Abstract:
A method for making polyethylene aerogels, including high molecular weight aerogels, commences by in a hydrocarbon solvent (e.g., toluene or benzene) in which polyethylene is insoluble at room temperature, adding polyethylene to the solvent heated to a temperature at which said polyethylene is soluble to form a reaction mixture. A free-radical catalyst is added to the reaction mixture and the reaction mixture is held until the desired gelation of the polyethylene has been achieved. The reaction mixture is cooled to about room temperature; and the hydrocarbon solvent is replaced with a gas (e.g., CO2 or air) to form the polyethylene aerogel. Optionally, the cooled reaction mixture can be contacted with an anti-solvent for polyethylene to replace the hydrocarbon solvent with the anti-solvent. Silica aerogel particles can be encapsulated in polyethylene aerogel by adding the particles to the polyethylene gelation reaction mixture.
Abstract:
Devices formed of or including biocompatible polyhydroxyalkanoates are provided with controlled degradation rates, preferably less than one year under physiological conditions. Preferred devices include sutures, suture fasteners, meniscus repair devices, rivets, tacks, staples, screws (including interference screws), bone plates and bone plating systems, surgical mesh, repair patches, slings, cardiovascular patches, orthopedic pins (including bone filling augmentation material), adhesion barriers, stents, guided tissue repair/regeneration devices, articular cartilage repair devices, nerve guides, tendon repair devices, atrial septal defect repair devices, pericardial patches, bulking and filling agents, vein valves, bone marrow scaffolds, meniscus regeneration devices, ligament and tendon grafts, ocular cell implants, spinal fusion cages, skin substitutes, dural substitutes, bone graft substitutes, bone dowels, wound dressings, and hemostats. The polyhydroxyalkanoates can contain additives, be formed of mixtures of monomers or include pendant groups or modifications in their backbones, or can be chemically modified, all to alter the degradation rates. The polyhydroxyalkanoate compositions also provide favorable mechanical properties, biocompatibility, and degradation times within desirable time frames under physiological conditions.
Abstract:
Biocompatible polyhydroxyalkanoate compositions with controlled degradation rates have been developed. In one embodiment, the polyhydroxyalkanoates contain additives to alter the degradation rates. In another embodiment, the polyhydroxyalkanoates are formed of mixtures of monomers or include pendant groups or modifications in their backbones to alter their degradation rates. In still another embodiment, the polyhydroxyalkanoates are chemically modified. Methods for manufacturing the devices which increase porosity or exposed surface area can be used to alter degradability. For example, as demonstrated by the examples, porous polyhydroxyalkanoates can be made using methods that creates pores, voids, or interstitial spacing, such as an emulsion or spray drying technique, or which incorporate leachable or lyophilizable particles within the polymer. Examples describe poly(4HB) compositions including foams, coatings, meshes, and microparticles. As demonstrated by the examples, these polyhydroxyalkanoate compositions have extremely favorable mechanical properties, as well as are biocompatible and degrade within desirable time frames under physioogical conditions. These polyhydroxyalkanoate materials provide a wider range of polyhydroxyalkanoate degradation rates than are currently available. Methods for processing these materials, particularly for therapeutic, prophylactic or diagnostic applications, or into devices which can be implanted or injected, are also described.
Abstract:
An expansible macromolecular material is produced by a method which comprises mixing an aqueous polyvinyl alcohol solution, an acidic aqueous macromolecular electrolyte solution, and a basic aqueous macromolecular electrolyte solution thereby preparing a composite polymer and subjecting this composite polymer to at least one cycle of alternate freezing and defrosting treatments. A macromolecular membrane constituted of said expansible macromolecular material and containing numerous through holes is obtained by mixing, freezing, and defrosting the aforementioned three mixed aqueous solutions under specific conditions.
Abstract:
Aerogel compositions that include polyamic amides, methods for preparing the aerogel compositions, and articles of manufacture that include or manufactured from the aerogel compositions are described.
Abstract:
Aerogel compositions, methods for preparing the aerogel compositions, articles of manufacture that include or are made from the aerogel compositions are described and uses thereof. The aerogels include a branched polyimide matrix with little to no crosslinked polymers.
Abstract:
The present disclosure provides a method for producing an aerogel, the method comprising reacting at least one acid monomer with at least one diamino monomer in a first solvent under conditions appropriate to form a polyimide polymer; conducting a solvent exchange wherein the first solvent is exchanged for a second solvent, said second solvent having a freezing point, wherein said solvent exchange further comprises (1) submersing the polyimide polymer in the second solvent in a pressure vessel and (2) creating a high pressure environment inside the pressure vessel for a first period of time; cooling the polyimide polymer to a first temperature below the freezing point of the second solvent; and subjecting cooled polyimide polymer to a first vacuum for a second period of time at a second temperature.
Abstract:
The present disclosure provides a method for producing an aerogel, the method comprising reacting at least one acid monomer with at least one diamino monomer in a first solvent under conditions appropriate to form a polyimide polymer; conducting a solvent exchange wherein the first solvent is exchanged for a second solvent, said second solvent having a freezing point, wherein said solvent exchange further comprises (1) submersing the polyimide polymer in the second solvent in a pressure vessel and (2) creating a high pressure environment inside the pressure vessel for a first period of time; cooling the polyimide polymer to a first temperature below the freezing point of the second solvent; and subjecting cooled polyimide polymer to a first vacuum for a second period of time at a second temperature.
Abstract:
The present disclosure provides a method for producing an aerogel, the method comprising reacting at least one acid monomer with at least one diamino monomer in a first solvent under conditions appropriate to form a polyimide polymer; conducting a solvent exchange wherein the first solvent is exchanged for a second solvent, said second solvent having a freezing point, wherein said solvent exchange further comprises (1) submersing the polyimide polymer in the second solvent in a pressure vessel and (2) creating a high pressure environment inside the pressure vessel for a first period of time; cooling the polyimide polymer to a first temperature below the freezing point of the second solvent; and subjecting cooled polyimide polymer to a first vacuum for a second period of time at a second temperature.