Interfacial interactions and complex segmental dynamics in systems based on silica-polydimethylsiloxane core–shell nanoparticles: Dielectric and thermal study

Interfacial dynamics of polydimethylsiloxane adsorbed on fumed metal oxide particles of a wide range of specific surface area

“…Pissis and coworkers suggested that the stronger polymereparticle hydrogen bonding is at the origin of the increased interfacial layer thickness in polydimethylsiloxane (PDMS)/titania as compared to PDMS/silica conventional PNCs [2,8]. Kumar and coworkers suggested that the interfacial layer thickness may decrease with curvature of the adsorbing surface [14] and increase with size of nanoparticles [15].We have recently demonstrated similarities in the behavior of linear PDMS adsorbed on fumed silica particles in coreeshell type PNCs [11] with that of polymers adsorbed on flat solid surfaces [16e18] and in conventional PNCs [8e10]. The surface and porosity characteristics of fumed silicas are reflected in the specific surface area, S [9,11,19].…”

“…We have recently demonstrated similarities in the behavior of linear PDMS adsorbed on fumed silica particles in coreeshell type PNCs [11] with that of polymers adsorbed on flat solid surfaces [16e18] and in conventional PNCs [8e10]. The surface and porosity characteristics of fumed silicas are reflected in the specific surface area, S [9,11,19].…”

DSC study of silicas with immobilized polysiloxane layer of different architecture

“…The appearance, though only slightly, of the cold crystallization exothermic peak indicates the formation of isotactic macromolecular chains. The appearance of the cold crystallization for dispersed silicas modified by adsorption with PMS1000 with the same polymer content (40 mass%) was noted by the authors [17,26], with high concentration of active sites on the surface of pristine nanoparticles (before modification). This provides evidence for the theory presented above about the formation of additional active sites during firststage modification (lowering of structure-related complications of adsorption/chemisorption).…”

“…Such study of immobilized PDMS-1000 allowed to establish that heterosites on silica surface increase the fraction of polymer chains at interfaces that is reflected in the respective dynamics (a int -relaxation) and enhanced cooperativity [16]. For the core-shell nanocomposites with high PDMS content (80 mass%), the interfacial relaxation was less affected by silica/polymer interaction [17]. However, at lower PDMS content (40 mass%), the interfacial relaxation process exhibits distinct differences, related with surface characteristics.…”

“…At the same time, bulk dynamics (glass transition temperature-T g , and time scale of a relaxation) were not significantly affected. This effect has been widely studied [16][17][18][19], and authors proposed a model of bimodal conformations of polymers adsorbed on solid surfaces, in terms of an increase in the apparent thickness of the interfacial layer with increasing surface roughness. According to this model, the conformations of polymer chains during the first stage of adsorption are mostly linear (tails) with following formation of loop-like structures with polymer content increase.…”