A. K. Bajpai

Water sorption behaviour of highly swelling (carboxy methylcellulose-g-polyacrylamide) hydrogels and release of potassium nitrate as agrochemical

Novel types of highly swelling hydrogels have been prepared by grafting crosslinked polyacrylamide chains onto carboxymethylcellulose (CMC) via a free radical polymerization method. The hydrogels were characterized by IR spectral analysis and by evaluating various network parameters such as average molecular weight between crosslinks (Mc), crosslink density (q) and the number of elastically effective chains (Vc). The hydrogels showed enormous swelling in aqueous medium and displayed swelling characteristics which were highly dependent on the chemical composition of the hydrogel and pH and ionic strength of the medium in which the hydrogel was immersed. The kinetics of water uptake and the water transport mechanism were studied as a function of the composition of the hydrogel and the pH of the medium. The hydrogels were also loaded with potassium nitrate as a model agrochemical and their potential for controlled release of potassium nitrate was judged by measuring conductivity. Various kinetic parameters such as the diffusion coefficient and swelling exponents were also calculated.

Swelling dynamics of a macromolecular hydrophilic network and evaluation of its potential for controlled release of agrochemicals

Abstract A hydrophilic macromolecular matrix has been prepared by performing graft copolymerization of crosslinked polyacrylamide chains onto carboxymethyl cellulose and polyvinyl alcohol, and water sorption capacity of grafted network was evaluated gravimetrically. The effects of chemical architecture of the gel, pH and temperature of the swelling medium and presence of electrolyte were investigated on water uptake by the grafted hydrogels. In order to evaluate the controlled release potential of the matrix, it was loaded with KNO3 as a model agrochemical and the release kinetics was studied as a function of the chemical composition of the hydrogel. The hydrogels were also characterized by IR spectral analysis and structural parameters such as molecular weight between crosslinks (Mc), crosslink density (qe) and number of elastically effective chains were determined. The mechanism of water transport through the synthesized grafts hydrogels was also explored.

Water sorption through a semi-interpenetrating polymer network (IPN) with hydrophilic and hydrophobic chains

Abstract Dynamics of water uptake by semi-interpenetrating polymer networks (IPNs) of poly(acrylamide-co-styrene) and poly(vinyl alcohol) were investigated at room temperature (27±0.2°C) and constant pH. The nature of the swelling process of the IPN was investigated in light of the Fickian transport and the effects of varying experimental conditions such as the change in the composition of the IPN, pH and ionic strength of the swelling medium were studied on the swelling kinetics of the IPN. The networks obtained were also characterized by IR spectral analysis and the molecular weight between crosslinks ( M c ) and crosslink density ( q ) of the networks were evaluated.

Responsive Polymers in Biology and Technology

Modern synthetic polymer chemistry has revolutionized the world of polymer materials. Among macromolecular systems of various chemical and architectural profiles the polymers exhibiting property of responsiveness to external signals have emerged as one of the most promising kind of materials in advanced materials science and owe versatile applications in biology and technology. The internal structural designs of these materials enable them to undergo a large and measurable transition in their physicochemical characteristics upon responding to a minor change in the external environment including experimental conditions. The present article reviews the state-of-the-art of the applications of various stimuli responsive polymers and describes their structure-property relationships. The article provides an account of different aspects of stimuli responsive macromolecular systems that include types of systems responsive to various stimuli such as pH, temperature, electric and magnetic fields, different biomolecules, etc. This review article also presents insights into synthetic strategies of these polymer systems and their major applications in areas such as controlled drug delivery, chromatography, sensors, biotechnology, etc. A brief mention of various challenges ahead and the future scope of this field has also been made.

Water sorption dynamics of a binary copolymeric hydrogel of 2-hydroxyethyl methacrylate (HEMA)

The water imbibing property of poly(2-hydroxyethyl methacrylate) (poly HEMA) has been improved by copolymerizing HEMA with acrylamide in the presence of a hydrophilic polymer such as polyethylene glycol (PEG). The hydrogel was characterized by IR spectral analysis and several network parameters such as average molecular weight between crosslinks (Mc), crosslink density (q) and number of elastically effective chains were evaluated. The swelling ratio of the hydrogel was found to be influenced by varying the chemical architecture of the hydrogel, i.e. by changing the proportions of PEG, HEMA, acrylamide and crosslinking agent in the feed mixture of the hydrogel. The degree of water sorption was studied as a function of the experimental conditions such as the pH and temperature of the swelling medium and presence of salt ions in the outer solution. The dynamics of the swelling process was studied quantitatively and kinetic constants such as the swelling exponent (n) and diffusion constant (D) were also evaluated. The hydrogels prepared of varying composition were judged for antithrombogenic nature of their surfaces by blood-clot formation test.

Magnetically Guided Release of Ciprofloxacin from Superparamagnetic Polymer Nanocomposites

Tailored with superparamagnetic properties the magnetic nanocomposites have been thoroughly investigated in recent past because of their potential applications in the fields of biomedicine and bioengineering such as protein detection, magnetic targeted drug carriers, bioseparation, magnetic resonance imaging contrast agents and hyperthermia. Magnetic drug targeting has come up as a safe and effective drug-delivery technology, i.e., with the least amount of magnetic particles a maximum of drug may be easily administered and transported to the site of choice. In the present work novel magnetic drug-targeting carriers consisting of magnetic nanoparticles encapsulated within a smart polymer matrix with potential of controlled drug release is described. To make such magnetic polymeric drug-delivery systems, both the magnetic nanoparticles and antibiotic drug (ciprofloxacin) were incorporated into the hydrogel. The controlled release process and release profiles were investigated as a function of experimental protocols such as percent loading of drug, chemical composition of the nanocomposite, pH of release media and strength of magnetic field on the release profiles. The structure, morphology and compositions of magnetic hydrogel nanocomposites were characterized by FT-IR, TEM, XRD and VSM techniques. It was found that magnetic nanocomposites were biocompatible and superparamagnetic in nature and could be used as a smart drug carrier for controlled and targeted drug delivery.

Adsorption of a blood protein on to hydrophilic sponges based on poly(2-hydroxyethyl methacrylate).

Spongy materials of poly(2-hydroxyethyl methacrylate) were synthesized and the adsorption of bovine serum albumin was carried out onto their surfaces. The sponges were characterized by IR spectral analysis, and water sorption property. It was noticed that the chemical architecture of the sponge has a pronounced impact on both the water sorption capacity and adsorption affinity of the sponge surfaces. The adsorption was also studied kinetically and the effect of pH was also investigated. The synthesized sponges were evaluated for antithrombogenic property by performing blood–clot formation tests.

Release dynamics of tetracycline from a loaded semi-interpenetrating polymeric material of polyvinyl alcohol and poly(acrylamide-co-styrene)

A semi-interpenetrating polymer network (IPN) of polyvinyl alcohol (PVA) and poly(acrylamide-co-styrene) (PAMS) was prepared and its potential for controlled release of tetracycline was assessed. The IPN was characterized by IR spectral analysis and network parameters such as the average molecular weight between crosslinks (M_c), crosslink density (q) and number of elastically effective chains (V_e) were evaluated. The influence of various experimental conditions such as different percent loadings, composition of the IPNs, thickness of the loaded device, pH and nature of the release medium were investigated on the release profiles of the drug. Various kinetic constants such as the diffusional exponent (n), diffusion constant (D) and penetration velocity (v) were evaluated for different release processes and based on the dynamic release data, an analysis of transport mechanisms of tetracycline was made using Ficks equations.

Release study of sulphamethoxazole controlled by swelling of gelatin nanoparticles and drug-biopolymer interaction

Gelatin (Type A) particles were prepared by a single W/O emulsion technique and characterized by infrared (IR) spectra, scanning electron microscopy (SEM) and particle size analysis. Whereas the IR spectra clearly confirmed the presence of gelatin and sulphamethoxazole (SM) in the loaded nanoparticles, the scanning electron micrograph (SEM) image depicts smooth surface, spherical shape and uneven size of nanoparticles (100 to 300 nm). The nanoparticles were evaluated for their potential to act as a carrier of sulphamethoxazole drug. It was found that the amount of released SM increases with increasing percent loading of the drug in the range 18 to 39%. The chemical architecture of nanoparticles was also found to influence its drug‐releasing capacity. It was observed that in the case of an increase in gelatin and crosslinker (gluteraldehyde) concentrations in the range 4.0–9.0 g and 5.3–31.8 mM, respectively, the amount of released SM initially increases up to 8.0 g of gelatin and 10.6 mM of crosslinker concentrations and thereafter decreases. It was also noticed that a greater release of SM occurs when type B gelatin is used as drug carrier. The influence of experimental conditions such as pH and temperature of the release medium were also investigated on the release profiles of SM. It was noticed that an optimum release is obtained at pH 7.4, while in the case of a variation of temperature in the range 10 to 35°C, a maximum release is found at 25°C. Beyond 25°C, a fall in the released SM was observed. The drug was also found to be chemically stable at pH 1.8 (gastric juice) as confirmed by UV spectral study.

Preparation and Characterization of Binary Grafted Polymeric Blends of Polyvinyl Alcohol and Gelatin and Evaluation of their Water Uptake Potential

Binary hydrophilic blends of poly(acrylamide‐co‐methylene bis acrylamide) grafted polyvinyl alcohol (PVA) and gelatin (GEL) were prepared by redox polymerization method and the end product was characterized by infra red (IR) spectral analysis, differential scanning calorimety (DSC) measurements, and scanning electron micrograph (SEM). Network parameters such as molecular weight between crosslinks (Mc) and crosslink density of the hydrogel were also determined by swelling measurements. In addition, the blend hydrogels were assessed for their water sorption characteristics and influence of various factors such as composition of the blend, pH and temperature of the swelling bath and, the presence of electrolytes were investigated on the water uptake potential of blend hydrogels.