Synthesis and characterization of a dyeable bio-based polyurethane/branched poly(ethylene imine) interpenetrating polymer network with enhanced wet fastness

Abstract

Bio-based polyurethane is synthesized from biodegradable polycaprolactone, methylene diphenyl diisocyanate and 1,4-butanediol. The bio-based polyurethane is blended with branched polyethyleneimine by a solution casting method and further treated with glutaraldehyde. From nuclear magnetic resonance, Fourier-transform infrared spectroscopy, leaching tests and contact angle measurements, it was found that a semi-interpenetrating polymer network structure is induced by the glutaraldehyde treatment of the bio-based polyurethane/branched polyethyleneimine blend film, which resulting from the crosslinking of branched polyethyleneimine by imine bonds formed from the amine-aldehyde reaction between branched polyethyleneimine and glutaraldehyde. In addition, the glass transition temperature, Young’s modulus and the shape retention results show that the mechanical strength of bio-based polyurethane, which is weakened by the plasticizing effect of branched polyethyleneimine, is restored by the formation of the semi-interpenetrating network structure. We found that the bio-based polyurethane/branched polyethyleneimine with a semi-interpenetrating network shows a much higher affinity for Acid Red 4 than bio-based polyurethane, and the wet fastness of dye is significantly improved by the formation of the semi-interpenetrating network.