Tuning of thermally-induced shape memory properties of low-cost biocompatible linear and chemically crosslinked isobornyl/isobutylacrylate copolymers

A series of binary low-cost biobased copolymers was elaborated from isobornylacrylate (IBOA) and isobutylacrylate (IsoBA) monomers applying UV–visible induced free radical polymerization, yielding linear and crosslinked architectures. Thermo-mechanical measurements revealed that the elaborated random copolymers exhibit single glass transition temperatures, which can be adjusted on a broad temperature range by varying the amount of IBOA- and HDDA-units. Governed by the glass transition, linear high molecular weight IBOA-IsoBA copolymers exhibit good thermally induced shape memory properties related to the occurrence of strong physical entanglements, reinforced by the presence of the voluminous isobornylene groups. Fixity and recovery ratios were found to be in the same order of magnitude when compared to crosslinked thermoplastics and thermosetting polymers. Linear IBOA-IsoBA copolymers maintain their form memory properties even after several application cycles, confirming the efficiency of the presence of physical crosslinking. These findings can be explained by the high entanglement molecular weight of 44 kg/mol providing an important elasticity as well as by an elevated glassy/rubbery moduli ratio of around 3000, facilitating deformation and fixing modes.