Synthesis, characterization, and gas permeabilities of cellulose derivatives containing adamantane groups

Cellulose derivatives containing adamantane groups are homogeneously synthesized by a simple, rapid and environmentally friendly way using 1-allyl-3-methylimidazolium chloride (AmimCl) ionic liquid as reaction media. Without any catalysts, cellulose adamantates (CAd) with degree of substitution (DS) in a range from 0.71 to 2.25 are prepared just in one-step. In addition, a series of mixed esters, cellulose adamantate acetate (CAdAc), are also synthesized via the “one-pot” process. The obtained CAd and CAdAc are characterized by means of FT-IR, NMR, XRD, DSC and TGA. Meanwhile, their gas permeabilities of these materials for O2, N2, CH4, CO and CO2 are studied. CAd exhibits improved solubility in organic solvents, low glass transition temperature and good thermostability. In particular, the free-volume topology of CAd membranes has been tailored by controlling the DS of adamantane, thus CAd membranes display a significant enhancement for gas permeability with good ideal permselectivity for several gas pairs, such as O2/N2, CO2/N2, CO2/CH4 and CO2/CO. For CAdAc, introducing only a small amount of adamantane groups in cellulose acetate could achieve better gas permeability and similar or slightly lower ideal permselectivity.