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Estimation of the conformational characteristics of polyurethane chains

✍ Scribed by Věra Kašpárková; Lubomír Šimek; Miloslav Bohdanecký

Publisher
John Wiley and Sons
Year
1996
Tongue
English
Weight
710 KB
Volume
197
Category
Article
ISSN
1022-1352

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✦ Synopsis

Abstract

Linear polyurethanes (PUR‐D~k~) were prepared by reacting 4,4′‐methylenediphenyl diisocyanate (MDI) with low‐molecular‐weight diols HO(CH~2~)~k~OH (k = 2, 3, 4, and 6) and fractionated by precipitation or extraction with mixtures of N,N‐dimethylformamide (DMF) and dibutyl ether (DBE). The fractions were characterized by their weight‐average molecular weights M~w~ (light scattering) and intrinsic viscosities [η] in DMF (good solvent) and mixtures of DMF with DBE (poor solvents). The Kuhn statistical segment length l~K~ was evaluated from the intrinsic viscosities in poor solvents. Low values of l~K~, (12 to 14) × 10^−8^ cm, indicate that benzene rings and virtual double bonds (urethane groups) confine neighbour interactions to bonds within the repeating units and assure independent rotations at the bonds adjoining them.

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