Showing papers on "Self-healing hydrogels published in 1975"

Disposable absorbent articles containing hydrogel composites having improved fluid absorption efficiencies and processes for preparation

Abstract: Hydrogel composites are provided having improved fluid absorption efficiencies which render them especially useful in disposable absorbent articles, such as diapers, catamenial devices and the like. The hydrogels are in particulate form, each particle or agglomerate of particles being substantially coated with fibers, a portion of which fibers extend from the particle. The fibers enhance the rate at which the hydrogel absorbs aqueous fluids and also serve to maintain the fluid in close proximity to the hydrogel. The extended fibers serve to anchor the hydrogel particle when it is contained in a fibrous or cellular matrix.

Diester crosslinked polyglucan hydrogels and reticulated sponges thereof

Abstract: Novel hydrogel compositions of diester crosslinked polyglucans and a process for their preparation are provided. Amylose, dextran, and pullulan succinates and glutarates when crosslinked as described were found to not only have use as general fluid sorbants but also to have exceptional hemostatic activity, adherence to a wound, and bioabsorption without causing undue irritation of the tissue or toxic effects. Reticulated hydrogel sponges made of the crosslinked diesters which are particularly useful as general fluid sorbants, and those of amylose succinate and amylose glutarate are most excellent bioabsorbable hemostatic agents. The sponges are made by lyophilizing water-soluble salts of the mono- or half-esters, such as water-soluble salts of amylose succinate or amylose glutarate, under process conditions of the invention in the presence of a reticulating agent which causes a controlled melting of the salt solution as it nears the dry state during the lyophilizing step. The resulting reticulated, porous, open-celled sponge is then crosslinked by heating the sponge under dehydrating conditions to form diester-crosslinks. The sponge is highly porous, is moderately strong, and has the ability to retain up to 40 times its weight of isotonic saline. When neutralized with physiologically acceptable salts, the sponge has exceptional hemostatic activity, adherence to bleeding tissue, and bioabsorption without causing substantial irritation of the tissue or toxic effects. The invention also comprises a process of providing hemostasis at the site of a wound, employing the diester cross-linked polyglucan hydrogels or reticulated sponges thereof.

Cell adhesion to polymeric materials: implications with respect to biocompatibility.

Abstract: The adhesion of radio-labeled chick embryo muscle cells to the surfaces of radiation grafted hydrogels and other polymeric materials was measured in vitro. The degree of adhesion was determined by measuring the percentage of cells which remained adherent to the surfaces after 180 min of contact time (plating efficiency). Plating efficiency was found to vary between 2 and 94% depending on the nature of the surface. Preadsorption of albumin, gamma-globulin or fibrinogen markedly affected subsequent adhesion of cells. Radiation grafted poly(2-hydroxyethyl methacrylate) and poly(N-vinyl-2-pyrrolidone) hydrogels on silicone rubber demonstrated exceptionally low adhesiveness in this assay. The potential for using this cell adhesion assay as a general screening test for biomaterials is discussed.

Chemically joined, phase separated self-cured hydrophilic thermoplastic graft copolymers and their preparation

Abstract: Disclosed are chemically joined, phase separated self-cured hydrophilic thermoplastic graft copolymers which are copolymers of at least one hydrophilic (water-soluble) ethylenically unsaturated monomer or mixtures thereof (or compounds rendered hydrophilic) and at least one copolymerizable hydrophobic macromolecular monomer having a copolymerizable end group which is copolymerizable with said hydrophilic monomer based on the relative reactivity ratios of the respective copolymerizable moieties, said copolymerizable hydrophobic macromolecular monomer being characterized as having a substantially uniform molecular weight distribution such that its ratio of Mw/Mn is not substantially above about 1.1, and being further characterized as having a molecular weight of at least about 2,000. The copolymers are water-dispersible and water-swellable and are useful in diverse applications such as suspension stabilizers, flocculants, hydrogels (i.e., biomedical hydrogels as contact lenses, artificial organs, etc.), industrial thickeners, ion exchange resins, drilling mud, and they can impart moisture absorption and water permeability (useful in dialysis tubing) as well as anti-static properties to products.

Cationic hydrogels based on heterocyclic N-vinyl monomers

Abstract: Novel cationic hydrogels, containing basic (cationic) groups in their molecular structure, and processes for their preparation are described. These novel hydrogels are stable, three-dimensional polymer networks, having good water permeability and mechanical properties. They are obtained by simultaneous polymerization and cross-linking in the presence of a polymerization catalyst, such as an organic peroxide, azobisisobutyronitrile or other free radical polymerization catalyst, of a mixture of (a) a heterocyclic monomer preferably an N-vinyl lactam, (b) a cationic monomer -- usually an ester of acrylic or methacrylic acid with an amino alcohol, the terminal amino group of which may be quaternized, such as dimethylaminoethyl methacrylate or acrylate and the quaternized derivatives thereof, and (c) a cross-linking agent, such as a glycol or polyglycol diacrylate or dimethacrylate and also, preferably, (d) at least one acrylic monomer capable of polymerizing to a very high molecular weight, such as hydroxyethyl- or hydroxypropyl-acrylate or methacrylate, or a lower alkyl acrylate or methacrylate; if desired there may also be present in the monomer mixture (e) other polymerizable ethylenically unsaturated monomers, which are copolymerizable with components (a), (b), (c) and (d). The thus obtained cationic hydrogels are useful for combining by reaction or complexing, with water soluble or dispersible materials having an opposite charge; such as acidic or anionic agricultural chemicals (insecticides, herbicides, fungicides, plant growth regulators, etc.), germicides, pharmaceuticals, cosmetics, hormones, enzymes, flavors, fragrances, antiperspirants, metals and the like, both to recover such acidic or anionic materials from an aqueous medium and for purifying water containing them, and also for the preparation of a complex or other combination of the cationic hydrogel with such anionic materials which may be useful per se or from which the complexed or combined acidic or anionic material may be slowly or controllably released.

Ionogenic hydrophilic water-insoluble gels from partially hydrolyzed acrylonitrile polymers and copolymers, and a method of manufacturing same

Abstract: The invention relates to new ionogenic hydrogels based on partially hydrolyzed polymers containing, in the starting material, at least 60, advantageously at least 80% (mol.) of acrylonitrile units, said hydrogels being characterized by a weakly ampholytic, character and by a multiblock structure of polymeric chains with continuous sequences of acrylonitrile units in an amount of from 2 to 95% (molar), alternating with continuous sequences of hydrophylic units consisting of a major amount of acrylic acid and a minor amount of acrylamide units, the sequences or blocks of acrylonitrile units forming together polyacrylonitrile domains detectable by X-ray analysis. In water-swelled condition the hydrogels consist of two distinct but inseparable phases, one of them said polyacrylonitrile, the other said amorphous hydrophilic, highly solvated chains with predominating acrylic acid units. Each macromolecular chain, containing, in average, several blocks or sequences of the said two sorts, (non-hydrolyzed polyacrylonitrile and hydrolyzed to acrylic acid and acrylamide units), takes part of several domains of the two phases. This structure is uniform and homogeneous in the whole cross-section of any article manufactured from the hydrogel.

Hydrogels - A Broad Class of Biomaterials

Abstract: The term “hydrogel” refers to a broad class of polymeric materials which are swollen extensively in water (30–90%) but which do not dissolve in water. They have been used in a wide variety and growing number of biomedical applications since they often exhibit good biocompatibility. They may be applied in bulk forms which vary from clear solids to opaque sponges; sometimes these forms are reinforced by woven fabrics since the highly water-swollen gels are mechanically weak. For this same reason, they are also useful as coatings, especially when the biomedical application involves the contact of a preformed device or implant with body fluids. Table I summarizes a number of applications of hydrogels which have been mentioned in the literature (see references also).

Fenestrated hydrogels for contact lens use and method for making same

Abstract: A process for the reproducible manufacture of fenestrated hydrogels is described whereby unpolymerized hydrogel monomers are cast, polymerized in the mold and fenestrations produced in situ.

Blood compatibility of radiation-grafted hydrogels.

Abstract: Radiation grafted hydrogels of poly(2-hydroxyethyl methacrylate) and poly(N-vinyl-2-pyrrolidone) on silicone rubber rings were evaluated by the standard vena cava ring implantation test. Both grafted hydrogel rings showed significant patency after 2 weeks implantation, in contrast to the untreated silicone rubber rings which were totally occluded after 2 hr.

Dynamic mechanical properties of poly(2‐hydroxyethyl methacrylate) hydrogels

Abstract: Homogeneous and heterogeneous poly(2-hydroxyethyl methacrylate) hydrogels were prepared by copolymerization of 2-hydroxyethyl methacrylate and small amounts of ethylene glycol dimethacrylate in the presence of water; concentrations of water (V1) in the polymerization mixture and the volume fractions of water (v1) of the gels swollen to equilibrium were 40, 50, 60, 70% by volume, and 0.475, 0.541, 0.669, 0.778, respectively. From the homogeneous (clear) hydrogel (V1 = 40%) preparation, four hydrogels were prepared with v1 = 0.434, 0.418, 0.378, 0.326. Tensile dynamic moduli were measured in the frequency range from 0.006 to 0.6 cps and the temperature range from 0 to 40°C. In these cases, the influence of swelling on the shape of the relaxation spectra and on the monomeric unit friction coefficient was studied. The dependence of the friction coefficient on water concentration was interpreted in terms of free volume. In the heterogeneous (opaque) gel preparations (V1 = 50, 60, 70%), the effect of the aqueous phase in the system on the mechanical behavior was described by a modification of the blending law of Ninomiya. For the systems with V1 = 60% and 70% the shapes of the storage and loss moduli in the main transition region and the friction coefficient were similar to those of the homogeneous gel with V1 = 40%, except for the decrease in absolute value of the storage moduli. For the system with V1 = 50% the shape of the relaxation spectrum changes appreciably and the wedge distribution does not hold.

Hydrogels of crosslinked poly(1-glyceryl methacrylate) and poly(2-hydroxypropyl methacrylamide)

Abstract: Two hydrophilic polymer networks of different crosslinking density and varying reference degree of swelling were prepared from 2,3-dihydroxypropyl methacrylate (glyceryl methacrylate) and N-(2-hydroxypropyl)methacrylamide. They were characterized by swelling and compression measurements, and the Flory-Huggins interaction parameters were determined. The results reveal the importance of hydrophobic forces in the physical properties of poly(1-glyceryl methacrylate). Poly(2-hydroxypropyl methacrylamide) gels do not exhibit the presence of these specific effects.

Starch-Polyacrylonitrile Copolymers. Properties of Hydrogels

Abstract: Gel sheets prepared from high-viscosity aqueous dispersions of hydrolyzed starch-polyacrylonitrile graft copolymers absorb several hundred times their own weight in water. Viscosity of the disperSiOns can be . reduced to low levels by mechanical shear before the films are cast to give solutions which yield water'soluble .films. These soluble films can be readily cross-linked to again form highly swellable but nonsoluble gel sheets by: (a) heating, (b) irradiating with 60CO. and (c) aging at high relative humidity.

Hydrophilic copolymer of N,N-di(C1 -C2 alkyl)acrylamide cross-linked with a glycidyl ester

Abstract: A hydrophilic copolymer of an N,N-di(C 1 -C 2 alkyl)acrylamide is disclosed. The copolymer is formed by reacting, based on 100 parts, from about 20-80 parts of a C 1 -C 2 alkyl substituted acrylamide, about 10-80 parts of a C 1 -C 4 alkyl acrylate, methacrylate, or combinations of acrylate and methacrylate, and about 2-20 parts of a glycidyl ester of acrylic, methacrylic or crotonic acid. 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.

Cationic hydrogels based on hydroxyalkyl acrylates and methacrylates

Abstract: Novel cationic hydrogels, containing basic (cationic) groups in their molecular structure, and processes for their preparation are described These novel hydrogels are three-dimensional polymer networks, having good water permeability and mechanical properties, and are obtained by simultaneous polymerization and crosslinking, in the presence of a polymerization catalyst, such as an organic peroxide, azobisisobutyronitrile or other free radical polymerization catalyst, of a mixture of (a) hydroxyalkyl acrylate or methacrylate, (b) a cationic monomer -- usually an ester of acrylic or methacrylic acid with an amino alcohol, the terminal amino group of which may be quaternized, such as dimethylaminoethyl methacrylate or acrylate and the quaternized derivatives thereof, and (c) a cross-linking agent, such as a glycol diacrylate or dimethacrylate; if desired there may also be present (d) one or more additional monomers, usually an acrylic monomer such as an alkyl acrylate or methacrylate, acrylamides etc (although other monomers such as vinyl acetate, styrene, etc may also be used) which is copolymerizable with (a), (b) and (c) The thus obtained cationic hydrogels are useful for combining, by reaction or complexing, with materials having an opposite charge; such as acidic or anionic agricultural chemicals (insecticides, herbicides, fungicides, plant growth regulators, etc), germicides, pharmaceuticals, cosmetics, hormones, enzymes, flavors, fragrances, antiperspirants, metals and the like, both to recover such acidic or anionic materials from an aqueous medium and for purifying water containing them, and also for the preparation of a complex or other combination of the cationic hydrogel with such materials which may be useful per se or from which the complexed or combined acidic or anionic material may be slowly or controllably released