Dispersion of nano-sized gold particles into polymers: dependence on terminal groups of polymers and morphology of vapor-deposited gold

Abstract

Dispersion of nano-sized gold particles into polymers was investigated from the viewpoint of terminal groups and molecular motion of the matrix polymers, and from morphology of vapor-deposited gold. NH ₂ -terminated poly(ethylene oxide) (PEO-NH ₂ ) and poly(ethylene glycol) (PEG) were used as the matrix polymers. When gold with a thickness of 20 nm was vapor-deposited onto a melt of PEO-NH ₂ at 60 °C, nano-sized gold particles were smoothly dispersed into the melt. On the other hand, gold vapor-deposited on a melt of PEG formed only conglomerates. When gold with a thickness of 3 nm was vapor-deposited onto PEO-NH ₂ and PEG films kept at 20 °C, it formed particulate films. The gold particles formed were not dispersed into the polymer films by heat-treatment below the melting point of the polymer. However, when the polymer films were melted by heat-treatment at 50 °C, the gold particles were dispersed only into PEO-NH ₂ . When gold with a thickness of 20 nm was vapor-deposited on the polymer films, it formed conglomerates, therefore the dispersion of gold particles into both polymers was not observed even upon heat-treatment at 50 °C. Measurements of spin-spin relaxation time by solid-state ¹ H NMR indicated that the molecular motion of PEO-NH ₂ was restricted below the melting point. Therefore, the dispersion of the nano-sized particles occurred only above the melting point of PEO-NH ₂ .