Anionic polymerization of Lewis acid-activated methyl methacrylate by enamines

A novel ionic polymerization of methyl methacrylate (MMA) with a series of enamines (1) in the presence of methylaluminum bis(2,6-di-tert-butylphenoxide) (2) was examined. Both nucleophile (1) and electrophile (2) are indispensable for the present polymerization, in which (1) acts as initiator and (2) as activator. MMA polymerization proceeded smoothly in toluene at or below room temperature (r.t.) in the presence of 1 and 2 (1 ∼ 4 mol %, respectively), went to completion within 1 h, and afforded syndiotactic-rich PMMA with molecular weight distribution (M_w/M_n) in the 1.1 ∼ 1.4 range. The number-average molecular weight (M_n) of the polymer was significantly higher than that calculated from the feed ratio of 1 to the monomer, indicating low initiating efficiency. Kinetic studies coupled with isolation of an intermediate species proved that the real monomeric species involved in both initiation and propagation was a complex of MMA with 2. The effects of the concentrations of 1, 2, and MMA as well as the temperature of polymerization were also examined. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3671–3679, 1999     

XPS investigation of water‐soluble copolymer surfactants on interface

The possible molecule conformation of a new type of polymer surfactant at air/solid interface, acrylamide‐poly(oxyethylene alkyl ether)acrylate‐anionic monomer random copolymers, was studied by X‐ray photoelectron spectroscopy in detail. By means of changing the detection angle, group composition at surface layer in thickness of 0 ∼ 2.5 nm can be obtained. The results show that the surface activity of the copolymers related closely with the conformation of the groups of the copolymers. The hydrophobic backbone of the copolymer plays the most important role in enhancing surface activity. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2297–2302, 1999     

Synthesis and characterization of a novel AB2 monomer and corresponding hyperbranched poly(arylene ether phosphine oxide)s

A novel AB₂ monomer, 4‐(fluorophenyl)‐4′,4″‐(bishydroxyphenyl) phosphine oxide, was synthesized. The monomer was successfully polymerized to a modest molecular weight with various catalysts, including K₂CO₃ and Cs₂CO₃/Mg(OH)₂. Hyperbranched polymers exhibited exceptionally high thermal stability and solubility in conventional polar organic solvents and basic water solutions. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3736–3741, 2000     

过渡金属离子(Cu2+、Cd2+)对藻红蛋白单体的漂白机制

藻胆蛋白是一组同源捕光色素蛋白,由多肽链及相连的开链四吡咯环色团构成。多肽链对色团的调控形成不同藻胆蛋白的特征吸收及荧光光谱。这些色团是藻蓝胆素(吸收带590～670 nm)、藻红胆素(吸收带530～570 nm)和藻尿胆素(吸收带490～500nm)。藻尿胆素由于在共轭体系中含有较少的双键,所以与前二者比,在较短波长有吸收。它们总是与藻红胆素伴生,在藻胆蛋白中作为敏化基团存在。     

MMA-BA无皂乳液共聚合(Ⅰ)

在甲基丙烯酸甲酯(MMA)和丙烯酸丁酯(BA)的无皂乳液聚合体系中,加入少量反应性乳化剂ω-十一烯酸钠(SUA),用粒度分布仪、透射电子显微镜表征了胶粒平均直径、浓度及形态,用离子交换-电导滴定分析了胶粒表面性质。     

聚丙烯共混物一步法反应共混增容的研究

研究了影响聚丙烯／（丙烯腈 苯乙烯）共聚物（ＰＰ／ＡＳ）合金反应挤出生成的各项因素,发现在过氧化二异丙苯（ＤＣＰ）存在的条件下进行反应共混可以发生接枝反应,生成ＰＰ与ＡＳ的相互接枝物．接枝物的生成显著地细化了分散相粒子,改善了合金相形态．为抑制反应共混过程中聚丙烯的降解,同时促进接枝反应,在ＰＰ／ＡＳ／ＤＣＰ反应共混中加入了含适量双键组分的添加剂亚油酸三甘酯（ＧＴＬ）．结果发现,较少量ＧＴＬ的加入就显著抑制了聚丙烯的降解,且进一步改善了合金的相形态．在合适的ＧＴＬ与ＤＣＰ用量下,反应共混不但显著改善了ＰＰ／ＡＳ合金的相形态,而且提高了合金的力学性能,初步确立了聚丙烯共混物一步反应共混挤出增溶的方法．     

P(AM-NVP-DMDA)疏水缔合水溶性共聚物的研究

采用自由基水溶液共聚合法制备了Ｐ（ＡＭ－ＮＶＰ－ＤＭＤＡ）疏水缔合水溶性共聚物。对共聚物的溶液性能进行了研究,包括盐效应、粘温关系、流变性能、热稳定性、与碱、表面活性剂的相互作用、稀溶液性质等。共聚物分子中由于引入了较多的疏水基团而具有较强的疏水缔合效应,在聚合物浓度较低时具有较高粘度。ＮＶＰ结构单元的引入可适当提高共聚物溶液的热稳定性。对共聚物溶液的电镜分析结果表明,在其水溶液中存在着微相分离结构,它对共聚物溶液的增粘起着重要作用。     

Poly(methyl methacrylate) hollow particles by water-in-oil-in-water emulsion polymerization

Poly(methyl methacrylate) particles having hollow structures were produced by water-in-oil-in-water (W/O/W) emulsion polymerization where sorbitan monooleate (Span80) was used as a primary surfactant and sodium laurylsulfate and Glucopen (APG, polypeptide derivative) were used as secondary surfactants. Urethane acrylate having a molecular structure with a hard segment in the molecular backbone, a long soft segment in the middle, and vinyl groups at both ends was employed as a reactive viscosity enhancer. At low concentration of urethane acrylate, only a few particles contained a void in the polymer phase. However, as the concentration of urethane acrylate increased, the number of the particles containing the void increased. This was because urethane acrylate increased the viscosity of the monomer mixture and helped to form the stable W/O/W emulsion droplets, which possibly restricted droplet coalescence during emulsion polymerization. Moreover, at high concentration of urethane acrylate (above 7 wt%), multi-hollow-structured particles were obtained. It is believed that the increase in the lyophilicity of the monomer mixture caused by urethane acrylate led to stronger interfacial activity of the primary surfactant (Span80) and finally resulted in many internal aqueous droplets. Received: 31 July 1998 Accepted: 13 October 1998     

Synthesis and properties of novel polymers having S-methyldibenzothiophenium salt moieties

A polymer having dibenzothiophenium salt moieties [poly(sulfonium salt), 2 ] was prepared by the reaction of poly(2-vinyldibenzothiophene) ( 1 ) with CH₃I and AgBF₄ in CH₂ClCH₂Cl at room temperature for 24 h. The obtained polymer 2 was found to contain 71% of the methyldibenzothiophenium tetrafluoroborate unit. A monomer carrying the sulfonium salt moiety, i.e., 5-methyl-2-vinyldibenzothiophenium tetrafluoroborate ( 4 ), was independently prepared and subjected to radical polymerization to give a polymer ( 5 ) in 88% yield (methyldibenzothiophenium tetrafluoroborate unit: 79%). The thermal decompositions of 2 and 5 took place in two steps; the first step involved the formation of polymer 1 by demethylation. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1779–1784, 1998