The present invention pertains to a film for detecting chemical substances comprising a homopolymer or a copolymer having recurring units represented by the following formula (I): ##STR1## wherein X is --H, --F, --Cl, --Br, --CH.sub.3, --CF.sub.3, --CN or --CH.sub.2 CH.sub.3 ; and R.sup.1 is --R.sup.2 or --Z--R.sup.2 ;wherein Z is --O--, --S--, --NH--, --NR.sup.2' --, --(C.dbd.Y)--, --(C.dbd.Y)--Y--, --Y--(C.dbd.Y)--, --(SO.sub.2)--, --Y'--(SO.sub.2)--, --(SO.sub.2)--Y'--, --Y'--(SO.sub.2)--Y'--, --NH--(C.dbd.O)--, --(C.dbd.O)--NH--, --(C.dbd.O)--NR.sup.2' --, --Y'--(C.dbd.Y)--Y'-- or --O--(C.dbd.O)--(CH.sub.2).sub.n --(C.dbd.O)--O--;wherein Y is independently O or S, and Y' is independently O or NH, and n is an integer of 0 to 20;and wherein R.sup.2 and R.sup.2' represent independently a hydrogen atom, a linear alkyl group, a branched alkyl group, a cycloalkyl group, an unsaturated hydrocarbon group, an aryl group, a saturated or unsaturated hetero ring or derivatives thereof, provided that R.sup.1 is not a hydrogen atom, a linear alkyl group or a branched alkyl group. The invention pertains also to a detector for chemical substances comprising such a film.