Synthesis of novel amphiphilic pH-sensitive polyurethane networks through water-in-oil soap-free emulsion polymerization process. I. Microstructural differences and swelling behaviors
Jy. Kim et al., Synthesis of novel amphiphilic pH-sensitive polyurethane networks through water-in-oil soap-free emulsion polymerization process. I. Microstructural differences and swelling behaviors, J APPL POLY, 76(14), 2000, pp. 2115-2127
pH-sensitive amphiphilic networks are synthesized from urethane acrylate an
ionomer (UAA) precursor chains. The microstructures of these networks are v
ery sensitive to the nature of and the amount of solvent used during crossl
inking. Whereas dioxane forms relatively homogenous solution, water prefere
ntially interacts with hydrophile segment of UAA chains, causing the microp
hase separation between hydrophilic moieties and hydrophobic main chains. T
his microphase separation was locked-in by crosslinking reaction, enhancing
largely the hydrophilicity of UAA networks and the hydrophobic aggregation
. The UAA gels, prepared with water (UAAG) and/or dioxane (UADG), exhibit q
uite different swelling behaviors in the same dissolution medium because of
their completely different microstructures. The improved hydrophilicity of
UAAG gels due to the hydrophilic/hydrophobic microphase separation is conf
irmed by measuring the contact angle to water. These microphase-separated h
ydrophilic domains on UAA gel matrix, which are observed by scanning electr
on microscopy measurement, influence the mechanical property of dried UAA g
els as well. (C) 2000 John Wiley & Sons, Inc.