Patakamuri Govindaiah

Monodisperse and fluorescent poly(styrene-co-methacrylic acid-co-2-naphthyl methacrylate)/Fe3O4 composite particles

This article describes the preparation and characterization of fluorescent and magnetic composite particles of poly(styrene-co-methacrylic acid-co-2-naphthyl methacrylate) (poly(St/MAA/NMA)). First, monodisperse (D(w)/D(n)<1.1) and fluorescent poly(St/MAA/NMA) submicron particles were prepared using emulsifier-free emulsion polymerization by varying the concentration of the fluorescent comonomer, i.e., NMA. Composition of the particles was characterized by (1)H NMR, FT-IR, GPC, and DSC analyses. The molecular weights and particle size of the particles were dependent on the NMA concentration. Second, Fe(3)O(4) nanoparticles were immobilized onto the poly(St/MAA/NMA) submicron particles to give rise to multifunctional properties. The morphology and particles size were characterized by FE-SEM and CHDF. These poly(St/MAA/NMA)/Fe(3)O(4) composite particles exhibited both fluorescent properties under UV irradiation at 365 nm and magnetic properties. Photo-luminescent (PL) intensity of the particles showed linear dependence with NMA concentration.

Synthesis and characterization of multifunctional Fe3O4/poly(fluorescein O-methacrylate) core/shell nanoparticles.

Multifunctional fluorescent and superparamagnetic Fe(3)O(4)/poly(fluorescein O-methacrylate) [Fe(3)O(4)/poly(FMA)] nanoparticles with core/shell structure were synthesized via surface-initiated polymerization. First, polymerizable double bonds were introduced onto the surface of Fe(3)O(4) nanoparticles via ligand exchange and a condensation reaction. A fluorescent monomer, FMA, was then polymerized to the double bonds at the surface via free-radical polymerization, leading to form a fluorescent polymer shell around the superparamagnetic Fe(3)O(4) core. The resultant Fe(3)O(4)/poly(FMA) nanoparticles were characterized by Fourier transform infrared, nuclear magnetic resonance, and X-ray diffraction spectroscopy to confirm the reactions. Transmission electron microscopy images showed that the Fe(3)O(4)/poly(FMA) nanoparticles have a spherical and monodisperse core/shell morphology. Photoluminescence spectroscopy and superconducting quantum interference device magnetometer analyses confirmed that the Fe(3)O(4)/poly(FMA) nanoparticles exhibited fluorescent and superparamagnetic properties, respectively. In addition, we demonstrated the potential bioimaging application of the Fe(3)O(4)/poly(FMA) nanoparticles by visualizing the cellular uptake of the nanoparticles into A549 lung cancer cells.

Preparation of Fe3O4-Embedded Poly(styrene)/Poly(thiophene) Core/Shell Nanoparticles and Their Hydrogel Patterns for Sensor Applications

This research describes the preparation and sensor applications of multifunctional monodisperse, Fe3O4 nanoparticles-embedded poly(styrene)/poly(thiophene) (Fe3O4-PSt/PTh), core/shell nanoparticles. Monodisperse Fe3O4-PSt/PTh nanoparticles were prepared by free-radical combination (mini-emulsion/emulsion) polymerization for Fe3O4-PSt core and oxidative seeded emulsion polymerization for PTh shell in the presence of FeCl3/H2O2 as a redox catalyst, respectively. For applicability of Fe3O4-PSt/PTh as sensors, Fe3O4-PSt/PTh-immobilized poly(ethylene glycol) (PEG)-based hydrogels were fabricated by photolithography. The hydrogel patterns showed a good sensing performance under different H2O2 concentrations. They also showed a quenching sensitivity of 1 μg/mL for the Pd2+ metal ion within 1 min. The hydrogel micropatterns not only provide a fast water uptake property but also suggest the feasibility of both H2O2 and Pd2+ detection.

Luminescent gold–poly(thiophene) nanoaggregates prepared by one-step oxidative polymerization

We report the facile synthesis, formation mechanism, and photoluminescent (PL) properties of gold–poly(thiophene) (Au–PTh) nanoaggregates. They were prepared by one-step oxidative polymerization, in which Au3+ ion was utilized as an oxidizing agent for the polymerization of thiophene. Transmission electron microscopy (TEM) and high-resolution TEM (HR-TEM) analyses demonstrated that the ‘raspberry-like’ Au–PTh nanoaggregates consist of individual Au NPs covered by PTh and stabilized by Tween 80. For Au–PTh nanoaggregates, a clear red shift in the SP peak was observed in the UV absorption spectra as compared with pristine Au nanoparticles (NPs). This red shift of the SP band is a consequence of the location of π-conjugated PTh on the surface of Au NPs, resulted from a strong binding between sulfur atoms of PTh and the Au NPs (sulfur–gold interaction). The strong interaction between the gold and sulfur atoms of PTh in the Au–PTh nanoaggregates was observed by X-ray photoelectron spectroscopy (XPS) analysis. The SP effect contributes to the PL intensity enhancement of the Au–PTh nanoaggregates and was confirmed by confocal laser scanning microscopy (CLSM).

Tunable fluorescent poly(styrene-co-methacrylic acid)/Au-Aphen hybrid nanoparticles via surface immobilization

Tunable fluorescent poly(styrene-co-methacrylic acid) [poly(St-co-MAA)]/Au-Aphen hybrid nanoparticles were fabricated by immobilizing the 5-amino-1,10-phenanthroline functionalized gold nanoparticles (Au-Aphen) on the surface of copolymer nanoparticles in aqueous solution. Aphen-Au cationic complex was absorbed on the surface of poly(St-co-MAA) nanoparticles by using electrostatic interactions and metalized by a reduction process. Thus, the functionalized metal nanoparticles can be immobilized onto the surface of the copolymer nanoparticles to significantly modify their optical properties. The structure of the hybrid nanoparticles was confirmed by infrared spectroscopy, scanning electron microscopy, X-ray diffraction, UV-vis spectrophotometery and spectrofluorophotometery studies. These hybrid nanoparticles exhibited fluorescence properties with enhanced photoluminescence quantum yield compared to the gold clusters. Furthermore, the fluorescent emission wavelength of hybrid nanoparticles can be tuned precisely by changing the amount of Aphen functionalized gold nanoparticles on the surface of poly(St-co-MAA) nanoparticles. PL spectra of hybrid nanoparticles showed a red-shift with increasing the amount of functionalized gold on the poly(St-co-MAA) nanoparticles surface in a water medium.

Enhanced Crystallization of Bisphenol-A Polycarbonate by Organoclay in the Presence of Sulfonated Polystyrene Ionomers

Polycarbonate (PC)/sulfonated polystyrene (SPS) ionomer/organoclay nanocomposites were prepared by a solution intercalation process using the SPS ionomer as a compatibilizer. The effect of an organoclay on the melt crystallization behavior of the ionomer compatibilized PC were examined by differential scanning calorimetry (DSC). The melt crystallization behavior of PC was dependent on the extent of organoclay dispersion. The effect of the ionomer loading and cation size on intercalation/exfoliation efficiency of the organoclay in PC/SPS ionomer matrix was also studied using wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). Dispersion of the organically modified clay in the polymer matrix improved with increasing ionomer compatibilizer loadings and cation size. The SPS ionomer compatibilized PC/organoclay nanocomposite showed enhanced melt crystallization compared to the SPS ionomer/PC blend. Well dispersed organoclay nanocomposites showed better crystallization than the poorly dispersed clay nanocomposites. These nanocomposites also showed better thermal stability than the SPS ionomer/PC blend.

One-pot synthesis of grafted brush copolymers via a chain-growth radical/oxidative dual polymerization system

This article describes the facile synthesis of grafted brush copolymers via the combination of metal-catalyzed chain-growth radical polymerization and oxidative polymerization, using a dual functional monomer. The most significant finding was the possibility of performing free-radical polymerization and oxidative polymerization in a single step, using copper bromide as a recyclable catalyst. Cu+ initiated the radical polymerization via a chain growth mechanism, and Cu2+ initiated the oxidative polymerization, leading to grafted brush copolymers in which π-conjugated polymers formed the main chains and poly(styrene sulfonate) (PSS) formed the high-density brushes. Nuclear-magnetic-resonance and Fourier-transform-infrared spectroscopic analyses revealed the formation of poly(thiophene)-co-poly(styrene sulfonate) (PTh-co-PSS) and poly(3,4-ethylenedioxythiophene)-co-polystyrene sulfonate (PEDOT-co-PSS). Ultraviolet and photoluminescence analyses confirmed the formation of the π-conjugated polymers during the dual polymerization process. These grafted brush copolymers had exceptionally good solubilities in N,N-dimethylformamide.