Mohammad M. Fares

Graft Copolymerization onto Starch–I. Synthesis and Optimization of Starch Grafted with N-tert-Butylacrylamide Copolymer and its Hydrogels

Grafting of N-tert-butylacrylamide (BAM) onto starch in aqueous medium initiated by ceric ammonium nitrate ion has been studied under N2 atmosphere. The optimum conditions with respect to monomer concentration, initiator concentration, polymerization temperature, polymerization time and material to liquor ratio were studied in terms of percent of grafting efficiency (%GE) and percent of grafting yield (%GY). The optimum conditions obtained for the grafting of BAM on 1.0 g starch were: [BAM]=0.020 mol/L, [CAN]=0.91×10−3 mol/L, Temperature=30 ○C, and Time=240 min. Starch-g-BAM copolymer was characterized by FTIR, TGA for thermal stability, X-ray diffraction (XRD) for the crystallinity and scanning electron microscope (SEM) for surface morphology of the copolymer. Acid hydrolysis and viscosity average molecular weight (Mv) of copolymer were evaluated for the copolymer. Hydrogels prepared by grafting of BAM onto gelatinized starch showed maximum water uptake and moisture retain of 162% and 63% respectively.

Inulin and poly(acrylic acid) grafted inulin for dissolution enhancement and preliminary controlled release of poorly water-soluble Irbesartan drug

In this article, inulin and poly(acrylic acid) grafted inulin copolymer were used to enhance the dissolution of poorly water-soluble Irbesartan drug and to control its drug release rate, respectively. Topological structure of inulin showed sleazy separable flower-like platelets and granules accumulated above each other, which adapt it to physically bind Irbesartan drug and enhance its dissolution. Consequently, the increase of inulin content in the polymeric matrix was found to increase the drug dissolution gradually until it reaches its maximum (∼90%) within the first 60 min. The release rate had followed zero-order transport mechanism. On the other hand, the poly(acrylic acid) grafted inulin copolymer, characterized using (1)H NMR, FTIR, TGA, and SEM techniques, was found to form highly consistent amorphous systems of two-dimensional surfaces with some voids topology. Such features adapted it to control Irbesartan drug dissolution (∼33%) and show Fickian diffusion mechanism.

Stimuli pH‐responsive (N‐vinyl imidazole‐co‐acryloylmorpholine) Hydrogels; Mesoporous and Nanoporous Scaffolds

Tunable mesoporosity and nanoporosity of stimuli pH-responsive (N-vinyl imidazole-ran-acryloylmorpholine) hydrogels studied in terms of %swelling at various ionic strength, pH, temperature, and crosslinker concentration values were investigated. Hydrogel properties including diffusional exponent, number of links between two crosslinks, rms end-to-end distance and mesh size of gels were evaluated. The structural sequence of the scaffolds was tested and verified using Kelen-Tudos technique, and Alfrey-Price relationship. Hydrogels were characterized using FTIR, thermogravimetric analysis, differential scanning calorimetry, and freeze-dried Scanning electron micrographs techniques. The reversible pH responsiveness and possible mesoporous and nanoporous (i.e., 0.88-4.03 nm) structures suggest their suitable candidate in membrane technology and/or is an adequate drug delivery vehicle in drug delivery systems.

Versatile pectin grafted poly (N-isopropylacrylamide) : modulated targeted drug release

This study describes synthesis and optimization of pectin grafted poly(N-isopropylacrylamide) hydrogels as vehicles for colon-targeted theophylline model drug release. The gels were prepared in the presence of N, N′–methylenebisacrylamide (MBAA) crosslinker and ceric ammonium nitrate (CAN) initiator under N2 atmosphere. Optimum conditions, in terms of percent of grafting (%G), were determined as follows: pectin = 1.0 g, [NIPAAm] = 26.51 mM, [MBAA] = 0.65 mM, [CAN] = 0.073 mM, polymerization temperature = 30°C and time = 4.0 h. Hydrogels were characterized by FTIR, TGA, DSC, XRD and SEM. The formed hydrogel did not have a thermo-sensitivity behavior. The in vitro percent drug release was studied in terms of different percent of grafting and different polymerization temperatures under two pH values namely 5.5 and 7.4. Conclusively, the optimum colon-targeted vehicle properties that provide the least drug release at pH5.5 and the most drug release at pH7.4 were as follows: [NIPAAm] = 26.51 mM and [MBAA] = 0.56 mM, polymerization temperature = 30°C and %G = 55.5.

Synergistic corrosion inhibition of aluminum by polyethylene glycol and ciprofloxacin in acidic media

The synergistic inhibition of the corrosion of aluminum in acidic medium by polyethylene glycol (PEG) and the antibiotic ciprofloxacin was investigated. Significant increase in the inhibition of the corrosion of aluminum was observed by the addition of ciprofloxacin than by PEG alone. It was found that ciprofloxacin increase the inhibition efficiency of PEG from 61 to 91%. The addition of ciprofloxacin increases the kinetic thermodynamic parameters of the corrosion of aluminum such as the free energy of activation, the enthalpy of activation, and the entropy of activation which is consistent with observed increase in the inhibition efficiency. The higher absolute indicates that the adsorption of PEG on the surface of aluminum is more spontaneous in the presence of ciprofloxacin. The scanning electron microscope (SEM) images of aluminum surface before and after the exposure to HCl reveals the mechanism of the inhibition. The SEM images show that the decrease in corrosion is due to the formation of well-ordered and smooth layer of PEG and ciprofloxacin on the surface of aluminum. Langmuir isotherm was found to fit properly the adsorption of PEG and ciprofloxacin over the aluminum surface. The observed synergy is attributed to a stronger binding of PEG to the surface of aluminum mediated by ciprofloxacin.

Smart pH-sensitive Alternating Copolymers of (Methylacrylamide-Hydroxyethylmethacrylate); Kinetic and Physical Properties

The synthesis and physical properties of smart pH-sensitive (Methacrylamide-alt-2-hydroxyethylmethacrylate) copolymers (i.e. MAAm-alt-HEMA) were studied. The pH smart behavior determined using the cloud point technique showed a linear increase with increasing molar feed ratios of the copolymer. The rate of copolymerizations (Rp) determined by conventional %conv. vs. time method, and their apparent activation energies (Ea) were calculated. The reactivity ratios determined by Kelen-Tudos and Fineman-Ross techniques showed that the copolymer formed is an alternating type copolymer (i.e. M1M2M1M2…). Furthermore, the calculated molar ratios ( F 1) and the experimental molar ratios determined using 13C-NMR and FTIR were in very good agreement. The linear relationship of ln (r 1 r 2) vs. reciprocal of the temperature (1/T) shown in Equation 2 demonstrated an activation energy difference (i.e., (E 12 + E 21)−(E 11 + E 22)) and were found to be –118.4 kJ/mol confirming the alternating sequence behavior of MAAm and HEMA repeating units. The copolymers were characterized using 1H-NMR, 13C-NMR, FTIR, UV-Vis, TGA, DSC, powder X-ray, and SEM techniques.

Synthesis, Characterization, and Some Properties of 4-Vinylpyridine-Cr(CO)5 Containing Polymers

The polymerization of 4-vinylpyridine (4VP) and 4-vinylpyridine chromium pentacarbonyl [(4VP)Cr(CO)5] was performed under N2 atmosphere at 60–80°C temperature range. Different percent of feed (%PF) of Cr(CO)5 groups were anchored into poly(4-vinylpyridine) (P4VP) by addition of the intermediate Cr(CO)5THF, which was generated photochemically from Cr(CO)6 in THF, to the polymer at ambient temperature. The determined percent of anchoring (%PA) has shown that the maximum anchored Cr(CO)5 groups was 40% (w/w) with respect to P4VP, and the optimum percent of anchoring was 20% (w/w). The rate of polymerization (Rp) and the activation energy (Ea) of 4VP in the absence and in the presence of 16.7% Cr(CO)5(4VP) were determined. Thermal analysis has shown various changes in the properties of the 4VP polymers after modification of the polymer by Cr(CO)5 groups. The X-ray diffraction and the melting enthalpy derived from the DSC thermogram revealed that the synthesized poly[(CO)5Cr(4VP)] has a crystallinity of about 40%, whereas no crystallinity was observed for pure P4VP.

Dissolution enhancement of curcumin via curcumin-prebiotic inulin nanoparticles.

Abstract Dissolution enhancement of curcumin via prebiotic inulin designed to orally deliver poorly water-soluble curcumin at duodenum low acidity (pH 5.5) was investigated. Different prebiotic inulin–curcumin nanoparticles were synthesized in ethanol–water binary system at different pre-adjusted pH values. Characterization via FTIR, XRD and TGA revealed the formation of curcumin–inulin conjugates, whereas surface morphology via SEM and TEM techniques implied the formation of nanoparticle beads and nanoclusters. Prebiotic inulin–curcumin nanoparticles prepared at pH 7.0 demonstrated a maximum curcumin dissolution enhancement of ≈90% with respect to 30% for curcumin alone at pH 5.5. Power law constant values were in accordance with dissolution enhancement investigations. All samples show Fickian diffusion mechanism. XRD investigations confirm that inulin maintain its crystalline structure in curcumin–inulin conjugate structure, which confirms that it can exert successfully its prebiotic role in the gastrointestinal (GI) tract. Therefore, the use of curcumin–inulin nanoparticles can perform dual-mission in the GI tract at the duodenum environment; release of 90% of curcumin followed by prebiotic activity of inulin, which will probably play a significant role in cancer therapeutics for the coming generations.

Two-Dimensional Texture of Intrinsic Conductive Poly(styrene-co-maleanilic Acid) Grafted with Polyaniline: Formation and Conductivity

Intrinsically conducting polyaniline is grafted onto a preformed poly(styrene-co-maleanilic acid) copolymer backbone via chemical oxidative coupling of aniline in acidified chloroform/water emulsion. The structure and textural morphology of the grafted poly(S-co-MA-g-PANI) are examined by different spectroscopic, thermal, powder X-ray diffraction and scanning electron microscopic techniques. The d.c. electrical conductivity of the grafted emeraldine base of the obtained materials displays a d.c. conductivity of the order of 10−7 – 10−9 Scm−1, which is ∼2 orders of magnitude greater than that of the reported PANI-EB homopolymer. This enhancement in d.c. conductivity is explained in terms of microstructure-electronic conductivity relationship.

Revisited Kinetic Chain Length and Reactivity Ratio Approaches for Linear Polymers and Copolymers

Two revisited mathematical kinetic relationships were derived, evaluated and applied on linear polymers such as polystyrene and copolymers such as (NIPAAm-alt-HEMA) and (MAAm-alt-HEMA) copolymers respectively. The va- lidity of these equations was successfully verified. The first relationship, equation 12, interrelates exponentially kinetic chain length, average molecular weight and degree of polymerization of linear polymers with different temperatures. Fur- thermore; equation 12 could novelly define the rate of polymerization (Rp) and consequently the overall activation energy ( E) of the polymerization process could be determined. The second derived relationship interrelates the reactivity ratio product (r1r2) of two monomers interacting with each other, with different temperature. Application of equation 16 could determine the behavioral sequence of monomer 1 toward monomer 2 in the copolymerization process. The value of (E12+E21) (E11+E22) could result with the determination of type of copolymers formed. The reactivity ratio values for (NIPAAm-alt-HEMA) and (MAAm-alt-HEMA) copolymers were determined using Kelen-Tudos technique.