| Abstract: | A series of polyurethane (PU) films, produced from toluene diisocyanate, 1,4‐butane diol and either hydroxyl‐terminated polybutadiene (HTPB), hydroxyl‐terminated polybutadiene/acrylonitrile (HTBN) or hydroxyl‐terminated polybutadiene/styrene (HTBS), was synthesized by solution polymerization. Differential scanning calorimetry (DSC), Fourier‐transform infrared (FT‐IR) spectroscopy, and positron annihilation lifetime (PAL) spectroscopy were used to investigate the morphologies and free volumes of these polyolefin‐based polyurethanes. The free volumes were closely related to the morphologies of such PUs. HTBN‐based PUs showed the lowest degree of phase separation, the smallest fraction of free volume and smallest hole radius among the three types of polyolefin‐based PUs, while the HTPB‐based PUs displaying the largest values. The diffusion and permeation coefficients decreased with decreasing degree of phase separation and increasing content of hard segments. The transport data were in relation to the free volume and fitted the Fujita free‐volume model. Copyright © 2004 Society of Chemical Industry |
