The polymeric hydrogels composed of polyacrylamide and food protein casein have been synthesized for the purpose of studying their SWELLING and drug release BEHAVIOUR. The two samples, differing in cross-linking ratio, show almost Fickian SWELLING BEHAVIOUR (n50 .50) except the less cross-linked sample at pH 7 .0 for which SWELLING exponent n was 0 .62, thus showing non- Fickian SWELLING BEHAVIOUR. The SWELLING parameters like diffusion exponent, penetration velocity, and diffusion coefficient have also been evaluated. The SWELLING BEHAVIOUR of hydrogels is greatly affected by variation in pH of the external medium. These gels show maximum SWELLING at pH 7.0 and it decreases in both acid and alkaline range. This BEHAVIOUR has been explained on the basis of osmotic SWELLING pressure theory, thus treating the hydrogel to  be of ionic nature due to presence of protein casein. The release of model drug bromocresol green (BCG) has been studied as a function of temperature of the external medium, and it has been observed that the amount of drug released decreases beyond 40°C. The purpose of undertaking the present work is to explore the possibilities of using casein the natural protein, as a drug delivery device so that Ike other natural polymers (collagen, guargum, gum arebica etc.) casein may also be used without causing any toxic effect in the human body system. These gels also undergo a number of reversible SWELLING-deSWELLING cycles.

SWELLING BEHAVIOUR is one of the important properties of hydrogel-based drug delivery systems, which always affects the diffusion of solvent into and release of drugs from drug loaded microcapsules. In this study, the SWELLING BEHAVIOUR of alginate-chitosan beads at acidic and basic conditions, to simulate gastric and intestinal media, were investigated. Spherical hydrogel beads were prepared by addition of aqueous sodium alginate and alginate-N,O-carboxymethyl chitosan (NOCC) solutions into CaCl2 solution. These hydrogel beads were then transferred into a chitosan solution to obtain chitosan coated beads. The effect of concentration of calcium chloride, residence time for ionic cross-linking, concentration of chitosan, addition of NOCC into alginate solution, coating of alginate-NOCC by chitosan as well as drying method on the SWELLING BEHAVIOUR of the alginate-chitosan beads was studied. It was found that SWELLING degree of the air-dried and chitosan coated beads was lower than that for freeze-dried and uncoated beads, respectively. In addition, the presence of NOCC in the network resulted in reducing SWELLING of hydrogel beads. SWELLING degree of hydrogels in basic media (pH 7.4) was also much higher than that in acidic media (pH 1.2). Thus, alginate-NOCC-chitosan beads are good candidate to be studied as colon-specific drug delivery systems.

Cross-linked poly (vinyl alcohol) (PVA) is a prolonged-release micromatrix, a hydrophilic polymer and a potentially interesting hydrogel, which is useful for drug delivery applications. As a part of drug development procedure the aim of this study was to investigate the effect of structural changes on drug release (theophylline) from this polymeric network. The studied parameters included: cross-linking agent (glutaraldehyde) concentration, PVA content of the films, theophylline percentage and their overall effect on SWELLING of the hydrogels, drug loading efficiency, diffusion and release characteristics of theophylline from PVA films. Changes in glutaraldehyde percentage (or cross-linking density) affected the SWELLING of the films. However, increasing PVA percentage caused more SWELLING, Drug loading efficiency was higher in gels with higher glutaraldehyde, PVA and theophylline percentages. Increasing contents of PVA and theophylline promoted the diffusion coefficient and drug release rate but glutaraldehyde had a reverse effect. The pH did not affect the SWELLING and diffusion coefficient. Water transport and drug release mechanism predominantly followed a Fickian model. It may be concluded that by changing the PVA structural parameters, a rate-controlled drug release is obtained.

A series of novel chitosan-g-poly(acrylic acid)/muscovite (CTS-g-PAA/MVT) granular superabsorbent composites were synthesized by free-radical graft polymerization in aqueous solution. The effects of different ion-exchanged MVT on equilibrium water absorbency, SWELLING rate and SWELLING BEHAVIOUR in various cationic saline solutions and different pH solutions of superabsorbent composites were systematically investigated under the same preparation conditions. The superabsorbents doped with different ion-exchanged MVT were characterized by Fouriertrans form infrared spectroscopy (FTIR), X-ray fluorescence spectrometry (XRF) and scanning electron microscopy (SEM). FTIR spectroscopy confirmed that AA has been grafted onto CTS and -OH groups of MVT seem to have participated in this reaction, simultaneously. These composites show good dispersion and favourable compatibility of inorganic and organic phases observed in SEM photographs. The introduction of ion-exchanged MVT into chitosan-g-poly(acrylic acid) polymeric network could improve water absorbency and SWELLING rate compared to those of the MVT. It is found that the SWELLING BEHAVIOUR of these composites depends on the concentrations of NaCl, CaCl2, and FeCl3 solutions; as by increasing the concentration from 0.01 to 10 mM leads to gradual decrease in the SWELLING rates. All prepared composite samples demonstrate similar SWELLING BEHAVIOUR at different pH, while the equilibrium water absorbency of the samples is kept roughly constant in pH range 4-10.

Biopolymer/layered silicate composites have shown unique advantages and potentials for the passive targeting of drugs because they can overcome the burst drawbacks of organic carrier, increase the drug utilization and enhance the controllable capability of drug release. Furthermore, the biocompatibility and nontoxicity of biopolymers is retained, and therefore it is promising and applicable in pharmaceutical fields. The main research aim of this work was to develop a series of biopolymer/layered silicate composite beads based on chitosan (CTS) and Laponite (LA) by a simple ionic cross-linking reaction using sodium tripolyphosphate as the cross-linker. The resultant beads were characterized by Fourier transform infrared spectroscopy, scanning electronic microscope and X-ray diffraction analysis. The SWELLING BEHAVIOUR in physiological pH solutions (7.4 and 1.2), drug encapsulation efficiency and controlled release BEHAVIOUR were also investigated by using Ofloxacin as the model drug to reveal the effects of introduced LA. The results indicate that the incorporation of LA remarkably improved the SWELLING BEHAVIOUR, enhanced the drug entrapment efficiency, and slowed down the drug release BEHAVIOUR in contrast to the pure organic CTS beads. The exfoliated LA clay could act as a physical cross-linker to facilitate the formation of network structure between the CTS and LA. It is suggested that LA may be developed as an effective additive for fabricating a sustained drug delivery system.

A series of oil gels based on the rigid hydrophobic monomer 4-tert-butylstyrene (tBS) and the soft oleophilic monomer ethylene-propylene-diene (EPDM) crosslinked with divinylbenzene (DVB) were synthesized by suspension polymerization. Effects of EPDM and DVB contents on SWELLING behaviors, compressive properties, effective cross-link density (ve), average molecular weight between cross-links (Mc), and polymer-solvent interaction parameter (X1) of oil gels were studied. It has been shown that the equilibrium oil absorbency (Qeq) is first increasing and then decreasing with the increase of EPDM contents in polymerization, as well as Mc values. On contrary, the values of e first rise and then decline with the increase of EPDM contents, as well as the volume fraction of polymer in gel (fr) and X1 values. The optimum reaction conditions are EPDM content 60 wt% and DVB content 3 wt%. Further increase of DVB content leads to changes of SWELLING behavior, network structure and polymer-solvents interaction in oil gels, viz. the decrease of Qeq and Mc values, the increase of  fr, ve , and X1 values. These changes represent macroscopically the varieties of compressive strength and Young's modulus of the oil gels. The comparison between efficient cross-linking density and theoretical cross-linking density (Vt) indicates that the double bonds in EPDM monomeric unit has participated in chemical cross-linking, and the physical cross-linking and entanglements have thr weakening effects on chemical cross-linking.

The effect of filler loading and bonding agent on the dynamic properties and SWELLING BEHAVIOUR of bamboo fibre filled natural rubber composites were carried out. Bamboo fibre was used as a filler and the loading range was from 0 to 50 phr. Dynamic properties were determined using a Monsanto moving die rheometer (MOR 2000) at 150°C. Results show that the maximum elastic torque (S"-MH) and minimum elastic torque (S 'ML) increase with increasing filler loading and the addition of bonding agent. However, the viscous torque (S" -MH) and tan Sae decrease with the addition of bonding agent. For SWELLING BEHAVIOUR, the water absorption of the composites increases with increasing filler loading but decreases with the addition of bonding agent. The presence of bonding agent is found to improve the adhesion between bamboo fibre and natural rubber matrix as indicated by the tensile fracture surfaces of the composites using scanning electron microscope (SEM).

The phenomenon of SWELLING-shrinkage has gained widespread attention in practice owing to the generation of eroded clayey layers of soil that amplify with global climate change and the seasonal water content. This provokes several serious disorders affecting the stability of nearby constructions and consequently generating human loss. The expansive clayey soils show the phenomena of wetting and drying cycles in their natural state (undisturbed soil). Hence, classical oedometric tests are found to be unable to take into account the thermal behavior of naturally SWELLING soils; this is proven by the resulting asymptotic volumetric behavior, as well as the steady values of the potential of SWELLING and shrinkage. The main aim of this experimental analysis is to derive a test that considers the significant effect of temperature. Experimental results of an oedometric approach are represented herein for the purpose of investigating the volumetric and hydric behavior of naturally SWELLING soil in the region of N’Gaous (Eastern Batna province, Algeria) through drying-wetting paths. Innovative expressions are derived for the direct computations of the SWELLING-shrinkage potential in terms of water content, appearance time and applied loads. It is of interest to mention that those expressions are applicable to other regions in the world with similar soil geotechnical and chemical characteristics and conditions. The cyclic outputs show that the SWELLING pressure variation with the appearance time is mainly related to the first cycle of SWELLING-shrinkage; as it exhibits a noticeable increase in the SWELLING potential with the amplification of applied loads until reaching a state of steadiness. The experimental results demonstrate a high degree of reliability and correlation with the soil behavior. Therefore, the SWELLING-shrinkage potentials are expressed innovatively in equations that help predict the soil behavior in expansive regions in order to enhance the safety of nearby foundations.