The Effect of Melt Extrusion Process Parameters on Rotary‐Evaporated Poly(propylene) Nanocomposites

Design of experiments is employed to investigate the interrelationships between processing and nanotube surface chemistry on the properties of PP nanocomposites. Statistically significant effects of nanomaterial type and concentration, extrusion temperature, screw speed, and recirculation time, and their interactions, on nanocomposite thermal properties and stability are isolated. The effects of these factors on the shear storage modulus, the low‐frequency slope of the shear storage modulus, decomposition temperature, and melt temperature are explored. Nanotube concentration has the most significant effect in enhancing the decomposition temperature of the nanocomposite, while long extrusion time and higher temperatures lead to deteriorated properties.

     

Pilocarpine‐loaded poly(DL‐lactic‐co‐glycolic acid) nanoparticles as potential candidates for controlled drug delivery with enhanced ocular pharmacological response

The poor corneal residence time of pilocarpine, an alkaloid extracted from the leaves of the Jaborandi plant, limits its ocular application. The aim of this study was to develop, characterize, and evaluate the potential of pilocarpine entrapped by poly(DL ‐lactic‐co‐glycolic acid) (PLGA) nanoparticle carriers for ocular drug delivery. Pilocarpine‐loaded nanoparticles were prepared with a double‐emulsion (water in oil in water) method and characterized with transmission electron microscopy and X‐ray diffraction analysis. The nanoparticles exhibited an average size of 82.7 nm with an encapsulation efficiency of 57%. Stability studies showed the absence of agglomeration and constancy in the amount of drug entrapped; this indicated the solidity of these particles for long‐term use. The in vitro release studies conducted in simulated tear fluid showed the sustained release of pilocarpine. In vivo evaluation of the nanoparticles was done in a rabbit model with a miosis assay and compared to an equal dose of commercially available eye drops of pilocarpine (Pilocar drops). The in vivo miosis studies showed that the duration of miotic response increased by 40% for the nanoparticles and produced an almost 68% increase in total miotic response when compared to the eye drops. In conclusion, this study clearly demonstrated the potential of pilocarpine‐loaded PLGA nanoparticles for multiplying the therapeutic effect of ophthalmic drug delivery with enhanced bioavailability and pharmacological response. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,aggregation and adsorption behaviour of a thermoresponsive pentablock copolymer

Poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymer (Pluronic F127) was modified by introducing poly(N‐isopropylacrylamide) (PNIPAM) at both the PEO ends, and the pentablock copolymer (PNIPAM₄₁–F127–PNIPAM₄₁, PN41) so prepared was characterized using gel permeation chromatography and ¹H NMR spectroscopy. The degree of polymerization of NIPAM blocks at the two ends was 41. The solution behaviour and microstructure of PN41 aggregates in water were examined using UV–visible spectroscopy, micro‐differential scanning calorimetry and small‐angle neutron scattering (SANS) and compared with F127. Two lower critical solution temperatures (LCSTs) were observed for the pentablock copolymer, corresponding to PPO and PNIPAM blocks, respectively. The adsorption of PN41 on thiol‐grafted hydrophobic gold surfaces at various temperatures was investigated using a quartz crystal microbalance. It was found that the adsorption behaviour and mechanism of PN41 were mainly determined by the interactions of the pentablock copolymers with different chain conformations in dilute aqueous solutions at various temperatures. SANS measurements were used to determine the temperature‐dependent structural evolution of polymer micelles in aqueous solution. A NOESY study revealed that above the LSCT of PNIPAM, the interaction of PPO and PNIPAM protons increases and the distance between PPO and PNIPAM decreases. © 2019 Society of Chemical Industry     

A comparative investigation of interfacial adhesion behaviour of polyamide based self-reinforced polymer composites by single fibre and multiple fibre pull-out tests

Abstract

Interfacial adhesion of composite materials plays an important role in their mechanical properties and performance. In the present investigation, analysis of the interfacial properties of self-reinforced polyamide composites by using microbond multiple fibre pull-out test is emphasised. Microbond specimens prepared through thermal processing are tested for their interfacial properties by multiple fibre bundle pull-out tests and compared with that of traditional single fibre pull-out test specimens. Multiple fibre pull-out addresses the volume fraction as well as eliminates the possibility of fibre breakage before matrix shear. Higher scatter in the data in the samples is addressed in the present studies. FTIR and Fractographic studies are carried out for deep understanding of the post pull-out interfacial adhesion.     

Experimental Investigation for Performance Study of Wire Electrochemical Spark Cutting of Silica Epoxy Nanocomposites

Purpose

Polymer Nanocomposites are advanced engineering composites with enhanced properties. These materials play a central role in various industrial sectors. The growing awareness of the key parameters (which influence the physical properties) with different combination of matrix-reinforcement, are making them more attractive in various applications. Machining of these materials is a challenging task for engineers with their properties (hardness and brittleness) due to various combinations of matrix-reinforcement. Therefore, the aim of present work is to investigate the machining behaviour of Silicon Dioxide (silica) Epoxy Nanocomposite due to straight cutting by using Wire Electrochemical Spark Cutting (WECSC) process.

Method

A specific number of experiments were conducted based on one parameter at-a-time approach to study the effect of influencing input parameters.

Result

The effect of various process parameters namely voltage supply, electrolyte concentration, wire velocity, pulse-on time and silica particle concentration (Cp) such as 3%, 4% and 5% (weight percent) on performance measures such as material removal rate (MRR) and surface roughness were demonstrated experimentally.

Conclusion

WECSC has been found effective technique for cutting of Silicon Dioxide Epoxy Nanocomposite. It is reported that MRR increases with decrease in silica particle concentration in Silicon Dioxide Epoxy Nanocomposite.

     

Poly(ethylene glycol) grafted polystyrene dendrimer resins: Novel class of supports for solid phase peptide synthesis

Poly(propyleneglycol)dimethacrylate cross-linked support using monomers Styrene and 4-chloromethyl styrene (PS-PPGDMA-VBC resin) was prepared by suspension polymerization method. Dendritic templates were synthesized from Schiff base and trimesic acid molecules and assembled independently on PS-PPGDMA-VBC support to the second generation. N,N-bischloro ethyl amine dendrimer was generated from Schiff base units and introduced to the chloromethyl groups uniquely through secondary amine. It was followed by acidolytic cleavage, diazotization and thionyl chloride reactions leading to first generation dendrimer. O-benzyl ether dendrimer was created using 1,3,5-tris(hydroxyl methyl)benzene unit which was produced by the LiAlH₄ reduction of carbonyl groups of trimesic acid molecule. The hydroxyl methyl groups formed were converted to chloro methyl groups by adding thionyl chloride that leads to first generation dendrimer. Similar synthetic routes were followed to produce second generation dendrimers too. Poly(ethylene glycol), M_n ≈ 1500) has been grafted to chlorine termini of both dendrimers and used to check various physical and chemical properties of different peptide synthetic conditions. Reactions were qualitatively analyzed by FTIR, ¹³C NMR, SEM and quantitatively analyzed by UV measurements and CHN analysis. Classically difficult ACP sequence was synthesized on both PEGylated dendrimer supports and compared to Tenta Gel. Biologically significant disulfide bonded endothelin class of peptides were also synthesized using novel supports using various literature reported methods.     

Saponin-loaded SBA-15: release properties and cytotoxicity to Panc-I cancer cells

In this study, first time a nanoformulation, saponin-loaded SBA-15 has been developed for an improved and continuous release. The SBA-15 nanopowder was synthesized by a hydrothermal process. Saponin was introduced into the mesoporous channels of SBA-15 and its concentration in SBA-15 was measured by UV–visible spectrophotometry. The pristine SBA-15 and saponin-loaded SBA-15 were characterized by small-angle XRD, FESEM, HRTEM, TGA, FTIR. N₂ adsorption–desorption isotherms were used to measure the specific surface area and pore channel structure parameters of pristine and loaded SBA-15. Saponin release was studied in phosphate buffered saline (pH 7.4), which revealed that the release rate could be effectively controlled. The controlled drug release is highly desired for cancer treatment. The cytotoxicity of pristine and loaded SBA-15 was analyzed on Panc-I cancer cells. Both the pristine SBA-15 and saponin-loaded SBA-15 nanoparticles showed specific toxicity on the cancer cells. The preliminary results showed that saponin-loaded SBA-15 could be an effective therapeutic agent for Panc-I cancer cells.     

Antagonism of microRNA function in zebrafish embryos by using locked nucleic acid enzymes (LNAzymes)

MicroRNAs (miRNAs) have crucial functions in many cellular processes, such as differentiation, proliferation and apoptosis; aberrant expression of miRNAs has been linked to human diseases, including cancer. Tools that allow specific and efficient knockdown of miRNAs would be of immense importance for exploring miRNA function. Zebrafish serves as an excellent vertebrate model system to understand the functions of miRNAs involved in a variety of biological processes. We designed and employed a strategy based on locked nucleic acid enzymes (LNAzymes) for in vivo knockdown of miRNA in zebrafish embryos. We demonstrate that LNAzyme can efficiently knockdown miRNAs with minimal toxicity to the zebrafish embryos.     

Synthesis and characterization of integrated layered nanocomposites for lithium ion batteries

The series of Li[Ni _x M _x Li_1/3-x Mn_2/3-x ]O₂ cathodes, where M is cobalt or chromium with a wide compositional range x from 0 to 0.33, were prepared by hydroxide coprecipitation method with subsequent quenching. The sample structures were investigated using X-ray diffraction results which were indexed completely on the basis of a trigonal structure of space group with monoclinic C2/m phase as expected. The morphologies and electrochemical properties of the samples obtained were compared as the value of x and substituted transition metal. The particle sizes of cobalt-substituted Li[Ni _x Co _x Li_1/3-x Mn_2/3-x ]O₂ samples are much smaller than those of the Li[Ni _x Cr _x Li_1/3-x Mn_2/3-x ]O₂ system. The electrode containing Li[Ni _x Co _x Li_1/3-x Mn_2/3-x ]O₂ with x = 0.10 delivered a discharge capacity of above 200 mAh/g after 10 cycles due to the activation of Li₂MnO₃.