Lewis酸引发的LLDPE/PS共混体系的原位反应增容及其结构与性能研究

本文以单组分和双组分Lewis酸为催化剂，采用反应加工的方法，制备了原位反应增容的线性低密度聚乙烯/聚苯乙烯共混物（LLDPE/PS），并对原位反应增容的机理、增容体系的结构性能以及Lewis酸对共混组分的降解作用进行了系统研究。 以FTIR和NMR为手段、二甲苯为模拟化合物，确认LLDPE/PS共混体系在Lewis酸为催化剂作用下发生了LLDPE与PS的接枝反应，LLDPE接枝在PS苯环的对位上。形成的原位接枝共聚物对体系起增容作用。 使用溶剂抽提、SEM、DMA、流变和DSC等手段对以单组分Lewis酸AlCl3 为催化剂的LLDPE/PS共混物的结构性能进行了研究。从溶剂抽提前后的重量比计算了接枝物的含量。催化剂用量较低时体系中的接枝物含量随AlCl3的增加而提高，随着AlCl3进一步增加，接枝物含量不会增加反而下降，发现AlCl3导致均聚物的降解。研究结果表明，共混体系中加入适量的AlCl3催化剂后，分散相尺寸减小，分布均匀，储能模量增加，低频区的复数黏度升高。但AlCl3用量过高时使共混物的分散相尺寸增加，分布均匀度下降，储能模量和复数黏度降低。以GPC为手段研究了单组分 Lewis酸AlCl3对共混组分的降解作用，发现对PS的降解作用显著。 由于单组分Lewis酸催化剂会导致共混组分降解，使共混体系的物理机械性能变劣，为此，我们在LLDPE/PS共混物中引入了双组分Lewis酸催化剂（Me3SiCl、InCl3•4H2O）。结果表明双组分Lewis酸催化剂不但能够催化LLDPE和PS的原位接枝反应，获得高性能的LLDPE/PS合金材料，而且不会引发共混组分PS的降解。在催化剂用量固定时，采用双组分催化剂时共混物的拉伸强度随着LLDPE含量的增加几乎保持不变，但冲击强度有十分明显的提高。对比了加入催化剂前后共混物形貌的变化，增容后的共混物中分散相粒子尺寸显著降低，证明了双Lewis酸良好的催化性能。 对以双Lewis酸为催化剂的共混物的流变行为和结晶行为进行了研究。随着催化剂的加入，两相之间的相互作用增强，因此共混物的复数黏度，储能模量和损耗模量都有不同程度的提高。增容后的LLDPE相区变小，因而在冷却过程中出现不同程度的分步结晶现象。 对单组分和双组分Lewis酸催化剂原位反应增容LLDPE/PS共混体系的机理进行了探讨。机理为Friedel-Crafts烷基化反应。在采用单组分Lewis酸催化剂时， AlCl3与体系中含有的微量水等杂质发生反应，形成一个复合物，然后进一步与聚乙烯中的不饱和的双键发生反应形成碳正离子，并攻击LLDPE分子链从而形成大分子的碳正离子LLDPE+，而这些LLDPE+则通过电子的重排而发生剪切断裂。在催化剂的存在下，这些断裂的LLDPE片断取代PS中的苯环上的质子而发生接枝反应，从而形成LLDPE-g-PS共聚物。采用双组分Lewis酸催化剂时，首先发生双Lewis酸的耦合；耦合后的Lewis酸与水等杂质反应生成复合物，然后与非饱和的LLDPE分子反应生成初级碳正离子；初级碳正离子进攻LLDPE主链，生成较大的碳正离子；LLDPE+碳正离子取代PS苯环对位的质子而生成接枝共聚物。

PS-b-PEO嵌段共聚物薄膜的结晶与微相分离

半结晶性嵌段共聚物中，嵌段间的不相容性导致的微相分离与结晶嵌段的结晶行为之间存在相互竞争与协同作用。现阶段的大部分工作主要集中于半结晶性嵌段共聚物相分离发生后的结晶行为的结晶动力学和内部链折叠，而对于结晶与微相分离同时发生时的结晶与微相分离行为的研究还较少。 本论文以半结晶性的聚苯乙烯和聚环氧乙烷的二嵌段共聚物（PS-b-PEO）薄膜为研究对象，研究其破坏性（break out）结晶行为，以及研究方形片晶与微相分离结构的关系。 首先，本论文研究了不同相分离取向对结晶行为的影响。我们通过控制膜厚得到垂直基底和平行基底的微相分离薄膜。在溶剂蒸汽中，微相分离取向垂直基底时，仅仅是有序度增加，片晶协同生成。退火时间增加，结晶成核控制生长向扩散控制生长转变，导致片晶周围树枝晶生长。微相分离结构为平行基底取向时，焓主要用于取向转变和有序度增加，体系没有片晶生成，仅边缘效应使树枝晶产生。在结晶取向方面，研究了溶剂蒸汽氛围内界面作用改变使分子链轴垂直基底（flat-on）结晶向分子链轴平行基底（edge-on）结晶的转变。随着溶剂分子扩散到基底界面，结晶嵌段PEO与基底相互作用从强变弱，是发生这种转变的决定因素。 其次，从片晶与微相分离相互转变和片晶上微相分离刷的形成两方面研究片晶与微相分离的竞争与协同关系。退火溶剂的选择性影响片晶与微相分离的竞争。在PEO不良溶剂蒸汽环己烷中发生以下转变：片晶生成，逐渐被微相分离破坏，片晶重新生成；PEO良溶剂水中仅存在结晶到微相分离的转变。即晶体溶解，与PS发生微相分离以获得能量上的有利状态。可溶解嵌段的自由体积增加和结晶嵌段的低溶胀性分别是微相分离和结晶发生的关键因素。片晶与微相分离协同关系研究上，通过调控二嵌段共聚物片晶上聚合物刷的密度（小于14.3大于3.8），获得具有微相分离结构的聚合物刷。PS-PS刷的弱相互作用以及PS与PEO（连接PEO片层结构未结晶的PEO链）之间的强不相容性对片层上微相分离刷的形成起来决定作用。

通过阴离子转Ziegler-Natta聚合机理转换合成PS-b-EPM

能够作为聚烯烃材料与其它聚合物材料共混增容剂的、含有聚烯烃链段的嵌段共聚物的合成，对于扩大聚烯烃材料的应用，获得性能优良的共混型聚合物材料具有重要意义。烯烃类单体聚合方法单一，而且其通用的聚合方法，Ziegler-Natta聚合，不是令人满意的合成嵌段共聚物的方法。因此，含有聚烯烃链段的嵌段共聚物的合成一直是比较困难的研究课题之一，近年来发展起来的阴离子转Ziegler-Natta聚合方法为合成这类嵌段共聚物开辟了新途径。阴离子转Ziegler-Natta聚合是利用阴离子聚合所得到的活性聚合物及其反离子与过渡金属化合物组成“Ziegler-Natta”催化剂使烯类单体聚合，从而得到含有聚烯烃链段和阴离子聚合物链段的嵌段共聚物的一种新的合成方法。这种结合两种聚合机理的聚合方法能够有效地避免单一机理聚合方法对单体的要求和限制，从而扩大了嵌段共聚物的合成范围。目前，有关阴离子转Ziegler-Natta聚合方法的研究工作尚属于初步阶段，许多基本问题还没有统一的结论。本工作的目的就是对这一聚合方法的聚合规律，特点等基本问题进行初步探讨，为今后这方面工作的开展奠定初步基础。本工作以阴离子转Ziegler-Natta聚合为方法，以PS-EPM嵌段共聚物为合成对象，并通过对产物的组成、分子量、序列分布、温度转变行为及形态的表征，可初步得到以下结论。1、在较低的催化剂浓度下，可使催化效率比较高。在本聚合体系下，最高可达694克EPM段/克Ti。这一数值与一般非载体钛催化体系相比是比较高的。2、在合适的聚合条件下，如聚合时间较短，聚合温度较低，可得到分子量分布较窄的嵌段共聚物，并且基本上不含有非嵌段烯烃共聚物。3、以聚苯乙烯作为阴离子段聚合物，可发生较明显的β-消除反应，使产物中含有难以分离的烯烃共聚物，本工作以几个单元的聚异戊二烯作为聚苯乙烯活性离子的端基，有效地抑制了β-消除反应的发生，得到了比较纯净的PS-EPM嵌段共聚物。5、由阴离子转来的“Ziegler-Natta聚合具有阴离子聚合和Ziegler-Natta聚合的共同特点，是介于阴离子聚合和Ziegler-Natta聚合之间的一种特殊聚合形式；在聚合初期主要呈现阴离子聚合特征随着聚合的进行，逐渐向具有Ziegler-Natta聚合特征的聚合形式过渡。

Generation of 10 GHz, 1.9 ps optical pulse train using semiconductor optical amplifier and silica-based highly nonlinear fiber

We propose a simple approach to generate a high quality 10 GHz 1.9 ps optical pulse train using a semiconductor optical amplifier and silica-based highly nonlinear fiber. An optical pulse generator based on our proposed scheme is easy to set up with commercially available optical components. A 10 GHz, 1.9 ps optical pulse train is obtained with timing jitter as low as 60 fs over the frequency range 10 Hz-1 MHz. With a wavelength tunable CW laser, a wide wavelength tunable span can be achieved over the entire C band. The proposed optical pulse generator also can operate at different repetition rates from 3 to 10 GHz.

PS-b-P4VP/CoSm杂化材料的制备及其磁性能

用溶液相金属盐沉积法在苯乙烯与4-乙烯基吡啶嵌段共聚物(PS-b-P4VP)胶束中制备了平均直径为12 nm的PS-b-P4VP/Co、PS-b-P4VP/CoSm(nCo∶nSm=3.8∶1,13.0∶1)、PS-b-P4VP/Sm纳米粒子。胶束溶液通过高温回流使磁性成核粒子和磁性金属原子的流动能力和扩散能力提高而获得尺寸均一的颗粒。

Microphase-Separated Brushes on Square Platelets in PS-b-PEO Thin Films

In polystyrene-block-poly(ethylene oxide) thin square platelets can be obtained via fast solvent evaporation by controlling the tethering density (0.08 < sigma < 0.11). The tethering density of the brushes is proportional to the thickness of the PEO crystal and increases with increasing initial solution heating temperature (T-i). When T-i < T-m, where T-m is the melting point of PEO, brushes with microphase-separated structures are observed. The formation of microphase-separated brushes depends on two factors: the strong incompatibility between PS and noncrystalline PEO chains (attached to the crystalline PEO) and the weak interaction between PS-PS brushes.

Reactive compatibilization of LLDPE/PS blends with a new type of Lewis acid as catalyst

The reactive compatibilization of LLDPE/PS (50/50 wt%) was achieved by Friedel-Crafts alkylation reaction with a combined Lewis acids (Me3SiCl and InCl3 center dot 4H(2)O) as catalyst. The graft copolymer at the interface was characterized by Fourier transform infrared spectroscopy and the morphology of the blends was analysized by scanning electron microscopy. It was found that the combined Lewis acids had catalytic effect on Friedel-Crafts alkylation reaction between LLDPE and PS, and the catalytic effect was maximal when the molar ratio of InCl3 center dot 4H(2)O to Me3SiCl was 1:5. The graft copolymer LLDPE-g-PS was formed via the F-C reaction and worked as a tailor-made compatibilizer to reduce the interfacial tension. The mechanical properties of reactive blend with combined Lewis acids as catalyst was notably improved compared to that of physical LLDPE/PS blend and serious degradation had been decreased compared to the reactive blend system with AlCl3 as catalyst; we interpreted the above results in term of acidity of combined Lewis acids.

Rheology, morphology and mechanical properties of LLDPE/PS blends catalyzed by combined Lewis acids

The rheological, morphological and mechanical properties of LLDPE/PS blends with a combined catalyst, Me3SiCl and InCl3 center dot 4H(2)O, were studied in this work. The higher complex viscosity and storage modulus at low frequency were ascribed to the presence of graft copolymers, which were in situ formed during the mixing process. From the rheological experiments, the complex viscosity and storage modulus of reactive blends were higher than the physical blends. The dispersion of LLDPE particles of reactive blending becomes finer than that of physical blends, consistent with the rheological results. As a result of increased compatibility between LLDPE/PS, the mechanical properties of reactive blends show much higher tensile and Izod impact strength than those of physical blends.

Improved amplified spontaneous emission by doping of green fluorescent dye C545T in red fluorescent dye DCJTB : PS polymer films

Amplified spontaneous emission (ASE) characteristics of a red fluorescent dye, 4-(dicy-anomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), and a green fluorescent dye, (10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1] benzopyrano [6,7,8-ij]quinohzin-11-one) (C545T) codoped polystyrene (PS) as the active medium were studied. It was found that the performance of ASE is greatly improved due to the introduction of C545T. By optimizing the concentrations of C545T and DCJTB in PS, an ASE threshold of 0.016 mJ pulse(-1), net gain of 52.71 cm(-1), and loss of 11.7 cm(-1) were obtained. The efficient Forster energy transfer from C545T to DCJTB was used to explain the improvement of the ASE performance in the coguest system.

Transformation from ordered islands to holes in phase-separating P2VP/PS blend films by adding triton X-100

Our previous investigation showed that the ordered hexagonal island pattern in the phase-separating polymeric blend films of polystyrene and poly(2-vinylpyridine) (PS/P2VP) formed due to the convection effect by proper control of PS molecular weight, solvent evaporation rate, and the weight ratio of PS to P2VP. In this paper, we further illustrate that, by adding a proper amount of the surfactant Triton X-100 to the PS/P2VP toluene solution, the ordered hexagonal island pattern can be transformed to the ordered honeycomb pattern. The effects of the amount of Triton X-100 on the surface morphology evolution and the pattern transformation are discussed in terms of the collapse of Triton X-100, phase separation between Triton X-100/P2VP and PS, the interfacial interaction between Triton X-100/P2VP and the mica substrate, and the Benard-Marangoni convection.