dicarboxylic acids has been studied. Certain amounts of terephthalic acid (TPA) have two- to threefold accelerating efficiency in the polycondensation process. To elucidate the causes of the acceleration the main reactions leading to PET formation in the presence of dicarboxylic acids have been investigated by the use of models. The evaluation of kinetic and equilibrium parameters obtained for model reactions made it possible to conclude that the influence of carboxyl-containing additives on the apparent rate of polycondensation manifests itself in accelerating direct reactions and facilitating the liberation of the eliminated by-product; that is, ethylene glycol (EG) from the polymer melt. Carboxylic acid acts as a catalyst on the ester interchange of 2-hydroxyethyl ester end groups and thus increases the rate of polymer formation in this reaction 10–40 times. The parallel interaction between the 2-hydroxyethyl ester end group and the carboxyl group of the added acid is also catalyzed by the acid and its rate constant is four times larger than that of the catalytic polycondensation of 2-hydroxyethyl ester end groups. Unlike EG, the reaction water formed in the process is more readily removed from the reaction system and thus promotes the intensification of the process. In addition, the carboxyl groups react with the eliminated EG to decrease its amount and shift the equilibrium toward polymer formation. The investigation of the consequent parallel reactions on models made it possible to draw a conclusion about the higher reactivity of 2-hydroxyethyl esters in the esterification processes. This fact has been explained by strengthening the nucleophilicity of the oxygen atom in the hydroxyl of a 2-hydroxyethyl ester group compared with that of EG; for example, by the formation of an intramolecular cycle involving a hydrogen bond. Simultaneously, it has been found that in the system simulating PET polycondensation in the presence of dicarboxylic acids the reaction mechanism involves the catalysis by a proton formed during the carboxyl group dissociation and accepted by the 2-hydroxyethyl ester group.     

Synthesis and photochemical properties of poly(ester–amide)s containing norbornadiene (NBD) residues

N,N′‐Bis[(3‐carboxynorbornadien‐2‐yl)carbonyl]‐N,N′‐diphenylethylenediamine (BNPE) was synthesized in 70% yield by the reaction of 2,5‐norbornadiene‐2,3‐dicarboxylic acid anhydride with N,N′‐diphenylethylenediamine. Other dicarboxylic acid derivatives containing norbornadiene (NBD) residues having N,N′‐disubstituted amide groups were also prepared by the reaction of 2,5‐NBD‐2,3‐dicarboxylic acid anhydride with certain secondary diamines. When the polyaddition of BNPE with bisphenol A diglycidyl ether (BPGE) was carried out using tetrabutylammonium bromide as a catalyst in N‐methyl‐2‐pyrrolidone at 100°C for 12 h, a polymer with number average molecular weight of 69,800 was obtained in 98% yield. Polyadditions of other NBD dicarboxylic acid derivatives containing N,N′‐disubstituted amide groups with BPGE were also performed under the same conditions. The reaction proceeded very smoothly to give the corresponding NBD poly(ester–amide)s in good yields. Photochemical reactions of the obtained polymers with N,N′‐disubstituted amide groups on the NBD residue were examined, and it was found that these polymers were effectively sensitized by adding appropriate photosensitizers such as 4‐(N,N‐dimethylamino)benzophenone and 4,4′‐bis(N,N‐diethylamino)benzophenone in the film state. The stored energies in the quadricyclane groups of the polymers were also evaluated to be about 94 kJ/mol by DSC measurement of the irradiated polymer films. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 917–926, 1999     

Investigation of the reaction of some unsaturated dicarboxylic acid anhydrides with cyclic carbonates

This work reports attempts to extend to unsaturated anhydrides the rapid reaction of dicarboxylic acid anhydrides with ethylene carbonate to form polymer directly. The reaction of unsaturated diacid anhydrides with two cyclic carbonates, ethylene and propylene carbonate, leads to gelled products whenever the anhydride is capable of Michael addition, while an anhydride without such unsaturation gave linear polymer in- stead. The GC/MS results, along with efforts to trap radical reactions, support Michael addition as an explanation of gelation in these systems.     

Synthesis of new photoresponsive polyesters containing norbornadiene residues by the polyaddition of donor–acceptor norbornadiene dicarboxylic acid diglycidyl ester with dicarboxylic acids and their photochemical properties

A donor–acceptor norbornadiene derivative, 5‐(4‐methoxyphenyl)‐1,4,6,7,7‐pentamethyl‐2,5‐norbornadiene‐2,3‐dicarboxylic acid diglycidyl ester (D–A NDGE), was synthesized by the reaction of the cesium salt of 5‐(4‐methoxyphenyl)‐1,4,6,7,7‐pentamethyl‐2,5‐norbornadiene‐2,3‐dicarboxylic acid with epibromohydrin in N‐methyl‐ pyrrolidone (NMP). The polyaddition reactions of D–A NDGE with certain dicarboxylic acids were carried out with tetrabutylammonium bromide as a catalyst in NMP, producing corresponding polyesters containing D–A norbornadiene (NBD) residues in the main chain in fair to good yields. The photoisomerization of the D–A NBD residues in the polyesters proceeded very smoothly, forming the corresponding quadricyclane groups. The photoreactivities of the D–A NBD residues in the polymer were 50 times higher than those of the NBD residues in the film state and 60 times higher than those in a tetrahydrofuran solution. The stored energy in the quadricyclane groups of the polymers was about 45–55 kJ/mol according to differential scanning calorimetry analysis of the irradiated polymer films. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2683–2690, 2001     

Direct polyesterification with thionyl chloride in pyridine improved by a modification of monomer sequences in copolymers

The direct polyesterification with thionyl chloride (SOCl₂) in pyridine was further investigated. Copolycondensations of dicarboxylic acids, bisphenols, and hydroxybenzoic acids were significantly affected by the reaction temperatures and combinations of monomers which could change relative rates of alcoholyses of the activated dicarboxylic acids and the hydroxyacids consequently to vary monomer sequences in the copolymers resulted. The sequences were tried to be varied more directly by stepwise reactions of monomers in copolycondensations of dicarboxylic acids, bisphenols, and p-hydroxybenzoic acid (PHB), as well as PHB and m-hydroxybenzoic acid (MHB). The reactions proceeded smoothly and satisfactorily when carried out by initial reaction of dicarboxylic acids and PHB followed by bisphenols likely to favor sequential to random distributions of monomers. Reverse addition of PHB and bisphenols, and then dicarboxylic acids resulted in rapid precipitation due to some oligomerization of PHB at an earlier stage of reaction, and largely retarded the reaction. This was also the case for the copolycondensation of PHB and MHB. Copolymers of high inherent viscosities with up to 65 mol% PHB could be obtained by initial reaction of MHB followed by PHB.     

Direct polyesterification with thionyl chloride in pyridine improved by a modification of monomer sequences in copolymers

The direct polyesterification with thionyl chloride (SOCl₂) in pyridine was further investigated. Copolycondensations of dicarboxylic acids, bisphenols, and hydroxybenzoic acids were significantly affected by the reaction temperatures and combinations of monomers which could change relative rates of alcoholyses of the activated dicarboxylic acids and the hydroxyacids consequently to vary monomer sequences in the copolymers resulted. The sequences were tried to be varied more directly by stepwise reactions of monomers in copolycondensations of dicarboxylic acids, bisphenols, and p-hydroxybenzoic acid (PHB), as well as PHB and m-hydroxybenzoic acid (MHB). The reactions proceeded smoothly and satisfactorily when carried out by initial reaction of dicarboxylic acids and PHB followed by bisphenols likely to favor sequential to random distributions of monomers. Reverse addition of PHB and bisphenols, and then dicarboxylic acids resulted in rapid precipitation due to some oligomerization of PHB at an earlier stage of reaction, and largely retarded the reaction. This was also the case for the copolycondensation of PHB and MHB. Copolymers of high inherent viscosities with up to 65 mol % PHB could be obtained by initial reaction of MHB followed by PHB.     

Synthesis of poly(ester carbonate) copolymers

The synthesis of poly(ester carbonate) copolymers based on bisphenol A, terephthalic acid, and phosgene is reviewed, and a new synthetic route is described leading to polymers which are different from those obtained by methods described in the literature. The most important features of the new method are quantitative incorporation of the dicarboxylic acid into the polymer and absence of undersirable side reactions. Synthesis of the random copolymer in which the dicarboxylic acid and carbonic acid groups are present in about equal molar amounts is discussed. Solution properties, effects of M?_n and copolymer composition on T_g, sequence length distribution, the effect of ester interchange reactions on molecular weight distribution, and effects of monofunctional chain termination on molecular weight of the final product are also discussed.     

Synthesis of novel macromonomers and telechelics of poly(2-alkyl-2-oxazoline)s

Novel macromonomers and telechelics of poly(2-alkyl-2-oxazoline) (PROZO) were syn-thesized by utilizing termination of propagating species (2-oxazolinium ions) in the living polymerization of 2-alkyl-2-oxazoline (ROZO) with suitable nucleophiles. Two types of p-vinylbenzyl–type macromonomers were obtained by terminating living PROZO with sodium p-vinylbenzyl alkoxide or with sodium p-vinylbenzyl mercaptide. The synthesis of telechelics having a functional group (SH, COOH) on both ends of PROZO was achieved by using a bis(2-oxazolinium salt) initiator. The PROZO dithiol was synthesized by two methods: (1) termination of the living species on both ends with NaSH, and (2) aminolysis of PROZO bis(O-ethyldithiocarbonate) given by treatment of the living PROZO with potassium O-ethyldithiocarbonate. Termination of the living PROZO with the sodium salt of di-t-butyl malonate yielded a PROZO with di-t-butyl malonate moieties on both polymer ends, from which the PROZO dicarboxylic acid was derived via free tetracarboxylic acid. © 1995 John Wiley & Sons, Inc.     

Investigation of thermo-reversibility of polymer crosslinked by reversible covalent bonds through torque measurement

Brominated butyl rubber (BIIR) was crosslinked through an esterification reaction using the sodium salt of dicyclopentadiene dicarboxylic acid (DCPDCA) as crosslinking agent. The crosslinked BIIR could de-crosslink upon heating and re-crosslink upon cooling due to Diels-Alder type reversible de-dimerization/re-dimerization of dicyclopentadiene moieties in the rubber networks. Torque measurement of the crosslinked rubber was conducted at various temperatures using a typical curemeter to investigate the thermo-reversibility. It was revealed that proper temperature for thermal processing of the crosslinked BIIR would be around 174 °C, at which the crosslinked polymer exhibits good flowability and is not too high to induce unexpected side reactions. The torque measurement was also carried out to investigate the efficiency of antioxidant on retarding the loss of the thermo-reversibility of the crosslinked polymer during heating-cooling cycles. It was found that addition of antioxidant 2246 [2,2′-methylenebis(6-tert-butyl-4-methylphenol)] into BIIR could significantly improve the thermo-reversibility of DCPDCA crosslinked BIIR. Torque measurement provides a convenient and sensitive method to understand the thermal behavior of reversible covalent crosslinked polymer.     

Polynuclear nonfused bis(1,3,4-oxadiazole)-containing systems

Nonfused bis-1,3,4-oxadiazoles were synthesized by reaction of 5-substituted mono-and bis-tetrazoles with mono-and dicarboxylic acid chlorides. The results of kinetic studies showed that the transformation of tetrazoles into 1,3,4-oxadiazoles is accelerated by 1 to 2 orders of magnitude on addition of a catalytic amount of dimethylformamide, triethylamine, or pyridine.     

Reduction of the 2‐azetidinone moiety in the polymer main chain: A novel synthetic route to polyamine with hydroxymethyl pendant

A polymer with a 2‐azetidinone moiety in its main chain was efficiently synthesized by [2 + 2] cycloaddition of bisimine with bisketene. The bisketene was easily prepared by dehydrochlorination of the corresponding dicarboxylic acid chloride and was used without purification. The treatment of the obtained polymer with lithium aluminum hydride resulted in a reductive ring‐opening reaction of the 2‐azetidinone moiety in the main chain that gave the corresponding linear polyamine with hydroxymethyl side chains. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3789–3796, 2001     

Untersuchung der Bildung von Polyesteramiden aus Dicarbonsäure-anhydriden und Oxazolidinonen-2

The well-known reaction of dicarboxylic acid anhydrides with epoxides, catalyzed by bases and yielding linear polyesters, has been extended by a variation of the reactants. The reactions of succinic and phthalic anhydrides with N-substituted oxazolidinones-2, which by their tendency to split off CO₂ may be regarded as ethyleneimine derivatives, give in the presence of a few mole percent of LiCl at 200–220°C. within 5–10 hr. polyester amides of molecular weights up to 3.500 in nearly quantitative yield. The polymer yield corresponds to the CO₂ evolution indicating an equal consumption of oxazolidinone and anhydride in the reaction. The experimental activation energies of 22.8 and 20.2 kcal./mole for the reaction of 3-phenyl oxazolidinone-2 with succinic and phthalic anhydrides, respectively, fairly agree with earlier values reported for the corresponding reactions of the cyclic carbonates.     

Study on modification of polymers with the aid of the Schmidt reaction

A study of the Schmidt reaction on several polymers with pendant carboxylic and ketone moieties was carried out. Four polymers were used as starting materials: (1) poly(methyl vinyl ketone), (2) poly(acrylic acid), (3) a copolymer of methyl vinyl ketone and acrylic acid, and (4) a copolymer of styrene and acrylic acid. Most reactions were conducted in an acetic acid medium with the exception of one reaction on poly(acrylic acid) which was done in dioxane and another on copolymer of styrene and acrylic acid done in chloroform. It was found that a Schmidt reaction on poly(acrylic acid) in acetic acid solution will lead to intermolecular reactions of the intermediate with the solvent in preference to reactions with neighboring carboxyl groups on the polymer backbone. A tendency of poly(acrylic acid) to form cyclic anhydrides under these reaction conditions interferes with the yield of acetamide units.     

Synthesis and properties of iridium polymer complexes based on novel bipyridyl ligands

A novel monomer, viz., bipyridyl-containing dicarboxylic acid, was synthesized from 6-pyridyl-3,4-pyridine dicarboxylic acid anhydride and 5-aminoisophthalic acid. Novel polymer macroligands, viz., copolyamides containing 5, 15, 30, and 45% of the bipyridyl side groups, were obtained based on this monomer by low-temperature polycondensation. Metal polymer complexes (MPC) with different Ir(ppy)₂ content were synthesized by the reaction of the polymer ligand with the binuclear complex [Ir(ppy)₂Cl]₂ (ppy is 2-phenylpyridine) and their properties were studied.     

Wholly aromatic polyamides by the direct polycondensation reaction using triphenyl phosphite in the presence of poly(4-vinylpyridine)

The polycondensation reaction of aromatic dicarboxylic acids and diamines by using triphenyl phosphite were carried out in N-methylpyrrolidone (NMP) in the presence of poly(4-vinylpyridine) (P4VP). The reaction, especially of terephthalic acid (TPA), was markedly facilitated to give the absence of P4VP. The reaction promoted by P4VP was further favored by the addition of various pyridine derivatives; of the pyridines examined, pyridine was most effective, giving the best results at a high level (pyridine/P4VP values up to 26). P4VP of the molecular weight in the range of 1.3 × 10⁴?3.0 × 10⁵ did not affect the viscosity of the resulting polymer. These favorable additive effects of P4VP on the reaction of TPA were not observed in the reactions of isophthalic acid, and m -and p-aminobenzoic acids.     

Catalytic reactions of oxetanes with protonic reagents and aprotic reagents leading to novel polymers

This paper reports new addition reactions of oxetanes with certain protonic reagents such as carboxylic acid, phenol, and thiol, and with certain aprotic reagents such as acyl chloride, thioester, phosphonyl dichloride, silyl chloride, and chloroformate using quaternary onium salts as catalysts. The kinetic study of the addition reactions of oxetanes was also investigated. These new addition reactions were applicable to the synthesis of new polymers. These polyaddition systems could also construct both polymer main chains and reactive side chains. The alternating copolymerization of oxetanes with carboxylic anhydride was performed. Furthermore, it was found that anionic ring‐opening polymerization of oxetanes containing hydroxy groups proceeded to afford the hyperbranched polymer (HBP) with an oxetanyl group and many hydroxy groups at the ends of the polymer chains. Alkali developable photofunctional HBPs were synthesized by the polyaddition of bis(oxetane)s or tris(oxetane)s, and their patterning properties were examined, too. The photo‐induced cationic polymerization of the polymers with pendant oxetanyl groups and the thermal curing reactions of polyfunctional oxetanes (oxetane resins) were also examined to give the crosslinking materials quantitatively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 709–726, 2007     

Careful investigation of the hydrosilylation of olefins at poly(ethylene glycol) chain ends and development of a new silyl hydride to avoid side reactions

Hydrosilylation of olefin groups at poly(ethylene glycol) chain ends catalyzed by Karstedt catalyst often results in undesired side reactions such as olefin isomerization, hydrogenation, and dehydrosilylation. Since unwanted polymers obtained by side reactions deteriorate the quality of end‐functional polymers, maximizing the hydrosilylation efficiency at polymer chain ends becomes crucial. After careful investigation of the factors that govern side reactions under various conditions, it was related that the short lifetime of the unstable Pt catalyst intermediate led to the formation of more side products under the inherently dilute conditions for polymers. Based on these results, two new chelating hydrosilylation reagents, tris(2‐methoxyethoxy)silane (5) and 2,10‐dimethyl‐3,6,9‐trioxa‐2,10‐disilaundecane (6), have been developed. It was demonstrated that the hydrosilylation efficiency at polymer chain ends was significantly increased by employing the internally coordinating hydrosilane 5. In addition, employment of the internally coordinating disilane species 6 in an addition polymerization with 1,5‐hexadiene by hydrosilylation reaction yielded a polymer with high molecular weight (M_n = 9300 g/mol), which was significantly higher than that (M_n = 2600 g/mol) of the corresponding polymer obtained with non‐chelating dihydrosilane, 1,1,3,3‐tetramethyldisiloxane. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 527–536     

Effect of end group polarity upon the lower critical solution temperature of poly(2-isopropyl-2-oxazoline)

Thermo-sensitive poly(2-isopropyl-2-oxazoline)s (PiPrOx) were functionalized with end groups of different polarity by living cationic ring-opening polymerization using the initiator and/or termination method as well as sequential block copolymerization with 2-methyl-2-oxazoline. As end groups, methyl, n-nonyl, piperidine, piperazine as well as oligo(ethylenglygol) and oligo(2-methyl-2-oxazoline) were introduced quantitatively. The lower critical solution temperature (LCST) of the aqueous solutions was investigated. The introduction of hydrophobic end groups decreases the LCST, while hydrophilic polymer tails raise the cloud point. In comparison to poly(N-isopropyl acrylamide), the impact of the end group polarity upon the modulation of the LCST was found to be significantly stronger. Surprisingly, terminal oligoethylenegycol units also decrease the LCST of PiPrOx, thus acting as moieties of higher hydrophobicity as compared to the poly(2-oxazoline) main chain. Together with the possible variation of the side group polarity, this allows a broad modulation of the LCST of poly(2-oxazoline)s.     

Synthesis and Properties of a New Polyesterimide from a Forest Product

Polyesterimide offers a class of resin which combines the advantage of high temperature stability with ease of process-ability. Gum rosin, the exudate of pine trees, has been developed as the raw material for preparation of polyesterimide. Abietic acid of rosin reacts readily with maleic anhydride to form the Diels-Alder adduct, which reacts with p-amino benzoic acid to produce a dicarboxylic acid containing an internal imide group. The dicarboxylic acid reacts with diethylene glycol under melt polycondensation at higher temperature (260–300°C)to produce polyesterimide. The polymer is found to be soluble in highly polar solvents. The polymer is amorphous and of low molecular weight. Thermal stability of the polymer has been characterized, and the polymer was found to be thermostable.