微晶
碳纳米管
材料科学
丙交酯
化学工程
差示扫描量热法
结晶
高分子化学
成核
共聚物
聚合
聚合物
复合材料
结晶度
有机化学
化学
热力学
物理
工程类
冶金
作者
Zhiqiang Cao,Xiaorong Sun,Rui‐Ying Bao,Wei Yang,Bin Xie,Mei Yang
出处
期刊:ACS Sustainable Chemistry & Engineering
[American Chemical Society]
日期:2016-04-13
卷期号:4 (5): 2660-2669
被引量:23
标识
DOI:10.1021/acssuschemeng.6b00176
摘要
Multiwalled carbon nanotube (CNT) grafted poly(l-lactide)-block-poly(d-lactide) copolymer (CNT-L-D) was synthesized by ring opening polymerization of d-lactide on the end hydroxyls of poly(l-lactide) (PLLA) prepolymers grafted on the surface of CNT. The stereocomplexation of solution cast and melt crystallized CNT-L-D, PLLA/CNT-L-D, and PDLA/CNT-L-D blends were investigated by differential scanning calorimetry, wide-angle X-ray diffraction, and optical microscopic observation. Solution cast and melt crystallized CNT-L-D copolymer form exclusive stereocomplex (sc) crystallites. The melting temperature, normalized crystallinity, and the fraction of sc crystallites for both solution cast and melt crystallized PDLA/CNT-L-D blends are higher than those of PLLA/CNT-L-D blends, indicating distinct stereocomplexation mechanisms in both blends. The heterogeneous nucleating effect of CNT makes the PLLA block grafted directly on CNT always participate in sc crystallite formation. So, for PDLA/CNT-L-D blends, the stereocomplexation mainly occurs between PLLA blocks and free PDLA molecules, and for PLLA/CNT-L-D blends, the stereocomplexation mainly occurs between PLLA blocks and PDLA blocks. The nucleating effect of CNT enhances the sc formation of free PDLA molecules during solution casting and melt crystallization by the introduction of CNT-L-D, and the sc crystallites can reform after complete melting. However, the dilution effect of free PLLA molecules to PDLA blocks lowered down the stereocomplex efficiency of PLLA/CNT-L-D blends compared with that of PDLA/CNT-L-D blends, especially during melt crystallization, and the morphology transition of sc crystallites occurs from original well-rounded Maltese-cross spherulites for PDLA/CNT-L-D blends to dendritic form in PLLA/CNT-L-D blends.
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