Polymer chain dynamics and glass transition in athermal polymer/nanoparticle mixtures

Abstract

Polymer nanocomposites (PNCs), prepared by incorporating nanoparticles within a polymer host, generally exhibit properties that differ significantly from those of the host, even with small amounts of nanoparticles. A significant challenge is how to tailor the properties of these materials for applications (structural and biomedical to optoelectronic), because PNCs derive their properties from a collective and complex range of entropic and enthalpic interactions. Here, we show that PNCs, prepared from athermal mixtures of polymer-chain-grafted gold nanoparticles and unentangled polymer chains, may exhibit increases or decreases in their relaxation dynamics, and viscosity, by over an order of magnitude through control of nanoparticle concentration, nanoparticle size, grafting density and grafting chain degree of polymerization. In addition, we show how the glass transition may also be tailored by up to 10 degrees with the addition of less than 1.0 wt% nanoparticles to the polymer host.

The lifetime of the deviations from bulk behaviour in polymers confined at the nanoscale

“…To quantitatively corroborate this physical picture, we measured, by means of capacitive dilatometry 41 , the T g 's of the Guiselin brushes of films of PS97 and of ultrathin films of PS97 and PS160 after different annealing times at 423 K. The shift in T g follows, as expected, the same kinetics as the irreversible adsorption process (Fig. 4a,b).…”

Effects of carbon nanotubes on polymer physics

“…Interestingly, the plateau and agglomeration weight percentages did not shift upon changing the molecular weight of a grafted coating, although T g shifted from a 10 C decrease to a 5 C increase. 56 Table 1 only includes changes that occur upon mixing a polymer with a nanotube and not covalently bonding a polymer to the nanotube; covalently attaching a polymer to the nanotube consistently increases the glass transition temperature of the attached polymer. 57,58 Some of the large slopes in Table 1 are due to something other than introducing a nanotube surface into a polymer.…”

Flocculation, Reinforcement, and Glass Transition Effects in Silica-Filled Styrene-Butadiene Rubber

“…[19][20][21][22][23][24] On the other hand, there are other reports which show that the filler can have a significant influence on the glass transition dynamics. [25][26][27][28][29][30][31] In particular, the research of Tsagaropoulos and Eisenberg 25,26 is often cited as support for the existence of severely retarded segmental motion of the polymer near the surfaces of small particles (glassy polymer shell). They observed a second tanδ peak in viscoelastic data for various nanofilled uncrosslinked polymers which was 60-100…”