Kim Chung Sol, Park Seung Soo, Kim Sung Dong, Kwon Su Jin, Baek Jun Won, Lee Bun Yeoul
Department of Molecular Science and Technology, Ajou University, Suwon 443-749, Korea.
Polymers (Basel). 2017 Oct 2;9(10):481. doi: 10.3390/polym9100481.
Triblock copolymers of polystyrene (PS) and a polyolefin (PO), e.g., PS--poly(ethylene--1-butene)--PS (SEBS), are attractive materials for use as thermoplastic elastomers and are produced commercially by a two-step process that involves the costly hydrogenation of PS--polybutadiene--PS. We herein report a one-pot strategy for attaching PS chains to both ends of PO chains to construct PS--PO--PS directly from olefin and styrene monomers. Dialkylzinc compound containing styrene moieties ((CH₂=CHC₆H₄CH₂CH₂)₂Zn) was prepared, from which poly(ethylene--propylene) chains were grown via "coordinative chain transfer polymerization" using the pyridylaminohafnium catalyst to afford di-end functional PO chains functionalized with styrene and Zn moieties. Subsequently, PS chains were attached at both ends of the PO chains by introduction of styrene monomers in addition to the anionic initiator Me₃SiCH₂Li·(pmdeta) (pmdeta = pentamethyldiethylenetriamine). We found that the fraction of the extracted PS homopolymer was low (~20%) and that molecular weights were evidently increased after the styrene polymerization (Δ = 27⁻54 kDa). Transmission electron microscopy showed spherical and wormlike PS domains measuring several tens of nm segregated within the PO matrix. Optimal tensile properties were observed for the sample containing a propylene mole fraction of 0.25 and a styrene content of 33%. Finally, in the cyclic tensile test, the prepared copolymers exhibited thermoplastic elastomeric properties with no breakage up over 10 cycles, which is comparable to the behavior of commercial-grade SEBS.
聚苯乙烯（PS）与聚烯烃（PO）的三嵌段共聚物，例如PS-聚（乙烯-1-丁烯）-PS（SEBS），是用作热塑性弹性体的有吸引力的材料，并且通过两步法进行商业生产，该方法涉及PS-聚丁二烯-PS的昂贵氢化过程。我们在此报告了一种一锅法策略，用于将PS链连接到PO链的两端，以直接从烯烃和苯乙烯单体构建PS-PO-PS。制备了含苯乙烯部分的二烷基锌化合物（（CH₂=CHC₆H₄CH₂CH₂）₂Zn），使用吡啶基氨基铪催化剂通过“配位链转移聚合”在其中生长聚（乙烯-丙烯）链，以得到用苯乙烯和锌部分官能化的双端官能化PO链。随后，除了阴离子引发剂Me₃SiCH₂Li·（pmdeta）（pmdeta = 五甲基二亚乙基三胺）之外，通过引入苯乙烯单体将PS链连接到PO链的两端。我们发现，萃取的PS均聚物的比例较低（约20%），并且在苯乙烯聚合后分子量明显增加（Δ = 27⁻54 kDa）。透射电子显微镜显示在PO基质内分离出尺寸为几十纳米的球形和蠕虫状PS域。对于丙烯摩尔分数为0.25且苯乙烯含量为33%的样品，观察到了最佳拉伸性能。最后，在循环拉伸试验中，制备的共聚物表现出热塑性弹性体性能，在超过10个循环中没有断裂，这与商业级SEBS的行为相当。
