HETEROCYCLIC METHACRYLATES FOR CLINICAL-APPLICATIONS FURTHER-STUDIES OF WATER SORPTION

The room temperature polymerizing system comprising poly(ethyl methacr ylate)-tetra hydrofurfuryl methacrylate (PEM/THFMA) has potential in o rthopaedic and dental applications, and earlier work has shown it to h ave unusual water absorption characteristics. This aspect has been stu died in further detail, by studying the water absorption behaviour fro m some biological solutions, and the effect of the addition of an anti biotic (gentamicin). For comparison purposes, a parallel system whereb y tetrahydrofuryl methacrylate was replaced by hydroxyethyl methacryla te (PEM/HEMA), was studied. In the case of PEM/THFMA, water uptake was substantially reduced when absorption was carried out from solutions (from about 30% in water to about 1.5% in solutions of higher concentr ations), and the corresponding diffusion coefficient increased (by a f actor of several hundred). The addition of gentamicin increased uptake , but the extent of increase also decreased ih solutions. It was concl uded that uptake was related to the osmolarity of the external solutio n, and also on the presence of osmotic sites within the polymer; hence the uptake process appears to be governed by chemical potential consi derations. At the higher uptakes, there was evidence of water clusters . In marked contrast, the uptake by the PEM/HEMA system was independen t of the osmolarity of the external solutions, presumably due to the h ydrophilic nature of HEMA.