Phase Behavior of Poly(2-vinylpyridine)-block-Poly(4-vinylpyridine) Copolymers Containing Gold Nanoparticles

We studied the phase behavior of the poly(2-vinylpyridine)-block-poly(4-vinylpyridine) copolymer (P24VP) containing gold nanoparticles, by rheometry, small-angle X-ray scattering, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). Although both blocks of P24VP exhibited attractive interaction to gold precursors, unusual phase behavior was observed depending on the amount of gold nanoparticles. As the amount of gold nanoparticles increased, the order-to-disorder transition temperature (TODT) of P24VP with gold nanoparticles decreased first, then increased, and finally decreased again. To explain this phenomenon, we prepared two block copolymers: polystyrene-block-poly(2-vinylpyridine) copolymer (PS2VP) and polystyrene-block-poly(4-vinylpyridine) copolymer (PS4VP) containing gold nanoparticles. With increasing the amount of gold particles, the TODT of PS2VP increased continuously, whereas that of PS4VP gradually decreased. For PS4VP containing gold nanoparticles, because P4...