1987 Volume 44 Issue 1 Pages 1-7
The effect of branching structure on dilute solution properties of a segment polyurethane was investigated. The segment polyurethane polymerized with methylene bis (4-phynyl isocyanate), polycaprolactone, and 2-aminoethanol was fractionated by successive precipitation fractionation using dimethylacetamide (DMAc) as the good solvent and a mixture of ethylether and n-heptane as the non-solvent. Limiting viscosity numbers [η], apparent weight-average molecular weights Mw, a apparent z-average radii of gyration <S2> 1/2g, a, and apparent second virial coefficients A2, a for segment polyurethane fractions in DMAc were determined by light scattering. For fractions having latger Mw, a, higher intramolecular branching densities were obtained from data for the polymer untreated and heated in DMAc containing 0.1vol% n-buthylamine at 50°C for 2h. This molecular weight dependence of branching density was reflected in upward curvatures found in log-log plots of [η] -Mw, a, <S2> 1/2z, <a-Mw, a and A2, a-Mw, a.
