Phase structure and crystallization behavior of polyethylene in its blends with cis-1,4-butadiene rubber

Phase structure and crystallization behavior of polyethylene(PE) in its blends with cis-1,4-butadiene rubber(BR) at different blend ratios and sample preparation conditions were studied. The PE is finely dispersed in the BR matrix. For samples hot pressed at 145 °C, circular PE microdomains with randomly oriented PE lamellar aggregates were produced. The domain size and number increase with increasing PE content. When the PE content is over 10 wt%, most of the PE domains impinged each other. The separated PE domains are connected by PE stripes with parallel arranged lamellar aggregates. For samples hot pressed at 140 °C, elongated PE microdomains with oriented PE lamellar aggregates were obtained due to the shear flow. The crystallization of PE in the blends depends on the phase structure. Confined crystallization of PE occurs in small microdomains at relatively low temperature. With the increase of domain size, the crystallization ability of PE increases while the confined crystallization decreases.     

Structure of friction-transferred highly oriented poly(3-hexylthiophene) thin films

Oriented thin films of P3HT were obtained by a friction-transfer technique. The morphology and structure of the film were studied by means of optical microscopy, atomic force microscopy and transmission electron microscopy. Optical microscopy observation indicates that large size well-ordered P3HT thin films can be produced by a friction-transfer technique. Highly ordered lamellae were observed in P3HT friction-transferred films by electron microscopy. Electron diffraction results confirm the existence of high orientation with the a- and c-axes of P3HT crystals aligned in the film plane while the c-axis parallel to the friction-transfer direction. The atomic force microscopy observation of the as-prepared P3HT thin film shows, however, a featureless top surface morphology, indicating the structure inhomogeneity of the obtained film. To get highly oriented P3HT thin films with homogenous structure, high temperature annealing, solvent vapor annealing and self-seeding recrystallization of the friction-transferred film were performed. It is confirmed that solvent vapor annealing and self-seeding recrystallization methods are efficient in improving the surface morphology and structure of the frictiontransferred P3HT thin film. Highly oriented P3HT films with unique structure can be obtained through friction-transfer with subsequent solvent vapor annealing and self-seeding recrystallization.     

Morphologies and mechanical properties of <Emphasis Type="Italic">cis</Emphasis>-1,4-butadiene rubber/polyethylene blends

The mechanical properties and phase morphologies of cis-1,4-butadiene rubber (BR) blended with polyethylene (PE) at different blend ratios were studied. The tensile test results show that the PE exhibits excellent reinforcing capabilities towards BR. Blending BR with PE results in a remarkable enhancement of tensile strength, modulus and the elongation at break simultaneously. An increment of tensile strength from 1.11 MPa to 16.26 MPa was achieved by incorporation of 40 wt% PE in the blends. The modulus and elongation at break of 40/60 PE/BR blends are also about 5 times higher than those of the pure BR treated under exactly the same conditions. The tear test indicates that the tear strength also increases with the increase of PE content. It reaches 58.38 MPa for the 40/60 PE/BR blend, which is approximately 10 times higher than that of the pure BR. Morphological study demonstrates that the PE forms elongated microdomains finely dispersed in the BR matrix when its content is over 30 wt%, which corresponds to the remarkably enhanced mechanical properties. According to the results, reinforcement mechanism of PE toward BR dependent on the microstructure has been discussed and two different mechanisms have been proposed.     

超分子构筑调控合成结构规整的梯形聚合物及其应用研究

综述了"超分子构筑调控的逐步偶联/聚合法",该方法将高分子化学与超分子化学相结合,利用多种类型的超分子弱键协同作用首先构筑预期的梯形超分子结构,再经聚合得到共价键梯形高分子.利用该方法合成了一系列结构规整的氧桥基和有机桥基梯形聚硅氧烷以及碳基梯形聚酯,并利用侧基间π-π叠加作用实现了对聚合物立体构型控制.扼要介绍了梯形聚合物在先进材料方面的应用,例如梯形聚硅氧烷液晶光致取向膜;由梯形聚硅氧烷合成的管状聚硅氧烷在高室温储存期微电子环氧塑封料方面的应用;以及基于梯形聚硅氧烷的拟筛板聚合物在二阶非线性光学材料方面的应用等.     

利用光学显微镜研究溶剂诱导的梯形苯基聚倍半硅氧烷结晶

通过溶剂诱导结晶的方法研究了梯形苯基聚倍半硅氧烷(PPSQ)的球晶结构. 采用光学显微镜研究了溶液的浓度、溶剂的挥发时间以及温度等影响因素对梯形苯基聚倍半硅氧烷的球晶结构形貌的影响. 实验结果表明:稀释溶液浓度与提高结晶温度在改变球晶的形态方面具有相同的效果. 球晶的尺寸会随着溶液浓度的降低或者结晶温度的升高而增加. 这都归因于梯形苯基聚倍半硅氧烷在二甲苯中的溶解度的增加. 在不改变其它结晶条件的情况下,延长溶剂的挥发时间也会形成更大的球晶. 当在光学显微镜下旋转样品时球晶的结构不会发生改变,这表明球晶具有均一的晶体学取向结构. 负性球晶的特征也表明梯形苯基聚倍半硅氧烷的分子链是沿着球晶的切线方向排列. 考虑到梯形苯基聚倍半硅氧烷具有刚性的分子链,还提出了梯形苯基聚倍半硅氧烷可能的球晶结构模型.     

前言:化工资源有效利用国家重点实验室专刊 ——过程强化与可控聚合

正化工资源有效利用国家重点实验室(北京化工大学)前身为2000年8月成立的可控化学反应科学与技术教育部重点实验室,2006年6月27日由中华人民共和国科学技术部批准筹建国家重点实验室,2009年1月4日正式通过验收.实验室首届学术委员会主任由中国科学院院士周其凤教授担任,首届实验室主任由中国科学院院士段雪教授担任.现任学术委员会主任为周其凤教授,常务副主任为段雪教授,实验室主任为何静教授.     

Induced crystallization behavior of poly(ethylene adipate) by highly oriented polyethylene

The crystallization behavior of poly(ethylene adipate) (PEA) on highly oriented high-density polyethylene (PE) substrate both from solution and isotropic melt was studied by means of optical microscopy, differential scanning calorimetry, atomic force microscopy and electron diffraction. The results show that the PE influences the crystallization of PEA strongly, which results in an epitaxial growth of PEA with well ordered structure. At the boundary of the PE substrate, a transcrystalline PEA layer is observed. Fine structural observation illustrates that the PEA grows on the PE substrate in edge-on lamellae with fixed orientation. Electron diffraction demonstrates that the epitaxial organization of PEA on PE occurs with both polymer chains parallel, which leads to the (00l) PEA diffractions inclined ±23.5° to the chain direction of PE crystals. Combining the real space morphological observation and electron diffraction results, it is concluded that the epitaxial PEA edge-on lamellae are folded in the {00l} lattice planes.     

等规聚丙烯β晶型向α晶型的相转变行为研究进展

等规聚丙烯(iPP)是典型的多晶型半结晶性聚合物,其常见晶型有单斜(α),三方(β),三斜(γ)以及四方或双四方(e),其中稳定性最好的α晶型和处于亚稳态的β晶型工业和经济价值较大,因此二者之间的相转变行为得到了人们的广泛关注.本文综述了近年来β→α-iPP生长相转变的研究进展.在高临界温度(141°C)和低临界温度(100°C)区间内,β-iPP生长速率高于α-iPP,而温度高于141°C,或低于100°C,由于α-iPP在动力学上占优势,β-iPP会发生向α-iPP的生长转变.但由于α-iPP是热力学上最稳定的晶型,β-iPP熔融重结晶过程也会发生β→α-iPP相转变.此外,拉伸形变过程中也会发生β→α-iPP相转变,广泛用于制备聚丙烯气体交换膜、过滤膜或锂电池隔膜等.目前对变形过程中的β→α-iPP相转变机理还存在争议,本文也对2种主要的机理进行了介绍,并对聚丙烯晶型转变行为的研究方向进行了展望.     

左旋聚乳酸/聚(ε-己内酯)共混物在取向聚乙烯基底上的附生结晶行为

利用电子显微镜结合电子衍射研究了左旋聚乳酸/聚(ε-己内酯)(PLLA/PCL)共混物在取向聚乙烯(PE)基底上的结晶行为.纯PLLA在取向PE基底上能够附生结晶,主要形成分子链相互垂直的片晶结构.PCL在PE基质上也能发生附生结晶,导致两者分子链平行.PLLA/PCL共混物在取向PE基底上结晶的形态结构依赖于共混组成.在PLLA含量大于95 wt%时,PCL不影响PLLA与PE的附生结晶行为.当PCL含量增加至10 wt%时,PLLA在PE上的附生结晶行为受到了一定程度的影响.当PCL含量超过40 wt%时,PLLA在PE上的附生结晶被抑制,取而代之是PCL在PE取向基质上附生结晶,产生两者分子链平行的取向片晶.另外,在PLLA含量在50 wt%~30 wt%之间时,体系产生明显的微相分离,微相分离并不影响PCL与PE的附生结晶,在PCL的富集区仍然发生平行链附生结晶,而PLLA的富集区结构变得模糊.当PLLA含量少于20 wt%时,微相分离不明显,少量PLLA应该分散在PCL片晶间的非晶区.     

STEREOREGULAR POLY(CYCLOHEXENE CARBONATE)S:UNIQUE CRYSTALLIZATION BEHAVIOR

<正>An example of crystalline CO_2-based polymer from the asymmetric alternating copolymerization of CO_2 and cyclohexene oxide is reported.Isotacticity of poly(cyclohexene carbonate)(PCHC)has the critical influence on the crystallinity,and only copolymers with a isotacticity of more than 90%are crystallizable.The stereoregular PCHC is a typical semi-crystalline thermoplastic,and possesses a high melting point(T_m)of 215-230℃and a decomposition temperature of ca.310℃.The spherulitic morphology of(R)-PCHC grows in a clockwise spiral from a center,and that of (S)-PCHC is a counterclockwise spiral,while the stereocomplex of(S)-PCHC/(R)-PCHC(1/1 mass ratio)presents lath-like dendritic crystal.The novel crystalline CO_2-based polycarbonate represents a rare example of optically active polymers with unique crystallization behavior.Our findings reflect the critical influence of stereoregularity on the crystallization for this kind of polymeric materials,and may lead to developments of thermal-resistance CO_2 copolymers for application in engineering thermoplastics.