Ali Md Showkat

Characterization of poly(diphenylamine)-gold nanocomposites obtained by self-assembly

Composites of poly (diphenylamine) and gold nanoparticles were chemically prepared from solutions which containing methane sulfonic acid (MSA) with the addition of gold chloride trihydrate as the oxidant as a source for initiation of polymerization and a generation of Au nanoparticles. Poly (diphenylamine) decorated with noble-metal gold nanoparticles were synthesized successfully and exposure of the solutions to caused polymerization of diphenylamine to polymerize with gold salt. The nanocomposites were characterized for the structure, morphology and electronic properties through X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM) and UV-visible spectroscopy.

Preparation and Characterization of Poly(4-vinylpyridine) Encapsulated Zinc Oxide by Surface-Initiated RAFT Polymerization

Poly(4-vinylpyridine) was covalently wrapped onto ZnO nanoparticles through surface initiated Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization upon grafting from protocol. The surface of ZnO nanoparticles was initially modified by the coupling reaction with silane leading to trithiocarbonate functionalized ZnO nanoparticles (ZnO-RAFT). The controlled radical polymerization of 4-vinylpyridine in the presence of the ZnO-RAFT afforded PVP-g-ZnO nanocomposites. FT-IR, EDX, XRD and XPS analyses demonstrated the grafting of PVP on the surface of ZnO nanoparticles, while thermal stability of PVP-g-ZnO nanocomposites was confirmed by TGA analysis. The TEM and SEM images suggested that ZnO nanoparticles were embedded in the polymer, and the dispersibility of the nanocomposites was improved in an organic solvent dramatically.

Synthesis of Poly(ϵ-caprolactone) Grafted Poly(2-hydroxyethyl methacrylate) Functionalized Hydroxyapatite by RAFT and ROP

Poly(ϵ-caprolactone) grafted poly(2-hydroxyethyl methacrylate) functionalized hydroxyapatite (HAP@PHEMA-g-PCL) nanocomposites were synthesized by the combination of reversible addition fragmentation chain transfer (RAFT) polymerization and ring-opening polymerization (ROP). The RAFT agent was anchored on the surface of hydroxyapatite nanocrystals (HAPs) through the silane condensation process of 3-chloropropyltrimethoxysilane followed by reaction with potassium xanthogenate. Poly(2-hydroxyethyl methacrylate) (PHEMA) was covalently functionalized on the surface of HAPs by RAFT polymerization. Then, poly(ϵ-caprolactone) (PCL) was grafted on HAPs by ROP based on the hydroxyl groups of PHEMA to afford HAP@PHEMA-g-PCL. The structure and composition of HAP@PHEMA-g-PCL nanocomposites were characterized by FT-IR, XRD, and TGA analyses. The morphology and formation of the polymer encapsulating HAPs were demonstrated from SEM and TEM images, while the 1H MNR analysis of the cleaved PHEMA-g-PCL confirmed the grafting.

A Facile Esterification Reaction Towards the Synthesis of Poly(methyl methacrylate)/Titanium Dioxide Nanocomposites

Poly(methyl methacrylate)/titanium dioxide (PMMA-g-TiO2) nanocomposites were prepared by the direct esterification reaction under mild conditions. Initially, the surface of titanium dioxide nanoparticles (TiO2 NPs) was modified by 3-glycidoxypropyl trimethoxysilane in order to prepare epoxy functionalized TiO2 NPs. The nanoparticles were refluxed in ethanol solution of HCl to convert the epoxy groups into alkyl-hydroxyl units. Subsequently, PMMA chains were attached to the surface of TiO2 NPs by the esterification reaction between alkyl-hydroxyl units at the nanoparticle surface and carboxylic acid terminated PMMA. Fourier transformed infrared spectrometry confirmed the presence of PMMA groups grafted on the surface of TiO2 NPs. X-ray diffraction and X-ray photoelectron spectroscopy revealed the existence of the grafted PMMA of the nanocomposites. An improved thermal property of the nanocomposites was observed by thermogravimetric analysis while transmission electron microscopy images confirmed well dispersed nanocomposites in chloroform due to the functionalization of PMMA brushes.

Luminescence of Terbium (III) Complexes Incorporated in Carboxylic Acid Functionalized Polystyrene/BaTiO3 Nanocomposites

Luminescence nanocomposites based on barium titanate nanoparticles (BaTiO3), polystyrene (PSt), and terbium ion (Tb3+) were synthesized by using a combination of reversible addition fragmentation chain transfer polymerization, Friedel-Crafts alkylation reaction and coordination chemistry. The modification of the surface of BaTiO3 was conducted by an exchange process with S-benzyl S’-trimethoxysilylpropyltrithiocarbonate to anchor macro-initiators for the polymerization of styrene. Subsequently, PSt grafted barium titanate was functionalized by the substitution reaction between 4-(chloromethyl) benzoic acid and PSt to produce hybrids, BaTiO3-g-PSt -COOH. The coordination of the hybrids with Tb3+ ions in the presence of 1,10-phenanthroline (Phen) afforded fluorescent Tb3+ tagged carboxylic acid functionalized polystyrene/barium titanate (BaTiO3-g-PSt-Tb3+-Phen). FT-IR, XRD, TGA, and SEM analyses revealed the formation of BaTiO3-g-PSt-Tb3+-Phen hybrids. The optical properties of BaTiO3-g-PSt-Tb3+-Phen were investigated by using fluorescence spectroscopy.

Synthesis and Properties of Poly(N-vinylcarbazole) Covalently Functionalized Zinc Oxide Nanocomposites

Poly(N-vinylcarbazole) covalently grafted zinc oxide nanoparticles (ZnO-g-PNVC) were synthesized with a simple route using surface initiated reversible addition-fragmentation chain transfer (RAFT) polymerization. Initially, the surface of ZnO nanoparticles was modified by the condensation reaction of 3-chloropropyltrimethoxysilane, and it was subsequently reacted with potassium xanthogenate to produce ZnO nanoparticles having RAFT functionality (ZnO-RAFT). The controlled radical polymerization of N-vinylcarbazole in the presence of ZnO-RAFT afforded ZnO-g-PNVC composites. FT-IR, EDX, XRD, and SEM analyses demonstrated the grafting of PNVC onto ZnO nanoparticles. Thermal stability of ZnO-g-PNVC composites was revealed by TGA analysis. UV-Vis absorption and photoluminescence results suggested ZnO-g-PNVC composites as a potential material in optical application.

Synthesis of Poly(2-Ethynylpyridinium Trifluoroacetate) by Spontaneous Polymerization

Poly (2-ethynylpyridinium trifluoroacetate) (P2EPF) was synthesized by the spontaneous polymerization of 2-ethynylpyridine (2-EP) and trifluoroacetic acid (TFA). TFA, as a strong acid for sufficient activation of the acetylenic triple bond, was used in the spontaneous polymerization of 2-EP producing conjugated and ionic polyacetylenes. P2EPF was soluble in polar organic solvents due to inherent characteristics of ionic polymers. The chemical structure and composition of P2EPF were characterized by 1H-NMR, 13C-NMR, FT-IR, and UV-Vis spectrometer. The fluorescence spectra of P2EPF suggested that P2EPF were successfully synthesized as potential conducting materials.