Prafulla K. Sahoo

Synthesis and kinetic studies of PMMA nanoparticles by non-conventionally initiated emulsion polymerization

Abstract The aqueous emulsifier-free emulsion polymerization of methyl methacrylate (MMA) was studied under the catalytic effect of in situ developed bivalent transition metal-EDTA complex with ammonium persulfate (APS, (NH4)2S2O8) as initiator. Out of these, Cu(II)-EDTA system was selected for detailed kinetic and spectrometric study of polymerization. The apparent activation energy Ea, 34.5 kJ/mol, activation energy of initiator decomposition Ed, 26.9 kJ/mol, energy of propagation Ep, 29 kJ/mol and energy of termination Et, 16 kJ/mol were reported. The emulsion polymer (PMMA) latex was characterized through the determination of the size and morphology by scanning electron microscopy, the average molecular weight by GPC and viscosity methods and the sound velocity by ultrasonic interferometer. From the kinetic results, the rate of polymerization, Rp at 50 °C was expressed by R p =K[ Cu ( II )] 0.35 [ EDTA ] 0.69 [ APS ] 0.57 [ MMA ] 0.75

Biodegradability and Swelling capacity of Kaolin based Chitosan-g-PHEMA Nanocomposite hydrogel

Chitosan, a natural biopolymer, obtained by alkaline deacetylation of chitin, exhibits excellent biological properties such as biodegradability, immunological and antibacterial activity. Recently, there has been a growing interest in the chemical modification of chitosan in order to widen its applications. The chemical modification of chitosan has been achieved via grafting of monomer, 2-hydroxyethyl methacrylate (HEMA) in the presence of the initiator, ammonium persulfate (APS) and kaolin was added to improve the mechanical strength of the newly developed nanocomposites hydrogel. The so prepared grafted nanocomposites hydrogel was characterized by FTIR, XRD, SEM, TEM and TGA. The equilibrium water content (EWC) of the samples were measured at different pH ranges 6.5-8.0 and found optimum at pH 7.5 for biomedical applications. Further, the biodegradability of the samples was studied at different time intervals from 15 days to 1 year but, the kaolin based nanohydrogels exhibited good biodegradability.

Synthesis and colon-specific drug delivery of a poly(acrylic acid-co-acrylamide)/MBA nanosized hydrogel.

Intravenous administration of 5-fluorouracil (5-FU) for colon cancer therapy produces severe systemic side-effects due to its cytotoxic effect on normal cells. The main objective of the present study was to develop novel oral site-specific delivery of 5-FU to the colon with less drug being released in the stomach or small intestine using biodegradable hydrogel, hydrogel nanoparticles and comparing the targeting efficiency of 5-FU to colon from both. Poly(acrylic acid-co-acrylamide) (P(AA-co-Am)) normal hydrogel and hydrogel nanoparticles (HN) were synthesized by free radical polymerization using N,N-methylene-bis-acrylamide (MBA) as cross-linker, potassium persulfate as reaction initiator and 5-FU was loaded. HN were found to be degradable in physiological medium and showed comparatively higher swelling in rat caecal medium (RCM). 5-FU entrapment was increased by increasing Am (wt%) monomer feed. In vitro release of 5-FU from normal hydrogel and HN in pH progressive medium, it was found that a AA/Am ratio of 25:75 showed higher release in RCM. The Higuchi model yielded good adjustment of in vitro release kinetics. A higher amount of 5-FU reached the colon in HN (61 ± 2.1%) than normal hydrogel (40 ± 3.6%) by organ biodistribution studies in albino rats.

Interpenetrating Polymer Network PVA/PAA Hydrogels

ABSTRACT A new type of interpenetrating polymer network (IPN) hydrogel based on polyvinyl alcohol (PVA) networking with difuctional monomer, acrylic acid (AA), and its polymer, polyacrylic acid (PAA), generated in situ, were prepared by a non-conventional emulsion method without any added crosslinker, using benzoyl peroxide as initiator and sodium chloride as additive. Structure and bonding in hydrogel due to interpenetrating network were confirmed by infrared spectroscopy. The networking was optimized by variation of reaction parameters such as concentrations of additive, monomer, time, and temperature. The response of the hydrogels with and without NaCl was observed by study of their swelling kinetics, and their apparent activation energies for diffusion (Ed) of water were calculated to be 29.28 and 35.97 J mol−1 K−1 with and without NaCl, respectively. The conductivity and pH were measured at different temperatures. The conductivity decreased largely with temperature whereas pH increased in presence of NaCl. The effect of swelling ratio was studied by variation of AA percentage and the optimal PVA/AA was determined. Biodegradability of the polymeric network was studied by culture media and the surface morphology investigated by scanning electron microscopy (SEM).

Emulsifier-free emulsion polymerization of acrylonitrile: Effect of in situ developed Cu(II)/glycine chelate complex initiated by monopersulfate

The catalytic effect of various Cu(II) salts and Cu(II) chelate complexes of certain amino acids on the emulsion polymerization of acrylonitrile in the absence of added emulsifier was investigated in experiments. The CuSO4/glycine chelate complex was chosen for a detailed kinetic study of acrylonitrile polymerization. The polymerization was studied at varying concentrations of initiator, monomer, Cu(II), glycine, solvents, and TiO2 over a temperature range of 30–60°C. The overall activation energy and the viscosity average molecular weight of the polymer were computed. From the kinetic and spectrophotometric studies, the mechanism of KHSO5 decomposition by the Cu(II)/glycine complex and initiation of polymerization was suggested.

Characterization, Biodegradation, and Water Absorbency of Chemically Modified Tossa Variety Jute Fiber via Pulping and Grafting with Acrylamide

Abstract Jute fiber (tossa variety) was chemically modified by the cooking alkaline sulfite process to unbleached and bleached pulps that were further modified via graft copolymerization with acrylamide monomer, using a complex initiating system: CuSO4/glycine/KHSO5. The samples so prepared were characterized and morphologically analyzed by IR, TGA, DSC, SEM, and XRD. The biodegradability and water absorbency of the samples were also evaluated for their novel commercial applications. It was found that the grafted samples were more resistant to biodegradation and showed higher water absorbency than their ungrafted counterparts.

Synthesis of zirconocene‐acetylene and zirconocene‐diacetylene polymer

A new class of organometallic polymer having a backbone of conjugated Poly-yne and Zr-metal atoms has been prepared. Trichloroethylene (TCE) and Hexachlorobutadiene (HCB) are quantitatively converted by n-butyllithium to dilithioacetylene (LiC≡CLi) and dilithiodiacetylene (Li-C≡C-C≡C-Li) respectively. Quenching with Cp 2 * ZrCl 2 affords high yields of the polymers [Zr(Cp 2 * )C≡C] n and [Zr(Cp 2 * )C≡C-C≡C] n where Cp * = C 5 (CH 3 ) 5 = pentamethyl cyclopentadienyl. The Cp 2 * ZrCl 2 and the polymers were characterized by viscosity, molecular weight, elemental analysis, FTIR, NMR spectra, and TGA.

Effect of Cu(II)/H2 Salen complex on the non-conventional initiated emulsion polymerization of acrylonitrile

Abstract Radical polymerization of acrylonitrile was carried out in an emulsifier-free condition initiated by KHSO5 catalyzed with Cu(II)/bis-salicylidene ethylene diamine (H2 Salen) complex. The Cu(II) salt alone, Cu(II)/salicylaldehyde and Cu(II)/ethylene diamine have a retarding effect on the polymerization reaction, while the chelate of Cu(II) with the tetradentate Schiff base ligand, H2 Salen has a catalytic effect. Prior to this, the catalytic effect of various bivalent transition metal salts and their couple with the Schiff base, H2 Salen on the polymerization reaction has been examined to be not significant. The in situ developed complex produces the stable emulsion leading to high conversion. In the polymerization, the variables studied were the concentration of monomer, initiator, Cu(II), H2 Salen and temperature. The overall activation energy was computed to be 13.1 kcal/mol. From the kinetic and spectral analyses, the mechanism of the initiator decomposition and initiation of polymerization by Cu(II)/H2 Salen complex were suggested. The rate of polymerization (Rp) was found to be dependent on the monomer, initiator, Cu(II) ion, H2 Salen concentrations to the 1.4, 0.3, 1.6, 1.5 power respectively. The polymers are characterized by IR and molecular weight by viscosity and GPC methods.

Complex-mediated microwave-assisted synthesis of polyacrylonitrile nanoparticles.

The polymerization of acrylonitrile (AN) is efficiently, easily, and quickly achieved in the presence of trans-[Co(III)en2Cl2]Cl complex in a domestic microwave (MW) oven. MW irradiation notably promoted the polymerization reaction; this phenomenon is ascribed to the acceleration of the initiator, ammonium persulfate (APS), decomposition by microwave irradiation in the presence of [Co(III)en2Cl2]Cl. The conversion of monomer to the polymer was mostly excellent in gram scale. Irradiation at low power and time produced more homogeneous polymers with high molecular weight and low polydispersity when compared with the polymer formed by a conventional heating method. The interaction of reacting components was monitored by UV-visible spectrometer. The average molecular weight was derived by gel permeation chromatography (GPC), viscosity methods, and sound velocity by ultrasonic interferometer. The uniform and reduced molecular size was characterized by transmission electron microscopy, the diameter of polyacrylonitrile nanoparticles (PAN) being in the range 50-115 nm and 40-230 nm in microwave and conventional heating methods respectively. The surface morphology of PAN prepared by MW irradiation was characterized by scanning electron microscope (SEM). From the kinetic results, the rate of polymerization (Rp) was expressed as Rp = [AN](0.63) [APS](0.57) [complex (I)].(0.88.)

Synthesis and study of thermal, mechanical and biodegradation properties of chitosan-g-PMMA with chicken egg shell (nano-CaO) as a novel bio-filler

The important objective of this study is to evaluate the effect of chicken eggshell (nano-Cao) as a functionalized bio-filler on the mechanical strength and thermal stability of acrylic based bionanocomposite of chitosan grafted with poly(methyl methacrylate)(PMMA). The chitosan grafted PMMA adsorbed with functionalized biofiller was prepared via emulsion polymerisation technique and physicochemically characterized as bone graft substitute. The so prepared grafted bioactive bone cement (BBC) bionanocomposite (BNC), chitosan-g-PMMA/nano-CaO was characterized by FTIR, XRD, FESEM and TGA. The water uptake, retention ability, their biodegradability and the nanosize particle arrangement in the polymeric BBC-BNCs were undertaken. These preliminary investigations of the BNCs will open the door for their use in bioadhesive bone cement implants in future.