Study of domain structure in linear and crosslinked polyurethanes using pulsed proton NMR

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Abstract
Pulsed proton magnetic resonance was used to study the domain structure of a series of polyurethanes which had been crosslinked to various degrees at 210°C. The difference between segmental mobility of the hard and soft phases decreases with crosslinking. The fraction of rigid segments in the linear material decreases in two distinct stages as the temperature increases, while the fraction of rigid segments in the crosslinked material decreases in a continuous fashion as the temperature increases. Crosslinking also decreases the rate of domain formation following thermal treatment. These effects are attributed to the inability of the segments in the crosslinked material to completely segregate into domains.