Evidence of pre-micellar aggregates in aqueous solution of amphiphilic PDMS-PEO block copolymer.

摘要: The self-assembly process in a water solution of an amphiphilic polydimethylsiloxane-b-polyethyleneoxide (PDMS-PEO) diblock copolymer was investigated by means small-angle X-ray scattering (SAXS) experiments the concentration region below (and near) critical micellar (c.m.c. = 0.007 g cm-3). In highly diluted region, at c 0.002 cm-3, early stage characterized formation small (primary) units (with radius R 2.7 nm) with core-shell morphology, which coexisted larger supramolecular aggregates entangled micelles average 9.5 nm). increase (to 0.005 and 0.01 cm-3) caused sizes both supra-micellar aggregates. Interestingly, size micelle aggregation number (Nagg) were found to on increasing temperature range 10 ≤ T 55 °C. This phenomenon characterised dehydration ethylene oxide (EO) segments, as evidenced calculation excess hydrophilic shell micelles. more compact (less hydrated) structure PEO chains, strongly influenced spontaneous curvature amphiphile turned out be driving factor that favoured temperature. obtained results evidence PDMS-PEO amphiphiles is gradual already present very low (far macroscopically determined c.m.c.); moreover, it multi-stage organization process, where primary building blocks self-assemble into complex secondary structures encompass multiple length scales.