Showing papers on "Self-healing hydrogels published in 1973"

Water and hydrogels.

Abstract: The apparent biocompatibility of many synthetic and natural aqueous gel materials has encouraged their study and testing for a wide variety of biomedical device applications. Many of the physical and in particular the interfacial properties of such gels are highly dependent on the organization of water within and on the surface of the hydrogel. Water is an important component of such gels, varying from about 30 to nearly 100 wt-%, yet the role of water in the gels has been virtually ignored. This paper briefly reviews the nature of water structure in pure bulk water, in solutions, and at interfaces. Polywater or anomalous water is also briefly reviewed. Evidence is presented that the water in many hydrogel systems can exist in at least three different, structurally distinct forms. A hypothesis is presented which can be used to evaluate and study the nature of water in bulk hydrogels. Consideration is also given to the role of organized water at the hydrogel surface on the interfacial properties of such systems.

Poly(vinyl alcohol) hydrogels. Formation by electron beam irradiation of aqueous solutions and subsequent crystallization

Abstract: Aqueous solutions of poly(vinyl alcohol) were submitted to varying doses of electron beam irradiation. By modification of the classical Flory-Huggins equations appropriate to the initial state of solution of the polymer, the molecular weight between crosslinks, Mc, was calculated as a function of radiation dose, initial polymer concentration, and temperature. Following crosslinking in the solution state, crystallization was induced by dehydrating the network at temperatures above 90°C. Following dehydration, the polymer network was reequilibrated with water and its tensile properties compared with identically prepared hydrogels not subjected to crystallization by dehydration. Greatly enhanced values of ultimate tensile strength and resistance to tear result from the treatment producing crystallization, compared with those of the crosslinked but not previously dehydrated gels.

Poly(vinyl alcohol) hydrogels for synthetic articular cartilage material.

Abstract: As part of a program to develop a synthetic articular cartilage material for use in reconstructive joint surgery, this paper is concerned with the desiderata for such a material and with the properties of poly (vinyl alcohol) hydrogels reinforced by crystallinity as developed for this purpose. Reference is further made to the ultimate preparation of cationic PVA hydrogels to provide the low-friction lubrication necessary in a cartilage prosthesis when in contact with natural synovial fluid.

Aspects of three types of hydrogels for biomedical applications.

Abstract: Some of the chemical and physical properties of three different hydrogels are analyzed as they relate to biological compatibility. The importance of the permeability and diffusion coefficients, porosity, and the possible role of quasiorganized water within the hydrogels are emphasized. It is suggested that the biological environment with its dissolved components such as ions, proteins, carbohydrates, lipids, and enzymes will influence the ultimate biological performance of hydrogels. This biological performance will depend not only on the hydrophilicity of the system but on numerous other parameters including the chemical composition, types and number of crosslinks, presence of functional groups, quasi-organized water structure, porosity, and the thermodynamic interaction parameters between the components of the biological environment and the gel. It is suggested that the presence of anionic gorups on certain synthetic hydrogel surfaces may be not essential for blood compatibility, provided that such materials are carefully distinguished from other hydrophilic gels.

Hydrophilic-hydrophobic graft copolymers for self-reinforcing hydrogels

Abstract: Materials for forming a hydrogel when contacted with water having improved anti-thrombogenic properties and a highly improved mechanical strength are obtained by the copolymerization of a free radical-polymerizable vinyl monomer capable of forming a hydrophilic polymer and a hydrophobic macromolecular compound having a chain-terminated polymerizable double bond and a molecular weight of 1,000 to 100,000.

Semi-permeable membranes, their preparation and their use

Abstract: Transparent hydrogels comprising isotactic polymethylmethacrylate and syndiotactic polymethylmethacylate make semi-permeable membranes of good strength and permeability which have particular utility in hemodialysis.

Hydrogels of unsaturated ester copolymers

Abstract: Bulk polymerized, water insoluble but water swellable polymer of monomers comprising water soluble monoester of acrylic or methacrylic acid with a polyhydric alcohol; and glycidyl methacrylate, and/or glycidyl acrylate, and/or glycidyl crotonate. The polymer may be swelled in aqueous solution to provide a transparent hydrogel having excellent physical properties, and suitable in an ophthalmic lens.

Hydrophilic copolymer of N,N-(C1 -C2 alkyl) acrylamide

Abstract: A hydrophilic copolymer of N,N-(C 1 -C 2 alkyl) acrylamide is disclosed. The copolymer is formed by reacting, based on 100 parts, from 20-80 parts of the C 1 -C 2 alkyl substituted acrylamide, 80-20 parts of C 1 -C 4 alkyl acrylates, methacrylates, or combinations, and small amounts of a cross-linking agent. The resulting copolymerization product can be equilibrated with water or other aqueous solutions to form hydrogels useful in forming shaped hydrogel articles. One particular shaped article which can be formed is a hydrophilic contact lens. A process for forming the hydrogels is also disclosed.