The first direct exfoliation of zeolites in high yield expands potential for catalysts, membranes, and tailored composites.

Thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) is grafted from wet bacterial cellulose (WBC) sheets using atom transfer radical polymerization (ATRP). WBC is recognized as a highly swollen biocompatible material with broad application potential. However, native WBC undergoes drying relatively fast and its reswelling ability diminishes after losing a substantial amount of water. In this work PNIPAM is grafted from WBC to slow down its drying, especially at elevated temperatures, which is relevant for biomedical applications. As a primary step, initiator molecules, 2-bromoisobutyryl bromide, are attached to WBC through linkers that are covalently bound to the cellulose hydroxyl groups. Grafting of PNIPAM is then realized via surface-initiated ATRP in a water/methanol mixture leading to WBC-g-PNIPAM. The modification steps are followed via FT-IR, XRD, elemental analysis, and atomic force microscopy. It is concluded that PNIPAM contributes to ca. 22% of the dry mass of WBC-g-PNIPAM. The samples are subjected to repeating swelling and drying steps at 25 °C and drying at 40 °C. The obtained results indicate that grafted PNIPAM significantly reduces drying of the modified WBC and enables better reswelling after treatment at 40 °C with respect to native WBC. The reported synthetic method may also be used for grafting other polymers bringing additional functionalities to WBC.

Direct exfoliation of layered zeolites into solutions of monolayers has remained unresolved since the 1990s. Recently, zeolite MCM-56 with the MWW topology (layers denoted mww) has been exfoliated directly in high yield by soft-chemical treatment with tetrabutylammonium hydroxide (TBAOH). This has enabled preparation of zeolite-based hierarchical materials and intimate composites with other active species that are unimaginable via the conventional solid-state routes. The extension to other frameworks, which provides broader benefits, diversified activity, and functionality, is not routine and requires finding suitable synthesis formulations, viz. compositions and conditions, of the layered zeolites themselves. This article reports exfoliation and characterization of layers with ferrierite-related structure, denoted bifer, having rectangular lattice constants like those of the FER and CDO zeolites, and thickness of approximately 2 nm, which is twice that of the so-called fer layer. Several techniques were combined to prove the exfoliation, supported by simulations: AFM; in-plane, in situ, and powder X-ray diffraction; TEM; and SAED. The results confirmed (i) the structure and crystallinity of the layers without unequivocal differentiation between the FER and CDO topologies and (ii) uniform thickness in solution (monodispersity), ruling out significant multilayered particles and other impurities. The bifer layers are zeolitic with Brønsted acid sites, demonstrated catalytic activity in the alkylation of mesitylene with benzyl alcohol, and intralayer pores visible in TEM. The practical benefits are demonstrated by the preparation of unprecedented intimately mixed zeolite composites with the mww, with activity greater than the sum of the components despite high content of inert silica as pillars.