Elution behavior of styrene oligomer fractions in supercritical fluid chromatography

Summary In supercritical fluid chromatography (SFC), the elution behavior of styrene oligomers in pentane depends greatly on the degree of oligomerization, n. The influence of capacity ratio, k, on the lower oligomers up to about n=11 resembles the behavior of other substrates of low molecular weight, like aromatic hydrocarbons. Thus, with pentane of 100 bar and below, minima are found in plots of k versus temperature. In contrast, the k of oligomers of higher molecular weight (n>11) increase monotonously with increasing temperature. The studies were performed using oligostyrene fractions obtained by semipreparative SFC fractionation.     

苯乙烯-马来酸酐自由基共聚反应 (Ⅰ)苯乙烯-马来酸酐电荷转移络合反应

电荷转移络合反应机理是研究苯乙烯－马来酸酐自由基交替共聚反应机理的关键。本文简述了苯乙烯－马来酸酐电荷转移络合反应的研究进展。     

A competitive particle nucleation mechanism in the polymerization of homogenized styrene emulsions

The effects of concentrations of surfactant (sodium lauryl sulfate [SLS]) and initiator (sodium persulfate [SPS]) on the polymerization of homogenized styrene emulsions, stabilized by SLS/lauryl methacrylate (LMA) or SLS/stearyl methacrylate (SMA), were studied. The rate of polymerization increases with increasing [SLS] or [SPS]. In addition to monomer droplet nucleation, the formation of particle nuclei in the aqueous phase (homogeneous nucleation) plays a crucial role in the polymerization kinetics. In comparison with the LMA containing polymerization system, monomer droplet nucleation becomes more important when the more hydrophobic SMA was used as the costabilizer. Furthermore, the degree of homogeneous nucleation increases with increasing [SPS].     

Styrene polymerization in ternary microemulsions: effects of water-soluble and oil-soluble initiators

The polymerization of styrene in ternary microemulsions stabilized by the cationic surfactant tetradecyltrimethylammonium bromide was studied as a function of concentrations of water-soluble (potassium persulfate, KPS) and oil-soluble (AIBN) initiators. At a particular molar ratio of the initiators, similar maximum rates of polymerization can be achieved from using both types of the initiators. In addition, both initiated systems produced microlatexes with similar hydrodynamic radius, number of polymer particles, molecular weight of polystyrene and number of polymer chain per latex particle. But the dependencies of these latex parameters on concentrations of KPS and AIBN may not be the same. The polymerization mechanism appears to be similar, irrespective of using KPS or AIBN. It is discussed in terms of effective radicals produced for the polymerization. While the different dependencies of some latex parameters on concentrations of the initiators are attributed to the different efficiencies of the initiators in producing effective radicals.     

碱金属改性Y分子筛的甲苯氧化甲基化反应性能及基酸碱性质

碱金属改性Ｙ分子筛的甲苯氧化甲基化反应性能及其酸碱性质＊周灵萍李伟苏明李赫口亘陶克毅＊＊（南开大学化学系，天津３０００７１）关键词Ｙ型分子筛，甲苯，甲烷，氧化甲基化，苯乙烯，乙苯，酸性，碱性分类号Ｏ６４３／ＴＱ４２苯乙烯和乙苯是重要的化工原料．以往合...     

REVERSE ATOM TRANSFER RADICAL POLYMERIZATION OF STYRENE WITH COPPER-BASED CATALYST

 "Living"/controlled radical polymerization of styrene was carried out with diethyl 2,3-dicyano-2,3-diphenylsuccinate (DCDPS)/CuCl₂/bipyridine (bipy) initiation system at 120℃. The molecular weights of resultant PSt increased with the monomer conversion and the polydispersities were in the range of 1.37 ～ 1.52. A linear ln([M]o/[M])versus time plot was also obtained indicating the constant concentration of growing radicals during the polymerization with this initiation system. End group analysis by ¹H-NMR spectroscopic studies showed that the end groups of the polymer obtained is cω-functionalized by a chlorine group from the catalyst and a-functionalized by a (carbethoxy-cyano-phenyl)methyl group from the fragments of the initiator. Having C1 atom at the chain end, the PSt obtained can be used as a macroinitiator to promote a chain-extension reaction with fresh St and block copolymerization reaction with a second monomer, such as methyl methacrylate, in the presence of CuC1/bipy catalyst via a conventional ATRP process.     

橡胶接枝苯乙烯本体共聚合全程动力学研究(Ⅰ)--接枝行为

橡胶接枝苯乙烯本体聚合的研究目前主要集中于预聚阶段接枝动力学和聚合条件对相转变的影响[1]. 对于后聚阶段, 即相转变后的接枝行为, 尤其是接枝率与橡胶相内包容物的关系、接枝率与高转化率聚合动力学的关系, 接枝率与橡胶相结构的关系等则研究很少. 这些因素对最终聚合物的性能起着至关重要的作用, 因此, 研究橡胶接枝苯乙烯本体聚合相转变以后接枝率的变化, 并找出橡胶相形态演绎过程的规律很有意义.     

Oxidation of Styrene in a Silent Discharge Plasma

A silent discharge plasma reactor has been developed to study the oxidation of styrene vapor in argon/oxygen mixtures. A number of analytical techniques were employed to determine the destruction efficiency and to characterize the intermediate products. The destruction efficiency was measured as a function of initial styrene concentration, temperature, and energy density of the plasma. The formation of solid products was observed in most experiments. At low temperature (100°C), the solid deposit was polymeric in nature, while at high temperature (300°C) the solid appeared to be amorphous carbon. A combination of high temperature and high energy density resulted in high destruction efficiency and minimal production of solid films. The destruction efficiency vs. energy density is shown to be more complex than a simple model predicting exponential behavior. Several reasons for the discrepancy are suggested. The e-folding energy density for the destruction of styrene is compared to literature values for other organic compounds, measured using similar types of plasma reactors.     

甲基丙烯酸-3-三甲氧基硅丙酯/苯乙烯共聚乳胶粒微结构

我们曾制备了核-壳结构的杂化乳胶粒, 并用溶剂将核去除得到杂化空心微胶囊. 但由于此乳液聚合过程十分复杂, 在不同条件下反应得到乳胶粒的微结构有较大不同, 目前尚未见到各反应条件下所得产物微结构的表征和形成机理的研究报道. 本文将系统分析在不同反应条下, MPS和St种子乳液聚合过程中, 得到的乳胶粒壳层杂化聚合物的微结构, 并研究了其形成原因.     

Synthesis and characterization of copolymers of limonene with styrene initiated by azobisisobutyronitrile

The radical copolymerization of limonene with styrene by azobisisobutyronitrile in xylene at 80 ± 0.1 °C for 2 h, under inert atmosphere of N₂, yields alternating copolymers. The kinetic expression is R_p∝[I]^0.5[Sty]^1.0[Lim]^−1.0. The overall activation energy is calculated as 41 kJ/mol. The FTIR and ¹H-NMR spectra of copolymers show bands at 3000 and 1715 cm⁻¹ and peaks at 6.8 δ and 5.3 δ due to phenyl protons of styrene and trisubstituted olefinic protons of limonene, respectively. The values of reactivity ratios r₁(Sty)=0.0625 and r₂(Lim)=0.014, calculated by Kelen-Tüdos method. The Alfrey-Price Q-e parameters for limonene are 0.438 and −0.748, respectively. The penultimate unit effect is favoured in the present system and the value of φ is 38.49.