Modification of Segmented Poly(Ether Urethanes) by Incorporation of Poly(Isobutylene)Glycol

Abstract

Poly(isobutylene)glycols (PIBGs) were incorporated as soft segments into poly(ether urethanes) (PEUs) prepared with poly(tetramethylene ether)glycol (PTMEG)/1,4-butanediol (BD)/4,4′-methylenebis-(phenyl isocyanate) (MDI) systems. Specifically, three series of PEUs were synthesized containing mixed PIBG/PTMEG soft segments by a two-step technique in THF/DMF solvent mixtures. The polymers having different soft segment lengths, compositions, and hard segment contents were characterized by stress-strain measurements, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and static and dynamic contact angle measurements. Substitution of even a small amount of PIBG for PTMEG leads to a significant decrease in the tensile strength. PEUs with a mixed soft phase still have acceptable strength and elongation. However, polyurethanes containing only PIBG soft segments exhibit poor mechanical properties. According to DSC and DMA, PEUs prepared with PIBG contain a) soft domains mixed with hard segments, b) domains of well-separated hard segments, and c) hard segment domains partially mixed with soft segments. Contact angle measurements show that in the presence of ∼25%percent; PIBG the surface of the PEU is essentially saturated with the nonpolar soft segment.