Abstract: This invention provides a cladding material in an optical fiber which comprises a polymer comprising:(1) a structural unit represented by the formula ##STR1## and (2) at least one of structural unit(i) ##STR2## and (ii) ##STR3##

Abstract: This invention relates to an optical material comprising a polymer which has a structural unit represented by the formula ##STR1## wherein X.sup.1 and X.sup.2 are the same or different and are each hydrogen or deuterium, and R.sup.1 is a chain hydrocarbon group having 1 to 5 carbon atoms, a cyclic hydrocarbon group (with or without a substituted lower alkyl group) having 3 to 6 carbon atoms or a deuterium-substituted chain hydrocarbon group having 1 to 5 carbon atoms in an amount of at least 5 mole % of the polymer.

Abstract: This invention provides a process for preparing an .alpha.-fluoroacrylic acid ester characterized by reacting 2,2,3,3-tetrafluorooxetane, a metal halide, an alcohol and a dehalogenating agent. This invention also provides a process for preparing .alpha.-fluoroacrylic acid fluoride, CH.sub.2 .dbd.CFCOF, which is an intermediate for preparing the .alpha.-fluoroacrylic acid ester.

Abstract: A copolymer for optical fibers of fluoroalkylmethacrylate and methacrylic acid, the fluoroalkylmethacrylate having such properties that a homopolymer made of only the fluoroalkylmethacrylate has a glass transition temperature and a refractive index each in the range given by the following formulae (I) and (II), respectively:(1/Tg).ltoreq.9.47.times.10.sup.-3 -4.556.times.10.sup.-3 n.sup.20 (I)n.sup.20 .ltoreq.1.42 (II)wherein Tg represents the glass transition temperature (.degree.K.) of the homopolymer and n.sup.20 represents the refractive index thereof.

Abstract: A copolymer for optical fibers of fluoroalkylmethacrylate and acrylic acid.

Abstract: An optical material comprising a thermal resisting fluoroalkylmethacrylate copolymer which essentially consists of(a) fluorine-containing methacrylate monomer unit of the formula ##STR1## wherein R.sub.f.sup.1 represents a fluoroalkyl group having 1 to 3 carbon atoms and(b) a fluorine-containing acrylate monomer unit of the formula ##STR2## wherein R.sub.1 and R.sub.2 are the same or different and represents a hydrogen atom or a lower alkyl group and R.sub.f.sup.2 represents a fluoroalkyl group having 1 to 3 carbon atoms.