Theoretical Study of the Effects of Templated Materials on Aggregate Formation

Summary: We have conducted Monte Carlo simulations to investigate a greatly simplified model for a blend composed of templated materials (polymers or monomers), smaller reacting particles and solvents on a two‐dimensional lattice. In the simulations, we compute the mean chain conformation of flexible templated polymers, and the distribution of the number of adjacent reacting particles aligned along the same axis to rationalize how templated materials affect the physical aggregation of smaller particles in a blend. We first examine the effects of the effective interactions between templated materials and smaller reacting particles. For repulsive interactions, flexible templated polymers tend to contract to reduce repulsions arising from smaller reacting particles, but for attractive interactions, mean chain dimension increases to maximize attraction. When templated material composition is increased, the conformational deformation of templated polymers becomes more pronounced. Moreover, in the presence of attractive interactions, reacting particles are more dispersed in the blend. In contrast, repulsive interactions increase the probability of aggregation of reacting particles. Also, our findings show that templated monomers (without chain connectivity) interact with reacting particles more effectively than with templated polymers due to the greater interacting area per monomer, which enhances the dispersion and segregation of reacting particles in the blend due to the attractive and repulsive interaction, respectively. In addition, as templated material composition is increased, the probability of forming a larger aggregate decreases. This simple model allows us to elucidate the role of templated materials on the physical aggregation of smaller particles in a blend.

Probability distribution P(m) of finding m adjacent reacting particles along the same axis in the presence of templated polymers (open symbols) and templated monomers (solid symbols) for different monomer‐reacting particle ratio, 1:3 (□/▪), 1:1 (○/•) and 3:1 (▵/▴):.     

Synthesis and characterization of 4‐vinyl pyridine‐grafted Teflon‐PFA film for water technologies

To get highly reactive polymeric materials for selective studies of enzyme immobilization, water purification, separation, and enrichment technologies, we attempted to graft 4‐vinyl pyridine (4‐VP) onto Teflon‐PFA by simultaneous γ‐ray initiation. The resulting graft copolymers were quaternized by treatment with some alkylating agents. Optimum conditions for grafting were evaluated through the variation of the total dose of radiation, the amount of water, and the monomer concentration. The effect of the solvent composition (H₂O/MeOH) was also studied. In the presence of MeOH, grafting occurred less often and was nonselective as 4‐VP was incorporated on both sides in comparison with highly selective grafting in an aqueous medium. The percentages of the grafting, total conversion, and grafting efficiency and the rates of the polymerization, grafting, and homopolymerization were also evaluated. Some other monomers such as methacrylic acid, methyl methacrylate, maleic acid, acrylonitrile, and vinyl imidazole were not incorporated onto the backbone film under the optimum grafting reaction conditions evaluated for the grafting of 4‐VP. Although some grafting occurred, the graft yield was too low to be considered of any significance. The grafted films were quaternized with benzyl chloride, and quaternized and unquaternized films were used for the immobilization of lipase. The former showed high activity with lipase and has potential for development as a bioreactor. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4506–4518, 2000     

Effect of magnetic field on a multi window ladder type electromagnetically induced transparency with 87Rb atoms in vapour cell

In this work, we experimentally study the effect of externally applied magnetic field on a ladder type EIT in a vapour cell consisting of ⁸⁷Rb atoms. The introduction of magnetic field causes the Zeeman splitting of the hyperfine levels of ⁸⁷Rb atoms and hence the number of available windows of transparency increases. We report the observation of nine such windows. Such multi window EIT systems are capable of storing pulses at the different frequencies, corresponding to these windows hence paving the way for realization of multi frequency quantum memories. Also, the total bandwidth of storage is 218.4 MHz which is two orders of magnitude higher than that typically obtained in single window EIT based storage systems. These systems have tremendous applications in the field of speedy transmission of data over a long distance quantum communication channel.     

Development and In Vitro Characterization of Capecitabine-Loaded Alginate–Pectinate–Chitosan Beads for Colon Targeting

Colon-targeted capecitabine beads were formulated by an ionotropic gelation method. The sodium alginate to pectin ratio and chitosan concentration were optimized using a 3² full factorial design. Analysis of response surface plots allowed the identification of an optimized formulation with high drug entrapment and controlled release. Insignificant differences in observed and predicted values for responses validated the optimization method. Optimized beads possessed an average diameter of 1395 µm and good flow properties. Their production as spherical beads having a smooth surface was confirmed by scanning electron microscopy. Fourier transform infrared spectroscopy revealed the compatibility of drug with added excipients, while differential scanning calorimetry study confirmed complete drug entrapment in polymer matrix. Higher swelling of beads in phosphate buffer pH 7.4 was obtained in comparison to pH 6.8. An in vitro wash off test indicated 70% mucoadhesion by the beads. In vitro dissolution studies of beads loaded into enteric-coated capsules revealed negligible release in simulated gastric and intestinal fluid, followed by 49.23% release in simulated colonic fluid, in 4 h. The optimized beads were found to be stable for three months at 25 ± 2°C/60 ± 5% RH. In conclusion, the formulated beads showed colon-specific controlled release properties, and thus could prove to be effective for colon cancer treatment.