Maher Z. Elsabee

Chitosan based edible films and coatings: A review

Chitosan is a biodegradable biocompatible polymer derived from natural renewable resources with numerous applications in various fields, and one of which is the area of edible films and coatings. Chitosan has antibacterial and antifungal properties which qualify it for food protection, however, its weak mechanical properties, gas and water vapor permeability limit its uses. This review discusses the application of chitosan and its blends with other natural polymers such as starch and other ingredients for example essential oils, and clay in the field of edible films for food protection. The mechanical behavior and the gas and water vapor permeability of the films are also discussed. References dealing with the antimicrobial behavior of these films and their impact on food protection are explored.

Surface active properties of chitosan and its derivatives

This review discusses the definition of surface active agents and specifically natural polymeric surface active agents. Chitosan by itself was found to have weak surface activity since it has no hydrophobic segments. Chemical modifications of chitosan could improve such surface activity. This is achieved by introducing hydrophobic substituents in its glucosidic group. Several examples of chitosan derivatives with surfactant activity have been surveyed. The surface active polymers form micelles and aggregates which have enormous importance in the entrapment of water-insoluble drugs and consequently applications in the controlled drug delivery and many biomedical fields. Chitosan also interacts with several substrates by electrostatic and hydrophobic interactions with considerable biomedical applications.

Preparation, Characterization and Antimicrobial Activity of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-g-Poly(N-vinylpyrrolidone) Copolymers

Graft polymerization of N-vinylpyrrolidone onto poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV was carried out in solution. The evidence of grafting was provided by FTIR, and 1H-NMR. The DSC results showed that the cold crystallization temperature from the glass state increased with increase of grafting %. TGA analysis revealed that the thermal stability of the host PHBV was improved remarkably with increasing extent of grafting. The swelling of the graft copolymer in water increases with increasing G%. The antibacterial activity of PHBV-g-PVP copolymers was improved dramatically with the extent of grafting. The biodegradability of PHBV and its graft copolymers was investigated in active soil.

Styrene-Maleic Anhydride Copolymer Esters as Flow Improvers of Waxy Crude Oil

Four comb-like copolymers derived from styrene-maleic anhydride copolymer were prepared and characterized by FTIR, 1H-NMR and elemental analysis. The molecular weight was determined using GPC and their intrinsic viscosity was measured. The prepared polymers were investigated as pour point depressants and flow improvers for waxy crude oil and it was found that, the maximum depression was obtained by the sample that has long branch chain (PPD4) from 27°C to −3°C (ΔPP = 30°C, at 10000 ppm). While, the minimum depression was exhibited by short branch chain, PPD1 (ΔPP = 21°C) at the same conditions. The effect of these polymers on the rheology and flow properties of Qarun waxy crude oil was investigated. It was found that the Bingham yield value (τβ) decreased from 6.0 pa.s. to 0.5 pa.s. for PPD4 at 27°C and 10,000 ppm. The dynamic viscosity also decreased from 110 m pa.s. to 24 m pa.s. for the same sample and the same conditions.

Copolymerization of Methyl Methacrylate with N-Phenylmaleimide in Different Solvents

Abstract The copolymerization of methyl methacrylate (MMA) and N-phenyl-maleimide (NPMI) in various solvents has been studied. It has beerr shown that monomer-monomer interaction exists and leads to the formation of a weak charge-transfer complex (CTC). The CTC concentration is found to depend on the type of solvent, and its equilibrium constant depends on the dielectric constant of the solvent and increases in the order DMSO < chloroform < benzene < CC14. NMR and dipole moment measurements have been used to investigate interaction between the monomers. The monomer reactivity ratios are found to vary appreciably with the type of solvent. The data obtained indicate that changes in the reactivity ratios are due to monomer solvation or to the solvent effect on the propagating radical, rather than to the participation of the CTC in the propagation step.

Metal uptake by a novel bidentate thiosemicarbazide chelating polymer

1-Cyanoethanoyl-4-acryloyl thiosemicarbazide (CEATS) has been prepared and polymerized by a free radical mechanism. The polymer PCEATS has chelating affinity, and metal-uptake capacities were determined for the chlorides of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) in the pH range 1.04–6.0. The extraction experiments show high capacity for Cu(II), (0.26 mmol/g) at pH 5.34 and lower uptake capacities for the other divalent metal ions around pH 5 in buffered solutions, under noncompetitive conditions. However, competitive experiments, performed with solutions containing a mixture of metal chloride salts and acetate buffer, showed a high selectivity for Cu(II) and Cd(II) over other cations. Distribution coefficients determined for the polymer and the metal ions indicate that the Cu(II) complex is more stable than the Cd(II) are and suggest that the stability of the complex decreases rapidly with decreasing pH. Kinetic experiments have shown that uptake of Cu(II), is slow, with t 0.5 = 10 h. Ligand regeneration experiments for Cu(II)-loaded PCEATS performed with 2.00 M H2SO4 have shown that the capacity for Cu(II) stays at the same level after several cycles of consecutive loading and stripping, indicating that the polymer is chemically stable. ESR spectra of Cu(II)–CEATS resin show that there are two different coordination complexes present in the polymer. IR spectra of the Cu(II) complex confirms the bidentate behavior (S, O; N, O) of CEATS and PCEATS (it is supposed that the cations bridge vicinal CEATS ligands through S, O and N, O atoms); the acetate group completes the octahedral coordination. The obtained data suggest that the polymer behaves as a bidentate ligand via the thiocarbonyl, carbonyl and imide groups. PCEATS and its complexes have an inhibitory effect on both the bacterium Azotobacter and the fungus Fusarium oxysporium. The effect on the microorganisms is proportional to the amount of free ligand in the complex.

Polymerization behaviour of a new vinyl thiourea derivative

Abstract 1-Methacryloyl-3-phenylthiourea (MAPTU) has been prepared and polymerized by a free-radical mechanism. The polymer formed has low molecular weight. The kinetic orders of the polymerization with respect to monomer and initiator, as well as the overall activation energy, were measured and found to be those expected for a free-radical scheme. This new monomer showed a tendency for cyclization to give a six-membered heterocycle. The effects of temperature and solvent on the rate of cyclization have been studied. MAPTU monomer and its homopolymer were found to form complexes with several metal ions. The stability constants of several phenyl-substituted MAPTU with Cu were measured and a correlation between log K X K H and the Hammett constant was established. The MAPTU-Cu and polyMAPTU-Cu complexes were prepared and their stability constants were calculated. MAPTU was copolymerized with styrene and acrylonitrile. The reactivity ratios have been calculated by several methods.

The Synthesis Characterization and Polymerization of Novel Thiophene Substituted Maleimide

Ethyl 2-amino 4,5,6,7-tetrahydrobenzo thiophene-3-carboxylate maleimide (ETTCM) has been synthesized and investigated as a new thio-maleimide derivative. The structure of the prepared compounds has been elucidated by elemental and spectral analyses. The free radical polymerization of (ETTCM) has been conducted in several solvents using azobisisobutyronitrile (AIBN) as an initiator. The kinetic parameters of polymerization of ETTCM were investigated, and it was found that the polymerization reaction follows the conventional free radical scheme. The initial rate of polymerization, the overall activation energy Ea was determined (Ea = 57.013 kJmol−1) and intrinsic viscosity was measured ([η] = 0.04 dl/g). The prepared polymer is a good chelating agent with some metal ions and a moderate antifungal and antibacterial effect. The monomer reactivity ratios for the copolymerization of ETTCM with methyl methacrylate MMA, vinyl acetate VA, and vinyl ether VE were calculated by two methods, the Kelen-Tüdös and a nonlinear method. Thermal stability of the ETTCM polymers and copolymers were investigated by thermogravimetric analysis.

Synthesis of Some Surfactants Based on Polytriethanolamine and Investigation of Their Surface Active Properties

New modified surfactants were developed by esterification of ethoxylated polytriethanolamine with oleic acid. Triethanolamine was polymerized at three different times 1.30, 2.30, and 3.30 hours to give (P4, P6, and P8) where 4, 6, and 8 refer to the degree of polymerization. The prepared polymer (P8) was ethoxylated at three different molar ratios of ethylene oxide (40, 100, and 120) and named E(en)P8. Then the ethoxylated polymers were esterified with oleic acid and abbreviated as E(en)P8Om. The surface properties for these surfactants were determined by measuring the surface tension. The structure was confirmed using the elemental analysis, (FTIR, 1H, 13C NMR) spectroscopic.

Copolymerization of Maleimide Monomers Containing Heterocyclic Groups

Abstract Thermal stable polymers were prepared by radical polymerization of two kinds of N-(substituted) maleimide containing heterocyclic groups. These monomers were readily copolymerized with styrene (ST), methyl methacrylate (MMA) and vinyl acetate (VA), and their reactivity ratios were determined by different methods. The Alfrey-Price Q-e values were determined from copolymerization analysis. The thermal behaviors of the polymers and copolymers were investigated by thermogravimetric method.