Evaluation of poly(N-isopropylacrylamide) modified hydroxyl-terminated polybutadiene based polyurethane membrane

Hydroxyl-terminated polybutadiene (HTPB) based polyurethane was synthesized by reacting equal equivalent of 4,4-methylene diphenyl diisocyanate (MDI) and hydroxyl-terminated polybutadiene with 1,4-butane diol (BDO) as chain extender. The HTPB based polyurethane was modified by UV radiation with N-isopropylacrylamide monomer to get poly(N-isopropylacrylamide) modified polyurethane (PUNIPAAm). The cohesive properties were calculated by group contribution methods. The characterization of the PUNIPAAm membrane was studied by the Fourier transform infrared spectroscopy, Nikon Microphot-Fx, and Universal Testing Machine for the chemical composition, morphology, and stress-strain curve. Water content and contact angles of distilled water on the PUNIPAAm membrane were evaluated and the surface tension of PUNIPAAm was calculated. The diffusion coefficient of distilled water in the membrane was determined. The measurement of water vapor transmission rate on PUNIPAAm membranes was also evaluated. It was found that the values of surface tension, water vapor transmission rate, and diffusion coefficient of water on PUNIPAAm membranes were higher than those on pure polyurethane. The property changes reduced the permeability of oxygen through PUNIPAAm membrane. The preexponential terms (P_O) and activation energies (E_act) for oxygen through various PUNIPAAm membranes were obtained by the Arrhenius law. The preexponential term P_O for PUNIPAAm membranes is lower than that of pure PU; whereas there is no significant difference for the activation energy of oxygen through PUNIPAAm and pure PU.