Role of carbon nanotube grafted poly(l-lactide)-block-poly (d-lactide) in the crystallization of poly(l-lactic acid)/poly (d-lactic acid) blends: Suppressed homocrystallization and enhanced stereocomplex crystallization
Role of carbon nanotube grafted poly(l-lactide)-block-poly (d-lactide) in the crystallization of poly(l-lactic acid)/poly (d-lactic acid) blends: Suppressed homocrystallization and enhanced stereocomplex crystallization
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碳纳米管接枝聚（L-丙交酯）-嵌段聚（D-丙交酯）在聚（L-乳酸）/聚（D-乳酸）共混物结晶中的作用：抑制同晶化和增强立构复合物结晶
DOI：
10.1016/j.eurpolymj.2016.08.005
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发表时间：
2016
影响因子：
6
通讯作者：
Yang Ming-Bo
中科院分区：
文献类型：
--
作者：
Cao Zhi-Qiang;Sun Xiao-Rong;Bao Rui-Ying;Yang Wei;Xie Bang-Hu;Yang Ming-Bo
自成核被认为是聚合物结晶成核的理想情况;然而，立构复合物（sc）微晶对聚乙烯sc结晶的成核作用，L-乳酸/聚（d-乳酸）（PLLA/PDLA）共混物难以评价，由于sc微晶是通过PLLA和PDLA分子链的分子间堆积形成的，并且sc微晶是均聚化的良好成核剂（hc）PLLA或PDLA的结晶。在目前的工作中，我们提出了一个简单的策略，定制的sc结晶行为的PLLA/PDLA共混物通过原位预制sc微晶。本文合成了多壁碳纳米管（CNT）接枝PLLA-嵌段-PDLA共聚物（CNT-L-D），并将其掺入等摩尔的高分子量PLLA和PDLA共混物中，研究其对sc微晶形成的影响。结果表明，CNT-L-D的加入显著增强了sc结晶，且在等温和非等温熔融结晶过程中，sc微晶只在CNT-L-D含量为10wt%的共混物中形成。在PLLA/PDLA共混体系中加入CNT-L-D后，CNT诱导的接枝PLLA-b-PDLA之间优先形成sc微晶，作为sc结晶的自成核位点。提高了形核密度，同时调控了影响sc晶粒排他性形成的关键因素hc和sc晶化之间的竞争。随着成核密度的显著提高和sc球晶尺寸的减小，sc球晶不能被任何其他生长的hc结晶片层进入，sc球晶的表面不能被hc微晶覆盖，导致sc微晶的排他性形成。
Self-nucleation is considered to be the ideal case for the nucleation of polymer crystallization; however, the nucleation effect of stereocomplex (sc) crystallites for sc crystallization of poly(l-lactic acid)/poly(d-lactic acid) (PLLA/PDLA) blend is hard to be evaluated, due to that sc crystallites form through intermolecular packing of PLLA and PDLA molecular chains and sc crystallite is a good nucleating agent for the homocrystallization (hc) crystallization of PLLA or PDLA. In the current work, we proposed a facile strategy to tailor the sc crystallization behavior of PLLA/PDLA blend through in-situ preformed sc crystallites. Herein, Multi-walled carbon nanotube (CNT) grafted PLLA-block-PDLA copolymer (CNT-L-D) was synthesized and incorporated into an equimolar high-molecular-weight PLLA and PDLA blend to study its effect on the sc crystallites formation. The results manifested that, sc crystallization is highly enhanced by the addition of CNT-L-D, and sc crystallites can be formed exclusively in the blend with 10 wt% CNT-L-D during isothermal and nonisothermal melt crystallization. With the addition of CNT-L-D into the PLLA/PDLA blend, the sc crystallites formed preferentially between grafted PLLA-b-PDLA induced by CNT work as self-nucleation sites for sc crystallization. The nucleation densities are increased, and the competition between hc and sc crystallization which is the key factor influencing the exclusive formation of sc crystallites is tailored simultaneously. With significantly improved nucleation density and reduced sc spherulites size, sc spherulites cannot be entered by any other growing hc crystalline lamellae and the surface of sc spherulites cannot be covered with hc crystallites, leading to exclusive formation of sc crystallites.