Hydrogel and method of making

A method of making acrylonitrile copolymers having multi block structure comprising acrylic acid, acryl amids and acrylamidine hydrophilic groups in hydrophilic blocks and residual nitrile groups in hydrophobic blocks, by partial hydrolysis of polyacrylonitrile to a predetermined hydrolysis conversion at which the hydrolysis is self terminating, by a process that improves quality and reduces product heterogeneity and which comprises:

• a.) forming a first reaction mixture which includes polyacrylonitrile dissolved in an aqueous reactive solvent containing sodium thiocyanate;
• b.) forming a second reaction mixture comprising a reaction catalyst of the general formula MY, wherein M is a metal selected from the group consisting of lithium, potassium and sodium and wherein Y is an anion derived from a week acid with pKa higher than about 5, dissolved in an aqueous reactive solvent containing sodium thiocyanate;
• c.) mixing the reaction mixtures of steps (a) and (b) above to form a master reaction mix;
• d.) dividing said reaction mix into a plurality of physical reaction compartments so as to increase outer surface area relative to volume as compared to outer surface area of a single reaction compartment to enhance cooling efficiency and to reduce undesirable center core thermal effects;
• and,
• e.) heating said divided master reaction mix to a predetermined reaction temperature range and maintaining said temperature range for a predetermined time sufficient for completion of a predetermined level of hydrolysis at which the resulting copolymer solution is substantially stable at ambient temperature.