Dissolution enthalpy of acrylamide and poly(acrylamide) after their plastic straining under high pressure

Plastic straining under 0.5-2 GPa destroys the crystal structure of acrylam ide and induces polymerization. At early deformation stages, polymerization occurs via crystal defects, and its rate increases exponentially with risi ng pressure. The enthalpy of dissolution of the monomer decreases, as the s train or conversion increases, to reach a limiting value that is one-fourth of the enthalpy of dissolution of the feed monomer. Presumably, this limit ing value corresponds to the enthalpy of dissolution of amorphous acrylamid e. Acrylamide dissolution is an exothermal process; the absolute value of t he enthalpy of dissolution is a strong function of pressure and increases w ith the degree of polymerization. X-ray data shows that a polymer with orde red structure is first produced; at high conversions, a product amorphous t o X-rays is formed.