The electroinitiated polymerization of styrene: Part 1

Electrolysis of a solution of styrene and sodium borofluoride in sulpholane gives rise to low molecular weight polystyrene at the anode. The polymerization occurs by a cationic mechanism initiated by electrolytically produced boron trifluoride co-catalysed by either hydrogen fluoride and/or water. Kinetics in a single compartment cell and a divided compartment cell show differences. Acceleration occurs in the anode compartment of the divided cell with current efficiencies higher than those observed in the single cell. This is ascribed to the presence of an electrolytic termination reaction occurring in the single cell.     

The electroinitiated polymerization of styrene: Part 2

Electrolysis of a solution of styrene and sodium borofluoride in dimethyl acetamide gives rise to polystyrene at the cathode. The polymerization occurs by an anionic mechanism initiated by solvated electrons produced during electrolysis. Kinetics in a single compartment cell and a divided compartment cell show differences. Acceleration occurs in the cathode compartment of the divided cell giving rise to high current efficiencies. Evidence is given for the presence of an electrolytic termination reaction occurring in the single cell.     

Minimum end time policies for batchwise radical chain polymerization—II A two-stage process for styrene polymerization

For styrene polymerization, a two-stage process is considered. The first stage, initiated by initiator, is operated along the best isothermal policy for a predetermined number average molecular weight and monomer conversion at end of the stage as described in the previous paper. The second stage is operated at higher temperature level at which thermal initiation polymerization is significant. A mathematical model is proposed for describing the changes of conversion and number average molecular weight with time in the second stage based on the experimental data obtained. All parameters involved in the model are calculable using the kinetic constants of the initiator initiation system and the thermal initiation system. Experimental verification on the optimal temperature policies for the second stage shows promising. Further calculations indicate that the optimal two-stage process can be significantly better than the optimal process of initiator initiation or thermal initiation polymerization.     

Anionic polymerization of styrene: The search for an industrial process

Anionic polymerizations were carried out in the laboratory using a CSTR reactor design and conditions typical of current commercial mass polystyrene plants. Polystyrene having excellent color and polydispersity was produced. Polymer quality, styrene conversion, and molecular weight control were all linked to use of polymerization feed of consistently high purity and polymerization in the 90–110°C temperature range. The results of this study clearly show that high quality polystyrene can be made utilizing anionic polymerization chemistry in existing well mixed mass polystyrene reactors of the CSTR design. The key to the successful practice of this technology is the ability to produce consistently high purity polymerization feed.     

Anionic polymerization of styrene: Integration with styrene monomer production

Anionic polymerization and ethylbenzene dehydrogenation were carried out in the laboratory using continuous reactor designs and conditions typical of current commerical processes. The dehydrogenator was operated at 43–55% conversion with continuous distillation of the ethylbenzene/styrene mixture to remove byproducts that would interfere with the subsequent anionic polymerization. The anionic polymerization was carried out using a reactor of the CSTR type which operated at > 99% conversion of styrene. The volatiles were recovered from the polymer syrup and recycled back to the dehydrogenator. During 4 months of continuous operation the integrated process showed no detrimental buildup of impurities which affected the anionic polymerization or dehydrogenation. The polystyrene produced had excellent color, clarity, thermal stability, and polydispersity (M_w/M_n = 2.1–2.4). The ability to control weight average molecular weight was within a range of 20,000 using an on-line GPC in concert with a colorimeter.     

Syndiotactic-specific polymerization of styrene: catalyst structure and polymerization mechanism

The mechanistic investigation of syndiotactic-specific polymerization of styrene is reviewed, mainly with reference to the research work carried out at the University of Salerno. NMR analysis of the stereochemical structure of s-PS macromolecules, in some cases suitably labelled, provided valuable information concerning the regiochemistry of polyinsertion, the type of addition to the monomer double bond, and the model of stereospecific propagation. Kinetic studies and spectroscopic investigation of the catalytic systems suggested a cationic Ti(III) complex with a strongly π-co-ordinated benzyl-type growing chain as the true active species. This revised version was published online in June 2006 with corrections to the Cover Date.     

Microemulsion polymerization of styrene

Summary Heats of polymerization of three carbazolyl-containing epoxides 9-(2,3-epoxypropyl)carbazole, 1,2-epoxy-6-(9-carbazolyl)-4-oxahexane and 3,6-dibromo-9-(2,3-epoxypropyl) carbazole have been determined on the differential microcalorimeter DAK 1-1A (USSR). The influence of the structure of monomers upon the values of polymerization heat is discussed.     

Thermal polymerization of styrene

An experimental investigation of the kinetics of bulk thermal polymerization of styrene in the temperature range of 200°–230°C is reported. Conversions and molecular weight averages were measured by gel permeation chromatography. At elevated temperatures, oxygen in the polymerization mixture appears to have negligible effect on the rate of polymerization and the molecular weights of the polymer. Experimental evidence suggests that the molecular weight development of the polymer is strongly influenced by transfer reactions.     

流变方法研究液晶体系中苯乙烯的聚合

以太阳光为引发光源、在液晶体系中制备了聚苯乙烯;利用流变的方法研究了苯乙烯的聚合对液晶体系的影响;用偏光显微镜在反应过程中对体系进行监测,得到了聚合前后体系的偏光显微照片;用透射电子显微镜表征了反应产物的形貌。结果表明:反应过程中液晶体系的流变模量逐渐升高,液晶结构有一定的变化;聚苯乙烯的结构和作为模板的液晶结构比较相似。     

Syndiotactic polymerization of styrene: Study of catalyst components and polymerization conditions

Syndiotactic polystyrene (s‐PS) was prepared using monotitanocene catalyst of cyclopentadienyl titanium trichloride (CpTiCl₃) activated by methylaluminoxane (MAO). Solution polymerization was carried out in toluene using different polymerization conditions. Syndiotacticity index (SI) between 68 and 91.6% was obtained. Increasing Al/Ti molar ratio shows an increase in both conversion percentage and SI. The conversion increased linearly with increasing Al/Ti molar ratio in the range studied. The conversion reached to an optimum value of about 65% at styrene/Al molar ratio of 2.83, while no regular behavior of SI was observed with changing the ratio. Effect of temperature of the range 50–80°C on polymerization was studied. The most favorable temperature for the polymerization regarding activity is 70°C; however SI decreased with temperature up to 80°C. H₂ value to 140 mL/100 mL solvent increased the productivity of the catalyst, however further increase of H₂ reduced the activity of the catalyst. Polymerization time of 15 to 125 min shows a decrease in activity. The decrease was sharper for about 30 min of polymerization than longer time. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2216–2221, 2006     

Improved understanding of in-situ polymerization of zinc dimethacrylate: The solid bulk polymerization

In this work, we chose the HNBR/ZDMA composite as a system reinforced by the metal salt of unsaturated carboxylic acids (MSUCA) and systematically studied the evolution of the in-situ polymerization of ZDMA particles during peroxide curing. Differential scanning caborimetry, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and polarization microscopy were used in this study. The microstructure of the remaining micron-sized dispersions in the cured HNBR/ZDMA was verified for the first time, and a new mechanism for in-situ polymerization of ZDMA, i.e., the solid bulk polymerization initialized onto the surface of ZDMA particles, was put forward. Moreover, we discussed how the micron-sized dispersions generated by the solid bulk polymerization of undiffused ZDMA particles affected the crosslink structures and mechanical properties of the vulcanizate.     

Rate of emulsion polymerization of styrene

In emulsion polymerization, the Smith and Ewart theory gives about two or three times the number of polymer particles obtained by experiment. In this paper, a reaction model is proposed which, from the standpoint of reactor design, can give an adequate explanation of the whole course of an emulsion polymerization of monomer highly insoluble in water. Among other things, the generating process of polymer particles is examined in detail. It is demonstrated experimentally that a new parameter proposed here, which represents the degree of difficulty of monomer initiation in micelles, is indispensable in explaining that process. Also confirmed is that monomer initiation takes place more easily in polymer particles than in micelles. According to the new model, the progress of polymerization, i.e., monomer conversion, the number of the polymer particles, and properties of polymer thus produced can be estimated with satisfactory accuracy. Furthermore, approximate equations are derived for easier estimation.     

间规聚苯乙烯催化剂研究进展

间规聚苯乙烯是一种高熔点的高分子材料,具有多方面优异特性,在多个领域有广泛的应用前景。综述用于苯乙烯间规聚合的单中心过渡金属催化剂的研究进展,总结各类催化剂用于聚合的特点。简单的单茂钛催化剂(Cp’Ti X3)是最早用于有效催化苯乙烯间规聚合的催化剂,但活性和间规聚合物含量都有待提高;结构如Cp’Ti Xn L的单茂钛催化剂,通过引进非茂给电子配体,可以大大提高聚合活性,提高间规聚合物比例,某些催化剂还可以实现活性聚合;ⅢB过渡金属(钪和稀土元素)化合物作为间规聚苯乙烯聚合催化剂的研究,有助于理解苯乙烯间规聚合,乃至烯烃配位聚合机理。对间规聚苯乙烯催化剂工业现状和研发需求进行分析。     

树状分子引发苯乙烯的原子转移自由基聚合

从第2代端羟基树状聚芳醚出发,合成了2－溴异丁酸聚芳醚酯（G2－Br),并用红外,核磁,MALDI－TOF质谱和元素分析对其进行了表征,以C2-Br为大分子引发剂,在CuBr/2,2′－联吡啶催化作用下引发苯乙烯的原子转移自由基聚合。考察了聚合时间,单体和引发剂配比,聚合温度等因素对聚合的影响,合成了结构规整,分子量分布较窄的树状－线型嵌段共聚物。     

Multiscale modeling of syndiospecific styrene polymerization

A detailed mathematical model for syndiospecific styrene polymerization based on combining features of the multigrain model (MGM) and the polymeric multigrain model (PMGM). This model has been established to predict the radial monomer concentration within the growing macro particles and the rate of polymerization. The latter, the parameters, have an effect on the molecular weight distribution (MWD). In this model, the effect of intraparticle diffusion resistance and the radius of catalyst particles on the rate of polymerization and MWD were studied. The model simulation showed the presence of a large distribution of monomer concentration across the radius of particles. It was further noticed that the diffusion resistance was most intense at the beginning of the polymerization process. For MWD, the model simulation showed that the existence of diffusion resistance led to have an increase in the molecular weight within a period of time similar to the one needed in the catalyst decay. Moreover, the validation of the model with experimental data given a good agreement results and show that the model is able to predict a correct monomer profile, polymerization rate, particle growth factor and MWD, an algorithm, which embeds physicochemical effects, has been developed to model the industrial reactors.     

Free radical polymerization of p-methyl styrene

An experimental investigation is reported of the free-radical synthesis kinetics of poly(p-methyl styrene) in cyclohexane at low monomer conversion in the temperature range 50°–70°C using AIBN initiator. The p-methyl styrene monomer contained greater than 97% paraisomer. Isothermal conversion/time curves were obtained using glass ampoule reactors and gravimetry and molecular weight distribution and weight-average molecular weights were measured by s.e.c. and low angle laser light scattering photometry (LALLSP). Transfer to small molecules (monomer, cyclohexane, —) was found to be small or negligible with virtually all of the polymer chains formed by termination by combination. Predicted and measured weight-average molecular weights are in good agreement for polymer synthesized at low conversions.     

甘胺酰马来酰亚胺与苯乙烯微乳液共聚合的研究

以苯乙烯-十二烷基硫酸钠-正戊醇-水微乳液(O／W)为体系。研究了甘胺酰马来酰亚胺(GMI)与苯乙烯在微乳液中的共聚合反应。通过实验确定了引发剂的用量，并对乳化剂的用量对单体配比的影响进行了优选。讨论了引发剂浓度对分子量及其分布的影响情况，单体配比对聚合物热性能的影响。用红外光谱(FT-IR)、凝胶色谱(GPC)、热失重(TG)对聚合物的结构与性能进行了表征。     

Diffusion-controlled semibatch emulsion polymerization of styrene

Semibatch emulsion polymerization of styrene under the monomer-starved condition is strongly affected by the gel effect. A mechanistic model based on diffusion-controlled reaction mechanisms is developed to predict the kinetics of semibatch emulsion polymerization. Experimental data available in the literature are employed to assess the proposed model. Reasonable agreement between the model predictions and experimental data is observed. The simulation results suggest that the reaction system approaches Smith–Ewart case II kinetics (n? = 0.5) when the concentration of monomer in the particles is close to the saturation value, whereas the reaction system under the monomer-starved condition is characterized by diffusion-limited reaction mechanisms (n?≥0.5). © 1995 John Wiley & Sons, Inc.