TEMPERATURE EFFECTED STRUCTURAL TRANSITIONS IN POLYURETHANES SATURATED WITH SOLVENTS STUDIED BY SAXS SYNCHROTRON METHOD

ABSTRACT

A set of segmented polyurethanes (PU) differing in the hard-segment structure was saturated with solvents and after the equilibrium saturation was reached, put to temperature-dependent SAXS investigations. The time-resolved mode of SAXS measurements with a linear increase of temperature from −70°C to +70°C, i.e., within the temperature range between T_g of soft and hard segments, was applied. The order-order transition leading to a greater degree of order was found at higher temperatures for almost all systems investigated. Some of the PUs exhibit two kinds of microphase separated domains. The results obtained are discussed with respect to the mean-field theory of copolymers and Koberstein and Stein model for hard microdomain structure in PUs, and correlated with temperature dependence of membrane permeability in pervaporation process.

Keywords:

• SAXS method
• Polyurethanes
• Structure
• Liquid permeability

ACKNOWLEDGMENTS

The financial support of this work by the State Committee for Scientific Research under Contract No. 1297/T09/99/16 is gratefully acknowledged. Authors also thank M.Sc. M.Plłusa for technical assistance.