Synthesis Of MCC-g-PDEAEMA Copolymers By ATRP In Ionic Liquids

Cellulose, as the most abundant renewable green natural material, has the best application prospect. so far the utilization rate of the cellulose is extremely low. The lack of the good homogeneous solvents of the cellulose is the bottleneck problem. Ionic liquids, as the emerging green solvents in recent years, provide an important way for the dissolution and modification of natural cellulose. Using ATRP technology modifies the natural cellulose in ionic liquids. Combined with the advantages of ionic liquids and ATRP realizes the controllable polymerization of natural cellulose. But the current studies in this field did not achieve the homogeneous ATRP reactions in ionic liquids. So in this article, the cellulose grafting polymers with the controllable structures tried to be synthesized in homogeneous and heterogeneous ionic liquid systems by ATRP.In this work, the pH sensitive monomers DEAEMA were grafted from natural MCC via ATRP in heterogeneous ionic liquid systems. The [AMIM]Cl ionic liquid was selected as the reaction solvent to dissolve the MCC. Cu Br/PMDETA was the catalytic system. Optimum reaction condition was attained at the DEAEMA/CuBr/PMDETA molar ratio of 50:1:1. The reaction temperature and time were 30 ℃ and 180 min. The polymers were characterized through FT-IR and 1H NMR. The results showed that the MCC-g-PDEAEMA were synthesized in heterogeneous systems. It proved by SEM that the surface morphology of MCC were changed when PDEAEMA were grafted from MCC. The number average molecular weight of the polymers in heterogeneous systems were only 3000~5000. It was a smaller molecular weight. And the molecular weight distribution were broad(Mw/Mn=3.012). The controllability of ATRP in this system was poor. The synthetic mechanism for the heterogeneous system was analyzed. It showed that the ATRP occurred in the DEAEMA/[AMIM]Cl interface. And the controllability of ATRP was restricted by the interface reactions and side reactions.The ethyl alcohol was used as the cosolvent to form a homogeneous reaction system in [AMIM]Cl ionic liquids. When ethyl alcohol was added, the viscosity of [AMIM]Cl were greatly reduced. The synthetic mechanism for homogeneous system was analyzed. It showed the polymerization were actively controlled in this system. Optimum reaction conditions were attained at ethyl alcohol/[AMIM]Cl molar ratio of 4:1. The molar ratio of CuBr/PMDETA/DEAEMA was 1:15:150. The reaction temperature and time were 30 ℃ and 210 min. The polymers were also characterized through FT-IR. The results showed MCC-g-PDEAEMA were synthesized in homogeneous systems. Thermogravimetry analysis showed that the thermal stability of MCC-g-PDEAEMA were good under 300℃. It was proved by SEM that the surface morphology of MCC-g-PDEAEMA were more neat and the distribution of side chains were more uniform in homogeneous systems. Kinetic analysis confirmed the reactions were first order polymerization and the apparent rate constant was 0.0058 min-1. The polymerization was “controlled/living”. The GPC test proved the number average molecular weight were 1.5×104~3.0×104. It increased one order of magnitude compared with the heterogeneous systems. And the molecular weight distribution were narrow(Mw/Mn=1.106). The MCC-g-PDEAEMA in heterogeneous systems were more suitable as drug carriers applied to drug delivery and controlled release systems.The MCC-g-PDEAEMA self-assembly micelles were prepared in different selective solvents. It was proved by TEM that the MCC-g-PDEAEMA could self-assemble into the spherical in acetone, DMSO and DMF. And it could self-assemble into stick in THF. DMF was determined as the ideal selective solvent and the self-assembly mechanism was studied. It was showed the morphology of MCC-g-PDEAEMA self-assembly micelles varied with the changes of pH in the environments. The MCC-g-PDEAEMA micelles had pH sensitivity. The MCC-g-PDEAEMA drug-loading micelles were prepared. The largest drug loadings of curcumin was 39.74% and the envelopment rate was 38.27%. It was proved by FT-IR that the MCC-g-PDEAEMA successfully loaded of curcumin. It was showed MCC-g-PDEAEMA drug-loading micelles could realize the controlled release of curcumin when the pH changed.