辛酸亚锡催化下开环聚合制备不同物质的量比L-丙交酯/ε-己内酯（LLA/CL）共聚物。核磁共振（1H和13C-NMR）结果表明,共聚物组成与投料比基本一致,聚合过程中酯交换反应导致序列结构重新分布,二级酯交换系数（TII[CLC]）随CL用量增加而增大。共聚物组成明显影响单元序列长度,各序列长度随相应单体投料量增加而增大,CL投料比≤50%的平均序列长度（LLL和LC）与相应的无规序列长度（LRC和LRLL）较接近,共聚物趋于无规分布。差示扫描量热（DSC）和广角X射线衍射（WAXD）表明共聚物是结晶态聚合物,结晶性与单元序列长度密切相关。共聚物组成显著影响其力学性能,随CL物质的量分数增加,且≤35%时表现出屈服形变的特点,具有热塑性弹性体的特征。
Poly（L-lactide-co-ε-caprolactone） with various L-lactide/ε-caprolactone（LLA/CL） mole ratios was pre- pared by ring-opening polymerization using stannous octoate as a catalyst.1H and13C-NMR measurements indicate that the copolymer compositions are in agreement with mole ratios of LLA/CL feed.The transesterification causes re- distribution of comonomer sequences.The coefficient of the second mode of transesterification（[CLC]） increases with CL content increasing.The copolymer composition affects the average sequence length of L-lactidyl（LLL） and caproyl（LC）.BothLLLandLCincrease with the feed proportion of their respective monomers.LLLandLCare close toLRLLandLRCcalculated from a random distribution of units as CL≤50mol%,and distribution of the copolymer is toward a random sequence.Results of DSC and WAXD show that copolymer crystallinity is closely related to the length of their sequence.The copolymer compositions influence significantly their mechanical properties.As the mole content of CL is less than or equal to 35%,the copolymers exhibit the characteristic of yield deformation and high e- lasticity of thermoplastic elastomer.
参考文献
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