Functional polythiiranes 7: Surface activity of polythiiranes with PEO side chains

 Some comb-like polythiiranes with PEO side chains were prepared from the corresponding macromonomers. These new materials are amphiphiles and act as surfactants. Their surface tension and interfacial tension are measured and studied in this paper on account of their structures. The lowering of surface tension measured in polymers bearing methyl terminal group in PEO side chains, are in the same range as these observed with polymers of identical structures but different main chains. An increase of the hydrophobic units in the main chain, obtained in copolymers with methylthiirane does not significantly modified the surface tensions. Better lowering is afforded with structures bearing large alkyl groups as terminal group of PEO side chains. On the contrary, some of these macro-molecules with an optimized EO content largely lower the water/xylene surface tension. The main interest of these new materials is their very low cmc and the stabilization of L₁-type microemulsions. Received: 20 May 1997 Accepted: 25 November 1997     

高分子效应

用许多杰出的实例,从高分子骨架的机械支架作用、邻基效应、协同效应、模板聚合等诸方面探论了高分子效应。     

高分子气体分离膜材料的化学结构与气体透过性能之间的关系

本文以硅橡胶和聚酰亚胺为基础,从高分子的化学组成、分子链段的运动能力、侧基的大小及其作用等几个方面,讨论了聚合物的化学结构对其均质膜的气体选择透过性能的影响,以溶解扩散过程对气体分离膜材料的透气行为进行了剖析,井简述高分子化学结构对其成膜时结晶情况的影响及对气体透过的作用;还概述了气体分离膜科学发展的历史以及基本原理.     

Polymeric Catalysts

The present-day position in the field of polymeric catalysts is outlined. The following selected groups of polymeric catalysts are discussed: synthetic hydrolases, immobilized enzymes, phase-transfer catalysts, nucleophilically active bases, polymers with conjugated π-systems, photosensitizers, polymers as carriers for catalytically active metals or ions, and immobilized homogeneous catalysts. Polymeric catalysts have the following valuable properties: insoluble polymeric catalysts are readily separable from reaction solutions and can often be re-used without loss of activity; a hydrophobic matrix protects the organometallic active center from deactivation by oxygen and water; by fixation of finely divided metals on an ion exchanger, multistage reactions may be effected successively in one reactor. Polymeric carriers may influence the catalytic properties; for example, in the case of immobilized enzymes on polyionic carriers the pH of the activity maximum may be shifted.     

Investigation of parameters affecting the on-line combination of supercritical fluid extraction with capillary gas chromatography

Two different injectors, a split/splitless injector and a programmed temperature vaporizer (PTV) injector were investigated as the interface in on-line supercritical fluid extraction (SFE)-capillary gas chromatography (cGC). The parameters affecting the chromatographic peak shapes as well as the quantitative performance of the interfaces in on-line SFE-cGC were identified and studied. Particular attention was paid to the case where modified extraction fluids were used. Experiments were performed on two different samples. The first sample consisted of PAHs spiked on sand at different concentration levels. The other sample was a polymeric material.     

Recent advances in the formation of ultrathin polymeric membranes for gas separations

During the past 20 years membrane systems have been applied to a limited number of commercial gas separations. To further advance membrane-based gas separations, current research efforts focus on optimization of (i) membrane materials, (ii) membrane structures and (iii) membrane system design. In this overview, recent developments in the formation of high-performance gas separation membranes are discussed. The gas separation properties of state-of-the-art integrally skinned asymmetric membranes and thin-film composite membranes are summarized. Future directions for the preparation of advanced gas separation membranes are highlighted.     

Poly(butylene terephthalate)/poly(ε-caprolactone) blends: Influence of PCL molecular mass on PBT melting and crystallization behavior

The isothermal crystallization kinetics and melting behavior of poly(butylene terephthalate) (PBT) in binary blends with poly(ε-caprolactone) (PCL) was investigated as a function of PCL molecular mass by differential scanning calorimetry and optical microscopy. The components are miscible in the melt when oligomeric PCL (M_w = 1250) is blended with PBT, whereas only partial miscibility was found in mixtures with higher molecular mass (M_w = 10,000 and 50,000). The equilibrium melting point of PBT in the homopolymer and in blends with PCL was determined through a non-linear extrapolation of the T_m = f(T_c) curve. The PBT spherulitic growth rate and bulk crystallization rate were found to increase with respect to plain PBT in blends with PCL1250 and PCL10000, whereas addition of PCL50000 causes a reduction of PBT solidification rate. The crystallization induction times were determined by differential scanning calorimetry for all the mixtures through a blank subtraction procedure that allows precise estimation of the crystallization kinetics of fast crystallizing polymers. The results have been discussed on the basis of the Hoffman-Lauritzen crystallization theory and considerations on both the transport of chains towards the crystalline growth front and the energy barrier for the formation of critical nuclei in miscible and partially miscible PBT/PCL mixtures are widely debated.     

Improving the lower detection limit of potentiometric sensors by covalently binding the ionophore to a polymer backbone

The lower detection limit of polymeric membrane ion-selective electrodes (ISEs) is impaired by zero-current ion fluxes through the organic phase. This adverse effect is largely eliminated by covalently attaching the ionophore to a polymer backbone. To this purpose, the Pb²⁺-selective ligand, 4-tert-butylcalix[4] arene-tetrakis(N,N′-dimethylthioacetamide) is substituted on its upper rim by a diol derivative which is subsequently copolymerized with poly(tetrahydrofuran)diol and 2,2,4-trimethylhexamethylene diisocyanate to the corresponding polyurethane. By measurements on sandwich membranes, it is shown that through binding the ionophore to the polymer, the mobility of Pb²⁺ in the ISE membrane is strongly reduced. As a consequence, the response range of such an ISE is extended by several orders of magnitude. This is the case even when using an internal electrolyte that with an ISE based on a mobile ionophore leads to strong deviations from the linear response because of ion uptake from the sample into the membrane or ion release from the membrane into the sample. With a conventional inner filling solution of 10⁻¹ M Pb(NO₃)₂, a lower detection limit of 1.7×10⁻⁹ M Pb²⁺ has been achieved in the presence of 10⁻⁴ M Na⁺.     

含氨基酸侧链的有机硅高分子催化剂 ⅩⅤ.γ-(L-酪氨酰胺基)丙基硅氧烷钯催化剂的合成加氢活性及其结构表征

本文报导了四种不同N/Pd摩尔比的聚γ-(L-酪氨酰胺基)丙基硅氧烷钯催化剂的合成及其催化加氢活性,这类催化剂与聚γ-((L-酷氨酸)丙基硅氧烷钯催化剂相比较,虽然均具有类似的N→Pd配位的活性中心组成,但它们对底物的加氢活性则明显不同,前者对丙烯腈、丙烯酸、环己烯和1-癸烯的催化活性比后者高,对苯乙烯则相反。N/Pd摩尔比、反应温度、溶剂以及体系的pH值对催化活性的影响,两者的情况大致相同,标题催化剂对衣康酸的催化加氢,产物的光学纯度为30％。     

Polymeric thiols as enzyme activators of serum creatine phosphokinase

Several hydrophilic polymeric thiols were prepared from aminoactivated polymeric supports by reaction with N-acetylhomocysteinethiolactone. Supports include agaroses, cellulose, Glycophase™ controlled-pore glass, and Matrex™ acrylic beads. Thiol content in these polymers was 3–72 μmol SH/g dry polymer. Several were effective solid-phase activators of the sulfhydryl-dependent enzyme creatine phosphokinase at concentrations comparable to that of monomeric thiol required for enzyme activation. The kinetic activation curves for the polymeric and the monomeric (thioglucose) activators were similar, suggesting unhindered interaction of the enzyme with the polymeric activator.