Physical and membranological characteristics of hydrophilic-hydrophobic interpenetrating polymer networks synthesized under high pressure

Abstract

Hydrophilic-hydrophobic interpenetrating polymer networks(IPN``s) of polyurethane(PU) and polystyrene(PS) were prepared by simultaneous polymerization method under high pressure up to 10,000 Kg/$cm^2$. The hydrophilic polyurethane networks were prepared by reacting the polyurethane prepolymer based on hexamethylene diisocyanate(HDI) and polyethylene glycol(PEG) with trimethylol propane as the crosslinking agent. the hydrophobicity of the PU phase, the molecular weight of PEG and the crosslink density were varied in preparing the IPN``s. Polystyrene networks were prepared by crosslinking styrene monomer with divinylbenzene. The morphology, dynamic mechanical properties, and swelling behavior of the IPN``s were analyzed to evaluate the effects of the synthesis pressure, hydrophilicity of PU phase, molecular weight of PEG and Mc on the degree of intermixing of the component polymers. The degree of intermixing increased with increasing synthesis pressure. The domain size of the PS phase decreased from about 2,000 $\mbox{\AA}$ at atmospheric pressure to 100 $\mbox{\AA}$ at 10,000 Kg/$cm^2$ for the IPN of U50S50(the PU was based on HDI and a polyol mixture of PEG50/PTMG50), and the dynamic mechanical behavior also showed an inward shift in Tg``s with increasing synthesis pressure. The swelling properties of the simultaneous interpenetrating polymer network (SIN``s) were influenced strongly by the morphology. The swelling ratio in water and enthanol, which were good solvents for PU network, decreased degree of intermixing. The compatibility between the PU and PS phases increased as the hydrophobicity in PU phase increased. The swelling ratio in water decreased with increasing the hydrophobicity of PU phase. The decreased compatibility was observed from the electron micrographs as the molecular weight of PEG and Mc were increased. The hydrophilic-hydrophobic IPN nembranes of PU and PS were prepared in a glass mold at atmospheric pressure and in a high pressure mold at ...