Modification Of Nano-crystalline Cellulose By Grafting With Poly(Methyl Acrylate)

Cellulose is one of the most abundant and renewable natural polymericmaterial, which can be processed into nano-crystalline cellulose(NCC) by acidhydrolysis. Being a kind of new biopolymer material with high strength, highcrystallization degree, NCC has the advantages of biodegradable, biocompatible,and can be applied to the fields of polymer composite materials, biologicalmedicine, architecture, paper and etc. But a large number of hydroxyls exist onthe surface of NCC, making it cannot be dispersed in hydrophobic solvent orpolymer, and its application is limited. The modification of NCC could improveits physical and chemical properties, thus expand their research and applicationscopes. The method of graft co-polymerization could not only reduce the contentof hydroxyl groups on the NCC surface, but also introduce new functionalgroups, which could further improve the functionality of NCC without changingtheir intrinsic properties. Grafting hydrophobic groups can make NCC dispersein hydrophobic system more easily.In this paper, NCC suspensions were prepared by the method of acidhydrolysis with40%sulfuric and hydrochloric acid at55℃. The structuresand properties of NCC were characterized and investigated. The results showedthat the products had the rod–like structures with the characteristic structures ofNCC. The dimensions of NCC varied from10~50nm in diameter and100~500nm in length. Their length-diameter ratios ranged from10to100. Thecrystallinity of NCC was84.63%, and the thermal decomposition temperaturewas334.59℃.Activated NCC was prepared by the reaction between NCC and reactiveintermediates. The intermediates were obtained from the CDI reacting with AA.The structures and properties of activated NCC were characterized by the FTIR,TEM, TG,13C-NMR. The results suggested that after the activation reaction, the carbon-carbon double bonds had successfully grafted to the surface of NCC, Thecrystallinity of NCC was81.5%, and the active degree was24.58%.Based on the mechanism of SET-LRP, PMA was synthesized. FTIR andGPC were used to characterize its structure and molecular weight. The resultsindicated that the molecular weight of PMA was about2000, and PDI was1.14.Under the mechanism of free radical polymerization and graft copolymerization,NCC were reacted with PMA using EBIB as the initiator, Cu as the catalyst, andPMDETA as the ligand. The grafted copolymer was characterized throughseveral analytical techniques such as FIIR, TEM, TG, XRD. The effects ofreaction conditions on the graft yield and graft efficiency were investigated. Itwas shown that the graft copolymer with grafting yield at23.42%was obtainedwhen the contents of initiator was10mmol, the molar ratio of activated NCCand PMA was1:2, the reaction time were8h, respectively. The results provedthat the PMA has grafted onto the surface of NCC successfully. The TEM andFTIR figures showed that the main chains of grafted NCC also had the basicstructure of cellulose. The results presented that the thermal stability and storagestability of the grafted NCC were improved.