The effect of PCL/PEG ABA block lengths on the crystallization of homo/block- based polyurethane/CNW nanocomposites

Abstract

We report synthesis and characterization of a set of thermoset polyurethane (PU) bionanocomposites based on a polyol blend of poly(e-caprolactone)/ polyethylene glycol (PCL/PEG) ABA block copolymers and their homopolymers (Mw: 2000 D). ABA block copolymers of PCL/PEG, with variable block lengths, were blended with their homopolymers. The relative weight content of Homo: Block (HB) was set 1:1 and the blend was used to synthesize a PU bionanocomposite using HDI and cellulose nanowhisker (CNW). The change in PEG and PCL block lengths resulted in an extensive change in the crystallization of the soft domains. The results of dynamic and thermal analysis revealed an increasing trend in the crystallization of the PCL/PEG segments as their lengths increase in the block copolymer structure. The shape memory analysis of the PU specimens showed high recovery (84-100%) and fixity (93-100%) ratios. Specimens with about one-order of magnitude fall in the storage modulus in the plateau region showed the highest fixity ratios. The relatively stable storage modulus at the elevated temperature indicate lack of flow for the PU nanocomposites and their thermoset nature. The cytotoxity analysis of the specimens showed a great cytocompatibility, indicating their great potential in the field of tissue engineering as a new biomaterial model. HB6 was selected as the optimum sample with SR and SF of 100%, with the highest cell viability.