Determination of molecular parameters of NR/PU block copolymers by transport studies

The equilibrium swelling experiments of block copolymers based on natural rubber (NR) as soft segment and polyurethane (PU) derived from toluene diisocyanate (TDI) and 1,3-butane diol (1,3-BDO) as hard segment were performed in various solvents. Block copolymers with different NCO/OH ratio, viz., from 1.26 to 1.96 were employed in this study. The crosslink densities are found to vary with the NCO/OH ratio employed in the synthesis of the samples. The sorption behaviour is also found to vary with the NCO/OH ratio. The equilibrium swelling experiments have been used to determine the molecular parameters such as molecular mass between crosslinks, crosslink density, polymer–solvent interaction parameter, etc. The equilibrium swelling values were also used to calculate the solubility parameter values of the block copolymers.