LOWER CRITICAL SOLUBILITY TEMPERATURE STUDY OF ALKYL ETHER BASED POLYPHOSPHAZENES

A series of poly[(alkyl ether)phosphazenes] was synthesized and their lower critical solution temperatures (LCST) were examined in water at concentrations from 0.1 to 30.0 wt %. The polymers synthesized were po ly[bis(2,3-dimethoxypropanoxy)phosphazene], is(2,3-bis(2-methoxyethoxy )propanoxy)phosphazene], 2-(2'-methoxyethoxy)ethoxy)propanoxy)phosphaz ene], poly[bis(2,3-bis(2-(2'-(2 ''-dimethoxyethoxy)ethoxy)ethoxy)phosp hazene], and poly[bis(2-(2'-methoxyethoxy)ethoxy)phosphazene]. All the polymers examined showed LCST behavior. The LCST values were approxim ately 44.0, 38.0, 49.5, 61.5, and 65.0 degrees C, respectively. Cross- linked polymer films were examined as hydrogels in water at various te mperatures and showed a rapid decrease in volume and weight as the tem perature was raised through the LCST. The change in LCST was also exam ined as a function of increasing ionic strength in the presence of NaC l. A linear decrease in LCST was detected as a function of increasing ionic strength. The enthalpies of phase separation for 5 wt % solution s of the polymers were determined by DSC analysis and were found to be directly related to the LCST for each polymer.