Structural Parameters and Swelling Behavior of pH Sensitive Poly(acrylamide-co-acrylic acid) Hydrogels

In the present work, hydrogels based on acrylamide (AAm) and acrylic acid (AAc), crosslinked with N,N’-methylenebisacrylamide (MBAAm) were prepared by free radical polymerization in solution. The effect of initial AAm/AAc mole ratio and nominal crosslinking ratio (moles of crosslinking agent/moles of polymer repeat unit) on the dynamic and equilibrium swelling behaviour of hydrogels was investigated. Hydrogels were characterized by the polymer volume fraction in the swollen state (ν2,s ), the number average molecular mass between crosslinks (Mc ) and the mesh size (ξ). The swelling capacity of hydrogels was found to decrease with increasing nominal crosslinking ratio. The results show a significant influence of AAc monomer concentration on swelling behavior of poly(acrylamide-co-acrylic acid) hydrogels. Hydrogels containing higher acrylic acid content had a higher equilibrium mass swelling at pH 7.4 and in distilled water than at pH 3.0 where the acrylic acid is present in nonionized state. Further, swelling data was fitted to various models and model parameters were evaluated using regression technique. Model analysis indicated that the swelling transport followed non-Fickian mechanism. Scanning electron microscopy (SEM) revealed the macroporous surface morphology of the matrix with pore size varying between 2–64 microns depending on the amounts of AAc in the hydrogel

Sorption and Drug Release Studies from Semi-interpenetrating Polymer Networks of Chitosan and Xanthan Gum

Hydrogel films of Chitosan (CS) and Xanthan gum (XA) of compositions 100/0, 90/10, 80/20, 70/30, 60/40 and 50/50 (w/w) % were prepared and swollen in simulated gastric fluid (SGF) of pH 1.2 and simulated intestinal fluid (SIF) of pH 7.4. To impart stability in acidic environment, semi-interpenetrating polymer network (semi-IPNs) films were formed using glutaraldehyde (GA) as the crosslinking agent. With increase in XA concentration, equilibrium degree of swelling reduced in SGF as well as SIF indicating maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The swelling data was observed to follow second order kinetics. Spectroscopic and thermal analyses of these semi-IPN films also suggest maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The potential of using 50/50 semi-IPN in drug delivery was studied using amoxicillin. In-vitro drug release studies indicated higher drug release in SGF than in SIF suggesting dependence of amoxicillin release kinetics and diffusion coefficient on pH of the environment and drug loading. The results suggest that CS-based semi-IPNs with different crosslinker and XA concentration could be promising candidates for formulation in oral gastrointestinal delivery systems

Interfacial Tension of Some Newtonian and non-Newtonian Fluids by the Drop-Weight Method

Experimental data on interfacial tension of 42 binary liquid-liquid systems using water, aqueous glycerol, aqueous polymeric solutions of polyvinylpyrrolidone (PVP), poly(ethylene oxide) (PEO), carboxymethyl cellulose (CMC) and polyacrylamide (PAM) as continuous phase, and carbon tetrachloride, chlorobenzene, bromobenzene, nitrobenzene, nitrotoluene and ethyl chloroacetate as dispersed phase at 20 °C are reported. The interfacial tension has been measured using the drop-weight method at different compositions of continuous phases

Kinetics of the Esterification Reaction between Pentanoic Acid and Methanol Catalyzed by Noncorrosive Cation Exchange Resin

Methyl pentanoate, commonly known as methyl valerate, is the methyl ester of pentanoic acid (valeric acid) with a fruity odour. Methyl pentanoate is commonly used in fragrances, beauty care, soap, laundry detergents at levels of 0.1 – 1 %. In its very pure form (purity 99.5 %) it is used as a plasticizer in the manufacture of plastics. In the present investigation, kinetics of esterification of pentanoic acid with methanol catalyzed by heterogeneous catalyst in a batch-type reactor is reported. The effect of reaction conditions such as temperature, molar ratio, catalyst loading, and initial concentration of pentanoic acid and methanol, and the inhibiting effect of water on the kinetics has been studied. The pentanoic acid conversion reached 93 % at 333.15 K at a methanol to pentanoic acid molar ratio of 10:1 with 7 % (g L–1) Amberlyst 15 as catalyst. Mass transfer effects were found to be negligible. Observed reaction rate data was fitted to the regression technique. Estimated Eley-Rideal kinetic model reaction rate constants were fitted to the Arrhenius type equation with activation energy EA 39.5 kJ mol–1 and pre exponential factor ko 1.8 · 103 L2 g–1 mol–1 h–1

Interfacial Tension of Some Newtonian and non-Newtonian Fluids by the Drop-Weight Method

Experimental data on interfacial tension of 42 binary liquid-liquid systems using water, aqueous glycerol, aqueous polymeric solutions of polyvinylpyrrolidone (PVP), poly(ethylene oxide) (PEO), carboxymethyl cellulose (CMC) and polyacrylamide (PAM) as continuous phase, and carbon tetrachloride, chlorobenzene, bromobenzene, nitrobenzene, nitrotoluene and ethyl chloroacetate as dispersed phase at 20 °C are reported. The interfacial tension has been measured using the drop-weight method at different compositions of continuous phases

Structural Parameters and Swelling Behavior of pH Sensitive Poly(acrylamide-co-acrylic acid) Hydrogels

In the present work, hydrogels based on acrylamide (AAm) and acrylic acid (AAc), crosslinked with N,N’-methylenebisacrylamide (MBAAm) were prepared by free radical polymerization in solution. The effect of initial AAm/AAc mole ratio and nominal crosslinking ratio (moles of crosslinking agent/moles of polymer repeat unit) on the dynamic and equilibrium swelling behaviour of hydrogels was investigated. Hydrogels were characterized by the polymer volume fraction in the swollen state (ν2,s ), the number average molecular mass between crosslinks (Mc ) and the mesh size (ξ). The swelling capacity of hydrogels was found to decrease with increasing nominal crosslinking ratio. The results show a significant influence of AAc monomer concentration on swelling behavior of poly(acrylamide-co-acrylic acid) hydrogels. Hydrogels containing higher acrylic acid content had a higher equilibrium mass swelling at pH 7.4 and in distilled water than at pH 3.0 where the acrylic acid is present in nonionized state. Further, swelling data was fitted to various models and model parameters were evaluated using regression technique. Model analysis indicated that the swelling transport followed non-Fickian mechanism. Scanning electron microscopy (SEM) revealed the macroporous surface morphology of the matrix with pore size varying between 2–64 microns depending on the amounts of AAc in the hydrogel

Hydrogels of Poly(acrylamide-co-acrylic acid): In-vitro Study on Release of Gentamicin Sulfate

Poly(acrylamide-co-acrylic acid) hydrogels, poly(AAm-co-AAc), were synthesized by free radical polymerization in solution using N,N’-methylenebisacrylamide (MBAAm) as the crosslinker. The structural parameters and the swelling behavior of the synthesized hydrogels were investigated for varying nominal crosslinking ratio and composition of the hydrogels. The use of hydrogels for drug release was investigated with gentamicin sulfate (GS) as the model drug. The drug release from hydrogels was investigated as a function of hydrogel composition, nominal crosslinking ratio (X) and drug loading. The observed drug release data was fitted to a power law model and the power law exponent (n) suggested that the drug release mechanism from these hydrogels was sensitive to hydrogel composition and was swelling-controlled for low concentrations of AAc and showed Fickian diffusion for high concentrations of AAc in the hydrogels. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies were performed on control hydrogel samples and drug loaded hydrogels to understand the chemical interactions between the drug and the polymer. Specific drug interactions were observed in these hydrogels

Sorption and Drug Release Studies from Semi-interpenetrating Polymer Networks of Chitosan and Xanthan Gum

Hydrogel films of Chitosan (CS) and Xanthan gum (XA) of compositions 100/0, 90/10, 80/20, 70/30, 60/40 and 50/50 (w/w) % were prepared and swollen in simulated gastric fluid (SGF) of pH 1.2 and simulated intestinal fluid (SIF) of pH 7.4. To impart stability in acidic environment, semi-interpenetrating polymer network (semi-IPNs) films were formed using glutaraldehyde (GA) as the crosslinking agent. With increase in XA concentration, equilibrium degree of swelling reduced in SGF as well as SIF indicating maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The swelling data was observed to follow second order kinetics. Spectroscopic and thermal analyses of these semi-IPN films also suggest maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The potential of using 50/50 semi-IPN in drug delivery was studied using amoxicillin. In-vitro drug release studies indicated higher drug release in SGF than in SIF suggesting dependence of amoxicillin release kinetics and diffusion coefficient on pH of the environment and drug loading. The results suggest that CS-based semi-IPNs with different crosslinker and XA concentration could be promising candidates for formulation in oral gastrointestinal delivery systems

Viscometric and Rheological Behaviour of Chitosan-Hydrophilic Polymer Blends

Blends of chitosan with hydrophilic polymers were investigated for miscibility. Chitosan/poly (vinyl alcohol) (CS/PVA), chitosan/poly vinylpyrollidone (CS/PVP) and chitosan/poly (ethylene oxide) (CS/PEO) blends were prepared in dilute aqueous acetic acid ( = 1 %) and found to be miscible over the entire composition range by dilute solution viscosity and rheological measurements. The miscibility of blends by viscosity measurements at 25 ± 0.1 C was estimated on the basis of experimental and ideal values of miscibility parameters bm, and μ. The rheological studies were performed on blends of mass fraction w = 2 % in dilute aqueous acetic acid ( = 1 %) at 25 ±0.1 C in controlled rate mode. The flow curves of blends and viscosities were found to lie between those of principal components of the blend over the entire compositional range. The flow behaviour index of blends was determined by the Power law model, indicating pseudoplastic behaviour with pseudoplasticity increasing with CS mass concentration. The rheological data of blends was best described by the Cross model. Results from Fourier transform infrared spectroscopy also indicate the blends to be miscible