Polymerization of coordinated monomers. III. Copolymerization of acrylonitrile–zinc chloride,methacrylonitrile–zinc chloride or methyl methacrylate–zinc chloride complex with styrene

The 1:1 or 2:1 complex of acrylonitrile, methacrylonitrile, or methyl methacrylate with ZnCl₂ was copolymerized with styrene at the temperature of 0–30°C without any initiator. The structure of the copolymer from methyl methacrylate complex and styrene was examined by NMR spectroscopy. The complexes of acrylonitrile or methacrylonitrile with ZnCl₂ gave a copolymer containing about 50 mole-% styrene units. The complexes of methyl methacrylate yielded an alternating copolymer when the feed molar ratio of methyl methacrylate to styrene was small, but with increasing feed molar ratio the resulting copolymer consisted of about 2 moles of methyl methacrylate per mole of styrene. The formation of a charge-transfer complex of styrene with a monomer coordinated to zinc atom was inferred from the ultraviolet spectra. The regulation of the copolymerization was considered to be effected by the charge-transfer complex. The copolymer resulting from the 2:1 methyl methacrylate–zinc chloride complex had no specific tacticity, whereas the copolymer from the 1:1 complex was richer in coisotacticity than in cosyndiotacticity. The change of the composition of the copolymer and its specific tacticity in the polymerization of the methyl methacrylate complex is related to the structure of the complex.     

苯乙烯-甲基丙烯酸甲酯悬浮-乳液复合聚合过程中聚合物复合粒子组成的变化

采用苯乙烯(St)悬浮聚合过程中滴加甲基丙烯酸甲酯(MMA)乳液聚合组分,悬浮乳液复合聚合(SECP)方法,制备大粒径聚苯乙烯聚甲基丙烯酸甲酯(PS- PMMA)复合粒子.采用FTIR、1H- NMR、13C- NMR分析方法,研究SECP各个时期复合粒子中MMA- St链节摩尔比,发现悬浮粒子中MMA St链节摩尔比逐渐增大,而PMMA乳胶粒子中逐渐减少,表明悬浮相和乳液相间存在物质传递过程.悬浮粒子中MMA链节质量与MMA总投料质量比主要由乳胶粒子生成速率和乳胶粒子向悬浮粒子凝聚速率决定.最终得到的复合粒子除含PS和PMMA均聚物外,还含少量MMA-St共聚物.     

Free-radical multicomponent polymerization reactors and chemical composition distribution

Formulae to calculate the statistically caused instantaneous copolymer composition distribution as well as the chemical distribution of accumulated macromolecules, which is due to polymerization statistics and shifts in mean polymer composition during the reaction process, are derived on the basis of a universal model for free-radical solution polymerization with any number of monomers proceeding in a batch, semi-batch or continuous, ideally mixed vessel. The influence of the reactor type on chemical composition distributions is investigated for a copolymerization of different reactive components (methyl methacrylate/styrene/maleic anhydride), a system with nearly equal reactive monomers (methyl methacrylate/styrene), and the ternary polymerization of methyl methacrylate/styrene/maleic anhydride. Though products of constant mean composition are obtainable in a semi-batch or steady-state continuous reactors, considerable statistical dispersion cannot be removed in any case.     

Determining the absolute, chemical-heterogeneity-corrected molar mass averages, distribution, and solution conformation of random copolymers

We present a method by which to obtain the absolute, chemical-heterogeneity-corrected molar mass (M) averages and distributions of copolymers and apply the method to a gradient random copolymer of styrene and methyl methacrylate in which the styrene percentage decreases from approximately 30% to 19% as a function of increasing molar mass. The method consists of separation by size-exclusion chromatography (SEC) with detection using multi-angle static light scattering (MALS), differential viscometry (VISC), differential refractometry (DRI), and ultraviolet absorption spectroscopy (UV) and relies on the preferential absorption of styrene over methyl methacrylate at 260 nm. Using this quadruple-detector SEC/MALS/UV/VISC/DRI approach, the percentage of styrene (%St) in each elution slice is determined. This %St is then used to determine the specific refractive index increment, corrected for chemical composition, at each elution slice, which is then used to obtain the molar mass at each slice, corrected for chemical composition. From this corrected molar mass and from the chemical-composition-corrected refractometer response, the absolute, chemical-heterogeneity-corrected molar mass averages and distribution of the copolymer are calculated. The corrected molar mass and intrinsic viscosity at each SEC elution slice are used to construct a chemical-heterogeneity-corrected Mark–Houwink plot. The slice-wise-corrected M data are used, in conjunction with the MALS-determined R _G,z of each slice, to construct a conformation plot corrected for chemical heterogeneity. The corrected molar mass distribution (MMD) of the gradient copolymer extends over an approximately 30,000 g/mol wider range than the uncorrected MMD. Additionally, correction of the Mark–Houwink and conformation plots for the effects of chemical heterogeneity shows that the copolymer adopts a more compact conformation in solution than originally concluded.     

Polymerization of coordinated monomers. XIV. Systematic deviations from alternating regulation in copolymerization of methyl methacrylate with styrene in the presence of metal halides

Methyl methacrylate (MMA) and styrene (St) copolymerize in the presence of zinc chloride at 3°C under photoirradiation. The contents of methyl methacrylate in the copolymers obtained at a [ZnCl₂]/[MMA] molar ratio of 0.4 are systematically larger than 53 mole %, which is the limiting value at a small feed ratio of methyl methacrylate. The resulting copolymers are confirmed as the sole products and not the mixtures by thin layer chromatography. The effect of dilution of the monomer feed mixture with toluene on copolymer composition suggests that it depends chiefly on the feed concentration of styrene and hardly at all on monomer feed ratios. Copolymerizations are also conducted in the presence of stannic chloride at ?17°C under photoirradiation and in the presence of ethylaluminium sesquichloride at 0°C with spontaneous initiation. The contents of methyl methacrylate in both copolymers obtained at feed ratios lower than 60 mole % almost correspond to the 1:1 alternating copolymer and increase systematically with higher feed ratios. The systematic deviations of copolymer composition obtained in the presence of metal halides are reasonably interpreted by the participation of the binary molecular complex composed of metal halide and methyl methacrylate in the polymerization of the ternary molecular complex composed of metal halide, methyl methacrylate, and styrene.     

Alternating copolymerization of polar vinyl monomers in the presence of zinc chloride. III. NMR study of methyl methacrylate–styrene copolymer

The copolymer composition curve of the methyl methacrylate–styrene copolymer obtained by the copolymerization in the presence of ZnCl₂ has more alternating tendency than that of ordinary methyl methacrylate–styrene copolymer obtained by radical copolymerization. The fine structure of the copolymer was examined by NMR, and the mechanism of the propagation step of the copolymerization in the presence of ZnCl₂, which was proposed in the first report of this series, was verified.     

Pulsed laser terpolymerization of styrene,methyl methacrylate and methyl acrylate

The propagation rate coefficient of the terpolymerization of styrene, methyl methacrylate and methyl acrylate in bulk was successfully determined at three different monomer compositions. The temperature was varied between 18 and 80°C. The resulting data at 50°C were not in agreement with predictions according to the terminal model with binary reactivity ratios that have been determined by fitting copolymer composition data with the terminal model. This indicates that here also the penultimate unit affects the kinetics.     

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.     

Bivariate distribution in copolymers: A new model

A new model for the bivariate distribution of chain sizes and composition in copolymers is presented. The model combines the sum of a two‐bivariate distribution, and it replaces the previous model that consists of a single entity. The compositional distribution histogram was obtained by summation of the sections of the bivariate distribution that belong to a narrow compositional range. The predictions of the model were compared with mass spectrometric data relative to a block copolymer sample containing structural units of pivalolactone and 3‐hydroxybutyrate with some literature data, namely, mass spectrometric data concerning a random copolymer sample reacted at high conversion containing units of styrene and methyl methacrylate as well as a block copolymer sample containing units of α‐methyl styrene and methyl methacrylate. The new model gives better results than the previous model because it fits better with the experimental compositional distribution histogram of the copolymer samples. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2442–2448, 2002     

Densimeter detector in gel permeation chromatography of copolymers

A commercially available densimeter with a vibrating stainless steel tube was used as a detector in the GPC analysis of styrene/methyl methacrylate copolymers under normal GPC operational conditions. The densimeter was thermostated to ±0.001°C and sample injection concentrations were 4.0 mg/mL. The copolymer samples were polydisperse in molecular weight but uniform in composition. A refractive index detector and the densimeter detector produced comparable estimates of the parameters of the molecular weight distributions. The densimeter is less sensitive to the effects of variations in copolymer composition than differential refractive index or ultraviolet detectors. The only serious drawback to the densimeter is a relative lack of sensitivity. Variations in composition of styrene/methyl methacrylate copolymers over a fairly wide range have no signficant effect on the relation between gel permeation chromatographic elution volume and copolymer molecular weight. In general, however, conventional means of summarizing these data are not applicable to compositionally heterogeneous mixtures. Instrumental and data-handling solutions to this problem are discussed.     

Estimation of Reactivity Ratios from Multicomponent Copolymerizations

Abstract

The composition of the copolymer formed from n monomers in addition polymerization can be expressed in terms of the monomer feed composition and n(n - 1) binary reactivity ratios, according to the familiar simple copolymer model. Reactivity ratios are determined experimentally from cor-responding feed and monomer compositions in binary co-polymerizations. This article reports methods for deriving such reactivity ratios directly from multicomponent polymerization data. Analytical solution of the multi-component copolymer equations is not feasible because of the limited number of experimental points and experimental uncertainty in the copolymer composition. Computer-assisted procedures have been developed to estimate re-activity rates by optimizing the fit of predicted and experimental copolymer compositions, given the monomer feed composition and preliminary values of the reactivity ratios. All n(n - 1) reactivity ratios are adjustable. The methods are demonstrated for styrene/methacrylonitrile/ a-methylstyrene, butadiene/styrene/2-methyl- 5-vinyl- pyridine and acrylonitrile/methyl methacrylate/& methylstyrene systems. Binary reactivity ratios predict ternary copolymer compositions generally well in these cues. Reasons are suggested why reactivity ratios from multicomponent experiments may not match the corresponding parameters from binary copolymerizations.     

Synthesis of Graft Polymers by Copolymerization of Macromonomer. III. Preparation and Copolymerization of Styrene-Terminated Poly(Oxyethylene) Macromonomer

Styrene-terminated poly(oxyethylene) macromonomers (SOE) with narrow molecular weight distribution and quantitative styrene monofunc-tionality were synthesized. In homopolymerization of SOE, conversion of monomer to polymer was shown to be low in spite of high consumption of the vinyl groups of the SOE molecules. Free-radical copolymer-ization of the macromonomer with methyl methacrylate and styrene occurred smoothly, as opposed to homopolymerization. Cumulative copolymer composition and total conversion were determined from the conversions of macromonomer and comonomer (by weight changes) and by proton NMR of the copolymer. The monomer reactivity ratios were found to be r_a = 0.06 and r_b = 2.0 for the copolymerization of SOE macromonomer (a) with methyl methacrylate (b). In this case the macromonomer exhibited considerably lower reactivity than predicted from its low molecular weight model compound. The monomer reactivity ratios estimated for SOE and styrene were r_a = 0.86 and r_b = 1.20. The reactivity of SOE was comparable to, but somewhat lower than, styrene. The graft copolymers were used as activators in the halogen displacement reaction, and it was found that their catalytic activity depends on copolymer composition and chemical structure.     

Influence of reactor operational policies on distributions of chemical composition,molar mass,sequence length and sequence frequency of multicomponent polymers obtained by free-radical polymerization

Remarkable shifts in chemical composition, molar mass, sequence length and sequence frequency will occur in the course of free-radical multicomponent polymerizations, if the reactivities of the comonomers are different and a simple batch reactor is used. It is shown for the terpolymerization system of methyl methacrylate/styrene/maleic anhydride that a semi-batch reactor with appropriate regimes is suitable to obtain products with improved chemical, molecular and sequential homogeneity. However, if polymers with defined inhomogeneities like bimodal molar mass or chemical composition distributions are desired, these are also obtainable by use of appropriate operational policies, which will be illustrated for the homopolymerization of methyl methacrylate and the binary copolymerization of methyl methacrylate/maleic anhydride. Concerning the instantaneous mean chemical composition of polymer molecules, which cannot be measured directly, a new procedure is presented to determine this quantity experimentally.     

An Anomalous Cathode-Initiated Copolymerization of Styrene and Methyl Methacrylate on the Electrode

The cathode-initiated copolymerization of styrene and methyl methacrylate (MMA) in dimethylformamide yielded a copolymer which was found to be a mixture of the high and low molecular weight copolymers. The composition of the former, rich in MMA, was similar to that of a typical anionic copolymer. The latter, of anomalously high styrene content, was assumed to be produced on the cathodic surface via an anionic process, where styrene monomer was preferentially adsorbed. This was confirmed by capacitance measurement of the electrode and sequence analysis of the copolymer.     

Quantifying and Controlling the Composition and ‘Randomness’ Distributions of Random Copolymers

The effect of disparity in the reactivity ratios of monomer pairs on the composition distribution and microstructure of the resultant copolymer formed through free‐radical polymerization is quantified computationally. This correlation has been determined for the monomer pairs of styrene/methyl methacrylate and styrene/2‐vinyl pyridine for a variety of monomer feed ratios. These monomer pairs were chosen as they represent systems that have been utilized to experimentally examine the importance of copolymer architecture on its ability to compatibilize an immiscible polymer blend. Moreover, their respective random copolymers show conflicting results for this examination. The results of this work show that the difference in the reactivity ratios of styrene and 2‐vinyl pyridine copolymer (r₁ = 0.5, r₂ = 1.3) significantly broadens the composition and randomness distribution of the resultant copolymer. This breadth is not easily avoided as it evolves even in the early stages of the copolymerization. Conversely, for the styrene/methyl methacrylate pair, the reactivity ratios are similar (r₁ = 0.46, r₂ = 0.52) and this results in a copolymer with a narrow composition distribution and sequence distribution dispersion. Stopping the polymerization at early conversion further narrows both distributions. The presented results, therefore, provide fundamental information that must be considered when planning an experimental procedure to evaluate the relative importance of sequence distribution and composition distribution of a random on its application.     

Preparation of micron-size monodisperse poly(2-hydroxyethyl methacrylate) particles by dispersion polymerization

Dispersion polymerization of 2-hydroxyethyl methacrylate using four categories of polymeric stabilizers in a mixture of good and poor solvents was performed to produce polymeric particles. The stabilizers employed were methyl methacrylate and styrene homopolymers, methacryloyl-terminated poly(methyl methacrylate) and polystyrene macromonomers, an amphiphilic poly(methyl methacrylate-co-methacrylic acid-graft-styrene), and polybutadiene derivatives containing reactive vinyl groups. Dispersion copolymerization with a small amount of the macromonomer gave micron-size particles with relatively narrow size distribution. The amphiphilic graft copolymer and the polybutadiene derivatives also afforded monodisperse particles. The mixed ratio between good and poor solvents greatly affected the particle size and size distribution. © 1996 John Wiley & Sons, Inc.     

Radiation Degradation of Copolymers. III. Poly(styrene-co-methyl Acrylate)

The distribution of volatile products from γ-irradiation of copolymers of styrene and methyl acrylate is independent of the composition of the copolymer and the same as that obtained from poly(methyl acrylate). The yields are less than proportional to the methyl acrylate content, Indicating a protective effect from the styrene units as observed previously in copolymers of styrene with methyl methacrylate. The flexural strengths of the copolymers, measured at 1°C, decrease with radiation dose for high styrene content, but increase for high methyl acrylate content. Samples irradiated in air have appreciably lower strengths than those irradiated in vacuum. Gel measurements show intermediate behavior for the copolymers between the homopolymers.     

Synthesis and characterization of miniemulsion copolymers of methyl methacrylate (or styrene) and stearyl methacrylate

The copolymers of methyl methacrylate (MMA) (or styrene (ST))/stearyl methacrylate (SMA) obtained from miniemulsion polymerization were prepared and characterized. All the miniemulsions showed satisfactory colloidal stability upon aging due to the effectively retarded Ostwald ripening by the reactive costabilizer SMA. In subsequent miniemulsion copolymerizations, monomer droplet nucleation predominated in the particle formation process, but homogeneous nucleation could not be ruled out even at such high levels of SMA (20–50 wt.%). The contact angle first increased rapidly and then leveled off when the SMA content increased from 20 to 50 wt.% for both the copolymers of MMA/SMA and ST/SMA. At constant level of SMA, the copolymer of MMA/SMA with a less hydrophobic composition showed a larger contact angle compared to the ST/SMA counterpart. The contact angle (103 ± 1°) of the copolymer MMA/SMA (50/50 w/w) was comparable to that (104°) of PSMA. A schematic model was proposed to explain the experimental results.     

乙烯基单体／N-苯基马来酰亚胺共聚物组成分布测定原理及应用

共聚物分子量往往根据溶液性质来测定 ,而组成变化对高分子溶液的性质有影响 .如果共聚物组成不随分子量而变化 ,则认为组成分布均匀 .用化学或光谱方法得到的共聚物组成只是一个平均值 ,不能完全表征组成分布情况 .根据溶液性质差异进行分级 ,需选择合适的溶剂 沉淀剂体系 ,且操作时间长 .采用薄层色谱法所需时间亦长 ,且由于存在扩散效应而掩盖真实的共聚物组成分布 .自从凝胶渗透色谱 (ＧＰＣ)出现后 ,将紫外吸收光谱 (ＵＶ)或红外吸收光谱仪与示差折光仪 (ＤＲ)串联 ,一个对组成敏感 ,一个对浓度 (共聚物总量 )敏感 ,将组成变化和分子量…     

Polymerization of vinylcyclopropanes. V. Radical copolymerization of 1, 1-dichloro-2-vinylcyclopropane with monosubstituted ethylenes

A peculiar copolymer composition equation applicable to the radical copolymerization of 1,1-dichloro-2-vinylcyclopropane with monosubstituted ethylenes was developed. The theory was applied to such ethylenes as methyl acrylate, methyl methacrylate, and styrene. The reactivity ratio parameters which give the best fit to the experimental data were determined.