Estimation of the conformational characteristics of polyurethane chains

Linear polyurethanes (PUR‐Dk) were prepared by reacting 4,4′‐methylenediphenyl diisocyanate (MDI) with low‐molecular‐weight diols HO(CH2)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...

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Bibliographic Details
Published in:Macromolecular chemistry and physics 1996-11, Vol.197 (11), p.3757-3772
Main Authors: KASPARKOVA, V, SIMEK, L, BOHDANECKY, M
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Organic polymers
Physicochemistry of polymers
Properties and characterization
Solution and gel properties
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Summary:Linear polyurethanes (PUR‐Dk) were prepared by reacting 4,4′‐methylenediphenyl diisocyanate (MDI) with low‐molecular‐weight diols HO(CH2)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 Mw (light scattering) and intrinsic viscosities [η] in DMF (good solvent) and mixtures of DMF with DBE (poor solvents). The Kuhn statistical segment length lK was evaluated from the intrinsic viscosities in poor solvents. Low values of lK, (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.
ISSN:1022-1352
1521-3935
DOI:10.1002/macp.1996.021971121