Synthesis Of Cellulose Graft Copolymers Via Homogeneous ATRP

With the increasing demand to use cellulose more effectively, modification of cellulose by graft polymerization provides a significant route to combine the advantages of natural and synthetic macromolecules for a wide range of potential applications. Synthesis of (cellulose-graft-polymer) copolymers via homogeneous atom transfer radical polymerization (ATRP) in ionic liquid was researched in this article. Selected three different kind of monomer and discussed each of the molecular weight distribution, stability and thermodynamics in different solutions.First of all, 1-allyl,3-methylimidazolium chloride [AMIM]C1 ionic liquid was prepared according to the reference. The solubility of cellulose in [AMIM]C1 and [BMIM]C1 was investigated. The results showed that it had higher solubility of cellulose in [AMIM]C1 than in [BMIM]C1. Then cellulose macroinitiator was successfully synthesized by direct acylation of cellulose with 2-bromopropionyl bromide in [AMIM]C1 without using any catalysts and protecting group chemistry. The synthesized macroinitiator cellulose-Br was characterized by FTIR, 1H-NMR and 13C-NMR spectroscopies.ATRP of methyl methacrylate (MMA),2-hydroxyethyl methacrylate (HEMA) and 2-hydroxypropyl methacrylate (HPMA) from the macroinitiator cellulose-Br were then carried out. The synthesized cellulose graft copolymers were characterized by FTIR and 1H-NMR spectroscopies The cellulose-g-PMMA and PMMA were analyzed by GPC, the Mw/Mn each were about 1.63 and 1.53. The grafted PMMA chain was obtained by the hydrolysis of the cellulose backbone with good molecular weight and polydispersity. And the Mw/Mn of cellulose-g-PHEMMA and cellulose-g-PHPMA were around 1.81 and 1.45. The results obtained from these analytical techniques confirm that the graft polymerization occurred from cellulose backbone. Throught TGA measurement, it was found the three kinds of cellulose graft copolymers all had good stability. Furthermore, the thermodynamics of cellulose-g-PMMA, cellulose-g-PHEMA and cellulose-g-PHPMA in different solutions were measured by TEM and AFM. The results showed that cellulose graft copolymers would assemblies or aggregates into sphere-like polymeric structure and the particle diameter of the copolymers in selective solvent acetone were bigger than in DMF.