Poly(lactic acid) stereocomplex microspheres as thermally tolerant optical resonators

Thermally tolerant polymer optical resonators are fabricated from a stereocomplex of poly(L-lactic acid) and poly(D-lactic acid) through the oil-in-water miniemulsion method. The thermal stability of the microspheres of the stereocomplex poly(lactic acid) (SC-PLA) is superior to that of the homochiral poly(lactic acid) (HC-PLA). As a result of the high thermal stability, the optical resonator properties of the SC-PLA microspheres are preserved at an elevated temperature of up to 230 °C, which is 70 °C higher than that of microspheres formed from HC-PLA.

New opportunities for sustainable bioplastic development: Tailorable polymorphic and three-phase crystallization of stereocomplex polylactide by layered double hydroxide

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) attracts 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.

Modulating the Crystallinity of a Circular Plastic Towards Packaging Material with Outstanding Barrier Properties

Chemically recyclable polymers have attracted increasing attention since they are promising materials in a circular economy, but such polymers appropriate for packaging applications are scarce. Here we present a combined thermal, mechanical, and transport (permeability and sorption) study of a circular polymer system based on biobased trans-hexahydrophthalide which, upon polymerization, can lead to amorphous, homochiral crystalline, and nanocrystalline stereocomplex materials. This study uncovers their largely different transport properties of the same polymer but with different stereochemical arrangements and synergistic or conflicting effects of crystallinity on transport properties versus thermal and mechanical properties. Overall, the homocrystalline chiral polymer shows the best performance with an outstanding barrier character to gases and vapors, outperforming commercial poly(ethylene terephthalate) and polyethylene. The results presented herein show that it is possible to modify the crystalline structure of the same polymer to tune the mechanical and transport properties and generate multiple materials of different barrier characters. This article is protected by copyright. All rights reserved.

A short review on polyurethane-based nanocomposites for various applications

In recent years, polyurethane (PU) has attracted researchers’ attention due to their easily tailored properties to meet specific application requirements. PU and PU-based composites are being developed to be applied in various demanding fields such as aerospace, automotive, and electronics. This is because PU-based nanocomposites have numerous types of functional nanofiller integration. This has led to the advancement of polymer nanocomposite of PU with the inclusion of nanosised fillers for various specific purposes. In this short review article, the authors haves reviewed the fundamental or basic understanding of PU and several types of nanofillers used such as clay, carbon nanotubes, and graphene for PU-based nanocomposites development, as well as its potential applications.

Correlation between molecular weight and confined crystallization behavior of polymers grafted onto a zero-dimensional filler

In this work, polymer chains of different molecular weights are grafted onto a zero-dimensional filler.

Monte Carlo simulations of stereocomplex formation in multiblock copolymers

Local miscibility and relative size of block length and crystal thickness codetermine stereocomplex formation in multiblock copolymers.