Relationship of the Sequence Distribution of a Polymer to the Catalytic Activity of Its Nd Complex

The sequence distribution of the monomelic units in the styrene-acrylic acid copolymer has been obtained by calculation. The probability of long sequences of styrene increases with an increase in the content of the monomer in the copolymer. The highest distribution of short sequences of styrene takes place for the copolymer containing equimolecular amounts of styrene and acrylic acid. The copolymer which has this latter structure is inadequate for the synthesis of highly active supported complexes. When the distributions of long and short sequences of styrene are approximately equal, the activity of the Nd and Fe prepared polymer complexes is higher.     

Modeling of unseeded emulsion copolymerization of styrene and methyl methacrylate

A mathematical model for the unseeded emulsion copolymerization of styrene and methyl methacrylate has been developed. This model, which includes a new rate coefficient for radical desorption, was used to analyze the effect of the styrene/methyl methacrylate molar ratio in the initial charge on the number of particles, overall conversion and copolymer composition. It was found that the number of particles increased with the methyl methacrylate content and that a drift of the copolymer composition resulted during the polymerization of styrene/methyl methacrylate molar ratios other than 50/50. Good agreement between experimental results and model predictions was achieved.     

Characterization of styrene–acrylonitrile copolymer by pyrolysis gas chromatography

Samples of styrene–acrylonitrile (SAN) copolymer of different compositions, molecular weights, block copolymers, and a blend of styrene and acrylonitrile homopolymers were prepared and characterized by the method of pyrolysis gas chromatography. On decomposition of SAN copolymer samples at 645°C, eleven components were identified, the most important of them being styrene, acrylonitrile, and propionitrile. By examination of the pyrolyzate composition during pyrolysis of the SAN copolymer of different compositions, it was established that the propionitrile yield was definitely decreased when the acrylonitrile concentration in copolymer was about 60 mole-%. Further, from the propionitrile yield, we could distinguish random SAN copolymer from the styrene-acrylonitrile homopolymer blend, and on the basis of propionitrile yield some information on the molecular structure of the copolymer could be obtained. The styrene yield depends linearly on the copolymer composition. This permits determination of copolymer composition on the basis of the styrene yield. Furthermore, the effects of decomposition temperature and of molecular weight on the yields of styrene and acrylonitrile were examined.     

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     

Crystallization behavior of poly(styrene-ethylene) copolymers prepared by sequential polymerization

Polystyrene-ethylene copolymers were prepared by sequential polymerization of styrene and ethylene. The crystallization behaviors of the PSE copolymers were studied by polarized light microscopy, wide angle X-ray diffraction and differential scanning calorimeter. The spherulitic growth rates have a tendency of reduction with increasing of styrene content. The growth rates, the melting points and onset temperatures of melting peaks are lower than those of pure polyethylene. The orthorhombic lattice parameters of relatively low styrene content are slightly larger than those in pure PE and the X-ray diffraction traces are no more typically orthorhombic when the styrene content is relatively high. The DSC analyses on the annealed fractions extracted with temperature gradation elution fractionation revealed that the components in the copolymer could be classified into three types based on the thermal behaviors: styrene ethylene random copolymer, ethylene-predominant copolymer and multi-ethylene segment copolymer.     

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.     

Features of styrene copolymerization with sodium p-styrenesulfonate in solvents of different polarities

The copolymerization of sodium p-styrenesulfonate with styrene is studied in solvents that form homogeneous solutions with mixtures of these monomers and differ in polarity: DMFA, a mixture of 1,4-dioxane with DMF, DMSO, and a DMSO-water mixture. It is shown that the diagrams of the copolymer composition depend on the type of solvent and that their shapes do not obey the Mayo-Lewis model. The copolymers become substantially enriched with styrene units during an increase in the solvent polarity. The main cause of deviation from the classical scheme of binary copolymerization is the selective solvation of growing macroradicals with styrene. This effect becomes more pronounced during an increase in the solvent polarity and a decrease in its dissolving ability with respect to polystyrene and during polymer separation into a heterophase. This conclusion is confirmed by the dependence of the copolymer composition on the initiator concentration.     

Sequence distribution and intramolecular excimer formation in styrene-acrylonitrile copolymers

Styrene-acrylonitrile copolymers, like many other copolymers containing styrene, exhibit both normal and excimer fluorescence. We have shown that the ratio of the excimer to monomer fluorescence intensities in random styrene-acrylonitrile copolymers is linearly dependent upon the concentration of styrene-styrene bonds in the copolymer. This observation is consistent with a photophysical model which allows the energy absorbed by styrene units to migrate freely along the copolymer chain. Some of the energy is emitted in the form of normal fluorescence; some of the energy, trapped by neighbouring styrene-styrene pairs suitably oriented to allow excimer formation, is emitted as excimer fluorescence. The fluorescence characteristics of acrylonitrile-styrene copolymers are contrasted with those of methyl methacrylate-styrene copolymers, in which the methylmethacrylate sequences are believed to present partial barriers to energy migration along the copolymer chains.     

苯乙烯-苯乙烯磺酸钠共聚物的制备及其流变性能

采用乳液聚合合成了一种可作为聚丙烯(PP)纤维可染改性添加剂的苯乙烯-苯乙烯磺酸钠共聚物P(St-co-NaSS)。通过傅里叶转换红外光谱仪(FT-IR)和核磁共振氢谱仪(~1 H-NMR)对共聚物的苯乙烯磺酸钠结构单元进行了表征,研究了反应条件对共聚物磺化度的影响;通过差示扫描量热仪(DSC)和热重分析仪(TG)研究了磺酸基团的引入对共聚物的玻璃化转变温度和起始分解温度的影响;通过旋转流变仪研究了磺化度对共聚物剪切黏度的影响;初步探讨了PP/P(St-co-NaSS)共混体系的染色性能。结果表明:当反应时间为2h,反应温度为70℃,引发剂质量分数为0.6%,苯乙烯磺酸钠的摩尔分数为0.01时,共聚物的磺化度f=6.68%(零切黏度η0=19 620Pa·s,属牛顿流体);在10~(-2)~10~(-1) s~(-1)的剪切速率范围内,P(St-co-NaSS)表现出假塑性流体的特征,具有较好的加工流动性。对于PP/P(St-co-NaSS)共混体系,使用阳离子染料染色时,染色深度(K/S值)为2.603 2,使用分散染料染色时,K/S值为10.168 8。P(St-co-NaSS)适合作为聚丙烯纤维的可染改性添加剂。     

Phase behavior of tetramethylpolycarbonate blends with styrene‐based methacrylate copolymers and their interaction energies

The miscibility of tetramethylpolycarbonate (TMPC) blends with styrenic copolymers containing various methacrylates was examined, and the interaction energies between TMPC and methacrylate were evaluated from the phase‐separation temperatures of TMPC/copolymer blends with lattice‐fluid theory combined with a binary interaction model. TMPC formed miscible blends with styrenic copolymers containing less than a certain amount of methacrylate, and these miscible blends always exhibited lower critical solution temperature (LCST)‐type phase behavior. The phase‐separation temperatures of TMPC blends with copolymers such as poly(styrene‐co‐methyl methacrylate), poly(styrene‐co‐ethyl methacrylate), poly(styrene‐co‐n‐propyl methacrylate), and poly(styrene‐co‐phenyl methacrylate) increase with methacrylate content, go through a maximum, and decrease, whereas those of TMPC blends with poly(styrene‐co‐n‐butyl methacrylate) and poly(styrene‐co‐cyclohexyl methacrylate) always decrease. The calculated interaction energy for a copolymer–TMPC pair is negative and increases with the methacrylate content in the copolymer. This would seem to contradict the prediction of the binary interaction model, that systems with more favorable energetic interactions have higher LCSTs. A detailed inspection of lattice‐fluid theory was performed to explain such phase behavior. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1288–1297, 2002     

SYNTHESIS AND CHARACTERIZATION OF COPOLYMER OF 2,5-BIS[（4-METHOXYPHENYL）OXYCARBONYL]STYRENE AND STYRENE WITH HIGH MOLECULAR WEIGHT

The random copolymers of styrene and 2,5-bis[(4-methoxyphenyloxycarbonyl)styrene] (MPCS) with different copolymerization ratio were synthesized by conventional free radical polymerization. The copolymer having high molecular weight was experimentally elucidated using a combination of proton nuclear magnetic resonance spectroscopy and gel permeation chromatography. The liquid crystalline behavior of the copolymer was studied using differential scanning calorimetry, X-ray diffractometry and polarized optical microscopy. It was found that the liquid crystalline behavior was dependent on the content of styrene. Experimental results show that the copolymer could turn into a liquid crystalline phase at about 180℃ when the content of styrene was less than 20%. The mechanical properties of the copolymer were also studied. Preliminary results indicate that the tensile strength decreases while the tensile modulus increases as the content of MPCS is increased.     

Processing of Acetophenon Bottoms from Distillation of Styrene with Maleic Acid

The kinetic features of dehydration of maleic acid during preparation of a copolymer based on the styrene distillation bottoms from joint production of styrene and propylene oxide were studied. The potential application fields for the copolymer synthesized were analyzed.     

Mechanism and kinetics of ordering in diblock copolymer thin films on chemically nanopatterned substrates

Lamellae forming diblock copolymer domains can be directed to assemble without defects and in registration with chemically nanopatterned substrates. Initially, thin films of the lamellar poly(styrene-b-methyl methacrylate) block copolymer form hexagonally close-packed styrene domains when annealed on chemical nanopatterned striped surfaces. These styrene domains then coalesce to form linear styrene domains that are not fully registered with the underlying chemical surface pattern. Defects coarsen, until defect-free directed assembly is obtained, by breaking linear styrene domains and reforming new structures until registered lamellae have been formed. At all stages in the process, two factors play an important role in the observed degree of registration of the block copolymer domains as a function of annealing time: the interfacial energy between the blocks of the copolymer and the chemically nanopatterned substrate and the commensurability of the bulk repeat period of the block copolymer and the substrate pattern period. Insight into the time-dependent three-dimensional behavior of the block copolymer structures is gained from single chain in mean field simulations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3444–3459, 2005     

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.     

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.     

Simultaneous determination of the styrene unit content and assessment of molecular weight of triblock copolymers in adhesives by a size exclusion chromatography method

The content of styrene units in nonhydrogenated and hydrogenated styrene‐butadiene‐styrene and styrene‐isoprene‐styrene triblock copolymers significantly influences product performance. A size exclusion chromatography method was developed to determine the average styrene content of triblock copolymers blended with tackifier in adhesives. A complete separation of the triblock copolymer from the other additives was realized with size exclusion chromatography. The peak area ratio of the UV and refraction index signals of the copolymers at the same effective elution volume was correlated to the average styrene unit content using nuclear magnetic resonance spectroscopy with commercial copolymers as standards. The obtained calibration curves showed good linearity for both the hydrogenated and nonhydrogenated styrene‐butadiene‐styrene and styrene‐isoprene‐styrene triblock copolymers (r  = 0.974 for styrene contents of 19.3–46.3% for nonhydrogenated ones and r  = 0.970 for the styrene contents of 23–58.2% for hydrogenated ones). For copolymer blends, the developed method provided more accurate average styrene unit contents than nuclear magnetic resonance spectroscopy provided. These results were validated using two known copolymer blends consisting of either styrene‐isoprene‐styrene or hydrogenated styrene‐butadiene‐styrene and a hydrocarbon tackifying resin as well as an unknown adhesive with styrene‐butadiene‐styrene and an aromatic tackifying resin. The methodology can be readily applied to styrene‐containing polymers in blends such as poly(acrylonitrile‐butadiene styrene).     

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.     

Anionic polymerization. IV. Effect of crown ethers on alkylsodium initiator

The polymerization of butadiene and copolymerization of butadiene-styrene with alkylsodium catalyst modified by crown ethers in hydrocarbon solvent has been investigated. This catalyst system produced polybutadiene of high viscosity (2.0–5.0) and high vinyl content (80%) in high conversion (75–95%). These results are in contrast to those obtained with aliphatic ether-modified alkylsodium polymerization which typically gives products of low molecular weight and at low conversion. The copolymerization of butadiene-styrene with alkylsodium catalyst modified by crown ethers gave a copolymer which did not contain block styrene. Although the copolymer did not contain block styrene, there was an unusually high level of incorporation of styrene in the copolymer at low conversion. This behavior is quite different from either modified organolithium or unmodified organosodium initiators, in which the styrene is uniformly and randomly incorporated along the chain.     

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.