Highly biobased thermally-stimulated shape memory copolymeric elastomers derived from lignin and glycerol-adipic acid based hyperbranched prepolymer

Abstract

Copolymers containing as high levels of bio-derived components were obtained mainly from two industrial byproducts, glycerol and lignin. A series of hyper branched prepolymers (HyBP) were prepared from in the first step by melt condensation of glycerol (Gly, B2B32) and adipic acid (AA, A2) and the prepolymer structure was also modified by the addition of commercially available diisopropanolamine (DIPA, DB42) and tris(hydroxymethyl) aminomethane (THAM, CB31) units. The HyBP were reacted with lignin to form thermally-stimulated shape memory copolymeric elastomers in the second step in the same pot by melt polycondensation. The prepolymers were characterized chemically by FTIR, NMR, and ESI-MS. Thermal and rheological behaviors were analyzed by DSC, DMA, TGA and dynamic rheometry. The higher branching crosslinkers, DIPA and THAM, were shown to influence the chemical and thermal properties of the prepolymers. The hyperbranched biobased lignin-copolymers demonstrated good shape memory and elastic properties. The shape transition temperature (Ttrans) could be tuned by variations of Gly, DIPA and THAM proportions for applications under different temperature circumstances. This study demonstrates that renewable Gly and AA based prepolymers could be incorporated into lignin based copolymeric systems with high biobased contents acting as soft segment to perform shape memory effect behavior.