Solute Permeation Through Hydrogel Membranes

Abstract

Poly(2-hydroxyethyl methacrylate) (p-HEMA) is a hydrophilic methacrylate polymer which was first prepared by Wichterle and Lim OJ.This polymer, and many other synthetic hydrogels, has been extensively examined for potential biomedical applications (2J.Although many studies have focused on the physicochemical nature of these hydrogels, many questions remain unanswered. Among these are the nature, organization, and role of water in determining such properties as interfacial and transport phenom ena.Problems which deal with the presence of water and the structure of water at the molecular level are often complex. For hydrogels, i t has been proposed (3) that water can be treated in terms of a three state model.These include: bound, interfacial, and "bulk-like" water.Bound water is strongly associated with the polymer, probably as water hydrating the hydrophilic groups of the polymer.Interfacial water is probably associated with hydrophobic interactions between the polymer segments.Finally, "bulk-like" water is that with properties which are similar to that of bulk water in aqueous solution.Several studies have been designed in an effort to verify this model. The total gel water content was estimated semiquantitative^ using NMR (4,_5).Simi lar approaches were made to investigate the state of"water in p-HEMA gels using the techniques of dilatometry, specific conducti vity and differential scanning calorimetry (6).Recently, we have examined solute permeation through hydrogel membranes in an effort to develop models which describe in detail the transport phenomena with particular emphasis on the role of water in this process.These studies have utilized p-HEMA and its copolymers, and both hydrophobic and hydrophilic solutes (7*8,9).It was determined that p-HEMA and its copoly mers are permeable to both hydrophobic and hydrophilic solutes. The factors which influence the permeabilities include the nature and per cent of crosslinkers and the water content of the hydrogel .In this manuscript, the permeabilities of water soluble non-

Morphology and permeability of cellulose/chitin blend membranes

“…To further clarify the pore mechanism, we studied the relationship between the drug diffusivity and the degree of hydration of the membranes (H) according to the free-volume theory. This theory has indicated that the relationship between drug diffusivity and membrane hydration could be written as following [35,36]:…”

Factors Determining Hydrogel Permeability

“…Sarbolouki suggested that solute transport does not occur through membranes which contain only bound water in the absence of specific interactions 41 . Several gel researchers have adopted this idea although this effect has not been clearly demonstrated in gel systems 36,42 …”

“…For example, a partition coefficient greater than one hundred was reported for progesterone in a poly(hydroxyalkyl methacrylate) hydrogel film 37 . Kim et al studied permeation in poly(2‐hydroxyethyl methacrylate) (PHEMA) membranes, a relatively hydrophobic hydrogel widely used in biomedical applications 42 . Partition coefficients much greater than one (20 to 235) were reported for the hydrophobic solutes.…”

Effect of fluorinated hydrophobic monomer on the drug release behavior for the thermosensitive hydrogels

“…In the partition mechanism, the solute transport is presumed to occur by a process involving the dissolution of the solute within the polymer followed by the diffusion through the membrane. 14 Conventionally, fluorinated copolymer hydrogels with high oxygen permeability for contact lenses are prepared by UV irradiation. [15][16][17][18][19][20] However, fluorinecontaining thermoreversible hydrogels have not been investigated in the literature.…”