A thiophene compound represented by formula (I):
##STR1##
in which A represents a C.sub.1-5 -alkylene bridge; R represents a
--R.sup.1 --(C.dbd.O)--R.sup.2 group; --R.sup.1 -- represents a --R.sup.3
-- or --R.sup.4 --X--R.sup.5 -- group; R.sup.2 is hydrogen, a hydroxy
group, a thiol group, --NR.sup.6 R.sup.7, --OR.sup.8 or a --SR.sup.9
group; R.sup.3, R.sup.4 and R.sup.5 are independently an alkylene group or
an arylene group; X is a --O--, --S-- or .dbd.NR.sup.10 ; R.sup.6 and
R.sup.7 are independently hydrogen, an optionally substituted amino group
or an optionally substituted alkyl group; R.sup.8 and R.sup.9 are
independently an optionally substituted alkyl group (optionally with at
least one substituent selected from the group consisting of an alcohol,
amide, ether, ester or sulfonate group), an optionally substituted aryl
group or a --SiR.sup.11 R.sup.12 R.sup.13 group; R.sup.10 is an alkyl,
aryl or acyl group; and R.sup.11, R.sup.12 and R.sup.13 are independently
an optionally substituted alkoxy or alkyl group; polymers derived
therefrom; a process for polymerizing a thiophene according to formula
(I), optionally chemically or electrochemically; and solutions,
dispersions, pastes and layers containing polymers derived therefrom.
