ORIGINAL PAPER Preparation of pH- and salinity-responsive cellulose copolymer in ionic liquid Xiaoyi Wei & Gang Chang & Jihua Li & Fei Wang & Lihong Cui & Tiaokun Fu & Lingxue Kong Received: 6 February 2014 /Accepted: 17 July 2014 /Published online: 30 July 2014 # Springer Science+Business Media Dordrecht 2014 Abstract A novel biodegradable pH- and salinity-responsive cellulose copolymer was prepared by grafting 2-(Dimethylamino) ethylmethacrylate (DMAEMA) onto ba- gasse cellulose in ionic liquid. The grafting polymerization was achieved in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) under microwave irradiation. Copolymers were then characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and thermo gravimetric analysis measurements. The results revealed that polymer chains had been successfully bonded to the cellulose backbone. Furthermore, the self-assembly of cellulose-g- DMAEMA copolymers at various salt concentrations and pH solution were investigated by means of swelling behavior measurement. It indicated that the copolymers presented dual pH and salinity-responsive properties. The synthetic strategy showed great potential in the modification of other cellulosic biomass to afford new biomaterials with desired properties. Keywords Cellulose . 2-(Dimethylamino) ethylmethacrylate . pH- and salinity-responsive . Homogeneous grafting Introduction Cellulose, one of the most abundant natural renewable poly- mers in nature, has attracted great interest due to increasing environmental concern [1, 2]. One of its applications is the development of cellulose modification for specific industrial applications through grafting or cross-linking [3]. However, most of the modifications are carried out in heterogeneous or non-green solvent systems because of its super molecular crystal structure, leading to a low grafting yield and degree of substitution. Recently, Swatloski and his group found that ionic liquids (ILs) could dissolve cellulose [4], and would be a good homogeneous medium for cellulose grafting polymeri- zation. For example, Lin synthesized a cellulose copolymer grafted with acrylic acid (cellulose-g-AA) in 1-butyl-3- methylinidazolium chloride ([Bmim]Cl) as a homogeneous solution under microwave irradiation [5]. It was indicated that [Bmim]Cl could dissolve cellulose by destroying the abun- dant strong inter- and intra-molecular hydrogen bonds to form a homogeneous medium. Grafting copolymerization could then be initiated by the decomposition of the inorganic agents (potassium peroxydisulfate), causing the grafting chains onto the backbone of cellulose [6, 7]. Intelligent high polymer materials, such as new multifunc- tional materials, have drawn increasing attention in biotech- nological applications, for example, drug carriers, sensors. They possess unique properties in response to external trig- gers, such as pH, temperature, or radiation [8–11]. Among them, one of the widely studied responsive polymers is 2-(Dimethylamino) ethylmethacrylate (DMAEMA), which has both pH and ionic strength sensitivity [12–14]. For exam- ple, Gu and coworkers prepared a poly (ethylene glycol) methyl ether acrylate-g-poly (2-(diethylamino) ethylmethacrylate) copolymer which is sensitive to both pH and salinity by atom transfer radical polymerization (ATRP). It could form reversible aggregates in a basic environment and easy dissociation of the aggregates with the addition of NaCl [12]. Bhut and colleagues grafted DMAEMA from cellulose membranes and used it as an anion exchange membranes for bio-separations [15]. However, few studies have focused on X. Wei : G. Chang : J. Li (*) : F. Wang : L. Cui : T. Fu Agriculture Products Processing Research Institute, Chinese Academy of Tropical Agricultural Sciences, Zhanjiang 524001, China e-mail: foodpaper@126.com L. Kong Institute for Frontier Materials, Deakin University, Waurn Ponds, Vic 3216, Australia J Polym Res (2014) 21:535 DOI 10.1007/s10965-014-0535-z