Novel nanostructured composite materialsbased on bacterial cellulose membranes (BC) and acrylate polymerswere prepared by in situ atom transfer radical polymerization (ATRP).BC membranes were functionalized with initiating sites, by reactionwith 2-bromoisobutyryl bromide (BiBBr), followedby atom transfer radical polymerization of methyl methacrylate (MMA)and n-butyl acrylate (BA), catalyzed by copper(I)bromide and N,N,N′,N″,N″-pentamethyldiethylenetriamine(PMDETA), using two distinct initiator amounts and monomer feeds.The living characteristic of the system was proven by the growth ofPBA block from the BC-g-PMMA membrane. The BC nanofibersleeving was clearly demonstrated by SEM imaging, and its extent canbe tuned by controlling the amount of initiating sites and the monomerfeed. The ensuing nanocomposites showed high hydrophobicity (contactangles with water up to 134°), good thermal stability (initialdegradation temperature in the range 241–275 °C), andwere more flexible that the unmodified BC membranes. [ABSTRACT FROM AUTHOR]