Thermal, mechanical, and morphological characterization studies of poly(2,6-dimethyl-1,4-phenylene oxide) blends with polystyrene and brominated polystyrene

The miscibility of the binary and ternary blends of poly(2,6-dimethyl-1,4-phenylene oxide), brominated polystyrene, and polystyrene was investigated using a differential scanning calorimeter. The morphology of these blends was characterized by scanning electron microscopy. These studies revealed a close relation between the blend structure and its mechanical properties. The compatibilizing effect of poly(2,6-dimethyl-1,4-phenylene oxide) on the miscibility of the polystyrene/brominated polystyrene blends was examined. It was found that poly(2,6-dimethyl-1,4-phenylene oxide), which was miscible with polystyrene and partially miscible with brominated polystyrene, compatibilizes these two immiscible polymers if its contention exceeds 33 wt 9b. Upon the addition of poly(2,6-dimethyl-1,4-phenylene oxide) to the immiscible blends of polystyrene/brominated polystyrene, we observed a change in the morphology of the mixtures. An improvement in the mechanical properties was noticed. (C) 2000 John Wiley & Sons, Inc

Phase behavior of blends of poly(2,6-dimethyl-1,4-phenylene oxide)/polystyrene/poly(o-chlorostyrene-co-p-chlorostyrene) copolymer

The phase behavior of ternary blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), polystyrene (PS) and a 50/50 mole % statistical copolymer of o-chlorostyrene and p-chlorostyrene [p(oClS-pClS)] has been investigated by differential scanning calorimetry (DSC) and analyzed in terms of a Flory-Huggins mean-field segmental interaction parameter treatment. Both PS/PPO and PPO/p(oClS-pClS) binary blends exhibit single glass transition temperatures over the full composition range whereas the PS/p(oClS-pClS) system displays a substantial immiscibilty window which extends into the ternary phase diagram. In principle, ternary systems provide enhanced opportunities relative to binary systems for evaluating segmental interaction parameters chi(ij)s from experimental data because of the high sensitivity of phase boundary locations to these parameters and to component molecular weights. In this system the effect of these parameters on the phase boundary was studied experimentally and compared to calculated values. (C) 2004 Elsevier Ltd. All rights reserved

Thermal characterization and morphological studies of binary and ternary polymeric blends of polycarbonate, brominated polystyrene, and poly(2,6-dimethyl-1,4-phenylene oxide)

The thermal behaviors of binary blends of polycarbonate (PC)/brominated polystyrene (PBrS) and ternary blends of PC/PBrS/poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) were investigated. The compatibilizing effect of PPO on the miscibility of the PC/PBrS blends was examined. The miscibility of binary and ternary blends was studied by using differential scanning calorimeter (DSC). The results of DSC indicate that the binary blends of PC/PBrS are immiscible but ternary blends of PC/PBrS/PPO in certain limits are miscible. The microstructural properties of the blends was characterized by environmental scanning electron microscope (ESEM) where the properties are determined in the natural state of the structural role of individual phases (PC/PBrS/PPO) and their effect on the overall microstructure of the products. DSC and ESEM results were supported by FT-IR measurements

Removal of Pb(II), Cd(II), Cu(II), and Zn(II) from aqueous solutions by adsorption on bentonite

Removal of Pb(II), Cd(II), Zn(II), and Cu(II) from aqueous solutions using the adsorption process on bentonite has been investigated, In order to find out the effect of temperature on adsorption, the experiments were conducted at 20, 35, and 50 degrees C. For all the metals, maximum adsorption was observed at 20 degrees C. The rate of attaining equilibrium of adsorption of metal ions follows the order Zn(II) > Cu(II) > Cd(II) > Pb(II). Equilibrium modeling of the adsorption showed that adsorption of Pb(II), Cd(II), and Cu(II) were fitted to a Langmuir isotherm, while the adsorption of Zn(II) was fitted to a Freundlich isotherm, Dynamic modeling of the adsorption showed that the first order reversible kinetic model was held for the adsorption process, The overall rate constant k', the adsorption rate constant k(1), the desorption rate constant k(2), and the equilibrium constant K-e for the adsorption process were calculated, From the results of the thermodynamic analysis, standard free energy Delta G(0), standard enthalpy Delta H-0, and standard entropy Delta S-0 of the adsorption process were calculated. (C) 1997 Academic Press

Polysaccharide Containing Gels for Pharmaceutical Applications

WOS: 000456875000007Bio-derived polymers are falling into the needs of pharmaceutical formulations for topical applications due to their gelling ability. Generally, in topical delivery, as an alternative way for local and systemic application of active substances, formulations in gelling form are preferred as they have multiple advantages, e.g., minimize systemic side effects, avoid gastrointestinal irritation, prevent the metabolism of the active substance in liver, etc. The present chapter reviews bio-based polymers with special reference to polysaccharides-based hydrogels with respect to their pharmaceutical applications