Synthesis and characterization of thermal-responsive chitin-based polyurethane copolymer as a smart material

A chitin-based polyurethane (TRCPU) organogel composed of isophorone diisocyanate (IPDI), polyethylene glycol (PEG) and chitin is shown to undergo a temperature-dependent sol-to-gel transition in polar organic solvents. The soft segments of the prepolymer that originated from the PEG imparted elastomeric and hydrophilic characteristics to the TRCPUs. The hard segments of chitin and IPDI that contained highly polar urethane linkages acted as physical alignment sites and provided lipophilic characteristics for the TRCPUs in the polar organic solvent. The average molecular weight and the degree of acetylation of chitin were determined based on the intrinsic viscosity and solid-state 13C-CP/MAS NMR spectrum. Chitin was incorporated into polyurethane via covalent bonding; the resultant copolymer was an injectable organosol at low temperatures that transformed to a semisolid organogel at approximately 105 °C. The TRCPUs were characterized by 1H NMR, FT-IR and DSC, and the rheological behavior of the TRCPU solutions in organic solvents was studied.