|
Polymacon
Polymacon is a non-proprietary (i.e., generic) term for a hydrophilic polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ... of 2- hydroxyethylmethacrylate (HEMA) cross-linked with ethylene glycol dimethacrylate (62%) and water (38%). It is used in the manufacture of soft contact lenses, and is considered a low hydration hydrogel of nonionic polymer. References Organic polymers {{polymer-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymer
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals. The term "polymer" derives from the Greek word πολύς (''polus'', meaning "many, much") and μέρος (''meros'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydroxyethylmethacrylate
Hydroxyethylmethacrylate (also known as glycol methyacrylate) is the organic compound with the chemical formula . It is a colorless viscous liquid that readily polymerizes. Hydroxyethylmethacrylate is a monomer that is used to make various polymers. Synthesis Hydroxyethylmethacrylate was first synthesized around 1925. Common methods of synthesis are: * reaction of methacrylic acid with ethylene oxide; * esterification of methacrylic acid with a large excess of ethylene glycol. Both these methods give also some amount of ethylene dimethacrylate. During polymerization of hydroxyethylmethacrylate, it works as crosslinking agent. Properties Hydroxyethylmethacrylate is completely miscible with water and ethanol, but its polymer is practically insoluble in common solvents. Its viscosity is 0.0701 Pa⋅s at 20°C and 0.005 Pa⋅s at 30°C. During polymerization, it shrinks by approximately 6%. Applications Contact lenses In 1960, O. Wichterle and D. Lím described its use in synthes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethylene Glycol Dimethacrylate
Ethylene glycol dimethylacrylate (EGDMA) is a diester formed by condensation of two equivalents of methacrylic acid and one equivalent of ethylene glycol.Bielstein 2, IV, 1532 EGDMA can be used in free radical copolymer crosslinking reactions. When used with methyl methacrylate, it leads to gel point at relatively low concentrations because of the nearly equivalent reactivities of all the double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betwee ...s involved. It is used as a monomer to prepare Hydroxyapatite/Poly methyl methacrylate composites. EGDMA can be used in free radical copolymer crosslinking reactions. References Monomers Methacrylate esters Glycol esters {{ester-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogel
A hydrogel is a crosslinked hydrophilic polymer that does not dissolve in water. They are highly absorbent yet maintain well defined structures. These properties underpin several applications, especially in the biomedical area. Many hydrogels are synthetic, but some are derived from nature. The term 'hydrogel' was coined in 1894. Chemistry Classification The crosslinks which bond the polymers of a hydrogel fall under two general categories: physical and chemical. Chemical hydrogels have covalent cross-linking bonds, whereas physical hydrogels have non-covalent bonds. Chemical hydrogels result in strong irreversible gels due to the covalent bonding, and they may also possess harmful properties which makes them unfavourable for medical applications. Physical hydrogels on the other hand have high biocompatibility, aren’t toxic, and are also easily reversible, by simply changing an external stimulus such as pH or temperature; thus they are favourable for use in medical applicat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
