Poly hydrogel

The water content of a hydrogel depends on the hydrophilicity of the monomer, eg, cured poly(HEMA) absorbs 60% of its weight of water and thus forms a hydrogel with about 38% water content. Other hydrophilic monomers, such as A/-vinylpyrrohdinone [88-12-0] (NVP) (6), and glycerol methacrylate [100-92-5] (GM) (7), and acrylamide monomers, such as diacetone acrylamide [2873-94-9] (DAA), have also been used to form hydrogels with higher water content. 

Because of the many choices of hydrophilic monomers, cross-linkers, and hydrophobic monomers, a large number of formulations have been developed and manufactured into hydrogel lenses. The water content of these hydrogel lenses ranges from about 38%, for HEMA-based lenses, to 80%, for poly(vinyl alcohol) and partially hydrolysed acrylonitrile lenses. Table 2 gives a representative Hst of FDA approved hydrogel materials available to the consumer in the early 1990s. 

The majority of hydrophilic and water-soluble polymers are manufactured on the commercial level. Their list includes PAAm, copolymers of AAm, PAAc, PEO, PVA, poly(jY-vinylpyrrolidone), some polyamines etc. So, it seems practically highly attractive to produce hydrogels based on these polymers using various crosslinking techniques. 

Lednicky et studied the structure of silicone rubber-hydrogel based on poly(HEMA) by... 

The hydrophilic/hydrophobic SIN composition of PDMS with poly(HEMA) and poly(AAC) were proposed as a potential apphcation for high-permeability soft contact lenses. Other sUicone-containing IPNs for contact lenses include polymerization of MMA in the presence of polymerized methacryloxypropyl trimethoxysilane, the cross-linking of a polymeric hydrogel of a copolymer of NVP during the final compression or injection-moulding process. 

Allcock HR, Kwon S, Riding GH, Fitzpatrick RJ, and Bennett JL. Hydrophilic polyphosphazenes as hydrogels Ration cross-linking and hydrogel characteristics of poly [bis(methoxyethoxyethoxy)phos-phazene. Biomaterials, 1988, 9, 509. 

Bryant, S.J. and Anseth, K.A., The effects of scaffold thickness on tissue engineered cartilage in photocrosslinked poly(ethylene oxide) hydrogels. Biomaterials, 22, 619-626, 2001. 

Poly[(4-carboxylatophenoxy)(methoxyethoxyethoxy)phosphazene] copolymers of variable compositions were synthesized by Allcock [645] in 1996. These polymers were found to be soluble in alkaline solutions. When crosslinked (by y-rays or by addition of CaCl2 to the polymer solution) the resulting hydrogels were found able to contract or expand as a function of the pH of the solution and their utilization as pH-responsive materials for drug delivery systems could be envisaged. 

Allcock, H. R., Kwon, S., Riding, G. H., Fitzpatrick, R. J., and Bennett, J. L., Hydrophilic poiyphosphazenes as hydrogels Radiation crosslinking and hydrogel characteristics of poly[bis-(methoxyethoxyethoxy)phosphazene], Biomaterials. 19, 509, 1988. 

Allcock, H. R., and Kwon, S., An ionically-crosslinkable poly-phosphazene Poly[di(carboxylatophenoxy)phosphazene] and its hydrogels and membranes. Macromolecules. 22. 75, 1989. 

Badiger, MV McNeill, ME Graham, NB, Porogens in the Preparation of Microporous Hydrogels based on Poly(ethylene oxides). Biomaterials 14,1059, 1993. 

The two matrices in these cements are of a different nature an ionomer salt hydrogel and polyHEMA. For thermodynamic reasons, they do not interpenetrate but phase-separate as they are formed. In order to prevent phase separation, another version of resin glass polyalkenoate cement has been formulated by Mitra (1989). This is marketed as VitraBond, which we term a class II material. In these materials poly(acrylic acid), PAA, is replaced by modified PAAs. In these modified PAAs a small fraction of the pendant -COOH groups are converted to unsaturated groups by condensation reaction with a methacrylate containing a reactive terminal group. These methacrylates can be represented by the formula ... 

Kenausis G, Taylor C, Katakis I, Heller A. 1996. Wiring of glucose oxidase and lactate oxidase within a hydrogel made with poly(vinyl pyridine) complexed with [Os(4,4 -dimethoxy-2,2 -bipyridine)2Cl]. J Chem Soc Faraday Trans 92 4131-4136. 

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