Macroporous open cell polyester amphigel using citric acid and PEO: Solvent absorption,thermal behavior,and slow release of pesticide

This article describes citric acid cross-linked amphiphilic poly(ethylene oxide) (PEO) macroporous open cell polyester amphigel, optimally synthesized using response surface methodology by applying central composite design to screen significant reaction parameters for maximizing percent water sorption. The chemical structure of the amphigel was confirmed by proton nuclear magnetic resonance (¹H NMR), FT-IR and the thermal behavior was studied using thermo-gravimetric and DSC. Due to amphiphilic nature, the amphigels also showed high chloroform (1151.33%–1193.33%) and water (755.33%–865%) absorption capacity. Thermal analysis revealed that amphigels are less thermal stability as compared to PEO, however, the degradation process was found to be multi step. The amphigel was effectively used as a carrier for easy loading of a hydrophobic pesticide and showed a slow release of the same.     

Protective effect of cashew gum nanoparticles on natural larvicide from Moringa oleifera seeds

Nanoparticles (NPs) have been used as carriers and as protective coatings of labile substances with applications in pharmacy, medicine, and agriculture. This work focused on the development of an entrapment process for the protection of a natural larvicide extracted from Moringa oleifera (MO) seeds with cashew gum (CG) NPs as a wall material. CG–MO NPs were characterized with regard to their size, morphology, kinetic release, thermal properties, and Stegomya aegypti larvae mortality. The result showed that the CG–MO NPs presented average particle sizes ranging from 288 to 357 nm, with unimodal distribution. MO larvicide active principle loading varied from 2.6 to 4.4%, and the entrapment efficiencies were in the range 39.1–60.8%. In vitro release kinetics showed a Fickian diffusional behavior. The thermal stability of the CG–MO NPs was related to the MO content, where their decomposition temperatures decreased with increasing MO active principle loading. Bioassays with third instar larvae showed that the mortality rate was related to larvicide loading and reached values up to 98 ± 3% mortality. The CG–MO NPs showed effective extract entrapment, with satisfactory larvicide effects even after 55 days of sample preparation and were effective as an improved and controlled release larvicide system. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Novel LDPE/vermiculite/ciclopiroxolamine hybrid nanocomposites: Structure,surface properties,and antifungal activity

The increasing number of indwelling medical materials and devices are connected with infections caused by yeast, especially Candida albicans. This pathogen produces biofilms on synthetic materials, which facilitates adhesion of the organisms to devices and renders them relatively refractory to medical therapy. Since antimicrobial polymer nanocomposites present one of the promising possibilities, this study explores a new approach to achieving this goal by developing nanocomposite based on low density polyethylene (LDPE) with clay mineral vermiculite as an active carrier for antifungal compound. The set of LDPE/clay nanocomposite with increasing amount of antifungal nanofiller was prepared by melt compounding procedure. As antifungal agent was selected generally used active substance ciclopiroxolamine and this compound was loaded into natural vermiculite through ultrasound technique. The structure of all prepared samples was studied by X-ray diffraction analysis and Fourier transforms infrared spectroscopy. Further thermal properties of polyethylene/clay nanocomposites were investigated by thermogravimetric analysis and the surface properties were evaluated by light optical microscopy, scanning electron microscopy and atomic force microscopy. From mentioned characteristics, we conclude that presence of nanofiller in LDPE primarily causes shift of thermal degradation to higher temperatures and increasing of microhardness. All prepared LDPE nanocomposites possess an excellent and prolonged antifungal activity against Candida albicans.     

Potential for Layered Double Hydroxides-Based,Innovative Drug Delivery Systems

Layered Double Hydroxides (LDHs)-based drug delivery systems have, for many years, shown great promises for the delivery of chemical therapeutics and bioactive molecules to mammalian cells in vitro and in vivo. This system offers high efficiency and drug loading density, as well as excellent protection of loaded molecules from undesired degradation. Toxicological studies have also found LDHs to be biocompatible compared with other widely used nanoparticles, such as iron oxide, silica, and single-walled carbon nanotubes. A plethora of bio-molecules have been reported to either attach to the surface of or intercalate into LDH materials through co-precipitation or anion-exchange reaction, including amino acid and peptides, ATPs, vitamins, and even polysaccharides. Recently, LDHs have been used for gene delivery of small molecular nucleic acids, such as antisense, oligonucleotides, PCR fragments, siRNA molecules or sheared genomic DNA. These nano-medicines have been applied to target cells or organs in gene therapeutic approaches. This review summarizes current progress of the development of LDHs nanoparticle drug carriers for nucleotides, anti-inflammatory, anti-cancer drugs and recent LDH application in medical research. Ground breaking studies will be highlighted and an outlook of the possible future progress proposed. It is hoped that the layered inorganic material will open up new frontier of research, leading to new nano-drugs in clinical applications.     

聚合物-层状双氢氧化物纳米复合材料的研究进展

综述了以聚合物为基体的聚合物-层状双氢氧化物(LDHs)纳米复合材料在阻燃材料中应用的研究进展,重点阐述了LDHs的层状结构、改性以及聚合物-LDHs纳米复合材料的制备,并介绍了当前国内外各类关于聚合物-LDHs纳米复合材料的阻燃研究应用,对其今后的发展提出了展望。     

Preparation and characterization of novel hybrid of bio‐assisted mineralized Zn‐Al layered double hydroxides using chitosan as a template

The purpose of this study was to prepare and characterize a novel nanohybrid prepared from the template‐assisted mineralization of Zn‐Al Layered Double Hydroxide (LDH) onto the surface of Chitosan (CSI), with an emphasis on morphology, biocompatibility, and its use as an efficient drug carrier agent. The as prepared LDH is highly crystalline, with platelet‐like morphology and curved tactoids when nucleated onto the surface of CSI. Our results indicate that the ? OH and ? NH functional moieties on CSI can direct an ordered structure of LDH, due to the electrostatic interaction between biopolymer and inorganic lamellae. We have been successful to intercalate an anti‐inflammatory drug, Sodium Ibuprofen (Ibu), into LDH, through conventional coprecipitation method. LDHs are endowed with great potential for delivery vector because their stacked layers lead to safe reservation of biofunctional molecules or genes, and their ion exchangeability and solubility in acidic media (pH < 4) give rise to the controlled release of drug molecules. According to the cell‐growth studies, LDHs are found as cell viable up to the concentration of 500 μg/mL. This study reveals that LDH not only plays a role of a biocompatible‐delivery matrix but also facilitates a significant increase in the delivery efficiency. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal decomposition behavior of carbon‐nanotube‐reinforced poly(ethylene 2,6‐naphthalate) nanocomposites

Polymer nanocomposites based on poly (ethylene 2,6‐naphthalate) (PEN) and carbon nanotubes (CNTs) were prepared by direct melt blending with a twin‐screw extruder. Dynamic thermogravimetric analysis was conducted on the PEN/CNT nanocomposites to clarify the effect of CNTs on the thermal decomposition behavior of the polymer nanocomposites. The thermal decomposition kinetics of the PEN/CNT nanocomposites was strongly dependent on the CNT content, the heating rate, and the gas atmosphere. On the basis of the thermal decomposition kinetic analysis, the variation of the activation energy for thermal decomposition revealed that a very small quantity of CNTs substantially improved the thermal stability and thermal decomposition of the PEN/CNT nanocomposites. Morphological observations demonstrated the formation of interconnected or network‐like structures of CNTs in the PEN matrix. The unique character of the CNTs introduced into the PEN matrix, such as the physical barrier effect of CNTs during thermal decomposition and the formation of interconnected or network‐like structures of CNTs, resulted in the enhancement of the thermal stability of the PEN/CNT nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structure–property relationship of sodium deoxycholate based poly(ester ether)urethane ionomers for biomedical applications

New sodium deoxycholate based poly(ester ether)urethane ionomers were prepared for the development of biomedical materials. A structure–property relationship in the tested biomaterials was established by cross‐examination of the dynamic mechanical and dielectric properties, attenuated total reflection–Fourier transform infrared investigation, thermogravimetric analysis, and surface morphology characterization. A stronger ionic interaction and solvation capacity of the ions and a higher ionic conductivity were manifested in the case of poly(ethylene oxide)‐rich segments than for poly(propylene oxide)‐rich segments in these polyurethane ionomers. The molecular and ionic interactions of the bile‐salt moiety with different polyether cosoft segments influenced chain packing and conformation, supramolecular organization, and the resulting surface morphological microstructures of the polyurethane biomembranes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42921.     

Thermal degradation of poly(dimethylsilylene) and poly(tetramethyldisilylene‐co‐styrene)

Thermal degradation of poly(dimethylsilylene) homopolymer (PDMS) and poly(tetramethyldisilylene‐co‐styrene) copolymer (PTMDSS) was investigated by pyrolysis‐gas chromatography and thermogravimetry (TG). PDMS decomposes by depolymerization, producing linear and cyclic oligomeric products, whereas PTMDSS decomposes by random degradation along the chain resulting in each monomeric product and various other combination products. The homopolymer was found to be much less stable than the copolymer. The decomposition mechanisms leading to the formation of various products are shown. The kinetic parameters of thermal degradation were evaluated by different integral methods using TG data. The activation energies of decomposition (E) for the homopolymer and the copolymer are found to be 122 and 181 kJ/mol, respectively, and the corresponding values of order of reaction are 1 and 1.5. The observed difference in the thermal stability and the values of the kinetic parameters for decomposition of these polymers are explained in relation with the mechanism of decomposition. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Flame retarding mechanism of Polyamide 6 with phosphorus‐nitrogen flame retardant and DOPO derivatives

A novel flame‐retardant composite was prepared by introducing a phosphorus‐nitrogen flame retardant and DOPO‐SiO₂ into PA6. DOPO‐SiO₂ was synthesized successfully in a one‐step process. PA6/OP1314/DOPO‐SiO₂ achieved a UL 94 V‐0 rating with an LOI value of 31%. The maximum mass loss rate of decomposition decreased significantly and char residue increased to 11.6 wt % compared with that of pure PA6. The compacted and dense char was formed due to the combination of the P‐N flame retardant and DOPO‐SiO₂. The complex viscosity of PA6/OP1314/DOPO‐SiO₂ increased considerably which tend to prevent the dripping phenomenon. The flame‐retardant mechanism of PA6/OP1314/DOPO‐SiO₂ was also investigated by Fourier transform infrared spectroscopy FTIR at different temperatures and the pyrolysis products were investigated by pyrolysis gas chromatography/ mass spectrum (Py‐GC/MS). It was assumed that DOPO‐SiO₂ and the hypophosphite of OP1314 possess excellent flame retardancy during the gaseous phase. Meanwhile, melamine and phosphate reacted with the pyrolytic products of PA6 to protect the matrix during the condensed phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42932.     

Effect of glycerol on electrical conducting of chitosan/polyaniline blends

Chitosan (Cs) and polyaniline (PANI) were studied in this article for possible application as conductive and flexible films. Cs is a biodegradable polymer, that presents interesting properties as film applications. Otherwise, PANI is a semiconductor polymer with a wide range of applications. The films were produced by casting adding 30% glycerol and glutaraldehyde. The morphology, thermally, chemical structure, and electrical properties of films were obtained. Results showed the casting technique becomes possible to obtain self-standing films, with a chemical structure identical to precursor materials. Glutaraldehyde reacted to amine groups of terminal PANI chains, acting in the increase of electric conductivity and decrease of sheet resistance. The plasticizing effect of glycerol increased the spacing between Cs chains and facilitated the PANI dispersion. Therefore, glycerol and glutaraldehyde proved to be extremely efficient in increasing the electrical conductivity of blends.     

A new Schiff base epoxy oligomer resin: Synthesis,characterization, and thermal decomposition kinetics

Oligo{2,2′‐{1,4‐phenylenebis[nitrilomethylylidene]}bis(6‐methoxyphenol)} (OPNMMP) was synthesized from o‐vanillin and p‐phenylene diamine by oxidative polycondensation with NaOCl in an aqueous alkaline. Then, a new Schiff Base epoxy oligomer resin, OPNMMP–epichlorohydrine (EPC), was produced with EPC. The structures of the resulting compounds were confirmed by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, ¹H‐NMR, and ¹³C‐NMR. Further characterization processes were preformed by thermogravimetry (TG)–differential thermal analysis, gel permeation chromatography, and solubility testing. Also, the kinetics of the thermal decomposition of OPNMMP–EPC were investigated by thermogravimetric analysis. The TG curves showed that the thermal decomposition of OPNMMP–EPC occurred in one stage. The kinetic parameters related to the decomposition kinetics of OPNMMP–EPC were obtained from TG curves with the following methods: Friedman, Flynn–Wall–Ozawa, Kissinger, invariant kinetic parameter, and Coats–Redfern (CR), under an N₂ dynamic atmosphere and different heating rates (5, 10, 15, and 20°C/min). The mechanism function and pre‐exponential factor were also determined by a master plots method. The apparent activation energies of the thermal decomposition were calculated from these methods for OPNMMP–EPC. The analysis of the results obtained by the CR and master plots methods showed that the decomposition mechanism of OPNMMP–EPC in N₂ was a deceleration‐type mechanism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The investigation of thermal decomposition pathway and products of poly(vinyl alcohol) by TG‐FTIR

A generalized form of a semiquantitative method has been developed based on the multilinear least‐squares regression technique applied on the entire FTIR absorbance spectrum of a gaseous mixture to determine components concentration. Thermal degradation of poly(vinyl alcohol) samples with high, PVA(98), and low degree of hydrolysis, PVA(80), has been investigated by TG‐FTIR simultaneous analysis performed in an inert atmosphere. Analysis of gaseous products was carried out using a routine developed in Matlab and this routine returns the product concentration with a reasonable RMS error. The correlation coefficients of the original mixture spectrum with the mixed output were obtained at some specific peak temperatures using irAnalysis software. The first process is the loss of physically adsorbed water which followed by two main processes of thermal degradation. In spite of the similarity of evolved gaseous products, two samples showed some differences in components concentrations identified in the volatile mixture. Acetaldehyde has been identified as the main volatile product in the first thermal degradation step of PVA(98) and PVA(80). The second major degradation product of PVA(80) is acetic acid due to presence of more residual acetate group while 2‐butenal have been identified for PVA(98). Water was mainly produced in the first stage of thermal degradation of PVA(98) while it was identified in the first and second stages for PVA(80). This might be attributed to existence of a competition between water and residual acetate group for elimination that postpones the complete elimination of OH group to the second degradation stage. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42117.     

Kinetic analysis of thermal degradation in poly(ethylene–vinyl alcohol) copolymers

Thermal analysis of EVOH copolymers with different ethylene content, were performed by TGA/DTGA under dynamic conditions. Apparent kinetic parameters were determined using different classical kinetic approaches. The apparent activation energy values obtained confirm that thermal stability of EVOH increases with ethylene content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3157–3163, 2003     

Ignition,combustion, toxicity,and fire retardancy of polyurethane foams: A comprehensive review

This review provides insight into the ignition, combustion, smoke, toxicity, and fire‐retardant performance of flexible and rigid polyurethane foams. This review also covers various additive and reactive fire‐retardant approaches adopted to render polyurethane foams fire‐retardant. Literature sources are mostly technical publications, patents, and books published since 1961. It has been found by different workers that polyurethane foams are easily ignitable and highly flammable, support combustion, and burn quite rapidly. They are therefore required to be fire‐retardant for different applications. Polyurethane foams during combustion produce a large quantity of vision‐obscuring smoke. The toxicity of the combustion products is much higher than that of many other manmade polymers because of the high concentrations of hydrogen cyanide and carbon monoxide. Polyurethane foams have been rendered fire‐retardant by the incorporation of phosphorus‐containing compounds, halogen‐containing compounds, nitrogen‐containing additives, silicone‐containing products, and miscellaneous organic and inorganic additives. Some heat‐resistant groups such as carbodiimide‐, isocyanurate‐, and nitrogen‐containing heterocycles formed with polyurethane foams also render urethane foams fire‐retardant. Fire‐retardant additives reduce the flammability, smoke level, and toxicity of polyurethane foams with some degradation in other characteristics. It can be concluded that despite many significant attempts, no commercial solution to the fire retardancy of polyurethane foams without some loss of physical and mechanical properties is available. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009