On the Microstructure of Copolymer Chains Obtained by the Linear Heterocopolycondensation Process

During the statistical analysis of copolymers obtained by the heteropolycondensation method, simulating the difference in the reactivity of the original comonomers by varying the preset reactive conditions, it is shown that the microstructure of the condensation copolymer chains should not depend on the relative reactivity of the comonomers. It is also shown that the microstructure of the chains can be influenced by choosing the copolycondensation conditions in such a way that the process would proceed from a insufficient quantity of the intermonomer in the reactive zone.     

STUDY ON SOLID STATE POLYCONDENSATION OF POLYETHYLENE TEREPHTHALATE COPOLYMERS

The kinetic data of solid state polycondensation of PET and its copolymers are determined.It is shown that the reaction rate of copolycondensation is higher than that of PET polyconden-sation, and increases with the comonomers content. But the reaction rate of copolycondensationin melt state of this kind of copolymers is lower than that of PET. It is considered that the chemi-cal reactivity of comonomer is the main factor which affect the polycondensation in melt state,whereas the aggregative structure of the polymer is the main factor in solid state. The crystallinity and crystallite size of the copolymers have been measured by X-ray method.     

Biomimetic condensation copolyesters

Copolyterephthalates of bis(4-hydroxy-3-methylphenyl)-2,2-propane and N-methyldiethanolamine and their hydrochloric salts of various compositions and microstructures have been prepared by the copolycondensation of hydrophilic and hydrophobic comonomers. It has been shown that the transition from random proteinlike structures to the block structures makes it possible to preserve biomimetic properties of the copolymers at a smaller content of charged units in macromolecules. The ability of charged polymers to survive in aqueous solutions has been used for the synthesis of copolyterephthalate of N-bis(hydroxyethyl)tetradecylmethylammonium bromide and N-methyldiethanolamine demonstrating fungicidal activity.     

The effect of synthesis conditions on the microheterogeneity of the butadiene-isoprene copolymer

The dependence of the microheterogeneity of butadiene-isoprene copolymers synthesized in the presence of a titanium-based catalytic system on the hydrodynamic regime used at the initial moment of formation of the reaction mixture of copolymerization is studied. When copolymers are synthesized with the direct addition of the catalyst to the solution of the comonomers, copolymers featuring a statistical distribution of units are formed, regardless of the composition of the initial comonomer mixture. In this case, the growth of copolymer chains obeys the Bernoulli statistics. Depending of the composition of the initial comonomer mixture, hydrodynamic factors promote different extents of deviation from the statistical growth of copolymer chains.     

Poly(siloxane carbonates) based on siloxane-containing bisphenols

Effects of the synthesis conditions and other factors on the formation of copolymers with random or block microstructures through the low-temperature homogeneous and heterophase copolycondensation of bisphenol A bis(chloroformate) with mixtures of α,ω-bis(4-hydroxy-3-methoxyphenylpropyl)oligodimethylsiloxanes and organic bisphenols have been considered. Several new poly(siloxane carbonates) have been synthesized and characterized; for copolymers with different chemical compositions and structures, molecularmass and thermal and mechanical characteristics have been compared.     

Preparation of gradient copolymers via ATRP in miniemulsion. II. Forced gradient

A series of forced gradient copolymers with different controlled distribution of monomer units along the copolymer backbone were successfully prepared by atom transfer radical polymerization in miniemulsion. The newly developed initiation technique, known as activators generated by electron transfer, was beneficial for forced gradient copolymers preparation because all polymer chains were initiated within the miniemulsion droplets and the miniemulsion remained stable throughout the entire polymerization. Various monomer pairs with different reactivity ratios were examined in this study, including n‐butyl acrylate/t‐butyl acrylate, n‐butyl methacrylate/methyl methacrylate, and n‐butyl acrylate/styrene. In each case, the added monomer diffused across the aqueous suspending medium and gradient copolymers with different forced distributions of comonomer units along the polymer backbone were obtained. The shape of the gradient along the backbone of the copolymers was influenced by the molar ratio of the monomers, the reactivity ratio of the comonomers as well as the feeding rate. The shape of the gradient was also affected by the relative hydrophobicities of the comonomers. Copolymerizations exhibited good control for all feeding rates and comonomer feeding ratios, as evidenced by narrow molecular weight distribution (M_w/M_n = 1.20–1.40) and molecular weight increasing smoothly with polymer yield, indicating high initiation efficiency. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1413–1423, 2007     

Poly(ethylene terephthalate) copolymers containing 5‐nitroisophthalic units. I. Synthesis and characterization

Poly(ethylene terephthalate‐co‐5‐nitroisophthalate) copolymers, abbreviated as PETNI, were synthesized via a two‐step melt copolycondensation of bis(2‐hydroxyethyl) terephthalate and bis(2‐hydroxyethyl) 5‐nitroisophthalate mixtures with molar ratios of these two comonomers varying from 95/5 to 50/50. Polymerization reactions were carried out at temperatures between 200 and 270 °C in the presence of tetrabutyl titanate as a catalyst. The copolyesters were characterized by solution viscosity, GPC, FTIR, and NMR spectroscopy. They were found to be random copolymers and to have a comonomer composition in accordance with that used in the corresponding feed. The copolyesters became less crystalline and showed a steady decay in the melting temperature as the content in 5‐nitroisophthalic units increased. They all showed glass‐transition temperatures superior to that of PET with the maximum value at 85 °C being observed for the 50/50 composition. PETNI copolyesters appeared stable up to 300 °C and thermal degradation was found to occur in two well‐differentiated steps. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1934–1942, 2000     

Structural effects of amphiphilic block copolymers on the gold nanoplates synthesis. Experimental and theoretical study

Geometric and multi-arms gold nanoplates were synthesized by direct reaction between two different amphiphilic block copolymers and KAuCl₄ in aqueous solution. Amphiphilic copolymers containing blocks of ε-caprolactone and N-vinyl-2-pyrrolidone were used. The block copolymer structures and concentration play a key role on the morphology and size of gold nanoparticles. Copolymers have a dual function as reductant and stabilizer agent. The gold nanoparticles obtained were characterized by transmission electron microscopy (TEM), UV–visible spectroscopy (UV–vis) and dynamic light scattering (DLS). On the other hand, electronic structure calculations, based on density functional theory were performed to support the experimental results. The simple models built with small clusters of gold and co-monomer units provide planar structures complexes with higher stabilization energies. These results agree with the nanoplates obtained experimentally. Moreover, the reactivity analysis based on monoelectronic properties suggests that the formation of aggregates between complexes is favored.     

Effect of sequence distribution on the isothermal crystallization kinetics and successive self-nucleation and annealing (SSA) behavior of poly(ε-caprolactone-co-ε-caprolactam) copolymers

Two types of miscible poly(ε-caprolactone-co-ε-caprolactam) copolymers were studied. In both cases catalyzed hydrolytic ring-opening polymerization was employed. For the first type, the comonomers were added simultaneously to obtain random copolymers. For the second type, the comonomers were added sequentially to obtain block copolymers. Successive self-nucleation and annealing (SSA) and isothermal crystallization studies were performed to both types of copolymers. The SSA results reflect the differences in molecular microstructure: block versus random copolymers. In a wide composition range only the polycaprolactam sequences were capable of crystallization in the random copolymers. Avrami indexes of approximately 3-4 were obtained corresponding to the spherulitic crystallization of these units within the copolymers. The block copolymer samples experienced a relatively small reduction of crystallization kinetics with composition, and this was attributed to the dilution effect caused by the miscible non-crystalline polycaprolactone units. On the other hand, for the random copolymers, the rate of crystallization strongly increased with polycaprolactam content while the energy barrier for secondary nucleation decreased exponentially. The comparison between miscible block and random copolymers provides a unique opportunity to distinguish the dilution effect of the polycaprolactone units (a moderate effect) on the isothermal crystallization and melting of the polyamide phase from the molecular microstructural effect in the random copolymers case (a dramatically strong effect), where the polycaprolactam sequences are interrupted statistically by polycaprolactone sequences.     

Investigation of polycondensation through the copolycondensation of preformed oligomers and bisphenols by a two‐stage solution reaction with tosyl chloride,dimethylformamide, and pyridine

A two‐stage copolycondensation of an equimolar mixture of isophthalic acid and terephthalic acid first with a bisphenol (BP) and then with another BP was carried out with a tosyl chloride/dimethylformamide/pyridine condensing agent. When the preformed oligomers from a BP with no substituent or a methyl substituent were allowed to react with another BP comonomer containing polar SO₂, CO, or Cl groups, the copolycondensation was significantly promoted. Such effects were absent with the unsubstituted BP and the methyl derivative. In addition, during the reaction of oligomers from BPs with polar groups, a similarly polar BP did not react so effectively, and the unsubstituted BP did not have any effect on the copolycondensation. On the basis of the sequence distributions for the resultant copolymers determined by ¹H NMR, it was likely that the copolycondensation could be promoted when the second comonomers were randomly distributed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4024–4031, 2002     

An original route to poly[silylene-co-(2,4-disilapentane-2,4-diyl)] oligomers,efficient precursors of silicon carbide-based ceramics with variable C/Si ratios

Novel oligomers possessing a backbone formed of ((TRIPLE BOND)Si(SINGLE BOND)CH₂(SINGLE BOND)Si(TRIPLE BOND)) and (SINGLE BOND)Si(SINGLE BOND)_n units were prepared by the copolycondensation of bis(chlorosilyl)methanes and various dichlorosilanes in the presence of sodium, in refluxing toluene. The effect of the respective molar ratios of comonomers on the yields and the structure of the copolymers was investigated. The role of substituents on silicon atoms in the ability of these materials to provide convenient ceramic precursors upon pyrolysis was examined. When (TRIPLE BOND)Si(SINGLE BOND)H bonds were present, thermal cross-linking was readily performed and ceramics possessing variable C/Si ratios were prepared.     

Poly(ethylene terephthalate) copolymers containing nitroterephthalic units. I. Synthesis and characterization

The synthesis, microstructure, and thermal behavior of a series of poly(ethylene terephthalate) (PET) copolymers containing nitroterephthalic units are described. These novel copolyesters were synthesized by transesterification followed by melt copolycondensation of dimethyl terephthalate and dimethyl nitroterephthalate mixtures with ethylene glycol. The molar ratio of the two comonomers in the feed varied from 95/5 to 25/75. Furthermore, PET and poly(ethylene nitroterephthalate) homopolymers were synthesized with the same method and comparatively studied. Copolyester compositions were practically the same as in the feed, and weight‐average molecular weights ranged from 10,000 to 60,000. The two monomeric units were randomly distributed along the polymer chain, and the experimentally determined average sequence lengths were in accordance with ideal copolycondensation statistics. Melting temperatures and enthalpies of the copolyesters decreased with increasing content in nitroterephthalic units, and they all showed a single glass‐transition temperature superior to that of PET. They appeared to be stable up to 300 °C, and thermal degradation occurred in two well‐differentiated steps. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3761–3770, 2000     

Pyrolysis of polyacrylonitrile and related polymers—IX: Copolymers of acrylonitrile with vinyl chloride,vinylidene chloride and α-chloroacrylonitrile

In the pyrolysis of copolymers of acrylonitrile with chlorinated comonomers, dehydrochlorination occurs readily and precedes the exothermic oligomerization of the nitrile groups. The comonomer units reduce the intensity of the exotherm reaction but do not effectively block the reaction since it is clear that the oligomerization of nitrile groups remains extensive. Vinylidene chloride and α-chloroacrylonitrile copolymers exhibit excellent thermogravimetric characteristics; it is concluded that crosslinking through the comonomer unit reduces the amount of fragmentation and hence of weight loss from the polymer. The favourable thermoanalytical behaviour suggests that acrylic compositions of this type could be used for carbon fibre processing.     

Contribution to the study of the mechanism of curing of unsaturated polyester resins

The mechanism of copolymerization of monomethyl and dimethyl maleates and fumarates with styrene was studied by analysis of the conformation of the acid units of the resulting copolymers. The absorption bands for C?O stretching and OH stretching in the spectra of the copolymers are fully identical. They are quite different from the spectra of the copolymers obtained from maleic anhydride and styrene that are subsequently treated with absolute methanol to give the monoester which is then esterified with diazomethane to give the diester. The acid units of the copolymers derived from maleic anhydride exist in a gauche configuration; copolymers derived from fumaric units exist in a trans conformation. The identity of copolymers derived from maleic units with those derived from fumaric units but not with those derived from maleic anhydride indicates that the first step in the copolymerization of the maleic units is an isomerization to fumaric units, which are actually the genuine comonomers.     

Synthesis and properties of propene copolymers with ether comonomers

The direct copolymerization of propene with polar comonomers using metallocene catalysts in solution was investigated. As comonomers, two ether compounds were used in comparison to 10-undecene-1-ol as well-investigated comonomer. The ether comonomers were diethylene glycol mono-10-undecenyl ether (DEGUE) and octaethylene glycol-10-undecenyl methyl ether (OEGUME). The influence of the different comonomers on the copolymerization behavior was studied. The copolymers were characterized with respect to their comonomer contents, molar masses, and thermal properties. The incorporation rate of DEGUE and OEGUME into the propene copolymers did not exceed 1.6 mol% for DEGUE and 0.31 mol% for OEGUME and was thus considerably lower than in the reference propene copolymerization with 10-undecene-1-ol. An uncompleted shielding of the oxygen atoms of the ether groups by triisobutyl aluminum (TIBA) to the metallocene catalyst is assumed to be responsible for this behavior. The crystallization kinetics in the copolymers with comparable molar masses is mainly influenced by the side chain density per 1000 propene units, n₁₀₀₀.The incorporation of hydrophilic comonomers into polypropene was expected to alter the surface properties. The slightly lowered water contact angles found on films of copolymers with higher comonomer content indicated the enhanced hydrophilicity of the polypropene copolymer surfaces compared to polypropene (PP).     

A new class of stereoregular vinylene‐arylene copolymers with double‐decker silsesquioxane in the main chain

A synthesis of a new macromolecular class of vinylene‐arylene copolymers with double‐decker silsesquioxane in the main chain is presented. Two transition‐metal‐catalyzed processes, which is silylative‐coupling copolycondensation (SCC) and ADMET copolymerization of divinyl‐substituted double‐decker silsesquioxanes (DDSQ‐2SiVi) with selected diolefins, are reported to be highly efficient tools for the formation of stereoregular copolymers containing DDSQ‐silylene‐vinylene‐arylene units. The copolymeric products are studied in terms of their structural, thermal, and mechanical properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1044–1055     

Copolymerization of N-vinylpyrrolidone with acrylic monomers in vitrifying solutions

The low-temperature copolymerization of N-vinylpyrrolidone with acrylic monomers (acrylic acid, acrylamide, and methyl acrylate) in vitrifying solutions in ethanol and DMF has been studied. It has been shown that the copolymerization proceeds after transition of preliminarily γ-irradiated at 77 K samples from the solid glassy state to a supercooled liquid. Experimental conditions that ensure formation of alternating and random block copolymers have been established. The composition of copolymers is determined by the relative mobility and initial ratio of comonomers in solution.     

Synthesis of AB(BA), ABA and BAB block copolymers of tert-butyl methacrylate (A) and ethylene oxide (B)

Well-defined AB(BA), ABA, and BAB block copolymers of tert-butyl methacrylate (tBMA) (A) and ethylene oxide (EO) (B) have been prepared by sequential living anionic polymerization of the two comonomers, irrespective of their addition order. Diphenyl methyl potassium and naphthalene potassium have been successfully used as mono- and difunctional initiators, respectively. In all cases, molecular weight and composition of the block copolymers can be predicted on the basis of the monomer over initiator molar ratio, and the molecular weight distribution is relatively narrow. Size exclusion chromatography, selective extractions of homopolymers, and ¹H- and ¹³C-NMR spectroscopy support that block copolymerization proceeds without homopolymer formation nor side reactions, e.g., transesterification reactions. The PtBMA blocks have been quantitatively hydrolyzed into polyacid ones with formation of polyacid-b-polyether block copolymers as supported by titration, ¹H-NMR, and IR analysis. © 1992 John Wiley & Sons, Inc.     

Synthesis and characterization of styrenic polymers with pendant pyrazole groups. II

The synthesis of styrenic monomers that have pyrazolic or bipyrazolic pendant groups is described. Their homopolymerization and their copolymerization with maleic anhydride (MA) and N-(3-acetoxy propyl) maleimide is reported. The monomers were prepared from the Williamson reaction between 2-pyridine carbinol, hydroxy monopyrazole, hydroxy bipyrazole, and chloromethyl styrene. The homopolymerizations of such styrenic monomers were tried under different conditions, which led to low molecular weight polymers with a high polydispersity. However, alternating copolymers were obtained using maleic anhydride or N-(3-acetoxy propyl) maleimide as comonomers, as shown by ¹H-NMR, elemental analysis, and reactivity ratios r₁ and r₂. Furthermore, the hydrolysis of the acetate function of different copolymers was performed quantitatively. Unlike the acetoxy copolymers, such products do not have any glass transition temperature. Thermogravimetric investigations have shown that these copolymers exhibit good thermostability. © 1994 John Wiley & Sons, Inc.     

Synthesis of high‐impact biodegradable multiblock copolymers comprising of poly(butylene succinate) and poly(1,2‐propylene succinate) with hexamethylene diisocyanate as chain extender

Block copolymers demonstrate excellent thermal and mechanical properties superior to their corresponding random copolymers and homopolymers. However, it is difficult to synthesize block copolymers comprising of different polyester segments by copolycondensation due to the serious transesterification reaction. In this study, multiblock copolymers comprising of two different polyester segments, i.e. crystallizable poly(butylene succinate) (PBS) and amorphous poly(1,2‐propylene succinate) (PPSu), were synthesized by chain‐extension with hexamethylene diisocyanate (HDI). Amorphous PPSu segment was incorporated to improve the impact strength of PBS. The copolymers were characterized by GPC, laser light scattering (LLS), NMR, DSC, and mechanical testing. The results of ¹³C NMR spectra suggest that multiblock copolymers with regular sequential structure have been successfully synthesized. The data of DSC and mechanical testing indicate that block copolymers possess excellent thermal and mechanical properties with satisfactory tensile strength and extraordinary impact strength achieving upto 1900% of pure PBS. The influence of PPSu ratio and chain length of both the segments on the thermal and mechanical properties was investigated. The incorporation of an amorphous soft segment PPSu imparts high‐impact resistance to the copolymers without obviously decreasing the melting point (T_m). The favorable mechanical and thermal properties of the copolymers also depend on their regular sequential structure. At the same time, the introduction of amorphous PPSu segment enhances the enzymatic degradation rate of the multiblock copolymers. Copyright © 2009 John Wiley & Sons, Ltd.