Microphase Separation of Bulk and Ultrathin Films of Polyurethane Elastomers

Abstract

AbstractSurmmary: Polyurethane elastomers (PUEs) were synthesized with poly(oxytetramethylene) glycol (PTMG), 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol (BD)/1,1,1‐trimethylol propane (TMP) by a prepolymer method. The degree of microphase separation of bulk and ultrathin films for these PUEs was confirmed by Fourier transform infrared (FT‐IR) spectroscopy, differential scanning calorimetry (DSC) and atomic force microscopy (AFM). In the bulk films, FT‐IR and DSC measurements revealed that the degree of micro‐phase separation strengthened with increasing BD content. AFM observation of the BD‐PUE showed hard segment domains surrounded by a soft segment matrix. The domains ranged in size from 10‐20 nm, while BD/TMP‐ and TMP PUEs did not have clear domains. On the other hand, AFM observation was carried out on thin films (200 mm in thickness) and ultrathin films (approximately 8‐5 nm) prepared by spin‐coating the different concentrations of PUE solutions. The microphase separated strucuture under 10 nm in thickness showed marked decreases in the size of the microphase‐separated domain.