Department of Food Science, Aarhus University, Agro Food Park 48, 8200 Aarhus N, Denmark; CiFOOD - Center for Innovative Food Research, Aarhus University, Agro Food Park, 48, 8200 Aarhus N, Denmark.
School of Packaging, Michigan State University, East Lansing, MI 48824-1223, USA.
Int J Biol Macromol. 2022 Dec 1;222(Pt A):1101-1109. doi: 10.1016/j.ijbiomac.2022.09.205. Epub 2022 Sep 26.
Stereocomplexation between enantiomeric poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) is a promising sustainable approach and gaining momentum to overcome the shortcomings of polylactide (PLA) for its use as a replacement for fossil-based plastics. Filler addition in tailoring the crystallization of stereocomplex PLA (SC-PLA) has attracted extensive attention; however, research has primarily focused on the heterogeneous nucleation effect of filler. The impact of filler on the chain behavior of SC-PLA during crystallization has not been exclusively discussed, and the rigid amorphous fraction (RAF) development remains unknown. In this study, the crystallization of PLLA/PDLA blends was modified by low loading of layered double hydroxide (LDH) (≤ 1 wt%) with the proposed local effect of such filler, and additional RAF development was incurred. In the early stage of crystallization, LDH facilitates the pairing of PLLA and PDLA and arrests the ordered SC pairs during the dynamic balance between the separation and pairing of racemic segments. This explains the severely suppressed homochiral (HC) crystallization, promoted SC crystallization, and additional RAF formation driven by the nucleation-induced chain ordering. This work, for the first time, highlights the role of LDH in creating SC-PLA with tailorable polymorphism and RAF, where the mechanism can be extended to other filler-type nucleator systems.
手性聚乳酸（PLLA 和 PDLA）之间的立构复合是一种很有前途的可持续方法，正在大力发展，以克服聚乳酸（PLA）作为化石基塑料替代品的缺点。在对立构复合 PLA（SC-PLA）的结晶进行调整时添加填充剂引起了广泛关注；然而，研究主要集中在填充剂的异质成核效应上。填充剂对立构复合 PLA 结晶过程中链行为的影响尚未专门讨论，刚性非晶区（RAF）的发展情况仍不清楚。在这项研究中，通过低负载的层状双氢氧化物（LDH）（≤ 1wt%）改性 PLLA/PDLA 共混物的结晶，提出了这种填充剂的局部效应，并导致了额外的 RAF 发展。在结晶的早期阶段，LDH 促进 PLLA 和 PDLA 的配对，并在非对映片段的分离和配对之间的动态平衡过程中阻止有序 SC 对的形成。这解释了同手性（HC）结晶严重受到抑制、SC 结晶得到促进以及由成核诱导的链有序化引起的额外 RAF 形成的原因。这项工作首次强调了 LDH 在创造具有可调节多晶型和 RAF 的 SC-PLA 中的作用，该机制可以扩展到其他填充型成核剂体系。
