Faridah Sonsudin

pH Sensitive Hydrogels in Drug Delivery: Brief History, Properties, Swelling, and Release Mechanism, Material Selection and Applications

Improving the safety efficacy ratio of existing drugs is a current challenge to be addressed rather than the development of novel drugs which involve much expense and time. The efficacy of drugs is affected by a number of factors such as their low aqueous solubility, unequal absorption along the gastrointestinal (GI) tract, risk of degradation in the acidic milieu of the stomach, low permeation of the drugs in the upper GI tract, systematic side effects, etc. This review aims to enlighten readers on the role of pH sensitive hydrogels in drug delivery, their mechanism of action, swelling, and drug release as a function of pH change along the GI tract. The basis for the selection of materials, their structural features, physical and chemical properties, the presence of ionic pendant groups, and the influence of their pKa and pKb values on the ionization, consequent swelling, and targeted drug release are also highlighted.

Electrical Properties of Starch Based Silver Ion Conducting Solid Biopolymer Electrolyte

In the present study, the electrical and dielectric properties of a solid biopolymer electrolyte system based on starch doped with different amounts of silver nitrate (AgNO3) were analyzed. The electrolyte system was prepared via solution cast technique. Electrical impedance spectroscopy (EIS) measurement for the system was conducted over a frequency range of 50 Hz - 1 MHz at room temperature. It was found that the sample containing 6 wt.% AgNO3 obtained the highest conductivity value of 1.03 × 10-9 S cm-1. The effect of salt concentration on the dielectric properties of the electrolytes was also studied in relation to the conductivity properties. The dielectric studies indicated that the electrolytes in the present study obeyed non-Debye behavior.

Conduction Mechanism and Dielectric Properties of Solid Biopolymer Electrolyte Incorporated with Silver Nitrate

onic conductivity and dielectric properties of starch based polymer electrolytes doped with silver nitrate (AgNO3) at elevated temperatures were studied. The solid polymer electrolytes were prepared using the solution cast method. X-ray diffraction (XRD) analysis implied that the incorporation of 6 wt.% AgNO3 increased the amorphous phase of the electrolyte. Temperature dependence conductivity plots showed that electrolyte containing 6 wt.% AgNO3 obeyed Arrhenius rule with activation energy, Ea of 0.71 eV. The effect of temperature on the dielectric properties of the electrolyte was also studied in relation to the conductivity properties. The variation of dielectric loss with frequency was obtained from the power law exponent. Temperature dependence of the power law exponent concluded that the conduction mechanism of the 94 wt.% starch-6 wt.% AgNO3 electrolyte followed the correlated barrier hopping (CBH) model.

2,2′-Diethoxy-4,4′-[(E,E)-hydrazine­diyl­idenebis(methanylylidene)]diphenol

The complete molecule of the title compound, C18H20N2O4, is generated by inversion symmetry. The conformation around the C=N bond is E. With the exception of the ethoxy substituent, the molecule is essentially planar with an r.m.s. deviation of 0.0455 Å. In the crystal, molecules are linked by O—H⋯N hydrogen bonds into a two-dimensional supramolecular network parallel to the bc plane.

Curing of epoxy/alkyd blends in self-healing coating

Self-healing of polymeric material using microcapsules has been developed to repair microcracks within the materials. The self-healing character is reflected from the curing behavior of the material. In this work, curing study of alkyd/epoxy blend was carried out by replacing part of amine hardener with alkyd in the epoxy formulation. The inclusion of alkyd in the epoxy blend resulted in higher degree of curing and higher thermal stability compared to the alkyd-free blend, as evidenced from higher heat of reaction values of differential scanning calorimetry and maximum degradation temperature at 379°C, respectively. Self-healing reaction of epoxy coating as evaluated by Fourier-transform spectroscopy revealed that the 914 cm−1 peak attributed to C–O–C of epoxy has decreased, as the epoxide group was consumed in the reaction. Appearance of a new peak at 1631–1632 cm−1 in the cured coating confirmed that the epoxide has reacted with the carboxylic acid group of alkyd to form ester.

Improved ionic conductivity in guar gum succinate–based polymer electrolyte membrane

Guar gum succinate (GGS) was chemically modified by reacting guar gum with succinic anhydride in the presence of 4-dimethylaminopyridine. Succination was confirmed by Fourier transform infrared (FTIR) spectroscopy with carbonyl bands at 1724 cm−1 and ester linkage at 1567 cm−1 of the succinate group. The resulting amorphous, GGS was used as a polymer host to prepare cost-effective solid polymer electrolyte (SPE) films via incorporating a blend of ethylene carbonate (EC), carboxymethyl cellulose (CMC), lithium triflate (LiTf) and lithium iodide (LiI). SPE system for GGS:EC (1.0:0.6) with 30 wt% LiTf showed highest conductivity of 6.29 × 10−5 S cm−1 and GGS:CMC:EC (0.5:0.5:0.6) with 25 wt% LiI showed highest conductivity of 2.10 × 10−4 S cm−1. FTIR revealed multiple complexation sites for ion mobility indicating that GGS possesses high prospects as a conductive SPE.

(E,E)-1,2-Bis[3-(prop-2-yn-1-yl­oxy)benzyl­idene]hydrazine

The molecule of the title compound, C20H16N2O2, is centrosymmetric, the inversion center being located at the mid-point of the central azine bond. The conformation around the C=N bond is E. The whole molecule (except for the H atoms) is essentially planar, with an r.m.s. deviation of 0.07 Å. In the crystal, molecules are linked head-to-tail by pairs of C—H⋯O hydrogen bonds, forming inversion dimers, and resulting in the formation of chains propagating along [011].