No abstract

Modification of starch is increasingly being studied and starch is used for applications in which synthetic polymers have traditionally been the materials of choice. In this work the surface of starch was successfully modified by the polymerization of polystyrene and polyacrylamide by atom transfer radical polymerization (ATRP) method in dispersion medium. For this propose the bromoactylated starch was prepared by the reaction between hydroxyl groups of starch and the bromoacetyl bromide in DMA/LiCl (5%) in the presence of pyridine. The bromoactylated starch acts as macroinitiator in ATRP of styrene. The polymer chains' growth on surface of starch was clearly showed by the AFM images. Other analyses were used in this work such as FT‐IR, DSC, and TGA.

No abstract

Natural polymers are defined as high value polymeric materials because of their biocompatibility with medical applications. The chemical modification of these materials by grafting synthetic polymers has received considerable attention in recent years. As the first part of this research, transmutation of the prepared carboxymethyl starch (CMS) to useful biopolymer‐based materials was done by grafting acrylamide and hydroxyethylacrylate monomers using free radical polymerization. Also by chloroacetylation of starch, the graft copolymerization of the mentioned monomers via atom transfer radical polymerization was performed successfully. Both methods lead to obtain biodegradable superabsorbent copolymers. Moreover, the degree of substitution of each copolymer from both methods was determined. The prepared CMS, chloroacetylated starch, and copolymers were characterized by FTIR, DSC, thermal gravimetric analysis, XRD, and AFM, in which the latter analysis clearly shows the chain growth of the synthetic polymers on the backbone surface. Finally, in vitro drug release of cephalexin antibiotic loaded in each type of copolymers was studied in three different media (HCl solution: pH 3 and buffer solutions: pH 6.1 and pH 8).

The N-substituted polyaniline (PANi) was synthesized by incorporation of bromine-terminated polystyrene (PS-Br) onto the emeraldine form of polyaniline. End brominated polystyrene was synthesized by atom transfer radical polymerization (ATRP) technique and then deprotonated polyaniline was reacted with PS-Br to prepare PS-grafted PANi (PS-g-PANi) copolymer through Ngrafting reaction. The degree of N-grafting can be controlled by adjusting the molar feed ratio of PS-Br to the number of repeat units of PANi. The microstructure and compositions of the PS-g-PANi copolymers with different degrees of N-substitution were characterized by FT-IR, elemental analysis, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The cyclicvoltammetry shows that the electroactivity of N-substituted PANi is strongly dependent on the degree of N-grafting. The solubility of PS-g-PANi copolymers in common organic solvents such as tetrahydrofuran and chloroform was improved by increasing the degree of N-grafting, and also the samples are partially soluble in xylene.