Surface-initiated atom transfer radical polymerization of butyl acrylate on cellulose microfibrils

Surface-initiated atom transfer radical polymerization (SI-ATRP) of butyl acrylate (BA) on cellulose microfibrils (CMF) was conducted to create controllable hydrophobic chains on CMF. The macroinitiator, CMF-Br, was prepared by the esterification of hydroxyl groups on CMF with 2-bromoisobutyrylbromide (BIBB); followed by the ATRP of BA using two catalyst systems, CuIBr/2,2′-bipyridine (BPY) and CuIBr/pentamethyl-diethylenetriamine (PMDETA). The molecular weight (MW) and polydispersity of the grafted PBA cleaved from CMF via hydrolysis was determined using GPC. The results indicated that the PMDETA system exhibited relatively poor control over the ATRP; whereas the BPY system produced the PBA with tailored chain lengths and relatively narrow polydispersities but experienced a rather slow polymerization process. To optimize the polymerization with the CuBr/PMDETA system, several influencing factors were investigated, including the type of solvents, reaction temperature and the use of co-catalyst CuIIBr2. The hydrophobic-modified CMF is of great potential as reinforcements biocomposites.