Effect of PEO grafts on the surface properties of PEO-grafted PU/PS IPNs : AFM study

Abstract

The change of the interfacial phenomena of muticomponent polymeric systems based on self-reorganization is very important for many applications of them. Specially, when they are used for biomedical application, the change of surface properties in water is a key factor because they are mostly used in the aqueous environment of the human body. An interpenetrating polymer network (IPN) is a mixture of network polymers. The morphology of an IPN can be controlled to obtain materials with nanoscale domains, and the morphology once formed is permanent due to the presence of the physical interlocking between the networks. In this study, surface compositional mapping was attempted with atomic force microscopy (AFM) images of poly(ethylene oxide)-grafted polyurethane/polystyrene IPNs (PEO-grafted PU/PS IPNs) to investigate the structural change under water, and the effect of hydrophilic PEO pendant chains on the change of local elasticity and surface energy of the IPN under water was studied by using the "force-distance (FID) analysis" of AFM. The compositional mapping in water showed that the area fraction of the hydrophilic PU-rich phase was increased by PEO grafting, but the structural reorganization did not occur. From the result of FID analysis in water, the mobile and flexible pendant PEO chains increased the surface elasticity and softness of PU/PS IPNs. The crystallinity also affected the surface hardness of the dried PEO-grafted PU, but it did not when the samples were swollen in water.