The effect of added gold nanoparticles on the volume phase transition behavior for PVCL-based microgels

The volume phase transition (VPT) behavior of poly(N-vinylcaprolactam-co-4-vinylpyridine) P(VCL-co-4VP) microgels and their hybrid counterparts containing Au nanoparticles (AuNPs) is explored and compared by FTIR measurements in combination with the perturbation correlation moving window (PCMW) technique and two-dimensional correlation spectroscopy (2Dcos) analysis. It is demonstrated that the incorporation of AuNPs inside the microgels cause a slight dehydration effect on the microgels in the swollen state and an increase of the VPT temperature. Moreover, the interaction between CO and AuNPs can be confirmed by combining the conventional IR and 2Dcos analysis. It is with the help of the additional cross-links between AuNPs and the polymer chains (CO and pyridine groups) in the microgel network and the tendency of AuNPs to aggregate that the hybrid microgels exhibit a much greater dehydration during the VPT, as compared with the nonhybrid ones.