Cyanine-based near-i.r. fluorescent probes have been applied as labels
to determine functional groups in polymeric materials. The advantage
of such probes is that they can be applied to polymers which are autof
luorescent or strongly coloured or to strongly scattering polymer emul
sions. Two examples are discussed: the labelling of a polymer latex wi
th aldehyde functional groups, by application of a cyanine with a hydr
azide functionality, and the labelling of amino functional groups in a
polyamide utilizing a cyanine label with an isothiocyanate functional
ity. The cyanines which have been applied absorb and fluoresce in the
650-700 nm range and in the 750-800 nm range, respectively. In additio
n to near-i.r. fluorescence, the cyanine dyes have strong absorption (
with extinction coefficients in the order of 2 x 10(5) l mol(-1)cm(-1)
). It is shown that by application of reflection absorption measuremen
ts also sensitive detection of labelled functional groups can be reali
zed. The combined application of fluorescence and reflection measureme
nts allows for the detection of concentration and distribution of func
tional groups in polymeric systems down to very low levels. (C) 1997 E
lsevier Science Ltd.