Abstract: Proposed is an improved optical waveguide consisting of a substrate plate such as a silicon wafer, an undercladding layer of silica glass thereon, a core line of silica glass extending on the undercladding layer and having a larger refractive index than the undercladding layer and an overcladding layer of silica glass having a smaller refractive index than the core line to cover the undercladding layer and the core line thereon altogether. Different from conventional optical waveguides of this type, of which each of the undercladding layer, core line and overcladding layer is formed by the flame deposition method of silica or electron-beam vapor deposition method followed by vitrification taking a relatively long time, the overcladding layer in the inventive optical waveguide is formed by forming a layer of an organopolysiloxane resin on the undercladding layer and core line followed by the oxidative thermal decomposition of the resin into silica and vitrification of the same.

Abstract: A composition comprising (A) an organopolysiloxane having a unit of the formula: R.sup.1 SiO.sub.3/2 wherein R.sup.1 is methyl, phenyl or vinyl in its molecule and having at least 0.05 alkenyl groups each directly attached to a silicon atom per silicon atom, (B) an organohydrogenpolysiloxane having at least 2 hydrogen atoms each directly attached to a silicon atom per molecule, (C) a platinum catalyst, and (D) an organosilane or organopolysiloxane of the formula: R.sup.2.sub.a (R.sup.3 O).sub.b SiO.sub.(4-a-b)/2 wherein R.sup.2 and R.sup.3 are hydrogen, methyl, phenyl or vinyl maintains good light transmission in cured form when exposed to humidity and is thus suitable for forming cores of optical fibers. Similar benefits are obtained with a composition comprising components (A) and (B), (C') a platinum catalyst and/or a radical polymerization initiator, and (E) a carboxylate.

Abstract: A polysilylethylene arylene polymer having an alkoxy or aryloxy group as a side chain substituent is used to form optical fiber cores which do not significantly increase their light transmission loss under an external pressure applied thereto even when exposed to a humid condition.

Abstract: A composition comprising (a) an organopolysiloxane having a unit of the formula: RSiO.sub.3/2 wherein R is a substituted or unsubstituted monovalent C.sub.1-10 hydrocarbon group in its molecule and having at least 0.05 alkenyl groups each directly attached to a silicon atom per silicon atom, (b) an organohydrogenpolysiloxane having at least 2 hydrogen atoms each directly attached to a silicon atom per molecule, and (c) a platinum catalyst, maintains good light transmission in cured form when exposed to humidity or stresses and is thus suitable for forming cores of optical fibers.

Abstract: A UV curable composition of a specific organopolysiloxane having mercaptoalkyl and phenylene groups and a vinyl-containing organopolysiloxane cures into a film which emits little stimulative sulfur odor and has enough resistance to light or UV radiation to retain its as-cured properties even after long-term exposure to sunlight or UV radiation.

Abstract: An organopolysiloxane homopolymer or copolymer comprising recurring units of the general formula: ##STR1## wherein R.sup.1 and R.sup.2 are independently selected from monovalent hydrocarbon groups, Q is a divalent aromatic hydrocarbon group, and letter n is an integer of from 1 to 4 has a high melting point and a high glass transition temperature and cures into products having a high modulus of elasticity and mechanical strength and thus suitable for various industrial applications. The polymer is prepared by a simple method involving the steps of reacting an alkali metal salt of a dihydroxy aromatic compound with a halogenated alkyl diorganoalkoxysilane, hydrolyzing the resulting bis(alkoxysilylalkoxy)arylene compound, and polycondensing the resulting bis(hydroxysilylalkoxy)arylene compound.

Abstract: Whereas the mechanism for the crosslink formation in the curable organopolysiloxane composition of the invention is the ultraviolet-induced addition reaction between alkenyl, e.g., vinyl, groups in a diorganopolysiloxane and mercaptoalkyl groups in another organopolysiloxane as in conventional compositions, the mercaptoalkyl-containing organopolysiloxane used in the invention is, differently from those in conventional compositions, an organopolysiloxane of a three-dimensionally branched molecular structure as composed of the siloxane units of the formulas R.sup.1.sub.3 SiO.sub.0.5, R.sup.1.sub.a (HSR.sup.2)SiO.sub.(3-a)/2 and SiO.sub.2, in which R.sup.1 is, for example, a methyl or phenyl group, R.sup.2 is, for example, --CH.sub.2 CH.sub.2 CH.sub.2 -- and a is zero, 1 or 2, in a specified proportion. In addition, the vinyl group-containing siloxane units in the vinyl-containing diorganopolysiloxane are localized in the molecular structure forming two blocks each bonded to one of the terminal silicon atoms.

Abstract: The coated optical fiber of the invention is prepared by providing a coating layer of an ultraviolet-curable organopolysiloxane or a composition comprising the same and irradiating the coating layer with ultraviolet. Specifically, each of the terminal silicon atoms of the organopolysiloxane, which preferably has a linear molecular structure, has two or more ethylenically unsaturated polymerizable groups bonded thereto through an oxygen atom, such as CH.sub.2 .dbd.CHCOOCH.sub.2 CH.sub.2 --, [CH.sub.2 .dbd.C(CH.sub.3)COOCH.sub.2 ].sub.3 C--CH.sub.2 --and (CH.sub.2 .dbd.CHCOOCH.sub.2).sub.2 C(C.sub.2 H.sub.5)CH.sub.2 --. By virtue of this unique molecular structure of the organopolysiloxane, the coating layer is rapidly cured by ultraviolet irradiation to give a cured coating layer exhibiting very low water absorption and small temperature dependency of the Young's modulus at low temperatures.

Abstract: In the alkenyl-containing diorganopolysiloxane of the invention, the distribution of the alkenyl groups in the molecule is not random as in conventional alkenyl-containing diorganopolysiloxanes but each of at least three siloxane units linked to each of the terminal silicon atoms has an alkenyl, e.g. vinyl, group while at least six of the uninterruptedly linked siloxane units excepting the above mentioned alkenyl-containing units adjacent to the molecular chain ends are free from aliphatic unsaturation. A method for the preparation of the diorganopolysiloxane having the alkenyl groups in such a localized distribution is disclosed. When the diorganopolysiloxane is used as the principal ingredient of a curable organopolysiloxane composition as combined with a crosslinking agent, the composition, despite its relatively low viscosity, can give a cured rubber having markedly improved mechanical strengths.

Abstract: The inventive method for forming a cured film on a substrate surface comprises coating the surface with a room temperature curable organosiloxazane polymer comprising, in a molecule, (a) at least one organosiloxane unit represented by the unit formula (a) at least one organosiloxane unit represented by the unit formulaR.sup.1.sub.a SiO.sub.(4-a)/2,and (b) at least one organosilazane unit represented by the unit formulaR.sup.2.sub.b Si(NR.sup.3).sub.(4-b)/2,in which R.sup.1, R.sup.2 and R.sup.3 are each a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, not all of them being simultaneously hydrogen atoms, and the subscripts a and b are each a positive integer of 1, 2 or 3 with the proviso that a and b cannot be simultaneously equal to 3, in a molecule and subjecting the coating film to exposure to a moisture-containing atmosphere. The method is useful for forming a surface-protecting film or for imparting surface releasability.

Abstract: The coated optical fiber of the invention is prepared by providing a coating layer of an ultraviolet-curable organopolysiloxane or a composition comprising the same and irradiating the coating layer with ultraviolet. Specifically, each of the terminal silicon atoms of the organopolysiloxane, which preferably has a linear molecular structure, has two or more ethylenically unsaturated polymerizable groups bonded thereto through an oxygen atom, such as CH.sub.2 .dbd.CHCOOCH.sub.2 CH.sub.2 --, [CH.sub.2 .dbd.C(CH.sub.3)COOCH.sub.2 ].sub.3 C--CH.sub.2 -- and (CH.sub.2 .dbd.CHCOOCH.sub.2).sub.2 C(C.sub.2 H.sub.5)CH.sub.2 --. By virtue of this unique molecular structure of the organopolysiloxane, the coating layer is rapidly cured by ultraviolet irradiation to give a cured coating layer exhibiting very low water absorption and small temperature dependency of the Young's modulus at low temperatures.