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Alok K Awasthi; Novel Ethylenically Unsaturated Polycarbosiloxane Monomers for Next Generation Silicone Hydrogel Contact Lenses. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4650.
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Design and development of materials for contact lenses that consist of a combination of characteristics such as robust mechanical properties, high oxygen permeability, great wettability, lubricity and minimal protein deposition on the lens surface to provide extended comfort in the eye still remains a great challenge. Recently, we have demonstrated that the use of an ethylene-dimethylsilyl (EDS) monofunctional with hydrophilic monomers results in contact lens materials with many of the ideal properties suitable for continuous wear application. However, the challenge remains the copolymerization of hydrophilic monomers with silicon hydrophobic monomers to produce silicon hydrogel material with optimum properties of a contact lens. Therefore, there is a need for a new type of siloxy comprising unit. In view of this ethylenically unsaturated polycarbosiloxane (M2-EDSn) were designed. This presentation describes the synthesis of these crosslimkers and their use in the formulation for next generation silicone hydrogel contact lenses.
Synthesis of novel M2-EDSn derivatives was carried out by conventional cationic polymerization technique for the purpose of using them as polymeric cross linkers for our contact lens formulations. Thus when 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane was treated with dimethacryloxybutyl-tetramethyldisiloxane in presence of catalytic amount of triflic acid, compound M2-EDSn was obtained in almost quantitative yield and were fully characterized. These compounds were further polymerized with hydrophilc monomers to yield contact lens/thin films with excellent properties necessary for the contact lens with best end of the day comfort as described in the table in results section.
The specific monomer mixes set forth were prepared according to Table below. Monomer mix was dispensed between polypropylene molds and prepared as lenses or flats in the case of Dk samples. Polymerization was carried out under UV light (~350 nm) for a period of two hours. The mechanical and chemical properties of the lenses/films were measured.
Novel ethylenically unsaturated polycarbosiloxane capable of polymerization to form polymeric compositions having suitable DK, water content and low modulus of elasticity and improved hydrolytic stability useful in the manufacture of ophthalmic devices were synthesized and characterized.
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