Elena Kamenska

(Diacetoxyiodo)benzene and [bis(trifluoro-acetoxy)iodo]benzene as photoinitiators for radical and cationic polymerization

Abstract The photodecomposition products of (diacetoxyiodo)benzene (DAI) and [bis(trifluoroacetoxy)iodo]benzene (BTI) were found to be efficient initiators for the homopolymerizations of 2-(dimethylaminoethyl)methacrylate (DMAEM) and methyl methacrylate (MMA) and also the copolymerizations of DMAEM with MMA or styrene (St). A free radical mechanism was confirmed. Copolymerization constants for DMAEM-MMA and DMAEM-St were determined (rDMAEM = 0.35 ± 0.08, rMMA = 0.57 ± 0.08; rDMAEM = 0.14 ± 0.01, rSt = 0.20 ± 0.01) and are discussed. DAI and BTI are also cationic photoinitiators for i-butyl vinyl ether (BVE). The efficiencies of DAI and BTI as photoinitiators for radical or cationic polymerization depend on the properties of the solvents and monomers.

Polyzwitterionic copolymer nanoparticles loaded in situ with metoprolol tartrate: synthesis, morphology and drug release properties

Polyzwitterions belong to the “smart” polymers’ group because of their specific swelling properties which depend on pH and ionic strength of the aqueous media. Novel polyzwitterionic copolymer nanoparticles of vinyl acetate (VA) and 3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate (DMAPS) (p(VA-co-DMAPS)) with loaded in situ metoprolol tartrate were synthesized by emulsifier-free emulsion copolymerization in water. The influence of in situ addition of metoprolol tartrate on the emulsifier-free emulsion copolymerization mechanism was studied. It was suggested that the interactions between metoprolol tartrate and the copolymer nanoparticles are responsible for the creation of “bridge” connections between them and these bonds led to the formation of coagulum. To validate possible mechanisms of interaction between metoprolol tartrate and copolymer nanoparticles Differential Scanning Calorimetry was employed. Scanning Electron Microscopy, Atomic Force Microscopy, Dynamic Light Scattering and ζ-potential measurements were used to determine the average diameter, size distribution and ζ-potential of the copolymer nanoparticles. It was shown that the copolymer composition was an effective parameter for control of the release kinetics of in situ loaded metoprolol tartrate in copolymer nanoparticles.

Photopolymerization of 2-(dimethylaminoethyl)methacrylate induced by diacetoxyiodobenzene and bis(trifluoroacetoxy) iodobenzene

SummaryThe title hypervalent iodine compounds are efficient photoinitiators for the polymerization of 2-(dimethylaminoethyl)methacrylate. The polymer is formed in daylight but faster under UV irradiation, with high conversion; its molecular weight 〈Mn〉 is 9×104 daltons. Copolymerization of this monomer with styrene occurs also under similar conditions at a high rate. A free radical mechanism is suggested for these polymerizations.

Verapamil Hydrochloride Release Characteristics from New Copolymer Zwitterionic Matrix Tablets

The aim of this study was to synthesize stable copolymer (vinyl acetate-co-3-dimethyl[methacryloyloxyethyl] ammonium propane sulfоnate) zwitterionic latex with different compositions for the first time by emulsifier-free emulsion copolymerization. Throughout the course of the study, a proposal was made for the explanation of the relationship between the “overshooting” phenomenon (a swelling kinetics with a maximum) and the specific self-association of the zwitterionic copolymers. The zwitterionic monomer unit mole fraction, pH, and ionic strength effects on this relationship, on the swelling kinetics of the zwitterionic copolymers, and on the sustained verapamil hydrochloride release from the model tablets were established by the studys authors.

Design and Concept of Polyzwitterionic Copolymer Microgel Drug Delivery Systems In Situ Loaded with Non-steroidal Anti-inflammatory Ibuprofen.

ABSTRACTNowadays, the modern pharmaceutical investigations are directed toward obtaining of new polymer micro- and nano-sized drug delivery carriers. In this respect, the use of hydrogel carriers based on polyzwitterions (PZIs) is an opportunity in the preparation of polymer drug delivery systems with desired characteristics. This paper describes the synthesis and characterization of micro-structured p(VA-co-DMAPS) systems with different compositions in situ loaded with Ibuprofen by emulsifier-free emulsion copolymerization (EEC) in water. The mean size of the prepared microparticles was measured by SEM and particles have been visualized by AFM. The inclusion of Ibuprofen in the polyzwitterionic copolymer microgel systems was established by using DSC. In vitro drug release experiments were carried out in order to estimate the ability of the obtained microgels to modify the release of water-insoluble Ibuprofen.

A qualitative criterion proving the participation of comonomer complexes in the chain propagation of radical copolymerization

The juxtaposition of the equations for copolymer composition for chain propagation following the terminal (T), penultimate (P) and complex (C) mechanisms shows that the copolymer composition depends on the total co-monomer concentration only when a comonomer complex participates in the pro-pagation. This makes it possible to define an easily applicable criterion proving comonomer complex participation yet not excluding propagation according to the T and P mechanisms. The criterion has been tested for the copolymerization of 1-vinyl-2-pyrrolidone with acrylic and methacrylic acids, and of styrene with maleic anhydride. It has been shown that such a dependence cannot be claimed for styrene–methyl methacrylate copolymerization.