Temperature effects on the stability of gold nanoparticles in the presence of a cationic thermoresponsive copolymer
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New hybrid complexes composed by a thermoresponsive copolymer and gold nanoparticles (Rh = 22 nm) have been characterized by dynamic light scattering (DLS) and UV-visible spectroscopy. A cationic thermoresponsive triblock copolymer, methoxy-poly(ethylene glycol)-block-poly(N-isopropylacrylamide)-block-poly((3-acrylamidopropyl) trimethyl ammonium chloride), abbreviated as MPEG-b-PNIPAAM-b-PN(+), has been synthesized by atom transfer radical polymerization (ATRP). We have evaluated the thermal response at low concentrations of this triblock copolymer in bulk solution and the effect of concentration on the interaction between this thermosensitive copolymer and the gold nanoparticles (AuNPs) to form new hybrid complexes (60–1000 nm) at different temperatures. The thermosensitive nature of the copolymer causes both aggregation and contraction of the aggregates at elevated temperatures. The AuNPs were found to be separately embedded in the hybrid complexes. Interestingly, the AuNPs prevent macroscopic phase separation of the system at high temperatures.
KeywordsDynamic light scattering Surface Plasmon resonance Thermoresponsive polymers Gold nanoparticles
Financial support has been provided by Ministerio de Economía y Competitividad within project CTQ-2012-33717 and Norwegian Research Council through a FRINAT project (177665/V3). R.P. thanks the financial support provided by Fundación Séneca—CARM within grant 19877/GERM/15.
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