College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University , Chengdu, 610065 Sichuan China.
College of Chemical Engineering, Sichuan University , Chengdu, 610065 Sichuan China.
ACS Appl Mater Interfaces. 2017 Mar 22;9(11):10148-10159. doi: 10.1021/acsami.7b00479. Epub 2017 Mar 9.
The challenge of hitherto elaborating a feasible pathway to overcome the conflicts between strength and toughness of polylactide (PLA) still remains among academia and industry. In the current work, a unique hierarchal structure of flexible poly(butylene adipate-co-terephthalate) (PBAT) in situ nanofibrils integrating with abundant PLA shish-kebabs as a strong building block was disclosed and expresses its capability to conquer this dilemma. Substantially simultaneous enhancement on tensile strength, impact strength, and elongation at break could be achieved up to 91.2 MPa, 14.9 KJ/m, and 15.7%, respectively, compared with pure PLA (61.5 MPa, 4.3 KJ/m, and 6.2%). Through investigating the phase (and crystalline) morphology and molecular chain behavior in the PLA/PBAT system, the formation mechanism of this structure facilitated by a coupling effect of PBAT flexible phase and shear flow was definitely elucidated. The dispersed phase of PBAT would be more inclined to existing as a fibrillar form within the PLA matrix benefiting from low interfacial tension. Interestingly, this phase morphology with large specific surface area changes the crystallization behavior of PLA significantly, once introducing an intense shear flow (∼10 s), in situ shear-formed nanofibrils of PBAT would show strong coupling effect with shear flow on PLA crystallization: they can not only induce abundant shish-kebabs of PLA at its interfaces, which possesses lengthened shish and more densely arranged kebabs, but also further retard the relaxation of PLA chains through hysteretic relaxation of its PBAT phase, which can effectively prevent the collapse of established shish. Of immense significance is this particular hierarchical-architecture composed by flexible nanofibers (PBAT) and rigid shish-kebabs (PLA), which provides significant guidance for the simultaneous reinforcement and toughness of polymer materials.
目前，学术界和工业界仍然面临着一个挑战，即如何制定可行的途径来克服聚乳酸（PLA）的强度和韧性之间的冲突。在目前的工作中，揭示了一种独特的柔性聚（丁二酸丁二醇酯-对苯二甲酸酯）（PBAT）原位纳米纤维的层次结构，其与丰富的 PLA 晶须作为一个强大的构建块相结合，展示了其克服这一困境的能力。与纯 PLA（61.5 MPa、4.3 KJ/m 和 6.2%）相比，拉伸强度、冲击强度和断裂伸长率分别可提高至 91.2 MPa、14.9 KJ/m 和 15.7%。通过研究 PLA/PBAT 体系中的相（和结晶）形态和分子链行为，明确阐明了这种结构的形成机制，这种结构是由 PBAT 柔性相和剪切流的耦合效应促进的。分散相的 PBAT 更倾向于在 PLA 基质中以纤维状形式存在，这得益于低界面张力。有趣的是，这种具有大比表面积的相形态显著改变了 PLA 的结晶行为，一旦引入强烈的剪切流（~10 s），原位剪切形成的 PBAT 纳米纤维会与剪切流对 PLA 结晶产生强烈的耦合效应：它们不仅可以在其界面上诱导丰富的 PLA 晶须，使晶须拉长且晶须排布更加密集，还可以通过其 PBAT 相的滞后松弛进一步阻碍 PLA 链的松弛，从而有效地防止已建立的晶须崩塌。由柔性纳米纤维（PBAT）和刚性晶须（PLA）组成的这种特殊的层次结构具有重要意义，为聚合物材料的同时增强和增韧提供了重要指导。
