Double Glass Transitions and Interfacial Immobilized Layer in in-Situ-Synthesized Poly(vinyl alcohol)/Silica Nanocomposites

Abstract

The results of dynamic mechanical analysis (DMA) revealed that there were double tan δ peaks in the poly(vinyl alcohol)(PVA)/silica nanocomposite samples at low frequencies. The two relaxations attribute to glass transition for PVA matrix and motions of segments for PVA chains confined by the surface of silica nanoparticles, respectively. The thickness of the interfacial immobilized layer was calculated, and schematic models were founded, which can well interpret the results. The changes of the two relaxations with various silica contents at different frequencies are discussed. It is considered that most of the interfacial PVA chains probably span the two layers. The peak position of the first relaxation moves to high temperature with the increase of frequency for strain lag of the sample whereas the second one shifts to low temperature for the "drag effect" between the intrinsic and interfacial segments of the spanned PVA chains.

Molecular probe technique for determining local thermal transitions: The glass transition at Silica/PMMA nanocomposite interfaces

“…The comparison of the experimental values with reference values also suggests that around w7 nm (calculated from 2% results), the T g observed by the fluorophore is the same as the bulk T g ; hence, this distance can be assumed to be the interfacial thickness (as defined with respect to T g ). This distance agrees well with the immobilized layer thickness that was calculated by Chen et al, [29] although the two definitions do not necessarily agree with each other. In the current work, the interfacial distance is defined directly from T g change, whereas Chen et al defined the immobilized region thickness from a structural point of view (approximate thickness of the amorphous layer around the nanoparticle).…”

“…Based on Long and Lequeux's percolation theory, [22] Ash et al proposed that a highly mobile interaction zone existed at the nanoparticle/polymer interface and acted to interrupt the percolation of slow domains as the temperature was decreased [28]. Chen et al [29] using silica/poly(vinyl alcohol) composites showed that the interaction zone thickness depended inversely on the silica concentration, and ranged between 10.1 nm for 1.5% silica content and 6.3 nm for 9% silica content. Srivastava and Basu [30] studied gold/poly(methyl methacrylate), PMMA, nanocomposites where the gold nanoparticles were also capped with PMMA at varying concentrations.…”

Modelling of the thermal conductivity in polymer nanocomposites and the impact of the interface between filler and matrix

“…For polymers with nanosized clay this layer was estimated with the electron spin resonance technique to be between 5 and 15 nm [65]. Chen et al [66] deduced that the thickness of the interfacial was 5-10 nm for poly(vinyl alcohol)/silica and dependent upon composition. The other estimations [67] for the interfacial thermal conductance between a single crystal silicon and amorphous polyethylene have shown that the interfacial layer of the polymer has a thickness of 16 nm.…”

A review on the role of interface in mechanical, thermal, and electrical properties of polymer composites

“…Therefore, there should have been other parameters which have either underestimated or not been considered in the prediction of composite behavior. In this regard, the interfacial interaction between polymer matrix and nanofiller became one of the parameters which have raised attention [16][17][18][19]. The presence of nanofillers in the matrix and their interfacial interaction can affect the mobility of polymer chains [20].…”