Study of Complex Coacervation of Gelatin A with Sodium Carboxymethyl Cellulose: Microencapsulation of Neem (Azadirachta indica A. Juss.) Seed Oil (NSO)

The efficiency of complex coacervation of gelatin A with sodium carboxymethyl cellulose (SCMC) was measured by checking viscosity, coacervate yield (%), and turbidity of the mixture. Maximum coacervation occurred at pH 3.5 and SCMC: gelatin ratio of 1.0: 2.33. Encapsulation efficiency, oil content, oil load, and release behavior of the microcapsules were studied. The size and nature of the microcapsules varied with the concentration of polymer and NSO as revealed by scanning electron microscopy study. Fourier transform infrared (FTIR) spectroscopy indicated that there was no significant interaction between the polymer and NSO.     

Urea–formaldehyde crosslinked starch and guar gum matrices for encapsulation of natural liquid pesticide [Azadirachta Indica A. Juss. (neem) seed oil]: swelling and release kinetics

Polymeric granules were prepared by matrix encapsulation containing 20, 35 and 50% (w/w) of natural liquid pesticide viz., Azadirachta Indica A. Juss. (neem) seed oil (NSO) per dry weight of urea formaldehyde crosslinked starch (UF-St), guar gum (UF-GG) and UF-(St + GG) matrices. Results of swelling and cumulative release kinetics are presented at 35°C for these matrices. The static dissolution experiments have been carried out at 35°C for seven days. The percentage cumulative release kinetic data have been analyzed using an empirical equation to study the release pattern of NSO through the polymeric membranes employed. Transport follows the Super Case II mechanism as tested by an empirical equation. It is found that the release of the active ingredient depends upon the type of the matrix and its swelling ability. The percentage loading of NSO with different matrices and their density exerted an influence on the release data. The FTIR results indicated the absence of chemical interactions between the matrices and the NSO. In the majority of cases, entrapment efficiency was generally more than 95% indicating the efficient encapsulation. Furthermore, the experimental results are discussed in terms of the nature and the combined effect of the individual matrices as well as the percentage loading of NSO. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2437–2446, 1999     

Interpolyelectrolyte complex of poly(2‐vinylpyridinium chloride) and poly(sodium phosphate)

A polyelectrolyte complex (PEC) was formed by mixing aqueous solutions of the polyanion poly(sodium phosphate) with the polycation poly(2‐vinylpyridinium chloride). Conductometric and potentiometric titrations indicated the electrochemical end point of each titration. In all cases the end point occurred at a unit molar ratio of polyanionic to polycationic groups that was approximately one. The stoichiometry was also confirmed by analysis of the supernatant liquid in conjunction with the weights of the initial components and complex. An analysis showed that the starting materials were regenerated after dissolution of the complex with a 2M HCl solution. The interaction of the bivalent cupric ions with PEC were also investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3022–3028, 2002; DOI 10.1002/app.2332     

Preparation and characterization of hyaluronan/chitosan scaffold cross‐ linked by 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide

A novel biocompatible scaffold was prepared by cross‐linking hyaluronan (HA) and chitosan (CS). The carboxyl groups of HA were activated by 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide (EDC) and then cross‐linked with amino groups of CS by forming amide bonds. The HA/CS scaffold thus prepared was characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and differential scanning calorimetry. FTIR spectra showed that the absorbance of the amide (1550 cm^?1) and carbonyl (1633 cm^?1) bond in the cross‐linked scaffold was stronger than that in HA or CS. SEM micrographs showed that the cross‐linked scaffold produced at low EDC concentration had an intertwisted ribbon‐like microstructure, while the product prepared at higher EDC concentration had a porous structure. The concentration of EDC in the reaction system greatly affected the structure and properties of the HA/CS scaffold. The prepared scaffold could strongly resist degradation by hyaluronidase, free radicals in vitro and stress. Copyright © 2007 Society of Chemical Industry     

Viscosity properties of homogeneous polyelectrolyte complex solutions from sodium carboxymethyl cellulose and poly(acrylamide‐co‐dimethyldiallylammonium chloride)

The viscosity properties of homogeneous polyelectrolyte complex solutions of sodium carboxymethyl cellulose (CMC) and poly(acrylamide‐co‐dimethyldiallylammonium chloride) have been investigated by means of a rotation viscometer at different complexation ratios, shear rates and temperatures. Compared with aqueous solutions of the component polyelectrolytes, such complex solutions can afford substantially increased viscosities at the complexation ratios examined, together with enhanced shear‐thinning rheology and temperature stability. According to this study, it is possible to improve the viscosity properties of water‐soluble polymers by homogeneous interpolyelectrolyte complexation in aqueous solutions. © 2000 Society of Chemical Industry     

Lipase‐mediated hydrolysis of flax seed oil for selective enrichment of α‐linolenic acid

Polyunsaturated fatty acids (PUFA) are important ingredients of human diet because of their prominent role in the function of human brain, eye and kidney. α‐Linolenic acid (ALA), a C18, n‐3 PUFA is a precursor of long chain PUFA in humans. Commercial lipases of Candida rugosa, Pseudomonas cepacea, Pseudomonas fluorescens, and Rhizomucor miehei were used for hydrolysis of flax seed oil. Reversed phase high performance liquid chromatography followed by gas chromatography showed that the purified oil contained 12 triacylglycerols (TAGs) with differences in fatty acid compositions. Flax seed oil TAGs contained α‐linolenic acid (50%) as a major fatty acid while palmitic, oleic, linoleic made up rest of the portion. Among the four commercial lipases C. rugosa has preference for ALA, and that ALA was enriched in free fatty acids. C. rugosa lipase mediated hydrolysis of the TAGs resulted in a fatty acid mixture that was enriched in α‐linolenic to about 72% yield that could be further enriched to 80% yield by selective removal of saturated fatty acids by urea complexation. Such purified ALA can be used for preparation of ALA‐enriched glycerides. Practical applications : This methodology allows purifying ALA from fatty acid mixture obtained from flax seed oil by urea complexation.     

Multifunctional gentamicin supplementation of poly(γ‐glutamic acid)‐based hydrogels for wound dressing application

The process of wound healing is composed of coagulation, inflammation, fibroplasia, collagenation, epithelization, and wound contraction. The wound dressing should protect the wound from bacterial infection, maintain a moist healing environment, and promote cell migration to reconstruct damaged tissue, and be easy to apply and remove to improve patient comfort. The purpose of our study was to develop multifunctional hydrogels composed of genipin‐crosslinked biodegradable biomaterials of poly(γ‐glutamic acid) and gelatin, encapsulating gentamicin to accelerate wound healing. The results of swelling ratio measurements clearly indicate that hydrogel composition of poly(γ‐glutamic acid)–gelatin had a higher swelling ratio and lower peel adhesion properties than gelatin hydrogel alone. In an in vitro study, the gentamicin incorporated in prepared hydrogels effectively inhibited target microorganisms and produced a higher expression of Type I collagen in fibroblast cells. Confocal laser scanning microscopy revealed that the fibroblast cells cultured in the hydrogel membranes produced fibroblast cell migration and showed a continuous lined cytoskeletal distributing status. In the in vivo study, it was found that the gentamicin incorporated in genipin‐crosslinked γ‐PGA–gelatin wound dressing demonstrates the potential of such biologically functionalized dressing to accelerate wound closure and, hence, its potential clinical usefulness. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and reactive features of a terpolymer: Poly(N‐vinyl‐2‐pyrrolidone‐co‐vinyl acetate‐co‐glycidyl methacrylate)

A polyvinyl pyrrolidone terpolymer system is described that can be chemically cross‐linked at moderate, 70–100°C, temperatures. The system has significant potential for development of durable long‐lasting pyrrolidone coatings in a wide range of applications, particularly in water filtration membrane construction where leaching is an unresolved, serious problem. The synthesis of the terpolymer, poly(N‐vinyl‐2‐pyrrolidone‐co‐vinyl acetate‐co‐glycidyl methacrylate), by free radical polymerization is described. The reactive features of this terpolymer are presented in the context of acidic anhydride curing. In a polar aprotic solvent, the terpolymer is reacted with poly(methyl vinyl ether‐co‐maleic acid) and cured thermally. Key aspects of the terpolymer synthesis and the acid anhydride cross‐linking reaction using DSC, rheology, FTIR, and a small molecule model system to study the cross‐linking chemistry are presented. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Peroxide induced cross‐linking by reactive melt processing of two biopolyesters: Poly(3‐hydroxybutyrate) and poly(l‐lactic acid) to improve their melting processability

Poly(3‐hydroxybutyrate) (PHB) and poly(l ‐lactic acid) (PLLA) were individually cross‐linked with dicumyl peroxide (DCP) (0.25–1 wt %) by reactive melt processing. The cross‐linked structures of the polymer gel were investigated by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopies. The size of the polymer crystal spherulites, glass transition temperature (T_g), melting transition temperature (T_m), and crystallinity were all decreased as a result of cross‐linking. Cross‐linking density (ν_e) was shown to increase with DCP concentration. Based on parallel plate rheological study (dynamic and steady shear), elastic and viscous modulus (G″ and G′), complex viscosity (η^*) and steady shear viscosity (η) were all shown to increase with cross‐linking. Cross‐linked PHB and PLLA showed broader molar mass distribution and formation of long chain branching (LCB) as estimated by RheoMWD. Improvements in melt strength offer bioplastic processors improved material properties and processing options, such as foaming and thermoforming, for new applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41724.     

Copolymerization of methyl methacrylate with 4‐vinylpyridine initiated by a novel Ni(II)α‐Benzoinoxime complex

Copolymerizations of methyl methacrylate (MMA) with 4‐vinylpyridine (4VP) were performed from different monomer feed ratios in 1,4‐dioxan at 30°C under free radical initiation experimental conditions, using Ni(II)α‐Benzoinoxime complex as initiator. The obtained copolymers (PMMA4VP) were examined by FTIR and ¹H NMR spectroscopies. The composition of these copolymers was calculated, using ¹H NMR spectra and elemental analysis. Monomer reactivity ratios were estimated from Fineman–Ross (FR, r_m = 0.550, r_v = 1.165) and Kelen–Tudos (KT, r_m = 0.559, r_v = 1.286) linearization methods, as well as nonlinear error in variables model (EVM) method using the RREVM computer program (RREVM, r_m = 0.559, r_v = 1.264). These values suggest that MMA‐4VP pair copolymerizes randomly. ¹H NMR spectra provide information about the stereochemistry of the copolymers in terms of sequence distributions and configurations. These results showed that the age of the Ni complex has an impact not only on its activity towards polymerization reactions but also on the features of the corresponding copolymers, whereas the chemical composition was insensitive to this prominent factor. The mechanism of MMA‐4VP copolymerization is consistent with a radical process as supported by microstructure and molecular weight distribution studies. Thermal behaviours of these copolymers were investigated by differential scanning calorimetry and thermogravimetric analysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Infrared spectra of γ‐irradiated poly(acrylic acid)–polyacrylamide complex

Samples of polyacrylamide (PAAm), poly(acrylic acid) (PAA), and their complex were γ‐irradiated at different doses, namely 48, 96, and 144 KGy. The examination of the infrared spectra of these samples showed that there are no significant observable changes in their spectral features apart from slight changes in the intensities of the absorption bands. The analysis of the absorbances ratios (A 1700 cm^?1/A 1450 cm^?1) and (A 1650 cm^?1/A 1450 cm^?1), denoted as R₁ and R₂, respectively, showed that these ratios depend on γ‐doses. It was found that in the case of PAA, R₁ assumed linear increase with increasing the dose to 96 KGy and then showed marked decrease. For the complex, R₁ increased slightly by increasing the dose to 96 KGy and then decreased. For PAAm, although irradiation with 48 KGy increases the values of R₂, irradiation with 96 and 144 KGy decreases its value. On the other hand, for the complex, R₂ suggested slight decrease on irradiation with 48 KGy followed by continued increases with increasing the dose up to 144 KGy. The increase in R₁ and R₂ may be due to crosslinking as a result of the formation of free radicals. The decrease in these ratios after irradiation with 96 KGy may be due to degradation. It was concluded that γ‐irradiation has a lower effect on the complex (i.e., the complex has a structure which is different from those of PAA and PAAm). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1619–1623, 2002     

Hydrolysis,polycondensation, and catalytic properties of Ru(II) complex of 3‐4,5‐dihydroimidazol‐1‐yl‐propyltriethoxysilane

The preparation and measurements of some properties of organic–inorganic hybrid materials derived from Ru(II)‐3‐4,5‐dihyroimidazol‐1‐yl‐propyltriethoxysilane inside a polysiloxane network have been achieved. The hydrolysis and polycondensation of Ru(II)‐3‐4,5‐dihyroimidazol‐1‐yl‐propyltriethoxysilane were performed in different experimental conditions, producing a new organic–inorganic silica. The alkoxysilyl groups available were used for the construction of inorganic backbone by the sol‐gel process, and the imidazole group was found suitable for incorporating Ru(II) by coordination. The coordination of metal complex is retained because there is no leaching from the metal complex containing gels. To ensure sufficient catalytic properties, a series of hybrid materials from tetraethoxysilane was prepared. These materials were identified and catalytic activities were tested for cyclization of (Z)‐3‐methylpent‐2‐en‐4‐yn‐1‐ol to 2,3‐dimethylfuran. Heterogeneous Ru(II) catalyst can also be recycled and reused without significant loss of selectivity or activity. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1329–1334, 2001     

Effect of seed characteristics on morphology development in poly(n‐butyl acrylate)‐poly(n‐butyl methacrylate) core‐shell dispersions

This article reports on the influence of synthesis characteristics such as seed cross linking, particle‐size distribution (PSD), and surfactant in the seeded emulsion polymerization of n‐butyl acrylate–butyl methacrylate core‐shell systems. These systems were studied using a combination of techniques such as light scattering (static and dynamic), asymmetric field flow fractionation coupled with multiangle laser light scattering and transmission electron microscopy. Complimentary data, obtained from static light scattering and electron microscopy studies, on the effect of seed crosslinking on morphology development reveals that the presence of a crosslinked seed favors the formation of nonequilibrium core‐shell morphology. For uncrosslinked seeds occluded structures were present with a diffuse boundary between the core and the shell. In both cases, i.e., with or without surfactant, a monomodal PSD was observed for the core‐shell systems and the relative size polydispersity and the shape of the seed PSD were retained. Use of surfactant was found to broaden the PSD but did not seem to affect the formation core‐shell morphology. The study also shows the influence of crosslinked seeds on the film properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Homogeneous complex solution formed through interactions of poly(acrylamide‐co‐acrylic acid)/poly(acrylamide‐co‐dimethyldiallylammonium chloride) complex with M n+ hydration metal ions in aqueous media

A homogeneous complex solution, formed through inter‐polyelectrolyte complexation of poly(acrylamide‐co‐acrylic acid) (P(AM‐AA)) with poly(acrylamide‐co‐dimethyldiallylammonium chloride) (P(AM‐DMDAAC)) and interaction of the P(AM‐AA)/P(AM‐DMDAAC) complex with M ⁿ⁺ hydrated metal ion, was prepared and the structure and properties of the P(AM‐AA)/P(AM‐DMDAAC)/M ⁿ⁺ homogeneous complex solution were studied by UV spectrometry, dynamic light scattering and viscometry. The experimental results show that the homogeneous complex solution can be obtained by controlling the composition of the P(AM‐AA)/P(AM‐DMDAAC) complex and the M ⁿ⁺ metal ion content. Compared to the constituents, ie the P(AM‐AA) solution, the P(AM‐DMDAAC) solution and the P(AM‐AA)/P(AM‐DMDAAC) complex solution, the P(AM‐AA)/P(AM‐DMDAAC)/M ⁿ⁺ complex solution has a new peak at 270 nm in its UV spectrum, a larger hydrodynamic radius, and hence a higher solution viscosity, all of which indicate that there exist specific interactions between polymers and M ⁿ⁺ metal ions. These interactions lead to the formation of a network structure and hence an obvious increase not only in solution viscosity but also in resistance of the polymer solution to simple salts, to temperature changes and to shearing. © 2001 Society of Chemical Industry     

Synthesis of branched polyethylene by ethylene homopolymerization with a novel (α‐diimine)nickel complex in the presence of methylaluminoxane

Branched polyethylene (PE) was prepared with a novel (α‐diimine)nickel(II) complex of 2,3‐bis(2,6‐dimethylphenyl)‐butanediimine nickel dichloride {[2,6‐(CH₃)₂C₆H₃? N?C(CH₃)C(CH₃)?N? 2,6‐(CH₃)₂C₆H₃]NiCl₂} activated by methylaluminoxane in the presence of a single ethylene monomer. The influences of various polymerization conditions, including the temperature, Al/Ni molar ratio, Ni catalyst concentration, and time, on the catalytic activity, molecular weight, degree of branching, and branch length of PE were investigated. According to gel permeation chromatography, the weight‐average molecular weights of the polymers obtained ranged from 1.7 × 10⁵ to 6.0 × 10⁵, with narrow molecular weight distributions of 2.0–3.5. The degree of branching in the polymers rapidly increased with the polymerization temperature increasing; this led to highly crystalline to totally amorphous polymers, but it was independent of the Al/Ni molar ratio and catalyst concentration. At polymerization temperatures greater than 20°C, the resultant PE was confirmed by ¹³C‐NMR to contain significant amounts of not only methyl but also ethyl, propyl, butyl, amyl, and long branches (longer than six carbons). The formation of the branches could be illustrated by the chain walking mechanism, which controlled their specific spacing and conformational arrangements with one another. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1123–1132, 2002; DOI 10.1002/app.10398     

Fabrication of polymer‐gadolinium (III) complex nanomicelle from poly(ethylene glycol)‐polysuccinimide conjugate and diethylenetriaminetetraacetic acid‐gadolinium as magnetic resonance imaging contrast agents

Methoxy poly (ethylene glycol)‐graft‐α, β‐poly (aspartic acid) derivatives (mPEG‐g‐PAA‐N₃) were synthesized by sequential ring‐opening reaction of polysuccinimide (PSI) with mPEG‐NH₂ (MW: 2000 Da), and 1‐azido‐3‐aminopropane, respectively. Then N²‐(hex‐5‐yne)‐diethylenetriamine‐tetra‐t‐butylacetate (DTTA‐der) was conjugated to mPEG‐g‐PAA‐N₃ by click cycloaddition. After deprotection of carboxylic groups, mPEG‐g‐PAA‐DTTA macromolecular ligands were obtained. MPEG‐g‐PAA‐(DTTA‐Gd) complex nanomicelles were fabricated from mPEG‐g‐PAA‐DTTA and Gadolinium chloride. The formation of nanomicelles was confirmed by fluorescence spectrophotoscopy and particle size measurements. It was found that all the nanomicelles showed spherical shapes with core‐shell structures and narrow size distributions. Their sizes ranged from 50 to 80 nm, suggesting their passive targeting potential to tumor tissue. With the increase of graft degree (GD) of mPEG, the sizes of mPEG‐g‐PAA‐(DTTA‐Gd) nanomicelles showed a tendency to decrease. Compared with gadopentetate dimeglumine (Gd‐DTPA), mPEG‐g‐PAA‐(DTTA‐Gd) nanomicelles showed essential decreased cytotoxicity to KB cell line and enhanced T₁‐weighted signal intensity, especially at low concentration of gadolinium (III), suggesting their great potentials as magnetic resonance imaging contrast agents. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011