Solution filtering affects the glassy dynamics of spincoated thin films of poly(4-chlorostyrene)

Abstract

We investigated the impact of sample preparation on the glassy dynamics of thin films of poly(4chlorostyrene), a polymer whose molecular mobility is particularly sensitive to changes in the specific volume. Samples were obtained by spincoating, the technique most commonly used to prepare thin organic layers, which consists of pouring dilute polymer solutions onto a plate rotating at a high rate. Our experimental results demonstrate that filtering the solutions before spincoating affects the value of the segmental relaxation time of the as-prepared films. Thin polymer layers obtained via filtered solutions show accelerated segmental dynamics upon confinement at the nanoscale level, once below 100 nm, while the samples obtained via unfiltered solutions exhibit bulk-like dynamics down to 15-20 nm. We analyzed these results by means of the cooperative free volume rate model, considering a larger free volume content in thin films obtained via filtered solutions. The validity of the model predictions was finally verified by measurements of irreversible adsorption, confirming a larger adsorbed amount, corresponding to a higher specific volume, in the case of samples obtained via unfiltered solutions. Our results prove that filtering is a crucial step in the preparation of thin films, and it could be used to switch on and off nanoconfinement effects.

Fast equilibration mechanisms in disordered materials mediated by slow liquid dynamics

“…Samples were spin-coated at a constant spinning rate (3000 rpm). Tests on P4ClS, a polymer whose dynamics is particularly sensitive to changes in the specific volume (3,45) and preparation conditions (46)(47)(48), revealed that the spinning rate does not affect molecular dynamics.…”

Polymer Nanocomposite Dielectrics: Understanding the Matrix/Particle Interface

“…270 The relaxation of polymer chain is governed by the number of cooperating segments, which is determined by the system's free volume, and the interfacial free volume can be quantified by the adsorption experiment. 270 The effects of temperature 271 and filtering 272 on the polymer thin films were also explained in this In a study by Mundra et al, 273 a 50-nm-wide PMMA line was etched from an 18-nm-thick PMMA film on the SiO 2 substrate. As shown in Figure 17a, the glass transition temperature T g of the system was studied by fluorescence.…”

Dynamics across a Free Surface Reflect Interplay between Density and Cooperative Length: Application to Polystyrene

“…The connection between confinement and density (or pressure) effects has been featured in a number of studies on polymer films and polymers and small molecules in nanopores. − ,− While most of the results from these works strongly support the connection, direct measurement of the density itself is challenging for confined systems. − Positron annihilation lifetime spectroscopy (PALS) data analyses ,, have verified that there is a difference in the effective density (free volume) for systems confined in nanopores. Further evidence comes from back-calculated specific volumes for (isobaric) films, which show the same coefficient of thermal expansion as the corresponding bulk but have densities that are shifted by ∼1−2% .…”