Homogeneous Modification Of Cellulose To Synthesis High Performance Adsorbents And Structure-controllable Graft Copolymers Using An Ionic Liquid As A Reaction Medium

Cellulose is the most abundant renewable biopolymers on earth, it has many good properties. The effective utilization of the cellulose has a great significance to the crisis of resource. In this paper, cellulose was modified homogeneously via different methods, including traditional radical polymerization and"living"/controlled radical polymerization, using an ionic liquid 1-butyl-3-methylimidazolium chloride (BMIMCl ) as reaction medium.Cellulose was grafted homogeneously with acrylic acid in BMIMCl by traditional radical polymerization, using ammonium persulfate (APS) as an initiator and N,N'-methylene- bisacrylamide(MBA) as a crosslinker. And then the spherical cellulose adsorbent was obtained through a water-in-oil suspension technique. The reaction conditions were optimized to obtained higher graft percentage (GP). The experimental results show that the use of BMIMCl as reaction medium can enhance the reaction rate and increase the grafting efficiency.Comprehensive studies on the adsorption properties of the spherical cellulose adsorbents were conducted in ways of static adsorption using metal ions(Cu2+, Ni2+ and Fe3+) and cationic dye (Methylene blue)as adsorbates.And,static isothermal adsorptions as well as various effecting factors were also studied. Moreover, the adsorption mechanisms including the adsorption thermodynamics and kinetics were explored.The adsorption of the metal ions and cationic dye on the adsorbents have found to be concentration,pH and temperature dependent.Furthermore,excellent adsorption efficiency of the above two adsorbates on the adsorbent can be obtained.And, the cellulose adsorbent has such advantages as easy regeneration, high recovery and reusability etc. The static adsorption process follows Langmuir and Freundlich adsorption isotherm equations. It can be concluded from the adsorption thermodynamics and kinetics that chemical adsorption is predominant for the adsorption of two adsorbates on the adsorbent.The adsorption rate is controlled by two diffusion models of surface diffusion process and intra-particle diffusion process,between which the intra-particle diffusion process plays a more significant role during the adsorption process.The microwave heating was adopted to replace the conventional heating to synthesize the graft copolymer of cellulose with acrylic acid. The effects of reaction conditions on grafting were studied and the results show that the use of microwave resulted in a drastic reduction of reaction time: 3 min irradiation was sufficient, compared with 30 min to 5 hours, as conventional heating was used. A probable free radical mechanism for grafting under microwaves was also proposed.The metal ion imprinted polymer was synthesized by homogeneous radical graft copolymerization of functional monomer acrylic acid onto cellulose with Pb2+ as template in BMIMCl. Investigation on the selective adsorption property of the imprinted copolymer was conducted. It is concluded that the obtained Pb2+-imprinted copolymer shows higher selectivity towards Pb2+ than the non-imprinted polymer."Living"/controlled radical polymerization combines the advantages of free radical polymerization and living polymerization. Polymers with fine structures, predetermined molecular weights and narrow polydispersities can be synthesized through"living"/controlled radical polymerizations in the polymerization condition which is similar to that of traditional free radical polymerization. In this paper, cellulose graft copolymers were synthesized via two"living"/controlled radical polymerizations, atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer polymerization (RAFT), respectively.Cellulose-based macroinitiator (Cell-ClAc) was first synthesized by direct homogenous acylation of cellulose in BMIMCl in absence of any catalyst. Then the homogeneous ATRP of MMA from cellulose macroinitiator was carried out in BMIMCl without homopolymer byproduct and the polymers were easily separated from the catalyst when the ionic liquid was used as reaction medium. Further the cellulose graft copolymer in solution could aggregate and self-assembly. The kinetic of the ATRP was also investigated and the results showed that the obtained copolymers had grafted polymer chains with well-controlled molecular weight and low polydispersity, and the polymerization was a"living/controlled"system. The reaction temperature and reaction ingredients ratios have great effect on the polymerization rate. The low apparent energy of activation (ΔEaapp , 16.6 KJ/mol) of the polymerization reaction illustrates that the reaction carried in BMIMCl is much easier.Cellulose based RAFT chain transfer agent (Cell-CTA) was obtained through substitution reaction of Cell-ClAc and bis(thiobenzoyl) disulphide. Then the MMA polymer chains were grafted onto the cellulose by RAFT in BMIMCl using 2, 2'-azobis(isobutyronitrile) (AIBN) as initiator. The experiment results demonstrate that the use of the ionic liquid as a reaction medium enhanced the polymerization rate to a moderate extent. Additionally, a controlled/living polymerization character was proven for cellulose-CTA-mediated RAFT polymerization in BMIMCl as a result of the first-order kinetics of the copolymerization, linear increase in Mn with conversion, and low PDIs.