Statistical Copolymers Of Styrene Research Articles

A correlation of the limiting viscosity number, molecular mass and composition of statistical linear styrene–methyl methacrylate copolymers

Statistical copolymers of styrene and methyl methacrylate of different compositions were synthesized by the radical solution copolymerization in a batch isothermal reactor. Copolymers were characterized by the size exclusion chromatography (SEC), elemental analysis and dilute solution viscometry. Experimental limiting viscosity numbers were described by the Mark–Houwink–Kuhn–Sakurada correlation as the function of the molar mass and by the Mendelson correlation as the function of both the molar mass and copolymer composition. A new correlation of the intrinsic viscosity number, molar mass and composition was developed, based on semiempirical considerations. The correlation takes into consideration all the effects which affect the dimensions of random linear copolymer coils in solvents. The new equation was found to be superior to the Mendelson’s one in correlating the experimentally obtained intrinsic viscosities.

Analysis of molecular weight distributions of styrene‐methyl methacrylate copolymers using size exclusion chromatography data

AbstractSize exclusion chromatography (SEC) is a common method for the determination of molecular weight distributions (MWD) of polymers. Using appropriate normalization procedures, MWD data may be put in a form suitable for the description by different theoretical distribution functions. In this paper such a procedure is described and applied to a model system. Statistical copolymers of styrene and methyl methacrylate (SMMA) of different compositions were synthesized by radical copolymerization in a batch isothermal reactor with toluene as solvent and azobisisobutyronitrile as initiator. Copolymer MWDs were obtained by SEC and average copolymer composition by elemental analysis. MWDs of SMMA copolymers were correlated with the lognormal, Flory, Schulz, and Tung theoretical function. The best match between experimental and calculated data was obtained by the Schulz distribution. The α‐parameter of Schulz's function was related to the average molecular weight and showed its maximum at the midpoint of the copolymer composition range, in connection with the observed minimal copolymerization rate. The variation of the b‐parameter was found to be less pronounced; the parameter was related to the polydispersity index. This feature indicated that there was no significant change in the copolymerization reaction mechanism throughout the entire copolymer composition range.

Statistical copolymers of styrene and 2-vinylpyridine with trimethylsilyl methacrylate and trimethylsilyloxyethyl methacrylate

Statistical copolymers of styrene with trimethylsilyl methacrylate, STMS, and trimethylsilyloxyethyl methacrylate, STME, and of 2-vinylpyridine with trimethylsilyloxyethyl methacrylate, VTME were prepared by free radical copolymerization in benzene with 2,2′-azobisisobutyronitrile, AIBN. The reactivity ratios of the different monomers were estimated using the Finemann–Ross, the inverted Finemann–Ross, and the Kelen–Tüdos or the extended Kelen–Tüdos graphical methods. Structural parameters of the copolymers were obtained by calculating the diad sequence fractions, which were derived using the monomer reactivity ratios. The results were compared with those obtained from the copolymerization of styrene and 2-vinylpyridine with methacrylic acid and 2-hydroxyethyl methacrylate.

Photolysis of vinyl ketone copolymers. 4: Macromonomeric products from photolyses of copolymers of styrene and methyl acrylate with methyl vinyl ketone

Some statistical copolymers of styrene and methyl vinyl ketone, prepared by free radical copolymerization, have been photolyzed in benzene solution using u.v. light of wavelength 300 or 350 nm. It is confirmed by n.m.r. spectroscopy that the oligomeric products so obtained have unsaturated end-groups with structures resembling that of α-methyl styrene, as would be expected on the basis of a predominantly Norrish type II photolysis mechanism. The molecular weights of the oligomers slightly exceed those expected from the copolymerization statistics, indicating probably that some slight cross-linking or repolymerization of end-groups accompanies the chain scission. Although not homopolymerizable, the unsaturated styrene oligomers produced by photolysis can be free-radically copolymerized with methyl acrylate, demonstrating that they behave as macromonomers. A copolymer of methyl acrylate with methyl vinyl ketone also gives fragments with unsaturated end-groups on photolysis, but here the accompanying cross-linking or end-group repolymerization is more dominant, leading to oligomeric products with extremely broad molecular weight distributions.

HPLC of synthetic polymers

Statistical copolymers of styrene and acrylonitrile have been separated by high performance precipitation chromatography according to the increase in acrylonitrile content. The separation mechanism was strongly depending on the combination of stationary phase and eluent composition. By applying a typical normal phase gradient from n-heptane (precipitation) to dichloromethane the polymers were adsorbed, after dissolution of the polar groups of the stationary phases. The elution curves became broader with increasing acrylonitrile content of the polymer. By the addition of 20% methanol to the dichloromethane the adsorption could be minimized and copolymer elution was dependent solely on solubility and independent of stationary phase polarity. Separation according to chemical composition was also possible without precipitation with a large pore silica and a normal phase gradient from dichloromethane to the same eluent containing 2.75% methanol.

Separation of stat‐copoly(styrene/2‐methoxyethyl methacrylate) samples according to composition by gradient high‐performance liquid chromatography

AbstractStatistical copolymers of styrene (S) and 2‐methoxyethyl methacrylate (MEMA) (13–87 mass % of the latter monomer) were investigated by gradient HPLC on columns with either silica or CN‐bonded phase packings. The samples were injected in THF solution. The starting eluent was in each case a nonsolvent (isooctane or mixtures of isooctane with THF and methanol). Separation was achieved by increasing the concentration of THF or methanol in the eluent. A calibration mixture of four copolymers (26, 49, 62, and 87% MEMA) was investigated according to the principles of chromatographic cross‐fractionation (CCF) by size exclusion chromatography and subsequent gradient HPLC. The influence of molar mass on HPLC retention was small and, for the samples investigated by CCF, independent of copolymer composition. The composition effect on detector signal was also studied. At 230 nm wavelength and with MEMA content in the range between 20 and 40%, the effect was small and caused the average composition calculated from CCF results to deviate from the directly measured value by not more than 0.2 or 0.8% for the two copolymers investigated.

Kinetics of enthalpy relaxation in glass transition of flexible-chain polymers

Heat capacity has been measured between 308 and 523 K for a number of polymers: four narrow-distribution polystyrene fractions and a non-fractionated polystyrene sample; statistical copolymers of styrene with methyl methacrylate and styrene with acrylonitrile; polycarbonate and polysulphone. The samples were first cooled from the melt at different rates. Parameters in the Moynihan model of enthalpy relaxation accompanying the glass transition were determined for the studied polymers. Empirical correlations were established between a phenomenological parameter characterizing the width of spectrum of relaxation times and the polymer molecular weight and, on the other hand, the dimensionless ratio ΔE/ RT g .

Autooscillating regime of sorption of low molecular weight solvent by ionomers

The kinetics of differential and integral sorption of toluene by statistical copolymers of styrene and acrylic acid (3.8 and 8.0 mole %) has been investigated over the temperature range 20–40°C. The observed autooscillating regime of toluene sorption is due to the competition of different relaxation processes. The effect on sorption kinetics of toluene of the morphology of ionomer films was investigated by infrared spectroscopy.

Kinetics of the radical copolymerization of styrene and 2-methoxyethyl methacrylate

Twenty low-conversion statistical copolymers of styrene and 2-methoxyethyl methacrylate with various composition were prepared. The dependence of the copolymer composition, molecular weight, initiation efficiency and other parameters on the composition of the monomer mixture is discussed. Kinetic data are correlated by means of various models of the copolymerization kinetics. The best fit with experimental data is provided by a diffusion-controlled termination model, especially its dyad variant suggested in this study.

A contribution to the study of the effects of chemical heterogeneity on the ultimate properties of copolymer blends

Blends of statistical copolymers of styrene and 2-methoxyethyl methacrylate differing in their chemical heterogeneity were subjected to slow stress-strain experiments. The chemical heterogeneity of blends was chosen so as to be comparable with the chemical heterogeneity of the common high-conversion random copolymers. No pronounced influence of chemical heterogeneity on the copolymer properties under investigation could be observed, if the variance of chemical composition wasD(w)<10−2.

Interactions in Solutions of Block and Statistical Copolymers of Styrene and Methyl Methacrylate

Interactions in Solutions of Block and Statistical Copolymers of Styrene and Methyl Methacrylate

Préparation de Polystyrènes à Ramification Contrôlée

AbstractPreparation of branched “comblike” polystyrene has been performed by two different methods derived from the anionic grafting techniques. Grafting by carbanionic initiation can be utilized: as its basis we have used statistical copolymers of styrene and p‐bromostyrene. Partial metallation of the p‐bromostyrene units is performed by naphthalene—lithium and the metallated sites are used as initiators for the polymerization of styrene. Thus, branched polystyrene samples were obtained. Grafting by carbanionic deactivation has also been applied. The “backbone” chain is a statistical copolymer of styrene and methylmethacrylate. The ester functions are used as electrophilic deactivators for “living” polystyrene chains. Easily characterizable samples of low polydispersity have been obtained, fractionated, studied by light scattering, and characterized as “comb” polymers. The advantages and disadvantages of both methods are discussed.

Préparation et Étude de Complexes à Transfert de Charge Macromoléculaires avec le Poly‐p‐N,N‐Diméthylaininostyrène

AbstractPreparation of macromolecular charge transfer complexes with several micromolecular acceptors—mainly halogenated quinones—and the individual monomer units of poly‐p‐dimethylaminostyrene, which exhibits electron donating properties, is described in this paper. The reaction is carried out in solvents, and its rate depends mainly upon temperature. The obtained complexes can be isolated easily. The amount of acceptor which is linked to the donor chain depends upon the experimental conditions used and is related to the nature of the acceptor. Reference experiments were carried out with dimethylcumidine, a model molecule, and with statistical copolymers of styrene and dimethylaminostyrene. Changes of the absorption spectra during the CTC formation can be explained in terms of interaction between neighboring donor monomer units by means of the coupled acceptor molecules. The electrical conductivity of these macro‐molecular CTC's has been measured. But when the acceptor is a quinone, the obtained values of the conductivity do not differ much from those of the separate constituents of the CTC.