Segmental Orientation Studies of Block Polymers. I. Hydrogen-Bonded Polyurethanes

Abstract

Differential infrared dichroism was used to study the orientation behavior of a series of elastomeric polyurethane block copolymers. The orientation of hard and soft segments was studied under uniaxial extension, as a function of time and temperature, and in cyclical deformation experiments. The mode of hard segment orientation was found to be a function primarily of hard segment length. Three distinct mechanisms were found, depending on a large scale whether or not the hard domains are interlocking and on the molecular level whether the aromatic urethane segments were amorphous or partially crystalline in internal order. Soft segment orientation is little affected by changes in polymer composition. Advantages of the differential method over conventional dichroism studies are discussed and illustrated. © 1973, American Chemical Society. All rights reserved.