Study of cationic N-isopropylacrylamide-styrene copolymer latex particles using fluorescent probes

Monodisperse cationically charged core-shell poly[styrene[N-isopropylacryla mide] latexes, differing in their shell structure, were studied at temperat ures around the lower critical solution temperature (LCST) of polyCN-isopro pylacrylamide]. Near the LCST, a transition on the latex dimensions was obs erved by quasi-elastic light scattering measurements. The same transition c ould also be detected using the intensity ratio of the pyrene fluorescence vibronic bands, I-1/I-13, and the excimer to monomer fluorescence intensity ratio of 1,10-bis(1-pyrenyl)decane. The fluorescence spectra and decay cur ve measurements of 1,10-bis( 1-pyrenyl)decane provided a better understandi ng of both the hydrophilic-hydrophobic variation and the conformational cha nges occurring in the poly[N-isopropylacrylamide] shell of the latex partic les upon temperature variation.