Showing papers on "Self-healing hydrogels published in 1985"

Hydrogel-forming polymer compositions for use in absorbent structures

Abstract: The present invention relates to improved hydrogel-forming polymer compositions which can be used as absorbents in absorbent structures and absorbent articles such as diapers, sanitary napkins and the like. Such hydrogel-forming polymer compositions are substantially water-insoluble, slightly cross-linked, partially neutralized polymers which are prepared from unsaturated polymerizable, acid group-containing monomers and cross-linking agents. These hydrogel-forming polymer materials, upon imbibing fluids, form hydrogels. Such polymer materials have relatively high gel volume and relatively high gel strength as measured by shear modulus of the hydrogel which forms therefrom. Such polymer materials also contain relatively low levels of extractable polymer material which can be extracted therefrom by contact with synthetic urine. Preferred hydrogel-forming polymers having these characteristics can be prepared by polymerizing the acid group-containing monomers in their free acid form at relatively low monomer concentrations, preferably using relatively low polymerization temperatures. Absorbent structures and absorbent articles containing these dried hydrogel-forming polymer materials are also disclosed.

Glucose-sensitive membranes containing glucose oxidase: activity, swelling, and permeability studies.

Abstract: The development of membranes that swell in response to glucose is reported. The membranes may prove to be useful in glucose monitoring or glucose-dependent insulin delivery. The polymers were synthesized by the radiation-induced polymerization of frozen solutions containing hydroxyethyl methacrylate, N,N-dimethylaminoethyl methacrylate, tetraethylene glycol dimethacrylate, ethylene glycol, water, and glucose oxidase. The polymers were hydrogels, with water contents in the range of 60–90%, depending on the pH or glucose concentration. Changes in swelling and permeability of the hydrogel were caused by exposure to glucose solutions. The gluconic acid formed by the glucose oxidase catalyzed oxidation of glucose in the membrane lowered the pH of the system and thus caused the changes in the membrane. The retention of enzyme activity by the membranes in vitro and in vivo is also reported. The large differences in properties among membranes made with different chemical formulations suggest that glucose-sensitive membranes with performance characteristics needed for an artificial pancreas may be an achievable goal.

Method of forming shaped hydrogel articles

Abstract: A method for forming shaped hydrogel articles such as soft contact lenses wherein hydrophilic monomers are mixed with an inert diluent prior to polymerization, and the diluent is replaced with water following the polymerization. Diluents yielding optically clear hydrogels with good mechanical properties are selected on the basis of their viscosity and their Hanson cohesion parameters relative to the cohesion parameters of the polymeric component of the hydrogel.

Hydrogels capable of supporting cell growth

Abstract: A method of growing anchorage-dependent cells is disclosed in which a substrate comprising a hydrogel is employed. The hydrogel is formed from an aqueous solution gelled with a crosslinked polymer of a hydrophilic monomer and includes a macromolecule capable of supporting cell growth.

Preparation of aerogels

Abstract: A process for the drying of inorganic hydrogels obtained from readily hydrolyzable compounds of the elements Al, Si, Ti, B, La, Zr, Cr, Sn, Th or Mg, and organic hydrogels based on gelatine, albumin or agar agar, from CO2, to give aerogels is easy to carry out industrially, and drying can be effected at from room temperature to 90° C. The resulting aerogels are transparent and have a low bulk density and low thermal conductivity. The aerogels can be used as packing materials for liquid chromatography, as catalyst carriers, as substrates for enzymes and as adsorbents.

Hydrogel from ultraviolet-initiated copolymerization

Abstract: In the particular embodiment described in the specification, a contact lens hydrogel is prepared by copolymerizing 75 parts of N-vinyl pyrrolidone and 23 parts of phenyl ethyl methacrylate together with allyl methacrylate as a crosslinker, t-butyl peroctoate as a thermal initiator and 2,2-dimethoxy-2-phenylacetophenone or benzoin methyl ether as a photoinitiator The mixture is maintained at a temperature of 5° C and protected from light prior to photopolymerization which is carried out under ultraviolet radiation The copolymer is then post-cured thermally Cloudy or hazy hydrogels are avoided by preventing prepolymerization of the mixture

Large deformation of hydrogels of poly(vinyl alcohol), agarose and kappa-carrageenan

Abstract: The deformation behaviour of hydrogels of poly(vinyl alcohol) (PVA), agarose and kappa-carrageenan was investigated and compared with each other. PVA gels prepared by periodically repeated freezing-thawing cycles showed a much larger breaking force and breaking deformation than agarose and kappa-carrageenan gels.

Modification of polyetherurethane for biomedical application by radiation‐induced grafting. I. Grafting procedure, determination of mechanical properties, and chemical modification of grafted films

Abstract: Radiation grafting of monomers onto suitable trunk polymers is a useful tool for tailoring new polymers for special purposes. This technique has been used in the past for the development of biocompatible materials, e.g., by grafting hydrogels onto mechanically stable polymers. In this first part of our work, the radiation grafting of hydrophilic or reactive monomers onto a polyetherurethane film using the pre-swelling technique is described. Following this technique the trunk polymer was swollen in the monomer before irradiation. As monomers 2-hydroxyethyl methacrylate (HEMA), 2,3-epoxypropyl methacrylate (GMA), 2,3-dihydroxypropyl methacrylate (GOMA), and acrylamide (AAm) were used. The kinetics of the grafting reactions were examined, and the distribution of the graft component inside the trunk polymer was investigated by means of infrared (IR) spectroscopy. Surface-grafted as well as bulk- and surface-grafted products could be obtained. The mechanical behavior of the grafted films--especially in the water-swollen state--was examined and compared with that of the pure trunk polymer. In nearly all cases it was found that the tensile strength sigma B and the elongation at break epsilon R decreases as the grafting yield increases. Modification of GMA- and AAm-grafted films via chemical reactions was performed to create new functional groups of biomedical interest. Inmore » this manner a diol structure, a carboxylic acid structure, and a sulfonic acid group could be introduced in the grafted polymer. The water uptake of such modified films is increased markedly when compared with that of the unmodified samples.« less

Hydrogel materials formed by radiation polymerization of carbohydrates and unsaturated monomers

Abstract: Homogeneous hydrogels comprise a water-soluble sugar, derivative or mixture thereof, radiation cross-linked with at least one ethylenically unsaturated compound. A preferred combination is sucrose or glucose cross-linked with acrylic acid. The hydrogels may contain additives e.g. plasticizers such as glycerol. The hydrogels are strong and expand to a large extent e.g. 30× on water absorption. They are particularly suitable for use in medical dressings, preferably bonded to a supporting film which may be a semi-permeable membrane allowing control of water loss. A method for preparing such a hydrogel and dressing is also described.

X-ray contrast spherical hydrogel particles based on polymer and copolymers of acrylates and methacrylates and the method for preparation thereof

Abstract: The invention pertains to X-ray contrast spherical hydrogel particles based on polymers and copolymers of acrylates and methacrylates and to a method of their preparation. The subject of this invention are X-ray contrast spherical hydrogel particles based on polymers and copolymers of acrylates and methacrylates characterized by the particles of spherical form with diameter 0.2 to 2 mm, which strongly swell in water and contain a derivative of amino-triiodobenzoic acid of general formula I, ##STR1## where R 1 ,R 2 is hydrogen, acyl group with 1 to 3 carbon atoms or alkyl with 1 to 10 carbon atoms and X is halogen, --OH or --NH(CH 2 ) n NH 2 , where n=1-6, covalently bonded to the polymer skeleton. A method for preparation of X-ray contrast hydrogel particles according to the invention in which hydrogel particles, containing hydroxyl or epoxide groups localized on side chains of the polymer skeleton, are allowed to swell in an excess of a solvent chosen from the group comprising dioxane, dimethylacetamide, dimethylformamide, tetrahydrofuran and dimethylsulfoxide, which contains the dissolved derivative of amino-triiodobenzoic acid of the general formula I, optionally together with a compound reacting with hydrogen halogenide formed, which is selected, for example, from the group comprising tertiary amines, the dispersion is heated to 100° C. at utmost and allowed to react for 150 hours at utmost, the solid phase is separated and freed of soluble substances by washing. The procedure according to the invention provides spherical hydrogels with X-ray contrast properties without changing their other properties substantial for application in medical practice.

Hydrogels for Controlled Drug Release

Abstract: Hydrogels have been investigated for use in controlled-release drug delivery systems. Hydrogels show superior biocompatibility and permeation of both hydrophobic and hydrophilic drugs depending on the combination of copolymers. Drug diffusion through hydrogels depends on the hydrogel nature, mainly the percentage of cross-linking agents and hydrogel water content. Various devices designed with hydrogels are discussed in this chapter: reservoir systems, drug-dissolved monoliths, drug-dispersed monoliths, monolith devices with barrier layers, and novel delivery systems.

Synthesis and characterization of hydrogels from graft copolymers

Abstract: Well-defined graft copolymers composed of a hydrophilic clyceryl methacrylate backbone and hydrophobic monodisperse molecular weight polystyrene branches were prepared by the macromonomer technique. The swelling behaviour and the oxygen permeability of hydrogels prepared from these graft copolymers were studied. It was found that equilibrium water content of these hydrogels was considerably high and depended on both the graft copolymer structure and the microphase separated structure of the prepared hydrogel. Oxygen permeability of the hydrogels was directly related to their water content. Hydrogel membranes prepared from the graft copolymers have also well-defined structures which can be easily controlled by the graft copolymer structure.

Shaped hydrogel articles

Abstract: A method forming shaped hydrogel articles such as soft contact lenses wherein hydrophilic monomers are mixed with an inert diluent prior to polymerization, and the diluent is replaced with water following the polymerization. Diluents yielding optically clear hydrogels with good mechanical properties are selected on the basis of their viscosity and their Hanson cohesion parameters relative to the cohesion parameters of the polymeric component of the hydrogel.

Kinetics of Drug Release from Glassy Polymers: Effect of Initially Nonuniform Drug Distribution

Abstract: The effect of nonuniform initial drug concentration distribution on the kinetics of drug release from polymer matrices is examined theoretically. It can be shown that a constant rate of drug release can be achieved via a specific sigmoidal drug concentration distribution without the need to have a saturated reservoir as in a membrane-reservoir system. Hydrogel polymers are particularly suitable for this application in that they are quite glassy in the dry state, and are capable of immobilizing any nonuniform drug distribution introduced prior to the dehydration step. In the presence of water, hydrogels can absorb a significant amount of water to form an elastic gel and, at the same time, release the dissolved drug by diffusion through the swollen region. Specific examples based on glassy hydrogel beads are given to illustrate this concept.

Effects of hydrogels with poly(ethylene oxide) chains on granulocyte compatibility.

Abstract: ポリエチレンオキシド (PEO) 鎖を有するハイドロゲルの顆粒球に及ぼす効果につき検討した. 鎖長の異なるPEOを側鎖に持つメトキシポリエチレングリコールモノメタクリラートをポリ塩化ビニル (PVC) に光グラフト共重合したハイドロゲルを合成した. また, グラフト率を変え, ゲル含水率を変化させた. 顆粒球粘着は, ゲルの含水率の増加に伴って低下し, 含水率36%以上で, 顆粒球の付着は全く認められなかった. 同一含水率では, PEO鎖長が長いほど, 顆粒球機能は良好であった. 長鎖PEO鎖を有するバッグ中で顆粒球を24時間保存した場合は, 新鮮顆粒球の約95%の機能活性を維持し, 医療用軟質PVCバッグより20～30%の機能向上を示した. これらの結果から, 長鎖PEO鎖を有するハイドロゲルは, その水和したPEO鎖の排除体積効果により材料表面への細胞粘着抑制ばかりでなく機能保持にも有効であることがわかった.

Molded hydrogel article

Abstract: A method forming shaped hydrogel articles such as soft contact lenses wherein hydrophilic monomers are mixed with an inert diluent prior to polymerization, and the diluent is replaced with water following the polymerization. Diluents yielding optically clear hydrogels with good mechanical properties are selected on the basis of their viscosity and their Hanson cohesion parameters relative to the cohesion parameters of the polymeric component of the hydrogel.

Hydrogels based on poly(2-hydroxyethyl methacrylate) with glucose moieties

Abstract: Hydrogels (crosslinked polymers with a definite water content) with glucose moieties, prepared by radical copolymerization of 3-0-methacryloyl-1,2; 5,6-diisopropylidene-α-D-glucofuranose, 2-hydroxyethyl methacrylate, the crosslinker ethylene glycol dimethacrylate and acid hydrolysis of the isopropylidene protecting groups, were examined for linear expansion to hydration, weight-percent hydration, water content on a dry basis, refractive index, oxygen permeability and the percental transmission of visible light.