Modulating Interactions between Molten Polystyrene and Porous Solids Using Atomic Layer Deposition

Abstract

Understanding and modulating the interactions between molten polymers and porous solids is important for numerous processes and phenomena including catalytic conversion of polymers and fabrication of nanocomposites and nanostructured materials. Although changing the surface composition of pores would enable modulation of interactions between polymers and nanoporous solids, it is challenging to achieve such a control without inducing significant changes to the size and structure of nanopores. In this work, we demonstrate that the interactions between molten polystyrene (PS) and disordered packings of SiO2 nanoparticles (NPs) can be modulated by changing the surface composition of the NPs using atomic layer deposition (ALD). A disordered packing of silica NPs is modified with varying surface coverages of TiO2, WO3, and CaCO3, with coverages estimated by the mass gain and the refractive index change of NP packings. Based on the time required to fully infiltrate these ALD-modified NP packings via capillarity, the contact angles for PS on different surfaces prepared via ALD are determined. The contact angle gradually changes from that of pure SiO2 to that of the fully covered surfaces. The contact angles for PS on SiO2, TiO2, WO3, and CaCO3 are found to be 20, 62, 70, and 10°, respectively. Interestingly, the contact angles and interfacial energies between PS and the ALD-modified surfaces do not correlate strongly with the water contact angle of these surfaces; thus, caution must be exercised in predicting how a polymer would wet or interact with porous solids solely based on their hydrophilicity. The method presented in this work can be extended to study the interactions between a wide range of polymers and surfaces in porous media, which will have important implications for designing new catalytic materials for polymer upcycling reactions and novel NP–polymer composite films and membranes with enhanced mechanical and transport properties.

Hydrodeoxygenation of m-Cresol over WOx-Pt/SBA-15 Using Alkanes as Hydrogen Carriers

“…For example, it has been shown that the composition of the solid surface can affect interfacial energies with hydrocarbons. 22 Since the surface composition and pore size of SBA-15 can be modified by Atomic Layer Deposition (ALD), 15,23 it should be possible to optimize the catalysts for operation at lower pressures. While surface coverage appears to be critically important, the mechanism behind coke suppression at high pressures is still uncertain; and alkane dehydrogenation and m-cresol HDO are significantly more complex than ethene dimerization.…”

“…Adsorbate coverages increase with decreasing pore size due to the increased adsorbate-pore van der Waals interactions, but there are additional ways to modify the adsorbate coverage. For example, it has been shown that the composition of the solid surface can affect interfacial energies with hydrocarbons . Since the surface composition and pore size of SBA-15 can be modified by Atomic Layer Deposition (ALD), , it should be possible to optimize the catalysts for operation at lower pressures.…”

Conflicting Effects of Extreme Nanoconfinement on the Translational and Segmental Motion of Entangled Polymers

“…In this work, only the size of silica NPs and the MW of the polymer are varied, thus keeping the interfacial energy between the polymer and the NP constant. In a recent work, a technique to modify the interfacial energy between PS and SiO 2 NPs by coating ultrathin metal oxides such as WO 3 and TiO 2 using atomic layer deposition has been reported . This approach can be used to investigate the effect of interfacial energy on the translational and segmental motion of highly confined polymers in NP packings.…”

“…In a recent work, a technique to modify the interfacial energy between PS and SiO 2 NPs by coating ultrathin metal oxides such as WO 3 and TiO 2 using atomic layer deposition has been reported. 72 This approach can be used to investigate the effect of interfacial energy on the translational and segmental motion of highly confined polymers in NP packings. The enhanced translational motion of high-MW polymers can be used to facilitate their infiltration into NP packings to fabricate highly loaded nanocomposite membranes and films.…”