十二烷基苯磺酸钡存在下负离子聚合控制聚苯乙烯立构规整性研究

以正丁基锂(n-BuLi)为引发剂,环已烷为溶剂,通过添加十二烷基苯磺酸钡/四氢呋喃(SDBB/THF),对苯乙烯负离子聚合进行了研究.该体系可在60℃聚合得到立构规整性聚苯乙烯,其丁酮不溶物含量可达80%左右.13C-NMR表征结果显示其微观序列组成以等规结构为主,三元组mm和等规五元组mmmm含量可达57%和45%;DSC谱图中不仅有聚苯乙烯玻璃化温度(100℃),而且在211℃有一熔融峰.GPC结果表明,实测分子量与设计分子量差别较大,且分子量分布较宽。     

用一稀土催化剂合成高分子量聚苯乙烯

由Nd(oct)3(Nd)、Al(i-Bu)3(Al)和C4H9Cl(BCL)三组分组成稀土催化体系,催化苯乙烯(St)在环己烷溶剂中进行配位聚合,考察Al/Nd摩尔比、BCL/Nd摩尔比、陈化温度、陈化时间、催化剂用量、聚合温度与时间等因素对苯乙烯聚合、催化活性以及聚苯乙烯产物(PS)分子量与分子量分布的影响.当Al/Nd=8-12(摩尔比),BCL/Nd=5-25(摩尔比),Ta=40-50℃,ta=6-20 h,Tp=40-50℃时,可以得到高分子量聚苯乙烯,其中重均分子量可高达7.6×105.聚合产物中不溶于丁酮的聚苯乙烯的熔点高达268℃,主要含有间规结构聚苯乙烯和少量等规结构聚苯乙烯;偏光显微镜观察结果表明,可溶于丁酮的聚苯乙烯也是含有部分立构规整链段的聚合物.     

二氧化硅胶体晶模板技术制备间规聚苯乙烯有序孔材料

结晶高分子在受限空间中的聚合行为及聚集态均与本体的有着显著的差异 ,因而呈现不同的性能[1] .受限空间是指介观有序的分子筛 .间规聚苯乙烯具有熔点高、结晶速度快、弹性模量高、绝缘及抗溶剂性能优良等特点 ,具有广阔的应用前景 .自从 Ishihara等 [2～ 5]首次报道苯乙烯间规聚合以来 ,国内外对间规聚苯乙烯的均聚和共聚反应进行了大量研究 .苯乙烯在二氧化硅胶体晶中通过自由基聚合得到三维有序聚苯乙烯孔材料 ,实验表明 ,即使在亚微米的受限空间内 ,聚苯乙烯的生成和性质也会发生明显变化 [6] .本文以有序二氧化硅胶体晶为模板 ,在其…     

釜内聚合法制备间规聚苯乙烯与聚丙烯共混复合材料

采用MgCl2 TiCl4 β 二酮 MAO催化体系合成间规聚苯乙烯 (sPS)与等规聚丙烯 (iPP)共混复合材料 .对催化剂的活性和共混复合材料的组成随Al∶Ti和聚合温度的变化进行了表征 ,催化剂的活性可达 1.5× 10 5gB[molTi·h]- 1 ,sPS的含量可控制在 5 5 %～ 82 % .采用示差量热扫描仪 (DSC)和扫描电镜 (SEM)对共混复合材料的热性能和微观结构进行了研究     

间规聚苯乙烯同质多晶现象的研究

间规聚苯乙烯(ｓＰＳ)是由日本出光公司在1985年首先合成,由于其优良的耐热性(熔点高达270℃),立刻被认为有可能或为下一世纪最重要的工程塑料.独特的分子结构,使间规聚苯乙烯具有密度低、尺寸稳定、耐热性、耐溶剂性好等诸多优点,因而引起研究人员的广泛重视.同时,间规聚苯乙烯存在复杂的同质多晶现象,共有α、β、γ和δ四种晶型.以不同的条件从熔体结晶,间规聚苯乙烯可形成平面锯齿结构的α晶和β晶.其中,α晶属六方晶系,晶胞参数为:ａ=263ｎｍ,ｃ=078ｎｍ;β晶是斜方晶,晶胞参数为:ａ=088ｎｍ,ｂ=263ｎｍ,ｃ=078ｎｍ.与传统的全同聚丙烯…     

聚苯乙烯结晶及其晶型转化

介绍了等规和间规聚苯乙烯的合成、晶型及晶体结构研究的进展情况。重点对高间规度聚苯乙烯的各晶型及其相互转化进行了综述。     

等规聚苯乙烯结构与性能研究进展

本文综述了等规聚苯乙烯的结构与性能的研究。着重讨论等规聚苯乙烯的差向立体异构化、结晶行为、凝胶特性及其机械力学性能与结构的关系，同时还讨论了等规聚苯乙烯的加工与应用前景。     

sPS/PA6/蒙脱土纳米复合材料的制备与性能

讨论了间规聚苯乙烯 (sPS) 尼龙 6(PA6) 磺化间规聚苯乙烯 (SsPS H) 蒙脱土纳米复合材料的制备技术和新材料的结构与性能特征 .蒙脱土经层间改性处理后 (MTN) ,可分别将SsPS H和aPS(无规聚苯乙烯 )插入其纳米层间 ,制备出插层型纳米复合物MTN SsPS和MTN aPS .在sPS/PA6/SsPS H三组分共混体系中加入MTN SsPS或MTN aPS ,进行四组分熔融共混即可制备出sPS/PA6/SsPS H/蒙脱土纳米复合材料 .TEM测定证实了蒙脱土在基体中的层厚分布约为 5 0nm .此外 ,采用DSC、DMA、XRD及力学性能测试仪等现代分析方法对sPS/PA6/SsPS H/蒙脱土纳米复合材料的结构与性能进行了详细研究 .研究结果表明这种纳米复合材料具有优良的综合性能     

配位催化苯乙烯乳液聚合的动力学研究

以Ni(COD)2和含磷、氧配体为催化剂,利用乳液聚合法合成了间规聚苯乙烯.对产物进行了13C-NMR、1H-NMR、GPC、TEM、DSC、TG等表征.在此反应体系下,最佳聚合条件为:乳化剂用量为1.50 g,[St]0=1.79 mol·L-1,T=60℃,t=2h,[Ni(COD)2]=1.102 mmol·L-...     

有规立构聚苯乙烯的稀溶液性质

本文报导了有规立构聚苯乙烯,无规立构聚苯乙烯和1∶1混合有规和无规立构聚苯乙烯的分级、粘度和光散射测试结果。发现上述三种聚苯乙烯试样的[η]-M的依赖关系、第二维利系数和均方末端距(当分子量相同时)是有差别的。这种差别超出实验误差范围,而作者们认为是合理的。从而讨论了前人在类似的工作中所得到的结果。     

A peptide motif recognizing a polymer stereoregularity

A combinatorial phage display method was applied to films composed of a stereoregular polymer of methacrylates. The phage clones with selective affinity for isotactic (it) poly(methyl methacrylate) (PMMA) were isolated. Greater amounts of the phage clones bound to it-PMMA, compared to other stereoregular PMMAs. The phage expressing ELWRPTR most strongly bound to the polymer, and the selectivity was also the best. The peptide motif essential for the specific interaction with the stereoregular polymer was revealed.     

Syntheses of polyolefin‐based stereoregular diblock copolymers for self‐assembled nanostructures

The preparation of polyolefin‐based stereoregular diblock copolymers by postpolymerization of ethenyl‐capped syndiotactic polypropylene‐based propylene/norbornene copolymer (sPP‐based P‐N copolymer) led to the successful generation of a structurally uniform stereoregular diblock copolymer for self‐assembly studies. The ethenyl‐capped prepolymer was prepared by conducting propylene/norbornene copolymerization in the presence of Me₂C(Cp)(Flu)ZrCl₂/MAO. Ozonolysis of ethenyl‐capped sPP‐based P‐N copolymer provided the formyl group end‐capped, end‐functionalized prepolymer with a quantitative functional group conversion ratio. Subsequently, connecting the formyl end‐group of the stereoregular prepolymer by coupling with living anionic polystyrene resulted in the high yield production of stereoregular diblock copolymer (sPP‐based P‐N‐block‐polystyrene), which is difficult to prepare by other methods. The resulting stereoregular diblock copolymer possesses precise chemical architecture to self‐organize into consistent nanostructures as evidenced by transmission electron microscopy and small angle X‐ray scattering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4843–4856, 2008     

A Novel GPPS/cis-SB Blend with High Performance

Summary: GPPS/cis-SB blends with high performance were prepared by adding 3–5 wt.-% stereoregular butadiene-styrene block copolymers (cis-SB) with a high cis-1,4 configuration of around 97% into general purpose polystyrene (GPPS). The micromorphology of the GPPS/cis-SB blends was characterized by transmission electron microscopy (TEM). Mechanical properties including tensile and impact properties were studied and the fracture surfaces of tensile and impact test specimens were characterized by scanning electron microscopy (SEM). PB domains of 10–30 nm with a blurry interface were tethered by continuous PS domains. The fracture surface of the tensile test piece of GPPS was relatively smooth while the fractography of patch patterns separated by river patterns was formed when the tensile specimens of GPPS/cis-SB blends were broken, which may be due to the nanometer-scale rubber phases with high cis-1,4 configuration and some partially crystalline PS segments in the cis-SB block copolymer. It is found that GPPS could be greatly toughened by introduction of a small amount of cis-SB and the tensile strength and elongation at break could also be increased.     

Novel Polyolefins Containing Crystallizable Isotactic Polystyrene Side Chains

Vinyl‐terminated isotactic polystyrene macromonomers were copolymerized with ethylene and 1‐octene to new polyolefin graft copolymers with crystallizable polystyrene side chains. The iPS content was varied from 4 to 78 wt.‐% using different metallocene and halfsandwich catalysts. No solubility problems of the stereoregular macromonomer occured, because iPS does not crystallize during polymerization. In addition the polymers show nanophase separation of the polyolefin backbone and the iPS side chains. The crystallization of iPS, having a melting point of about 200 °C, can be achieved by annealing. This synthesis strategy allows the fabrication of a new class of thermoplastic elastomers with improved heat distortion temperatures.

     

Stereoregular polymerization of methyl vinyl ether with fluoro aluminum initiators

The reactions of HF, BF₃, or certain organic fluorine compounds with AlCl₃, (C₂H₅)₃Al, or ethylaluminum chlorides in chlorinated hydrocarbons give rise to gels which exhibit pronounced stereoregular polymerization initiating ability toward methyl vinyl ether. The active sites are believed to involve species of the type RAlF₄. Polymeric products having a wide range of stereoregularities are obtained. Several polymerization variables were examined. The reaction systems exhibit a variety of appearances and interesting rheological sequences. These are the consequences of differential solubility behaviors of the various stereoregular fractions. The most highly stereoregular fractions may be fabricated as fibers, films, or molded objects. Fractions of intermediate stereoregularity exhibit interesting emulsion-forming properties. Stereoregularity is shown to afford a novel control over degree of water absorption in films.     

Orientational control of guest molecules in an organic intercalation system by host polymer tacticity

Four kinds of stereoregular poly(muconic acid)s, which are synthesized by topochemical polymerization and subsequent solid-state hydrolysis, are used as the organic host materials for intercalation. We describe the reaction behavior and layered structure of intercalation compounds using stereoregular poly(muconic acid)s and n-alkylamines as host and guest, respectively. The packing structure of the guest alkylamines was determined by X-ray diffractions as well as IR and Raman spectroscopies. We have found that the orientation of the guest molecules is controlled by the host polymer tacticity, depending on the structure of the two-dimensional hydrogen-bonding network formed in the polymer sheets of the crystals.     

Electric field induced cis-to-trans isomerization of polyphenylacetylene in solid state

A field induced isomerization from cis to trans form in stereoregular cis-rich polyphenylacetylenes (PPAs) was found, and it provides an alternate method to control the order of chromophores in thin solid films.     

Isotactic-b-syndiotactic stereoblock poly(methyl methacrylate) by chiral metallocene/Lewis acid hybrid catalysts

Stereoblock polymerization with chiral ansa-metallocene/strong Lewis acid hybrid catalysts capable of switching stereospecificity of the methyl methacrylate polymerization produces the highly stereoregular isotactic-b-syndiotactic stereoblock poly(methyl methacrylate).     

Ring-opening Polymerization of Enantiopure Bicyclic Ether-ester Monomers toward Closed-loop Recyclable and Crystalline Stereoregular Polyesters via Chemical Upcycling of Bioplastic

Although great successes have been achieved, the preparation of closed-loop recyclable polyesters with high working temperatures still remains as a big challenge. Herein, we present the syntheses of a series of enantiopure bicyclic ether-ester monomers by upcycling of poly(3-hydroxybutyrate) bioplastic. The “living”/controlled ring-opening polymerizations of these enantiopure monomers to produce stereoregular polyesters with controlled molecular weights and well-defined chain ends were achieved. The effects of stereoconfiguration and substituent on polymerization kinetics and thermodynamics as well as the thermal properties of resultant polyesters were investigated. Of note, the stereoregular polyesters are semi-crystalline materials with melting temperatures up to 176 °C, even higher than the commodity polyolefin plastics. These polyesters can be depolymerized back to recover pristine monomers, thus successfully establishing a closed-loop life cycle.     

New Ziegler–Natta polymerization catalysts and new polymers

Models for the explanation of the stereospecific behaviour of Ziegler-Natta catalysts, homogeneous and heterogeneous, are discussed. Structural data on new types of stereoregular polymers, obtained with homogeneous catalysts, are reported.