NOVELTY - A dithiocarbamate-containing precursor polymer, is new.    USE - The precursor polymer is useful in the preparation of polymers such as conjugated poly(arylene vinylene) polymers e.g. poly(2,5-thienylene vinylene) useful in a device such as solar cell, light emitting diode, chemical sensor, biological sensor, integrated circuit (claimed) and light emitting diode.    ADVANTAGE - The precursor polymer and poly(2,5-thienylene vinylene) polymer exhibits average molecular weight of 5000 - 1000000 Daltons and has polydispersity of 1.5 - 5.5 (preferably below 2). The poly(2,5-thienylene vinylene) polymer prepared by using (I) shows a peak at a wavelength higher than 520 nm in the absorption spectrum. The precursor polymer is easily accessible and can be manufactured on large scale. The polymers can be obtained in good yields, with high molecular weight and with good quality e.g. low defect level on a large scale. The precursor polymer is soluble in organic solvents; can polymerize without gel formation; does not require toxic gases or strong acid during conversion step. The polymer precursor can be synthesized by a method that does not require complicated purification step or column chromatography. The polymers prepared by using (I) are more stable with less defects, and have better property resulting in better electronic devices.    DETAILED DESCRIPTION - A dithiocarbamate-containing precursor polymer of formula (-Ar-C(R3)(S-C(S)-R')-CH(R4)-)n (I) is new.    Ar = (hetero)aromatic divalent group;    R' = amine -NR1R2, 5-20C alkyloxy, aryloxy, alkyl, aryl, alkylaryl, arylalkyl, thioether, ester or acid carboxylic acid;    R3 and R4 = H or organic group selected from 1-20C alkyl, cyclic 3-20C alkyl, aryl, alkylaryl, arylalkyl or heterocyclic groups;    n = number of repeating units (disclosed);    R1 and R2 = 1-20C alkyl, cyclic 3-20C alkyl, aryl, alkylaryl, arylalkyl or heterocyclic group.    INDEPENDENT CLAIMS are included for:    (1) preparation of (I); and    (2) preparation (P1) of a polymer comprising structural units (-Ar-C(R3)=C(R4)-) (III) involving subjecting (I) to thermal conversion step at a temperature of 30 - 300degreesC.