Abstract: There is disclosed an organic nonlinear optical material which comprises a polymer having the following constitutional units, in amounts of 5 to 100 mole % of (I) and 0 to 95 mole % of (II), and a weight average molecular weight (Mw) of the polymer being 10,000 to 2,000,000. ##STR1## wherein the symbols represent the same meanings as defined in the specification. ##STR2## A nonlinear optical element has large nonlinear optical effect and yet is excellent in molding processability so that it can be widely applied to the filed of optical processings.

Abstract: There is disclosed an organic nonlinear optical material which comprises a polymer having the following constitutional units, in amounts of 5 to 100 mole % of (I), 0 to 50 mole % of (II) and 0 to 50 mole % of (III), and a weight average molecular weight (Mw) of the polymer being 10,000 to 2,000,000: ##STR1## wherein m, n, X, Y and A have the meanings as defined in the specification, ##STR2## wherein R.sup.2 represents an alkyl group, and ##STR3## A nonlinear optical element which is tough with wide surface as well as having large nonlinear optical effect can be obtained.

Abstract: Disclosed is a vinylidene cyanide copolymer obtained by copolymerization of vinylidene cyanide and two kind of vinyl compounds.By formation of a ternary copolymer, a monomer difficultly copolymerizabke with vinylidene cyanide can be incorporated into the polymer, and high piezoelectric performance can be obtained when polarized.

Abstract: A vinylidene cyanide copolymer obtained by copolymerizing vinyldene cyanide represented by formula (I) ##STR1## and a vinyl compound represented by formula (II) ##STR2## wherein Z represents a hydrogen atom or a saturated hydrocarbon group having from 1 to 6 carbon atoms; when Z is a hydrogen atom, R represents C.sub.n H.sub.2n+1 COO--, wherein n represents 0 or an integer of from 4 to 9; and when Z is a saturated hydrocarbon group, R represents CH.sub.3 COO-- or a group having a benzene ring. The copolymer is excellent in transparency and provides an electret exhibiting excellent pyroelectricity or piezoelectricity upon polarization.

Abstract: An optical material obtained by electrically polarizing a high polymer molded article obtained from a composition comprising a copolymer of vinylidene cyanide and at least one comonomer selected from vinyl compounds, other vinylidene compounds and dienes having uniformly dispersed therein from 0.1 to 70% by weight of an organic molecular crystal having nonlinear optical effects, with the total amount of the copolymer and the organic molecular crystal being 100% by weight. The optical material has excellent orientation of the organic molecular crystal, great nonlinear optical effects, and excellent moldability.