The chemical modification of biopolymer-based materials by grafting synthetic polymers has received considerable attention in recent years, inasmuch as there are wide varieties of monomers available. Nowadays, the most abundant biomacromolecule, cellulose, has attracted considerable attention due to its biodegradable, biocompatible, and renewable characteristics. In this study, the surface of hydrophilic cellulose microfibers was successfully modified by polymerization of hydrophobic polystyrene using atom transfer radical polymerization (ATRP) technique in dispersion medium. In this medium, only the outer surface of the macroinitiator is available for the polymerization, so the grown polymer chains are formed as monolayer on the surface of the macroinitiator. This type of modification not only increases the mechanical properties of the cellulose backbone, but also turns the hydrophilic characteristics of cellulose into hydrophobic state. For this purpose, in the first part of this research, chloroacetylated cellulose was synthesized as macroinitiator. In the second part, the acyl content of the macroinitiator and the degree of substitution, which show the efficiency of the esterification reaction, have been determined by basic hydrolysis of the macroinitiator with KOH and back-titration of the excess alkali with HCl. Finally, the chloroacetylated cellulose was modified by graft copolymerization of styrene using ATRP method. The polystyrene chain growth is confirmed by the atomic force microscopy images.

The first example of N -tetradecyl-N -methyl-2-pyrrolidonium was synthesized by using bromide as both an ionic liquid and a surfactant in ionic liquid-based microemulsion polymerization of methyl methacrylate under atom transfer radical polymerization at activator generated electron transfer conditions. The polymerization was carried out at room temperature using copper (II) chloride (CuCl2) /hexamethylene tetramine (HMTA) as a catalyst and CCl4 as an initiator in the absence of surfactant. Ascorbic acid was used as reducing agent. A pseudoternary phase diagram was constructed at 25oC using the water titration method in the presence and absence of hexadecyltrimethylammonium bromide (CTAB). Kinetics experimental results showed that the polymerization proceeded in a controlled/‘living’ process as evidenced by a linear increase of molecular weights of polymers with monomer conversion with a relatively narrow polydispersity (<1.35) in all cases and Mn, GPC values of the resulting polymer were in excellent agreement with the theoretical values Mn, th. The polymerization rate increased with the amount of surfactant. However, the polydispersity became broader. The polymerization rate increased with the amount of ligand and decreased with the amount of monomer. In this system, particles of nanoscale (33-51 nm) were prepared. The average particle diameter was found to be affected by the amount of surfactant. The AGET- ATRP of MMA retained the characteristic of living polymerization when the ionic liquid C14MPnBr and catalyst complex were recovered and reused. Living nature of the polymerization was confirmed by the successful homo chain extension experiment. The resultant PMMA was characterized by 1H NMR spectroscopy and gel permeation chromatography techniques.

Diblock copolymers consisting of methylmethacrylate (MMA) and N-hydroxyethylacrylamide (HEAAm) polymer were successfully synthesized via direct two steps atom transfer radical polymerization (ATRP). At first, poly (methylmethacrylate) (PMMA) macroinitiators were prepared using methyl 4-(bromo-methyl) benzoate initiator and were used for synthesizing PMMA-b-PHEAAm block copolymers. PMMA homopolymers were synthesized in N, N′-dimethylformamide (DMF) using CuBr/2, 2′bipyridine catalyst system at 110oC temperature in nitrogen atmosphere. Block copolymers were synthesized in mixture of DMF/water (8.2 v/v%) and in pure DMF in the presence of CuBr/1, 1, 4, 7, 10, 10-hexamethyltriethylenetetramine (HMTETA) catalyst system at 85 and 100oC, respectively, while argon was used for deoxygenation and inert environment. Purification of block copolymers was conducted through dialysis against deionized water using a dialysis tubing (MWCO 3,500, cellulose membrane). Molecular weights of PMMA polymers (Mn= 4,400, 6,200 and 8,400 Da) were determined by size exclusion chromatography using tetrahydrofuran (THF) as eluent. The chemical structure and actual copolymer compositions were determined using elemental analysis (EA), attenuated total reflectance infrared (ATR-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopic analysis. Phase separation of diblock copolymers resulting in two glass transition temperatures as detected by differential scanning calorimeter (DSC) proves their amphiphilic behavior. Thermogravimetric analysis (TGA) also showed that diblock copolymer, with two-step decomposition has higher thermal stability than PMMA.

In the present article, we have reported a detailed study of the surface modification for magnetite nanoparticles (MNP, Fe3O4) using a natural, biodegradable, and biocompatible polymer. For this purpose, the cellulose was converted to its bromoacetylated derivative (BACell) by reacting with bromoacetyl bromide. Next, the MNPs were functionalized by the reaction of the hydroxyl groups with the methylene bromide of the prepared BACell to form Fe3O4/BACell. Then, the atom transfer radical polymerization (ATRP) method was developed for the covalent immobilization of the N-vinylpyrrolidone (NVP) on the Fe3O4/BACell surface to produce the Fe3O4/Cellulose-grafted NVP (Fe3O4/Cell-NVP) as a novel synthetic product. The Fourier transform infrared spectroscopy (FT-IR) indicated the presence of copolymer on the MNPs surface. Moreover, the thermogravimetric analysis (TGA) results of the Fe3O4/Cell-NVP indicated that there had been an acceptable percentage of the content of polymer chains on the surface of the Fe3O4 nanoparticles. Furthermore, the structure and magnetic properties of the Fe3O4/Cell-NVP were confirmed by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and scanning electron microscopy (SEM). The loading capacity and release profiles of Doxorubicin (DOX) as a model drug from the Fe3O4/Cell-NVP were determined by UV–Vis absorption measurement at λmax=483 nm. The results showed that the DOX-loaded nanoparticles had been well controlled during the release period of the DOX. Therefore, it seems that the Fe3O4/Cell-NVP is an appropriate candidate for the controlled and targeted delivery of cancer treatment.