POLYURETHANE ANIONOMERS .2. PHASE INVERSION AND ITS EFFECT ON PHYSICAL-PROPERTIES

The two series of polyether polyurethane anionomers discussed in part I, undergo emulsification on addition of water to solutions in methyl ethyl ketone. The phase inversion mechanism depends on the structure o f the counterion, ionic content and dispersion temperature. The disper sion process can be divided into three stages: separation of hard segm ent aggregates due to adsorption of water on their surface, water ente ring into more disordered and then less disordered hard domains, and f inally a rearrangement of agglomerates to form microspheres. Films cas t from emulsions have crystallizable soft domains, as do films cast di rectly from solutions. The dispersion can cause a disruption of the pa cking arrangement in the hard domains, leading to an increased phase s eparation for the TEA system and an increased phase mixing for the EDE A system. Films cast from solutions have hard domains dispersed in the continuous phase of soft domains. After dispersion, the hard segments originally distributed in the dispersed phase can be inverted to beco me a hard domain network or a continuous phase.