Domain structure and interphase dimensions in poly(urethaneurea) elastomers using DSC and SAXS

Small-angle X-ray scattering (SAXS) and differential scattering calorimetry (DSC) were used to demonstrate distinct differences in domain size, phase separation, and hydrogen bonding in a series of segmented urethaneurea elas tomers prepared from isocyanate-terminated prepolymers and aromatic diamine chain extenders. Two types of prepolymers were studied. The first containe d a broadly polydisperse high molecular mass oligomer with relatively high levels of free isocyanate monomer. The second type of prepolymer contained low levels of high molecular mass oligomers with mass fractions greater tha n 90% of the two-to-one adduct of toluene diisocyanate (TDI) to polytetrame thylene glycol (PTMEG). The mass fraction of the residual unreacted diisocy anate was less than 0.1% in the second type. Two chain extenders, 4,4'-meth ylene bis-(2-chloroaniline)(Mboca) and 4,4'-methylene bis-(3-chloro-2,6-die thylaniline) (MCDEA), were used to convert the prepolymers to poly(urethane urea) elastomers. Materials prepared from the prepolymers with low oligomer polydispersity exhibited smaller hard segment domains with more ordered mo rphology, greater phase separation, and more hydrogen bonding than those pr epared from prepolymers with high oligomer polydispersity. These tendencies were enhanced in those elastomers prepared by chain extension with MCDEA c ompared to those made with Mboca. (C) 1999 John Wiley & Sons, Inc.