Supramolecular interactions between polylactide and model cyclosiloxanes with hydrogen bonding-capable functional groups

Abstract

Interactions between polylactide matrix and additives bearing –COOH and –OH groups were studied for compositions of polylactide (PLA) and functionalized cyclotetrasiloxanes (CX–R, R = OH, COOH, COOMe). Inherent conformational flexibility of cyclotetrasiloxane rings enabled evaluation of supramolecular phenomena between hydrogen bondingcapable functional groups and the polylactide backbone, as well as their role in polymer crystallization. The modification of PLA with CX–R was clearly reflected in the polymer dielectric response, unobscured by interfacial polarization effects frequently observed for other additives. New relaxation processes appeared next to the strong α-relaxation characteristic of the PLA matrix. Addition of CX–R influenced thermally induced crystallization of amorphous matrix as well as isothermal crystallization from melt. Development of crystals with 103 helical chain conformation was accelerated at relatively low temperatures in the presence of CX–OH with hydrogen bond donating hydroxyl groups. A specific phase separation that hindered mobility of polymer chains was observed in samples prepared with CX–COOH of strong hydrogen bond donor/acceptor ability. The presented results may be used as a reference for other systems with nanoadditives such as carbon nanotubes (CNT), graphene oxide (GO) or carbon quantum dots, in which interactions between –COOH/–OH groups and the polymer matrix play an important role.

Keywords

• material testing
• biodegradable polymers
• dielectric relaxation
• supramolecular interactions
• cyclosiloxanes