苯乙烯/烯烃共聚物的结构与性能研究

Styrene/olefin copolymers have played important roles in polyolefins. The relationship between the structure and properties is of great significance as the bridge between the synthesis and applications of these polymers. The characterization of their complicated chain structure plays a key role in the establishment of the above relationship but it is difficult. Therefore, some styrene/ethylene/alpha-olefin bi- and terpolymers without impurity synthesized by constrained geometry catalysts will be investigated. The composition, comonomer incorporation, monomer insertion mode, stereo configuration and comonomer sequence of the polymers will be determined by some latest Nuclear Maganetic Resonance（NMR）techniques such as polarization transfer and two dimensional quantum coherence techniques, while sequence distributions and lengths of the structural unit will be calculated by the spectral information. In addition, the influence of structure on melting, crystallization, glass transition, stress-strain and rheological behavior of the polymers will be studied. Consequently, the intrinsic relationship between polymer structure and processing, mechanical properties are expected to be achieved, which will guide the synthesis of high-performance polyolefin elastomers with versatile function.

苯乙烯/烯烃共聚物在聚烯烃材料中具有十分重要的地位，其结构与性能间的相互关系是研究该类材料合成与应用的桥梁。而明确表征复杂的聚合物链结构是建立上述关系的关键，也是难点。针对这一情况，本项目以限制几何构型茂金属配合物为催化剂，合成不含杂质的苯乙烯/乙烯/(或)alpha-烯烃二元和三元共聚物作为研究对象。利用极化转移和二维量子相干等多种现代核磁共振技术，明确表征共聚物的结构组成、单体插入率、单体插入方式、空间立构和序列结构，计算结构单元的序列分布与长度。研究上述结构因素对聚合物的熔融、结晶、玻璃化转变、应力-应变以及流变行为的影响，揭示聚合物的结构与加工、力学性能之间的内在联系，指导开发和合成具有不同用途的高性能聚烯烃弹性体材料。

苯乙烯/乙烯共聚物因其诸多优良的性能和广泛的应用而备受关注。其中的苯乙烯/乙烯/alpha-烯烃三元共聚物具有更低的玻璃化转变温度（Tg），可拓宽其在低温条件下的应用.然而，这类聚合物的链结构极其复杂，表征非常困难，因而目前几乎没有对此类聚合物链的碳谱、三元组序列结构、序列分布、序列长度等的研究报道。本项目以限制几何构型钛配合物(CGCs)为催化剂，通过对聚合温度、单体比例、助催化剂用量的调控，我们合成了平均重均分子量高达315.5 kg/mol，苯乙烯和alpha-烯烃含量分别在1.0-47.8 mol%和8.4-65.6 mol%宽范围内调控、Tg低至零下48°C的三个系列苯乙烯/乙烯/丙烯（或1-己烯，1-辛烯）三元共聚物。通过三元共聚物的二维NMR实验(HSQC,HMBC)，对比二元共聚物的化学位移，成功将核磁碳谱中所有共振信号进行合理归属。然后，推断三元组序列结构的序列分布与序列长度的定量计算公式。结果表明，对于苯乙烯含量较低的样品，XXX和XXE为主要的三元组序列单元 (X = alpha-烯烃)。 当苯乙烯含量增加到10mol%以上，XES 和XXX为主要的序列单元，而EES,SES和ESE的含量在所有样品中都比较低。XES序列分布以及X的序列长度都随之增加,而乙烯的序列长度降低。玻璃化转变温度随X含量增加而降低，断裂伸长率则呈增加趋势。