K. Mohana Raju

Controlling of silver nanoparticles structure by hydrogel networks

Silver nanoparticles are the most widely used antibacterial agents with a number of advantages. The higher degree of biocompatibility and long-term antibacterial activity can be achieved with hydrogel-silver nanoparticles. In this work, a simple and facile synthetic strategy is developed to control the size and shape of the silver nanoparticles within the hydrogel networks. The variation in cross-link density of the polymer network has been found not only to control the size of the nanoparticles between 1 and 10nm, but it also regulates shape of the nanostructures such as nanorods, nanocubes, etc. This approach takes the advantage of the existing free-space between the networks of hydrogels that not only acts as a template for nucleation of particles but also provides long term stability. Further, nanoparticles can be recovered at any time from the hydrogel networks. These hybrid nanocomposites release nanoparticles with time which can eventually promote for antibacterial application. It can be inferred from the study that fine tuning of the hydrogel synthetic parameters will enhance the possibilities of desired nano-product tailor made for particular applications.

Synthesis and Characterizations of Macroporous Poly(acrylamide-2-acrylamido-2-methyl-1-propanesulfonic acid) Hydrogels for In Vitro Drug Release of Ranitidine Hydrochloride

Macroporous hydrogels were prepared with acrylamide (AM) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as well as with anhydrous dextrose (AD) as porogen by crosslinking with N,N1-methylenebisacrylamide (MBA). The chemical structure of hydrogels is characterized by Fourier transform infrared (FTIR) spectroscopy. Morphological studies done by scanning electron microscopy (SEM) showed the macroporous nature of the hydrogels. Swelling studies of hydrogels were done in distilled water, in aqueous NaCl solution and in different pH solutions. In addition, drug release studies of selected macroporous hydrogels (DAMPS1, DAMPS4, DAMPSM1 and DAMPSM3) are also investigated.

Swelling Properties of Chemically Crosslinked Poly(acrylamide-co-maleic acid) Hydrogels

ABSTRACT Chemically crosslinked poly(acrylamide-co-maleic acid) [poly(AAm-co-MA)] hydrogels were prepared by simultaneous free radical copolymerization of acrylamide (AAm) with maleic acid (MA) in presence of di or tri functional crosslinking agents using ammonium persulfate-N,N,N′,N′-tetramethylethylenediamine (APS-TMEDA) redox-initiating system. The poly(AAm-co-MA) hydrogels formation was confirmed by IR studies. The influence of crosslinkers such as N,N′-methylene-bis-acrylamide (MBA) and 2,4,6-triallyloxy-1,3,5-triazine (TATA) on swelling/de-swelling characteristics were studied in detail for poly(AAm-co-MA) hydrogels containing different amounts of maleic acid. The present investigation also deals with the influence of concentration of crosslinker and initiator on the swelling behavior of poly(AAM-co-MA) hydrogels. The effect of various salts on swelling capacity was studied. In addition, the effect of simulated biological fluids and pH solutions on the swelling of hydrogels was also studied in detail.

Development and Characterization of Curcumin Loaded Silver Nanoparticle Hydrogels for Antibacterial and Drug Delivery Applications

The present work involves the development of curcumin loaded silver hydrogel nanocomposites based on acrylamide and 2-acrylamido-2-methyl propanesulfonic acid, as a template by redox co-polymerization in the presence of hydrophilic crosslinker N,N1-methylenebisacrylamide. Silver nitrate was taken as the metal precursor and sodium borohydride as a reducing agent. The formation of silver nanoparticles was monitored using UV–Vis absorption spectroscopy. The developed hydrogel silver nanocomposites (HSNC) were characterized by FTIR, UV–Vis, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy. The curcumin loading and release characteristics were performed for different hydrogel systems. The developed HSNCs were evaluated for preliminary antibacterial applications.

Poly(acrylamide-chitosan) Hydrogels: Interaction with Surfactants

Semi-interpenetrating hydrogels were prepared from hydrophilic acrylamide and cationic natural biopolymer chitosan, N,N1-methylenebisacrylamide and water-soluble redox initiating system (ammonium persulfate/N,N,N1,N1-tetramethylethylenediamine). The interaction of these hydrogels with different surfactants such as sodiumdodecylsulphate (SDS, anionic), N-cetyl N,N,N-trimethyl ammonium bromide (CTA, cationic) and Tween20 (T20 non-ionic) was studied. The chemical structure of the hydrogels treated with surfactant was characterized by FTIR spectroscopy and the morphology of hydrogels was characterized by scanning electron microscopy (SEM). The thermal properties of surfactant-treated hydrogels were evaluated by TGA analysis.

Synthesis of azido polymers as potential energetic propellant binders

Composite propellants are considered as major sources of chemical energy for rocket propellants. In the preparation of composite propellant energetic formulations, the propellant binder plays a vital role. Various energetic polymeric binders were developed during last five decades to satisfy safety, high energy and processing conditions. In this review, we discuss the various synthetic routes for of preparation of high energetic polymeric binders, including glycidyl azide polymers (GAP)s, GAP co-polymers, oxetane polymers, oxirane polymers, azido polyesters, N, N′-bonded epoxy binders, aliphatic vinyl azide polymers and poly(allyl azide) (PAAz).

Synthesis and Characterization of GAP-PEG Copolymers

ABSTRACT A series of glycidylazide–poly(ethylene glycol) (GAP-PEG) copolymers were synthesized by cationic ring-opening polymerization of epichlorohydrin (ECH) in the presence of poly(ethylene glycol) (PEG) using borontrifluoride etherate (BF3-etherate) as catalyst, followed by the conversion of the CH2Cl groups of poly(epichlorohydrin) (PECH) to CH2N3 groups. The formation of PECH-b-PEG-b-PECH triblock copolymers was confirmed by IR, 1H NMR, and 13C NMR spectroscopy. The corresponding GAP-b-PEG-b-GAP triblock copolymers were characterized by UV, IR, 1H NMR, and 13C NMR spectroscopy. The copolymers have shown an increment in their molecular weights as the higher analogue molecular weight PEGs were used in the polymerizations. The thermogravimetry-differential thermogravimetry (TG-DTG) and differential scanning calorimetry (DSC) studies of the GAP triblock copolymers indicate an increase in the decomposition temperature of the azide groups of GAP block in the copolymers caused by the introduction of higher molecular weight PEG blocks. GAP-PEG copolymers have shown lower glass transition temperatures than the homo glycidylazide polymer. The nitrogen content of the GAP-PEG copolymers was estimated by various methods and the value was in good agreement with the estimated values.

SYNTHESIS AND SWELLING BEHAVIOR OF SUPERABSORBENT POLYMERIC MATERIALS

A series of novel crosslinked copolymers based on the monomers acrylamide (AM), calcium acrylate (CA), and sodium methacrylate (SMA) were prepared by aqueous solution polymerization using ammonium persulfate (APS) as initiator and N, N-methylene-bis-acrylamide (MBA) as crosslinking agent. The synthetic variables monomer concentration, crosslinker concentration, initiator concentration were also studied. The experimental results of SAPs show good absorbency in both water and NaCl solutions. The copolymers were characterized by IR spectroscopy. The water retention of SAPs was studied in an oven at 60 and 100°C.

Development of Gelatin Based Inorganic Nanocomposite Hydrogels for Inactivation of Bacteria

In this investigation, silver nanocomposite hydrogels were developed by using acrylamide and biodegradable gelatin. Silver nanoparticles were generated throughout the hydrogel networks using in situ method by incorporating Ag+ ions and the subsequent treatment with sodium borohydride. The effect of gelatin on the swelling studies was investigated. The hydrogel synthesized silver nanocomposites were characterized by using Fourier transform infrared, UV–Visible spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron and transmission electron microscopy techniques. The biodegradable gelatin-based silver nanocomposite hydrogels were tested for antibacterial properties. The results indicate that these biodegradable silver nanocomposite hydrogels can be useful in medical applications, as antibacterial agents.

Synthesis and Swelling Behavior of Acrylamide-Potassium Methacrylate Superabsorbent Copolymers

ABSTRACT A series of acrylamide-potassium methacrylate superabsorbent copolymers were synthesized by simultaneous free radical aqueous polymerization using acrylamide (AAm), potassium methacrylate (KMA), and ammonium persulfate (APS)/ N,N,N′,N′-tetramethylethylenediamine (TMEDA) as initiating system in the presence of a crosslinker. The effects of variables such as concentration of hydrophilic monomer (KMA), crosslinker, initiator and activator, and polymerization temperature on swelling capacity have been investigated in detail. In these polymerizations, two different crosslinking agents, namely 1,4-butanediol diacrylate (BDDA) and ethylene glycol dimethacrylate (EGDMA), were employed to study the effect of crosslinker on swelling properties. The swelling kinetic parameters as well as type of water diffusion into the polymer matrix were evaluated at different temperatures for two series of superabsorbent copolymers. The swelling experiments revealed that EGDMA crosslinked superabsorbents have shown higher swelling capacity for all the compositions of AAm/KMA ratio than BDDA crosslinked analogues. Further, the salt sensitivity and de-swelling capacity of the superabsorbent polymers were studied. The pH effect on the swelling ratio of crosslinked copolymers was also investigated.