A series of four‐armed poly(d,l‐lactide)‐block‐poly(d‐lactide) (4‐DL‐D) copolymers were synthesized by ring‐opening polymerization. By fixing the poly(d,l‐lactide) (PDLLA) block length (1 kg mol⁻¹) and changing the poly(d‐lactide) (PDLA) block length (M_n,PDLA = 0, 0.5, 1.1, 1.3, 1.8 and 2.6 kg mol⁻¹), the crystallization and alkaline degradation of the PLLA/4‐DL‐D blends were investigated. The four‐armed PDLLA core of the copolymer inhibited the crystallization of PLLA, while the outer PDLA block could affect the crystallization differently when its length changed. If M_n,PDLA was 0 or 0.5 kg mol⁻¹, the crystallization of PLLA in the PLLA/4‐DL‐D blend was retarded markedly and the degradation rate of the blend films was much faster than that of neat PLLA film. Interestingly, when M_n,PDLA was 1.1 kg mol⁻¹ or higher, stereocomplex (SC) crystallites with different morphologies were formed, and the degradation rate of the PLLA/4‐DL‐D blend decreased gradually with increasing M_n,PDLA. In the PLLA/4‐DL‐D1.1 blend, the SC crystallites acted as nucleators for PLLA homocrystallites, while in the PLLA/4‐DL‐D1.3 blend, small isolated SC crystallites were observed inside the PLLA homospherulites. When M_n,PDLA was 1.8 or 2.6 kg mol⁻¹, a network structure of SC crystallites was formed and the degradation resistance of the films was markedly enhanced. A possible isothermal crystallization mechanism was proposed for the PLLA/4‐DL‐D blends, and the relationship between the crystallization state and degradation behavior was explored. This work revealed that the crystallization state, which was controlled by the PDLA block length, had a significant effect on the degradation behavior of PLLA/4‐DL‐D blend films. © 2020 Society of Chemical Industry

中文翻译：

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聚（l-丙交酯）/四臂聚（d，l-丙交酯）-嵌段-聚（d-丙交酯）共混物（具有不同的聚（d-丙交酯）嵌段长度）的结晶状态与降解行为之间的关系

一系列四臂聚（d，升-丙交酯） -嵌段-聚（d共聚物通过开环聚合而合成丙交酯）（4-DL-d）。通过固定聚（d，l-丙交酯）（PDLLA）嵌段长度（1 kg mol ^-1）并更改聚（d-丙交酯）（PDLA）嵌段长度（M _n，PDLA = 0，0.5，1.1，1.3 ，1.8和2.6 kg mol ^-1），研究了PLLA / 4‐DL‐D共混物的结晶和碱性降解情况。共聚物的四臂PDLLA核抑制了PLLA的结晶，而外部PDLA嵌段在长度变化时对结晶的影响不同。如果M _n，PDLA为0或0.5 kg mol ^-1，则PLLA / 4-DL-D共混物中PLLA的结晶会明显受阻，并且共混膜的降解速度比纯PLLA膜快得多。有趣的是，当M _n，PDLA为1.1 kg mol ^-1或更高时，会形成具有不同形态的立体复合（SC）微晶，并且PLLA / 4-DL-D共混物的降解速率随着M的增加而逐渐降低。_n，PDLA。在PLLA / 4‐DL‐D1.1共混物中，SC微晶充当PLLA均晶的成核剂，而在PLLA / 4‐DL‐D1.3共混物中，在PLLA均球晶中观察到小的孤立的SC微晶。当M _n，PDLA为1.8或2.6kg mol ^-1时，形成SC微晶的网络结构，并且膜的耐降解性显着提高。提出了PLLA / 4‐DL‐D共混物可能的等温结晶机理，并探讨了结晶状态与降解行为之间的关系。这项工作表明，受PDLA嵌段长度控制的结晶状态对PLLA / 4-DL-D共混膜的降解行为具有重要影响。©2020化学工业协会