Hydrophilic polymers polyhydroxyethyl methacrylate

Hydration of polymeric membranes may be influenced by the chemical identity of the polymers. A hydrophilic polymer has a higher potential to hydrate than a hydrophobic one. Sefton and Nishimura [56] studied the diffusive permeability of insulin in polyhydroxyethyl methacrylate (37.1% water), polyhydroxy-ethyl acrylate (51.8% water), polymethacrylic acid (67.5% water), and cupro-phane PT-150 membranes. They found that insulin diffusivity through polyacrylate membrane was directly related to the weight fraction of water in the membrane system under investigation (Fig. 17). 

The structures of a number of synthetic hydrophilic polymers as a representative range of those commonly used are shown in Fig. 1. Many common hydrophilic polymers are based on methacrylate or acrylate backbones. One of the most common is polyacrylic acid, which forms the basis of many hydrogel materials (Fig. lA). Although simple polyacrylic acid is water soluble, it can be easily cross-linked to form an insoluble network polymer that still, however, retains high affinity for water and is capable of adsorbing large amounts of water to form hydrogels these are discussed later. Polymethacrylic acid-based polymers are similar in nature (Fig. IB). One of the most commonly used polymers for contact lenses, polyhydroxyethyl methacrylate, is based on a similar backbone (Fig. 1C). 

Fig. 1 Structures of some common synthetic hydrophilic polymers (A) poly aery lie acid, (B) polymethacrylic acid, (C) polyhydroxyethyl methacrylate, (D) polyvinyl alcohol, (E) polyvinyl acetate, (F) PEG/PEO, (G) polyacrylamide, (H) polyvinylpyrrolidinone, (I) Nylon 6, and (J) a simple polyurethane.

Details are given of pilocarpine trapped in a matrix diffusion-controlled drug delivery system using hydrophilic inserts of polyhydroxyethyl methacrylate. The physical and chemical properties of pilocarpine were investigated to determine the mechanism of drug-polymer interaction and the effect of drug release behaviour of controlled release polymeric devices. 22 refs. 

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