Dielectric and calorimetric study in renewable polymer blends based on poly(ethylene adipate) and poly(lactic acid) with microphase separation. (27th October 2022)

• Record Type: Journal Article
• Authors: Klonos, Panagiotis A.; Lazaridou, Maria; Samiotaki, Christina; Kyritsis, Apostolos; Bikiaris, Dimitrios N.
• Is Part Of: Polymer. Volume 259(2022)
• Publication Date: 2022-10-27
• Subjects: Poly(lactic acid) -- poly(ethylene adipate) -- Renewable polymers -- Glass transition -- Crystallization -- Polymer dynamics; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2022.125329
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: A series of sustainable polymeric blends based on poly(lactic acid) (PLA) and poly(ethylene adipate) (PEAd), are studied herein, from the point of view of thermal transitions, crystallization and molecular mobility. The blending aims at the manipulation of the chains' mobility and crystallization of PLA, as PEAd exhibits quite lower glass transition temperature and is expected to act as plasticizer. In a next step, such systems are envisaged for use as patches for transdermal administration of antimicrobial drugs, formed as fibril-systems via the electrospinning technique. For the present work, we have employed calorimetry and the advanced technique of dielectric spectroscopy as main investigation tools, which are supplemented by polarized microscopy. Regarding molecular mobility, the overall dynamics (local and segmental) map was constructed for these systems, for the first time. The presence of PEAd imposed plasticization on the PLA chains, as manifested by the lowering of T g and acceleration of segmental dynamics. On the other hand, PEAd is deplasticized at the presence of PLA. In addition, the fragility of PLA chains drops at the presence of PEAd, suggesting increasing in the cooperativity length, or else, a chain-chain detaching. The overall data are also indicative of the partially miscible polymers. Regarding crystallization, neat PLA exhibits neither hot nor cold crystallization, whereas, strikingly, with the addition of PEAd, the nucleation of PLA is facilitated and strong cold crystallization is systematically recorded. The phenomenon seems to be connected with both the plasticization of the PLA chains along with the homogeneous microphase separation of the two polymers (partial immiscibility), overall, with size-effects. Local dynamics, originating from more localized molecular motions, exhibit systematic alternation in the blends in both the time scale and dielectric strength. Our results show that the PLA/PEAd blends are 'phase change materials' with potentials to tune the materials performance, connected, among others, with the semicrystalline morphology and the interchain distances. Graphical abstract: Image 1 Highlights: PLA-PEAd blends studied by calorimetry and dielectric spectroscopy and found partially miscible. The PEAd addition results in plasticization and increase in free volume of the PLA phase. The crystallization of PLA (initially amorphous) being strongly facilitated in the blends. Recording of the overall molecular dynamics map, local and segmental. The blends exhibit microphase separation/organization and can serve as phase change materials.