AN/St悬浮共聚体系中AN在水/油两相间分配及其对共聚物组成的影响

研究了丙烯腈/苯乙烯(AN/St)悬浮共聚体系中AN在水/油两相间的分配及其对AN/St共聚物组成的影响.结果表明,AN分配于水/油两相间,使油相AN的含量低于相同单体配料比的本体聚合,导致生成的AN/St共聚物组成偏离本体共聚.为了准确预测进而控制AN/St悬浮共聚物的组成,提出了在考虑AN相分配的基础上计算AN/St悬浮共聚物组成的模型.计算结果与实验值一致,计算中用到的油相实际竞聚率与本体聚合相同,但该悬浮聚合的表观竞聚率随水/油比的变化而发生较大改变.     

借助微机测算三元共聚体系的竞聚率及不同转化率下共聚物的组成

将单纯形调优法与数值积分法相结合，建立了Ａｌｆｒｅｙ－Ｇｏｌｄｆｉｎｇｅｒ微分方程的数学模型，编制了计算机通用程序。应用此程序可以直接根据三元共聚体系的起始组成、任一转化率下共聚物的组成而求出相应单体的竞聚率；反之，也可求算不同转化率下三元共聚体系共聚物的组成。同时，以苯乙烯、丙烯腈、β－溴代苯乙烯所组成的三元共聚体系为例，验证了此程序的有效性     

正丁基锂、四氢呋喃引发的丁苯共聚合(Ⅱ)——动力学及活性种的反应性

本文提出了n·BuLi-THF引发的阴离子丁苯共聚体系中诸活性种之间的平衡及增长图式,导出了共聚组成方程,讨论了单体的表观竞聚率的含义。此外,还建立了表观增长速度常数k_B和kS与[THF]的关系式,估算出一络合活性种对形成聚丁二烯链节中乙烯基结构的几率。     

丙烯腈,丙烯酸甲酯,衣康酸三元共聚竞聚率的测定

本文主要论述三种单体以不同配比在硫氢酸钠水溶液中进行共聚合，探讨其反应规律，用电子计算机由三元共聚组成方程求出了反应体系中三个单体的六个竞聚率，建立了配料组成、共聚物的组成及计算的竞聚率之间的关系，并对三元共聚竞聚率进行了分析。     

α-甲基苯乙烯与丁二烯阴离子共聚组成研究

本文研究了BuLi-THF引发α-甲基苯乙烯与丁二烯在环己烷中阴离子共聚的共聚组成与聚合活性种的关系,建立了多活性种存在下伴有解聚的共聚组成方程,求得了不同[THF]下的单体表观竞聚率γ_1和γ_2值,并估算了它们的误差。     

核磁共振法测定苯乙烯和甲基丙烯酸正丁酯竞聚率的研究

以苯乙烯（Ｓｔ）－甲基丙烯酸正丁酯（ＢＭＡ）共聚体系为研究对象，在共聚单体组成敏感点附近做重复实验，进行了４０、６０、８０、１００，１２０、１４０℃下的共聚合，用ＮＭＲ方法测定共聚物的组成，用Ｍａｙｏ－Ｌｅｗｉｓ微分组成方程的误差变量法计算竞聚率，同时给出竞聚率的９５％可信椭圆区间．并根据竟聚率对温度的依赖关系得到一组合理的竞聚率值．     

在α-甲基苯乙烯二聚体调节作用下的苯乙烯-丙烯腈乳液共聚

<正> 由于苯乙烯(St)和丙烯腈(AN)竞聚率的差异,在乳液共聚中所得产物为组成不均匀的共聚物,因此一般在反应后期通过复杂计算和实验验证补加消耗快的单体,或采用回收大量单体等方法得到组成均匀的共聚物。St-AN乳液共聚物的分子量较大,产物不     

红外光谱法测定St—BMA的竞聚率

对于共聚合反应中同一对单体的竞聚率,由于采用的实验方法、计算方法不同,可能有几对、甚至上百对不同的数据。在实际生产中已逐渐趋向于在较高温度下进行共聚合,而文献的竞聚率一般均在较低温度下获得,因此缺乏实用意义。本文用FTIR方法测定苯乙烯(St)-甲基丙烯酸正丁酯(BMA)共聚竞聚率参数r_1和r_2,讨论了温度的影响。     

有电荷转移络合物参与的共聚体系竞聚率

从有电荷转移络合物参与的共聚体系增长基元反应出,提出一种有ＣＴＣ参与的共聚体系竞聚率的求法,从中得到４个竞聚率,自由单体和ＣＴＣ的相对活性等信息。     

α-甲基苯乙烯与苯乙烯阴离子共聚合研究——Ⅱ.共聚组成及单体表观竞聚率

本文研究了以正丁基锂为引发剂、四氢呋喃为极性添加剂,在环己烷中进行α-甲基苯乙烯与苯乙烯阴离子共聚合。通过共聚组成及聚合活性种研究,由反应机理推导了该体系的共聚组成方程,求得了不同[THF]下的表观竞聚率值(?)和(?)。     

Alternating copolymerization of polar vinyl monomers in the presence of zinc chloride. I. Propagation and initiation of the copolymerization of acrylonitrile with styrene copolymer

Copolymerization of acrylonitrile with styrene spontaneously occurred on addition of zinc chloride without addition of any other radical initiator. The composition of the copolymer approached that of strictly alternating copolymer as zinc chloride added to the copolymerization system increased. The significance of the apparent monomer reactivity ratios of this copolymerization system was studied from a kinetic point of view, and it was shown that the monomer sequence distribution is indicated by the apparent monomer reactivity ratios. Further, equations which represent the relation between the apparent monomer reactivity ratios and Q,e values at a given salt concentration were derived. These equations reasonably accounted for the decrease of the apparent monomer reactivity ratios of the copolymerization of acrylonitrile with styrene in the presence of zinc chloride and the behavior of the other acrylonitrile copolymerization systems in the presence of zinc chloride. The initiation step of the spontaneous radical copolymerization of acrylonitrile with styrene in the presence of zinc chloride was explained by a cross-initiation mechanism.     

全氟甲基乙烯基醚和其它含氟单体乳液共聚合的竞聚率测定

分别通过气相色谱法测定了全氟甲基乙烯基醚 (PMVE)与偏氟乙烯 (VDF)以及PMVE与四氟乙烯(TFE)二元乳液共聚反应中的气相单体组成和共聚物组成 ,然后用非线性回归法 (RREVM )计算得TFE PMVE及VDF PMVE乳液共聚合反应的表观竞聚率分别为γTFE =3 89和γPMVE =0 0 5以及γVDF =1 0 6和γPMVE =0 11.结合已经测定的TFE VDF二元乳液共聚的表观竞聚率 ,计算了由VDF TFE PMVE三元乳液共聚合反应合成的共聚物组成 ,后者与由1 9F NMR实测的共聚物组成吻合     

Studies on propagating species in cationic polymerization of styrene derivatives by acetyl perchlorate or iodine. III. Effect of salt on cationic copolymerization of styrene derivatives with vinyl ethers by acetyl perchlorate

A common-ion salt, tetra-n-butylammonium perchlorate, was found to affect the monomer reactivity ratios in the cationic copolymerization by acetyl perchlorate of styrene with p-methylstyrene and of 2-chloroethyl vinyl ether with p-methylstyrene, but not those for the copolymerization of 2-chloroethyl vinyl ether with isobutyl vinyl ether. In the copolymerization of p-methylstyrene with styrene or with 2-chloroethyl vinyl ether, the addition of the common-ion salt in a polar solvent shifted the monomer reactivity ratios to those in a less polar solvent. The molecular weight distribution analysis of the copolymer suggested that the addition of the common-ion salt depresses the dissociation of propagating species. Therefore, it was concluded that a propagating species with a different degree of dissociation shows a different relative reactivity towards two monomers. The nature of propagating species was also discussed on the basis of the common-ion effect on the monomer reactivity ratios in various solvents.     

Estimation of monomer reactivity ratios by nonlinear least-squares procedure with consideration of the weight of experimental data

To obtain the optimum values of the monomer reactivity ratios for the copolymerization systems with largely different reactivities between both monomers, a nonlinear least-squares procedure which took into account the weights of experimental data, was proposed and discussed. The weights of the data were treated for the errors arisen from the amounts of monomers charged, the densities of monomers, the weights of copolymer formed, and the composition of copolymer. The least-squares procedure with the consideration of the weights was applicable to both differentiated equation and integrated equation derived by Lewis and Mayo. This procedure was applied to radical copolymerizations of α-substituted crotonic esters with styrene, and reasonable monomer reactivity ratios were obtained. It was noted that errors from the copolymer composition were more important than those from the other factors and that the use of the integrated equation was recommended even when the copolymers were isolated at low conversions.     

Real-Time FTIR Monitoring of the Carbocationic Copolymerization of Isobutylene with Styrene

The carbocationic copolymerization of isobutylene (IB) and styrene (St) was investigated using real time FTIR monitoring. Depending on the concentration of the individual monomers, and their ratio in the feed, initial rapid monomer consumption was observed. Instantaneous reactivity ratios (r_IB(inst) and r_St(inst)) obtained from apparent rate constants of monomer consumption strongly depended on concentration.     

MEASUREMENTS OF MONOMER REACTIVITY RATIOS FOR COPOLYMERIZATION OF STYRENE AND METHYL METHACRYLATE IN CARBON DIOXIDE AT VAPOR-LIQUID EQUILIBRIUM STATE

The monomer reactivity ratios of free radical copolymerization of styrene and methyl methacrylate in carbon dioxide at vapor-liquid equilibrium state(vlCO_2)at 65℃and under 7.5-8.5 MPa were measured.The experimental results showed that,in comparison with the data in bulk copolymerization,the monomer reactivity ratio of St in vlCO_2 increased acompanied by a somewhat decrease in that of MMA.Further analysis of the sequence distributions of these copolymers by ~1H-NMR spectra indicated that there was a sig...     

Monomer reactivity ratios in graft copolymerization

This paper discusses monomer reactivity ratios in various radiation- and redox-initiated graft copolymerizations. The polymers studied were polyethylene, cellulose acetate, poly(vinyl chloride), polytetrafluoroethylene, poly(vinyl alcohol), and poly(methyl methacrylate); the comonomer mixtures were styrene–acrylonitrile, methyl acrylate–styrene, acrylonitrile–methyl acrylate, and vinyl acetate–acrylonitrile. The polymer–comonomer mixture systems were so chosen as to permit study of both homogeneous and heterogeneous systems. The homogeneous systems included systems of low and high viscosity. The heterogeneous systems included both polymers swollen by the comonomer mixture and polymers not swollen by the comonomer mixture. None of the homogeneous grafting systems studied showed deviations from the normal copolymerization behavior under a variety of experimental conditions. Monomer reactivity ratios in graft copolymerization were the same as the values in nongraft copolymerization. The heterogeneous systems in which the polymer was swollen by the comonomer mixture yielded grafted copolymer compositions which were the same as those in nongraft copolymerization. The heterogeneous grafting system polytetrafluoroethylene/styrene–acrylonitrile showed deviations from normal copolymerization behavior at low degrees of grafting when the reaction was only on the polymer surface. The behavior became normal at higher degrees of grafting when the system approaches that in which the polymer is swollen by the comonomers. In all reaction systems, it was found that the use of radiation to initiate the reaction does not in any way affect the copolymerization behavior of the two monomers in a comonomer pair.     

Microemulsion copolymerization of styrene and acrylonitrile with n‐butanol as the cosurfactant

The microemulsion copolymerization of styrene and acrylonitrile in an n‐butanol/cetyltrimethylammonium bromide/oil/water microemulsion system was studied. The solubilization sites of the two monomers were determined with an NMR technique. The results showed that the solubilization behaviors of the two monomers were quite different. Most of the styrene was solubilized in the palisade layer of the microemulsion, whereas the acrylonitrile had an equilibrium distribution in the aqueous phase and palisade layer of the microemulsion. The reactivity ratios of styrene and acrylonitrile in the microemulsion system were different from those in other media. The effect of the monomer feed composition on the copolymerization kinetics was investigated, and the mechanism of nucleation of the latex particles was examined. The experimental results showed that the copolymerization loci were changed from the microemulsion droplets to the aqueous phase when the concentration of acrylonitrile in the monomer feed reached approximately 80%; this could be further proved by the effect of the monomer feed composition on the copolymerization kinetics. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 203–216, 2005     

Radical Copolymerization of Acrylic Monomers. II Effect of Solvent on Radical Copolymerization of Methyl Methacrylate and Styrene

The influence of various solvents on the copolymerization behavior of methyl methacrylate with styrene has been investigated. In these systems there is a significant solvent effect on both r_S and r_M which may be attributed to changes in the dielectric constant of the solvents used. The calculated relative reactivity of the polystyryl radical towards the methyl methacrylate monomer increases with increasing solvent polarity, whereas the reactivity of poly(methyl methacrylate) radical towards styrene monomer decreases. The results obtained are discussed taking into account the behavior of both monomers in homopolymerization with the same experimental conditions as in copolymerization.     

N-vinylthiopyrrolidinone

The polymerization reactivity of N-vinylthipyrrolidinone is described. This monomer readily homopolymerizes and forms copolymers with a wide variety of vinyl monomers. Reactivity ratios in the copolymerization of N-vinylthiopyrrolidinone with styrene and methyl methacrylate are reported and the Alfrey-Price Q and e values calculated. These results indicate the high copolymerization reactivity of this monomer in comparison with the oxo-analog, N-vinylpyrrolidinone. Some of the results are in conflict with previously reported data.