Aryl-substituted poly-p-arylenevinylenes comprising a repeating unit of the formula (C1), ##STR00001## in which one or more of the unsubstituted aromatic carbon atoms may be replaced by nitrogen atoms, --OC.sub.m and --OC.sub.n are alkoxy groups, m and n are integers from 2 to 6 with m+n=8, p is 0, 1, 2 or 3 and in which R is CN, Cl, F, CF.sub.3, NO.sub.2, or SO.sub.3Z wherein Z is a monovalent cation such as Na.sup.+, or in which R is --XR.sup.1 wherein the unit --X-- represents a single bond, --O--, --S--, --CO--, --COO--, --OCO--, --SO--, --SO.sub.2--, --N(R.sup.2)-- or --N(R.sup.2)CO--, and wherein R.sup.1 and R.sup.2 are the same or different and constitute a straight-chain branched or cyclic C.sub.1-C.sub.20 alkyl group or together an C.sub.1-C.sub.20 alkylene group, in which C.sub.1-C.sub.20 alkyl or C.sub.1-C.sub.20 alkylene group one or more hydrogens are optionally substituted by F or a C.sub.4-C.sub.12 aryl group and/or one or more non-adjacent --CH.sub.2-- units are optionally substituted by C.sub.4-C.sub.12 arylene, --O--, --S--, --CO--, --COO--, --OCO--, --SO--, --SO.sub.2--, --N(R.sup.3)-- or --N(R.sup.3)CO-- where R.sup.3 is C.sub.1-C.sub.20 alkyl, or in which R is a C.sub.4-C.sub.12 aryl group which may or may not be substituted, polymers having viscosities at least equal to the viscosity of said aryl-substituted poly-p-arylenevinylenes and organic electroluminescent devices comprising such polymers.