title: Gold nanoparticles protected with pH and temperature-sensitive diblock copolymers.
abstract: Aqueous dispersions of gold nanoparticles protected with a stimuli-sensitive diblock copolymer were studied as a function of pH and temperature. Poly(methacrylic acid)-block-poly(N-isopropylacrylamide), PMAA-b-PNIPAM, copolymer was synthesized using the RAFT technique. A one-pot method utilizing the dithiobenzoate functionalized polymer was used to prepare gold nanoparticles protected with PMAA-b-PNIPAM. The gold nanoparticles coated with block copolymers, with the PNIPAM block bound to the particle surface and PMAA as an outer block form stimuli-sensitive aggregates in water. The changes in the absorption maxima of the surface plasmon resonance, SPR, of the gold particles and in the size of the aggregates were investigated as a function of pH and temperature. pH was observed to affect the size of the aggregates, whereas the effect of temperature was moderate. However, a blue shift in the SPR was observed both with decreasing pH and increasing temperature. Whereas the PMAA blocks control the colloidal stability of the particles and their aggregates, the thermo-sensitive PNIPAM blocks have a noticeable effect on the polarity of the immediate surroundings of the particles.
authors: Laboratory of Polymer Chemistry, University of Helsinki, PB 55, FIN-00014 HY, Finland.
authors: Markus
authors: M
authors: Nuopponen
authors: Heikki
authors: H
authors: Tenhu
mesh_terms: D000180:Acrylic Resins; D006046:Gold; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles; D011109:Polymethacrylic Acids; D020349:Surface Plasmon Resonance
chemical_list: D000180:Acrylic Resins; D011109:Polymethacrylic Acids; C052970:poly-N-isopropylacrylamide; D006046:Gold