CO₂-Responsive Cellulose Nanofibers Aerogels for Switchable Oil–Water Separation

Abstract

Cellulose nanofibers (CNFs) aerogels with controllable surface wettability were prepared by grafting poly(N,N-dimethylamino-2ethyl methacrylate) (PDMAEMA) polymer brushes via surface-initiated atom-transfer radical polymerization. After grafting PDMAEMA polymer, the surface of the aerogel was hydrophobic. However, in the presence of CO 2 , the surface of the aerogel gradually changes from hydrophobic to hydrophilic. The porous structure and CO 2 -responsiveness of PDMAE-MA brushes within the CNFs aerogels allowed for the on−off switching of the oil−water mixture separation process. These CNFs aerogels were recyclable and displayed attractive separation efficiency for oil−water mixture and surfactant-stabilized emulsions. Furthermore, the switchable surface wettability holds an advantage of avoiding oil-fouling, which will greatly improve its recyclability.

Micro‐/Nanostructured Interface for Liquid Manipulation and Its Applications

“…For example, Sui et al reported a switchable, CO 2 ‐responsive oil–water separation material based on aerogels of cellulose nanofibers. The material was prepared by grafting poly( N , N ‐dimethylamino‐2‐ethyl methacrylate) (PDMAEMA) polymer brushes via surface‐initiated atom‐transfer radical polymerization . Bai et al reported a superhydrophilic and underwater superoleophobic membrane for oil/water emulsion separation based on the in situ crosslinking copolymerization of polyethyleneimine (PEI) and poly(methyl methacrylate‐ co ‐glycidyl methacrylate) P(MMA‐ co ‐GMA) on poly(vinylidene fluoride) (PVDF) membrane .…”

“…The material was prepared by grafting poly(N,Ndimethylamino-2-ethyl methacrylate) (PDMAEMA) polymer brushes via surface-initiated atom-transfer radical polymerization. [128] Bai et al reported a superhydrophilic and underwater superoleophobic membrane for oil/water emulsion separation based on the in situ crosslinking copolymerization of polyethyleneimine (PEI) and poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA) on poly(vinylidene fluoride) (PVDF) membrane. [129] Wu et al reported a superhydrophobic cotton fabric via radiation-induced graft polymerization of γ-methacry loxypropyltrimethoxy silane (MAPS) and subsequently end-capping modification with hexamethyldisilazane (HMDS).…”

Design of Active Interfaces Using Responsive Molecular Components

“…Although these systems are capable of demonstrating remarkable separation efficiencies, the extreme pH required does leave room for milder triggers. For example, Li et al impart CO 2 ‐response in poly( N , N ‐dimethylamino‐2‐ethyl methacrylate) grafted cellulose nanofiber aerogels to effect the desired pH change . The decrease in pH upon bubbling through CO 2 results in protonation of the dimethylamino functional groups at the membrane surface, leading to a changeover in oil–water separation over 50 s as the water contact angle recedes from 130° to 0°.…”

Making Nanocomposites of Hydrophilic and Hydrophobic Polymers Using Gas‐Responsive Cellulose Nanocrystals

“…CO 2 ‐responisve polymers were already grafted on cellulose in different reports . However, the purpose of those grafted CNCs was mainly for applications using gas‐responsive CNCs as Pickering emulsifier or membrane for oil–water separation.…”

“…[19] CO 2 -responisve polymers were already grafted on cellulose in different reports. [4,18,[20][21][22] However, the purpose of those grafted CNCs was mainly for applications using gas-responsive CNCs as Pickering emulsifier or membrane for oil-water separation. In the present work, we demonstrate a novel application by using gas-responsive CNCs to solve the challenging issue of compatibility when using CNCs as a reinforcing agent in both hydrophilic and hydrophobic polymer matrices for nanocomposite materials.…”