Molar Ratios Of Cross-linking Agent Research Articles

Coupling reaction and vacuum distillation to prepare β-CD-based adsorption material for organic dyes

A new method involving a coupling reaction and vacuum distillation (RVD) was introduced to prepare the β-CD cross-linking polymeric adsorbent (PCDRVD). The preparation conditions, including the molar ratio of cross-linking agent and β-CD, dosage of the solvent, reaction time, and vacuum distillation temperature and time, were investigated in detail. Compared with a product prepared at normal pressure, PCDRVD possessed a lower content of β-CD, a higher content of carboxyl groups, a lower adsorption selectivity, and a higher efficiency as well as adsorption capacity to remove dyes methylene blue (MB), and Rhodamine B (RhB), methyl orange (MO). The PCDRVD was characterised by FT-IR, TG, and SEM, and was employed for the adsorption of MB and RhB from an aqueous solution. Results showed that the adsorption quantity of MB (Qe,MB) was higher than that of Qe,RhB, except in the acidic medium. The equilibrium data followed the Langmuir isotherm model, and the calculated Qm,MB and Qm,RhB were 250.0 mg/g and 231.5 mg/g, respectively. The adsorption kinetics fitted the pseudo-second-order model. It was inferred that PCDRVD exhibited a high adsorption capacity for both dyes due to its more homogeneous polymeric network formed during RVD and the higher content of carboxyl groups. The differences between Qe,MB and Qe,RhB were mainly attributed to the size of MB and RhB.

New pH-Sensitive Hydrogels for Oral Delivery of Hydrophobic Drugs

A series of acrylic copolymers containing silyl pendant groups was prepared by free radical cross-linking copolymerization. Me3Si, Et3Si, and Ph3Si together with cubane-1,4-dicarboxylic acid (CDA) were covalently linked with 2-hydroxyethyl methacrylate (HEMA). CDA linked to two HEMA group is the cross-linking agent (CA). Free radical cross-linking copolymerization of the methacrylic acid (MAA) and organosilyl monomers with two different molar ratios of CA was carried out at 60–70°C. The compositions of the cross-linked three-dimensional polymers were determined by FT-IR spectroscopy. The glass transition temperature of the network polymers was determined calorimetrically. Equilibrium swelling studies were carried out in enzyme-free simulated gastric and intestinal fluids (SGF and SIF, respectively). A model hydrophobic drug, the steroid hormone estradiol, was entrapped in these gels, and the in vitro release profiles were established separately in both SGF (pH 1) and SIF (pH 7.4). Incorporation of silyl groups in a new macromolecule system modified network polymers for drug delivery. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Novel Carriers for Oral Delivery of Hydrophobic Drugs

For the first time, the glucose-6-acrylate-1,2,3,4-tetraacetate (GATA) monomer was prepared under mild conditions. The removal of protecting acetate groups from GATA was carried out before the silylation and then Me3Si was covalently linked with glucose acrylate (GA). Cubane-1,4-dicarboxylic acid (CDA) was covalently linked with 2-hydroxyethyl methacrylate (HEMA). The silyl-linked GA is abbreviated as TMSiGA. CDA linked to two HEMA groups was used as the cross-linking agent (CA). Free radical cross-linking co-polymerization of the methacrylic acid (MAA) and hydrophobic glycomonomer (TMSiGA) with two different molar ratios of CA was carried out at 60–70°C. The compositions of the cross-linked three-dimensional polymers were determined by FT-IR spectroscopy. A model hydrophobic drug, the steroid hormone estradiol, was entrapped in these gels and the in vitro release profiles were carried out in enzyme-free simulated gastric and intestinal fluids (SGF and SIF, respectively). To overcome the hydrophobicity of estradiol, the buffers for estradiol were modified by adding ethanol. The influence of the structures and amounts of silane monomers on the swelling and drug-release behaviors were studied.

Towards ochratoxin A selective molecularly imprinted polymers for solid-phase extraction

Molecularly imprinted polymers (MIPs) displaying selective binding properties for the mycotoxin ochratoxin A (OTA) in polar/protic media were prepared. Crucial to the success of these efforts was the implementation of rationally designed OTA mimics as templates and a set of novel basic and neutral functional monomers, allowing the maximization of the template–functional monomer association via ion-pairing, hydrophobic and steric interactions. MIPs prepared with a 20:1:1:3 molar ratio of cross-linking agent, template mimic, basic functional monomer and hydrophobic auxiliary monomer produced polymers with superior recognition properties compared to materials generated with other stoichiometries. Chromatographic evaluation using the OTA mimics, OTA and a set of structurally closely related compounds as analytes revealed pronounced substrate selectivity of these MIPs in polar/protic media, the templates and OTA being bound with significantly higher affinities. Complementary substrate selectivities/affinities were observed in aprotic and apolar solvents. The possibility of solvent-dependent tuning of substrate selectivity/affinity and the high binding capacity recommend the developed MIPs as promising solid-phase extraction adsorbents for clean-up and pre-concentration of OTA from various biologically relevant matrices.