We present the theoretical analysis of the photoinduced absorption inf
rared spectra of Durham type polyacetylene and diblock copolymers. Goo
d agreement with experimental data is found, taking into account the c
ontribution of short segments, in all these samples, expecially in the
case of Durham type (CH)(x) exposed to air. In particular we have wel
l reproduced the different structures of the low frequency absorption
band in the photoinduced spectra.