Isothermal Crystallization of Poly(L-lactide) Induced by Graphene Nanosheets and Carbon Nanotubes: A Comparative Study
Isothermal Crystallization of Poly(L-lactide) Induced by Graphene Nanosheets and Carbon Nanotubes: A Comparative Study
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石墨烯纳米片和碳纳米管诱导聚L-丙交酯的等温结晶：比较研究
DOI：
10.1021/ma100304n
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发表时间：
2010-06-08
期刊：
影响因子：
5.5
通讯作者：
Hsiao, Benjamin S.
中科院分区：
文献类型：
--
作者：
Xu, Jia-Zhuang;Chen, Tao;Hsiao, Benjamin S.
低维纳米粒子具有很强的诱导聚合物基体结晶的能力。一维碳纳米管（CNTs）和二维石墨烯纳米片（GNS）都是碳基纳米粒子，它们为研究不同尺寸纳米粒子对聚合物结晶行为的影响提供了良好的机会。为此目的，通过溶液凝固法制备了以聚（L-丙交酯）（PLLA）为基体的碳纳米管和GNS纳米复合材料。时间分辨傅里叶变换红外光谱（FTIR）和同步辐射广角X射线衍射（WAXD）进行探针链构象变化，并确定在等温结晶过程中的PLLA纳米复合材料和纯PLLA，特别是在早期阶段的结晶动力学。CNTs和GNS均能作为成核剂加速PLLA的结晶动力学，但CNTs的诱导结晶能力强于GNS。当碳纳米管含量从0.05wt%增加到0.1wt%时，诱导期缩短，晶化速率加快，而纳米碳纳米管复合材料的情况则相反。在纯PLLA的情况下，-CH 3链间相互作用之前-（COC + CH 3）链间相互作用在结晶过程中。相反，在碳纳米管和GNS纳米复合材料中，构象有序开始与-（COC + CH 3）链间相互作用，这直接导致在减少诱导期。这种类型的链间相互作用可以解释在表面诱导的构象顺序（SICO）。最后讨论了纳米粒子的尺寸对PLLA结晶行为的影响。
Low-dimensional nanoparticles have a strong ability to induce the crystallization of polymer matrices. One-dimensional carbon nanotubes (CNTs) and two-dimensional graphene nanosheets (GNSs), both of which are both carbon-based nanoparticles, provide a good opportunity to investigate the effects of differently dimensional nanoparticles on the crystallization behavior of a polymer. For this purpose, respective nanocomposites of CNTs and GNSs with poly(L-lactide) (PLLA) as matrix were prepared by solution coagulation. Time-resolved Fourier-transform infrared spectroscopy (FTIR) and synchrotron wide-angle X-ray diffraction (WAXD) were performed to probe chain conformational changes and to determine the crystallization kinetics during the isothermal crystallization of the PLLA nanocomposites and neat PLLA, especially in the early stages. Both CNTs and GNSs could serve as nucleating agents in accelerating the crystallization kinetics of PLLA: however, the ability of CNTs to induce crystallization was stronger than that of GNSs. On increasing the content of CNTs from 0.05 to 0.1 wt %, the induction period was shortened and the crystallization rate was enhanced, hut the reverse situation was found for GNSs nanocomposites. In the case of neat PLLA, -CH3 interchain interactions preceded -(COC + CH3) interchain interactions during the crystallization. Conversely, in the CNTs and GNSs nanocomposites, the conformational ordering began with -(COC + CH3) interchain interactions, which resulted directly in a reduced induction period. Interchain interactions of this type could be explained in terms of surface-induced conformational order (SICO). Finally, the effect of the dimensionality of the nanoparticles on the crystallization behavior of PLLA is discussed.