The potential of biodegradable polymers has long been recognized. In this work, composites of low density polyethylene (LDPE) and low density polyethylene/thermoplastic starch (LDPE/TPS) at different ratios of TPS (40%-60% w/w) were prepared in internal mixer. Polyethylene-grafted maleic anhydride (PE-g-MA) at 3 wt % was used as coupling agent. Chemical reactions between functional groups of composite components were studied and confirmed by Fourier transforms infrared (FTIR) spectroscopy. The morphology of film surfaces was studied using scanning electron microscopy. The physical, mechanical, and dynamic-mechanical thermal analyses of LDPE/TPS composites were evaluated. The FTIR results showed transmission peak at 1642 cm À1 , which is the result of chemical reaction between the hydroxyl groups of starch and anhydride groups of coupling agent. This verifies the presence of the carboxylate group due to the formation of ester bonding. The results showed that the water absorption and density of composite films increased by increasing the starch content in LDPE/TPS composites. The tensile strength and elongation at break decreased by increasing the starch level in the composites, but the young's modulus increased. The morphological studies showed that the biodegradability of composites increased by increasing the starch content and the results was confirmed by weight loss in buring the samples in wet soil during time intervals. The dynamic mechanical thermal analyzer thermograms showed that there are two relaxation temperature peaks. The amplitude of peaks increased by increasing the starch content from 40 to 60% probably due to increasing amorphous phase of composite. The starch was uniformly distributed throughout the LDPE polymer matrix and compatible and biodegradable composites were formed.

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Water‐soluble polymers are found in a very broad range of industrial applications. An important class of these is acrylamide‐based polymers which bear negative charges along the polymer chain and are called anionic polyelectrolytes. These negatively charged polymers are widely used as flocculants, rheology control agents, and adhesives. They are employed especially in oil field operations as viscosity control agents for enhanced oil recovery and to a lesser degree in engineering fluids used for lubrication, for effluent reclaiming, and for opening oil passage channels in oil‐bearing rock. Paper manufacture, mining, and water treatment processes also benefit from the use of acrylamide‐based polymers to flocculate solids in aqueous dispersions. The acrylamide‐based polymers are made by the free‐radical polymerization of acrylamide and its derivatives via bulk, solution, precipitation, suspension, emulsion, and copolymerization techniques. Among these, solution polymerization is a preferred technique because of difficulty with temperature and agitation control in bulk polymerization and the cost of surfactants and solvents for suspension, emulsion, and precipitation polymerization. The anionic polymers may interact with particles in aqueous dispersions in several ways that result in the stability or instability of the dispersions. The particles in solid‐liquid phases can be destabilized through three main mechanisms which promote flocculation and cause destabilization. These mechanisms are polymer bridging, charge neutralization, and polymer adsorption. The particles in solid‐liquid phases can be stabilized by the anionic polymers through both electrostatic and steric repulsive forces. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers

The use of various chemical cross-linking agents for the improvement of scaffolds physical and mechanical properties is a common practical method, which is limited by cytotoxicity effects. Due to exerting contract type forces, chondrocytes are known to implement shrinkage on the tissue engineered constructs, which can be avoided by the scaffold cross-linking. In the this research, chitosan scaffolds are cross-linked with hydrothermal treatment with autoclave sterilization time of 0, 10, 20 and 30min, to avoid the application of the traditional chemical toxic materials. The optimization studies with gel content and crosslink density measurements indicate that for 20min sterilization time, the gel content approaches to ~80%. The scaffolds are fully characterized by the conventional techniques such as SEM, porosity and permeability, XRD, compression, thermal analysis and dynamic mechanical thermal analysis (DMTA). FT-IR studies shows that autoclave inter-chain cross-linking reduces the amine group absorption at 1560cm and increase the absorption of N-acetylated groups at 1629cm. It is anticipated, that this observation evidenced by chitosan scaffold browning upon autoclave cross-linking is an indication of the familiar maillard reaction between amine moieties and carbonyl groups. The biodegradation rate analysis shows that chitosan scaffolds with lower concentrations, possess suitable degradation rate for cartilage tissue engineering applications. In addition, cytotoxicity analysis shows that fabricated scaffolds are biocompatible. The human articular chondrocytes seeding into 3D cross-linked scaffolds shows a higher viability and proliferation in comparison with the uncross-linked samples and 2D controls. Investigation of cell morphology on the scaffolds by SEM, shows a more spherical morphology of chondrocytes on the cross-linked scaffolds for 21days of in vitro culture.

Polyampholytes are charged macromolecules bearing both anionic and cationic groups along the polymer backbone. Polyampholytes can be synthesized by classic and controlled free radical polymerization, anionic polymerization, and group transfer polymerization (GTP). The aqueous solution behavior of polyampholytes is dictated by columbic interactions between the basic and acidic residues. Polyampholytes show both polyelectrolyte and anti-polyelectrolyte behavior in aqueous media. Factors such as charge density, charge asymmetry (i.e., degree of charge balance), charge spacing and distribution, substrate surface charge, structural conformation, and solution ionic strength are critical parameters. Polyampholytes are interesting for numerous reasons and are used for many technology processes such as water treatment, enhanced oil recovery (EOR), sludge dewatering, papermaking, pigment retention, mineral processing, and flocculation. In the present study, the main structural features, behaviors, mechanisms of interaction, and recent field applications of polyacrylamide (PAM)-based polyampholytes are reviewed.