Free-rotation dimensions of some polyurethane chains

The ratio of the unperturbed mean-square end-to-end distance to the molecular weight in the random-coil limit, (〈 R 2〉 0, f / M) ∝, in the freerotation approximation was calculated for chains of linear polyurethanes PUR-D k prepared from 4,4′-methylenediphenyl diisocyanates and low-molecular-weight diols HO(CH 2) k OH ( k = 2, 3, 4 and 6). It was found that the experimental values of (〈 R 2〉 0/ M) ∝ estimated in the previous paper are very close to the values of (〈 R 2〉 0. f / M) ∝ calculated under the assumption that the groups of bonds CH 2C 6H 5NH and NHCOOCH 2 can be replaced by rigid virtual bonds.