Ilya B. Rashkov

Preparation and Properties of Modified Chitosan Films for Drug Release

A novel method of preparing modified chitosan films was developed. Bi- and tri-component chitosan films were prepared by blending chitosan with high molecular weight polyoxyethylene. The films were loaded with 8-hydroxy-7-iodoquinoline-5-sulfonic acid which was chosen as a model drug. The properties of the films were studied with respect to crystallinity, thermal stability and swelling degree. These properties were shown to depend on the ratio of polyoxyethylene/chitosan. The drug release profile from the films was measured in a buffer at pH 6.8 and 37°C. The antimycotic effect of the films against Candida albicans was determined.

Preparation and properties of poly(oxyethylene)s with 5-chloro-8-quinolinoxyl end-groups

Abstract Chemical modification of α,ω-dichloropoly(oxyethylene)s (MW from 400 up to 3000), for obtaining poly(oxyethylene)s with 5-chloro-8-quinolinoxyl end-groups, is described. The products have been characterized by GPC, 1H-NMR and electronic spectra. Their ability to form complexes with polymers of acrylic and methacrylic acids in dilute aqueous solution has been investigated. 5-Chloro-8-quinolinoxyl end-groups stabilize the polycomplexes. It has been shown that, in the polycomplexes, the N-atom from the quinoline group is not protonated. The fact has been explained by the localization of the 5-chloro-8-quinolinoxyl end-groups mainly in the hydrophobic domains of the complexes.

Preparation and properties of poly(ethylene glycol) esters of 1-naphthylacetic acid and 2,4-dichlorophenoxyacetic acid

Abstract Diesters of well determined molecular weight and relatively narrow molecular weight distribution have been obtained by esterification of poly(ethylene glycol) with 1-naphthylacetic acid or 2,4-dichlorophenoxyacetic acid. The obtained diesters form interpolymer complexes with poly(acrylic acid) and with poly(methacrylic acid). They do not form complexes with pectin of low degree of esterification. The diesters exhibit auxin activity. The increase in the molecular weight of the polyether chain results in turning the inhibition effect into growth stimulation of mono- and dicotyledons.

Potassium-graphite intercalation compounds as initiators for ethylene oxide polymerization in benzene and tetrahydrofuran

Abstract The ability of alkali graphitides KC 24 and LiC 12 to initiate the polymerization of ethylene oxide in benzene and THF has been studied. Polymerization by LiC 12 leads to small quantities of oligomers; KC 24 causes quantitative polymerization. Initiation and chain growth take place in the interlayer space and the solvent nature does not affect the polymerization. The orders of the polymerization with respect to monomer and initiator have been determined. The polymerization rate is constant up to high conversion and initiator efficiency increases with the yield.

Preparation, properties and complexation ability of polyoxyethylene-bis-anaesthesine

Abstract Poly(ethylene glycol) derivatives of anaesthesine have been prepared and characterized. Complex formation between poly(acrylic acid) or poly(methacrylic acid) and anaesthesine derivatives in dilute aqueous solutions has been studied by potentiometric titration and viscometry. The presence of the hydrophobic anaesthesine groups stabilizes the polycomplexes. The stability is increased with the introduction of hydrophobic end-groups. Anaesthesine derivatives have been found to be of lower toxicity than anaesthesine. The local anaesthetic effect of anaesthesine has been prolonged by its attachment to a polyoxyethylene chain.

Copolymerization of styrene with some oxiranes initiated by KC24

The copolymerizations of styrene (St) with ethylene oxide (EO), propylene oxide (PO) and butylene oxide (BO) initiated by the graphite intercalation compound KC24 are studied. The possibility to obtain block copolymers in a single stage synthesis is shown. It is established that, in the initial stages of the copolymerization (St: EO = 1, 20°, yields < 30%) the products contain over 90% of St-units. At higher conversions (yields about 80%), the copolymers contain 60–70% of St-units and the molecular weight distribution is monomodal. The influences of the ratio of comonomers and the temperature of copolymerization on the composition and the molecular weight distribution of the copolymers are also studied. The copolymerizations of St with PO and BO give yields below 30%. Considerable quantities of homopolymers are formed along with the high molecular fractions, rich in St.