Influence of tacticity and sorbed water on the material properties of poly(N,N'‐dimethylacrylamide)

The effects of variation in tacticity on the thermal, morphological, stress–strain and stress–relaxation properties (both in the dry state and 140°C, and at a RH of 72% and ambient temperature) were evaluated for a series of homopolymers of poly(N,N‐dimethylacrylamide). In the range of 19 to 23% tacticity (isotactic content), a fundamental change in the level of crystallinity and morphology occurs for this series of polymers which in turn greatly affects the above‐mentioned properties. Below 19% tacticity, the polymers are amorphous, but above 23% they are distinctly semicrystalline. Sorbed water plasticizes all these polymers, but the influences of the water on the stress–strain properties is greatest for the amorphous polymers, where the relative sorption of water is also highest.