Poly ( N-isopropylacrylamide-co-N-vinylpyrrolidone) [P(NIPAM-co-NVP)] copolymers were synthesized

and their reversible aggregation in aqueous solutions were investigated in the whole heating and cooling process with elastic light scattering (ELS) spectroscopy

fluorescence and dynamic light scattering (DLS).The ELS results indicated that IELS gradually increases in the heating process while decreases in the cooling process.Fluorescence spectra also suggested that the hydrophobic interaction occurred during heating and caused the aggregation of copolymer molecular chains and the increasing of fluorescence intensity

while the intensity was opposite during cooling owning to the dissociation of molecular chains.When the temperature increased

the hydrodynamic radius of this copolymer molecules measured by DLS increased rapidly at the LCST value and then decreased

and the cooling process was also contrary to the heating.Thus

fluorescence spectra and light scattering confirmed with the elastic light scattering in measuring the aggregation behavior of copolymer chains.Besides

ELS can get the conclusion easily that the copolymer with hydrophilic comonomer NVP has a higher transition temperature than the PNIPAM homopolymer has.It was concluded that reversible aggregation of P(NIPAM-co-NVP) copolymers in aqueous solutions could be described by ELS as well as by Fluorescence and DLS.