Preparation of poly(styrene‐b‐N‐isopropylacrylamide) micelles surface‐linked with gold nanoparticles and thermo‐responsive ultraviolet–visible absorbance

Poly(styrene‐ b ‐ N ‐isopropylacrylamide) (PSt‐ b ‐PNIPAM) with dithiobenzoate terminal group was synthesized by reversible addition‐fragmentation‐transfer polymerization. The dithiobenzoate terminal group was converted into thiol terminal group with NaBH 4 , resulting thiol‐terminated PSt‐ b ‐PNIPAM‐SH. After PSt‐ b ‐PNIPAM‐SH assembled into core‐shell micelles in aqueous solution, gold nanoparticles were in situ surface‐linked onto the micelles through the reduction of gold precursor anions with NaBH 4 . Thus, temperature responsive core/shell micelles of PSt‐ b ‐PNIPAM surface‐linked with gold nanoparticles (PSt‐ b ‐PNIPAM‐Au micelles) were obtained. Transmission Electron Microscopy revealed the successful linkage of gold nanoparticles and the dependence of the number of gold nanoparticles per micelle on the molar ratio of HAuCl 4 to thiol group of PSt‐ b ‐PNIPAM. Dynamic Light Scattering analysis demonstrated thermo‐responsive behavior of PSt‐ b ‐PNIPAM‐Au micelles. Changing the temperature of PSt‐ b ‐PNIPAM‐Au micelles led to the shrinkage of PNIPAM shell and allowed to tune the distance between gold nanoparticles. Ultraviolet–visible (UV–vis) spectroscopy clearly showed the reversible modulation of UV–vis absorbance of PSt‐ b ‐PNIPAM‐Au micelles upon heating and cooling.