Water‐Induced Separation of Polymers from High Nanoparticle‐Content Nanocomposite Films

Abstract

Polymer nanocomposites with high loadings of nanoparticles (NPs) exhibit exceptional mechanical and transport properties. Separation of polymers and NPs from such nanocomposites is a critical step in enabling the recycling of these components and reducing the potential environmental hazards that can be caused by the accumulation of nanocomposite wastes in landfills. However, the separation typically requires the use of organic solvents or energy‐intensive processes. Using polydimethylsiloxane (PDMS)‐infiltrated SiO2 NP films, we demonstrate that the polymers can be separated from the SiO2 NP packings when these nanocomposites are exposed to high humidity and water. The findings indicate that the charge state of the NPs plays a significant role in the propensity of water to undergo capillary condensation within the PDMS‐filled interstitial pores. We also show that the size of NPs has a crucial impact on the kinetics and extent of PDMS expulsion, illustrating the importance of capillary forces in inducing PDMS expulsion. We demonstrate that the separated polymer can be collected and reused to produce a new nanocomposite film. The work provides insightful guidelines on how to design and fabricate end‐of‐life recyclable high‐performance nanocomposites.

Flexible Antireflection Coatings with Enhanced Durability and Antifogging Properties

“…The rapid formation of the gradient sharply contrasts with the phenomena observed when monodisperse polymers, such as polystyrene or poly­(2-vinylpyridine) are used. In those cases, a dense layer of polymer with a distinct front invades the NP packing, resulting in a clear boundary between polymer-infiltrated and polymer-free NP regions. − We confirm that a homogeneous nanocomposite film without a gradient is produced when monodisperse PMMA (with a weight-average molecular weight ( M w ) of ∼350 kg/mol) infiltrates the interstices of a nanochain film, as shown in Figure S3. Consequently, we attribute the instantaneous and spontaneous formation of the refractive index gradient to the polydispersity of PMMA in the commercial sheet.…”