Effect of geometric curvature on vitrification behavior for polymer nanotubes confined in anodic aluminum oxide templates

Abstract

The glass transition behavior of polystyrene (PS) nanotubes confined in cylindrical alumina nanopores was studied as a function of pore diameter (d) and polymer tube thickness (δ). Both the calorimetric glass transition temperature and the microstructure measured by a nonradiative energy transfer method indicated that the polymer nanotube, or concave polymer thin film, exhibited significant differences in vitrification behavior compared to the planar one. A closer interchain proximity and an increased T_{g} were observed for polymer nanotubes with respect to the bulk polymer. T_{g} for polymer nanotubes was primarily dependent on the curvature radius d of the template, while it was less dependent on the thickness δ of the PS tube wall in the range of 11-23 nm. For small nanotubes (d=55nm), the T_{g} increased as high as 18 °C above the bulk value. This vitrified property reverted back to the bulk value when the substrate was chemically removed, which indicated the crucial importance of the interfacial effect imposed by the hard wall with a concave geometry.

21st Century Advances in Fluorescence Techniques to Characterize Glass‐Forming Polymers at the Nanoscale

“…While this perturbation length scale is smaller than the 12 nm threshold observed by Itagaki et al, Barbaro and Steiner suggest that lower entanglement density could be responsible for reductions in viscosity measured in films as thick as 100 nm . Contrary to this, the quenching ratio of dyes attached to separate PS or PnBMA chains confined to AAO nanopores have been shown to increase with decreasing pore size indicating greater entanglement density under cylindrical hard confinement …”

Dependences of Confining Size and Interfacial Curvature on the Glass Transition of Polydimethylsiloxane in Self‐Assembled Block Copolymers

“…To better understand the influences of geometrical difference on glass transition dynamics, many studies have focused on extending research beyond planer system to other geometric shapes such as nanotubes or nanobowls . More recently, a work by Xue and co‐workers demonstrated that the interfacial effect on the glass transition of polymers confined in nanotubes was imposed by hard wall with a concave geometry . In our system, different confining geometries have different polymer–polymer interfacial curvatures, therefore, we propose that the effect of confining geometries on T g is mainly due to the different curvature of PDMS–PMPCS interface.…”

“…With the rapid development of advanced nanotechnologies, the glass transition behavior of polymers under nanoscale confinement has been controversially and dynamically discussed in past two decades. Briefly, the increase, reduction, as well as the unchanged of polymer glass transition temperatures ( T g ) compared to the bulk have been reported . In the pioneering work of Keddie et al, the T g of polystyrene (PS) thin films supported on silica decreases below the bulk value as the film thickness is thinner than 40 nm .…”

“…Napolitano et al have shown a striking correlation between the T g deviation from bulk and the irreversible chain adsorption, which means T g of polymers under nanoconfinement could be tuned by controlling the local free volume at interface through thermal annealing . To conduct a more comprehensive research of polymer under confinement, the glass transition behaviors of polymers in different confining dimensions or geometric curvatures have been investigated recently . Here, in order to conduct a further research on the interfacial effects, we wish to construct a well‐defined system with explicit and controllable interfacial character.…”

Coherent electron transport in a helical nanotube

“…Recently, the geometric effects on the coherent electron transport have been investigated in bent cylindrical surfaces [28], and in the surface of a truncated cone [29]. Additionally, the curvature effects on vitrification behavior has been discussed for polymer nanotubes [30]. In the nanotubes the geometrical curvature plays an important role to influence their quantum properties.…”