Tailored self-assembly of semi-transparent polymer/clay nanocomposites for gas-barrier applications assisted by aqueous liquid crystalline scaffolds

Abstract

A new strategy for preparing flexible and semi-transparent gas-barrier coatings was developed using tailored self-assembly of montmorillonite (MMT)/polyvinylpyrrolidone (PVP) nanocomposites assisted by aqueous liquid crystalline (LC) scaffolds. First, we established a composition wherein aqueous MMT exhibited the LC phase in the presence of polyethyleneimine (PEI) and hydrochloric acid (HCl). The viscoelastic rheological features of MMT LC enable the formation of uniform and conformal MMT coatings on various types of substrates, including flat or topographically featured surfaces. Moreover, the MMT LC serves as a structural scaffold that enables the rapid transport of PVP within the inner gallery space of the MMT LC, resulting in the formation of stacked MMT/PVP nanosheets after drying. Owing to its highly aligned layered structure, MMT/PVP exhibited flexible mechanical properties with enhanced hardness and modulus compared to neat MMT. Furthermore, the MMT/PVP can suppress gas permeation, as demonstrated by 0.1 Barrer of H2 permeability for the best coating conditions (containing 63 wt% MMT and 37 wt% PVP), while maintaining semi-transparent optical properties. Considering the aforementioned properties and that all components in MMT/PVP are bio-safe materials, this coating system has potential applications as a gas-barrier coating in conventional packaging materials, food packaging, and H2 storage tanks.