PDMS hybrid nanocomposites reported herein comprised (1) a low Tg PDMS phase cross-linked by (2) a siliceous phase (SP) generated by in situ hydrolysis/condensation of poly(diethoxysiloxane) (PDES), and (3) amorphous fumed silica nanoparticles (FSN), diameter ca. 50 nm. In fact, Hydrosilylation or condensation-cured PDMS networks are weak materials usually needing fillers for good mechanical properties. Height and phase TM-AFM images were used to examine nanocomposite near-surface topography. Surprisingly, the near-surface image was dramatically changed after 100 °C cure. Even with hard tapping, the near-surface FSN “disappeared” completely. Experiments were carried out to clarify the origin of this change. The results shed new light on structure in condensation-cured PDMS hybrid elastomers and show that nanoparticles can act as “reporters” for secondary structure buildup.
Tapping mode AFM evidence for an amorphous reticular phase in a condensation cured hybrid elastomer: a,w-dihydroxypoly(dimethylsiloxane)/poly(diethoxysiloxane)/fumed silica nanoparticles
GALLI, GIANCARLO;CHIELLINI, EMO;
2004-01-01
Abstract
PDMS hybrid nanocomposites reported herein comprised (1) a low Tg PDMS phase cross-linked by (2) a siliceous phase (SP) generated by in situ hydrolysis/condensation of poly(diethoxysiloxane) (PDES), and (3) amorphous fumed silica nanoparticles (FSN), diameter ca. 50 nm. In fact, Hydrosilylation or condensation-cured PDMS networks are weak materials usually needing fillers for good mechanical properties. Height and phase TM-AFM images were used to examine nanocomposite near-surface topography. Surprisingly, the near-surface image was dramatically changed after 100 °C cure. Even with hard tapping, the near-surface FSN “disappeared” completely. Experiments were carried out to clarify the origin of this change. The results shed new light on structure in condensation-cured PDMS hybrid elastomers and show that nanoparticles can act as “reporters” for secondary structure buildup.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
