THERMOREVERSIBLE GELATION OF HYDRATED POLYMERS

Phase diagrams of aqueous polymer solutions which gel on heating are theoretically derived and compared with experimental observation on cellulose derivatives in water. Such an inverted gelation, often observed in aqueous polymer solutions, interferes with phase separation at high temperatures. It is shown by lattice-theoretical analysis that the competition between polymer-polymer direct hydrogen bonding and polymer-water hydrogen bonding leads to the coexistence of inverted gelation and phase separation at high temperatures. Systematic shift of the sol-gel transition fine relative to the miscibility gap is observed by changing the strength of the two kinds of hydrogen bonds.