Latchezar K. Christov

(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.

Photopolymerization of methyl methacrylate and 2-(dimethylamino) ethyl methacrylate induced by diacetoxyiodobenzene in the presence of radical inhibitors

SummaryPolyvalent iodine compounds such as diacetoxyiodobenzene, (CH3COO)2IC6H5 (DAI), and bis(trifluoroacetoxy) iodobenzene, (CF3COO)2IC6H5 (BTI), are efficient initiators of cationic and radical polymerizations. To confirm the radical mechanism of DAI-induced polymerization of methyl methacrylate (MMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA), a study has been performed in the presence of the radical inhibitor 2,3,5,6-tetrachloro-p-benzoquinone (TCQ) and its complex with triethylamine (TEA). The polymerization kinetics and the effect of irradiation intensity have been studied.

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.

Chaperone-Like Effect of Polyzwitterions on the Interaction of C1q with IgG

The amphiphilic polyzwitterion (PZ) poly(ethylene oxide-b-N,N-dimethyl(methacryloyloxyethyl) ammonium propanesulfonate), zwitterionic surfactant (ZS) n-dodecyl- N,N-dimethyl-3-ammonium-1-propanesulfonate, and zwitterionic monomer (ZM) N,Ndimethyl( methacryloyloxyethyl)ammonium propanesulfonate were analyzed for their suggested chaperone-like effect on the interaction of C1q and IgG. Our results proved that the PZ retarded the C1q interaction with IgG, demonstrating a specific protein-folding helper effect. The ZS enhanced this interaction, when the ZS concentration was lower than the critical micelle concentration (CMC), and retarded it, when the ZS concentration was above the CMC. The ZM, with no self-assembling ability, did not influence this interaction. These results support the hypothesis of a hydrophobic interaction between Pts and hydrophobic domains of partly denatured protein molecules. The amphiphilic self-assemblies, formed by polyzwitterionic macromolecules or zwitterionic surfactants, have the ability to transform the hydrophobic domains of the protein molecules into hydrophilic ones, covering them with their hydrophilic parts.

Calculation of the shifts of argon spectral lines

Shifts due to collisions with charged particles (Stark broadening ) and neutral atoms, were determined for nine argon spectral lines corresponding to the transitions 3p5nd‐3p54p for n = 4‐7, 3p56s‐3p54d and 3p54p’ ‐3p54s in order to estimate their usability for the research and diagnostics of a plasma in a surface‐wave discharge at atmospheric pressure.

Using line broadening to determine the electron density in an argon surface‐wave discharge at atmospheric pressure

Broadening due to collisions with charged particles (Stark broadening ) and neutral atoms, was determined for Ar I 522.1, 549.6 and 603.2 nm spectral lines from the spectral series 3p5nd‐3p54p, in order to evaluate the electron density in a surface‐wave discharge at atmospheric pressure.

Calculation of Shift of Argon Lines by Elastic Collisions Emitter—Neutral Atoms

The shift of three argon spectral lines due to the interactions between the excited atoms and atoms in a ground state has been calculated. These lines belong to one spectral series 3p5nd 2[7/2]4−3p54p 2[5/2]3 for n = 5–7. The dependence of the shift coefficient on gas temperature under atmospheric pressure has been obtained. The semi‐classical impact theory has been applied and Kaulakys potential has been used.

On the Broadening of Spectral Lines in Surface Wave Discharges

The broadening of argon spectral lines emitted in surface wave discharges has been examined under pressure range 1 Torr–1 atm. The different mechanisms of broadening have been studied. Interpretation of the experimental results is discussed. The study is of interest for plasma diagnostics.

Dependencies of the first and second moments of copolymer composition on conversion – a new discrimination tool of radical copolymerization mechanisms

A method discriminating between terminal and complex copolymerization mechanisms based on the comparison of the experimentally-determined dependences of the average and the instantaneous copolymer composition and its dispersion on conversion with those derived from the model schemes is suggested. The analysis of the conversion dependences allows the assessment of the copolymer compositional homogeneity and the dominating mechanism of chain propagation. An easily applicable criterion proving monomer complex participation for the cases when the composition curve crosses the azeotropic line has been defined on the dependence of the monomer feed composition at which dispersion has minimum value on conversion. It is also shown that conversion curves carry information about changes in the kinetic, hydrodynamic and thermodynamic characteristics of the reaction medium. The efficiency of the suggested methods has been tested for the copolymerization of acrylic acid and 1-vinyl-2-pyrrolidone. © 1999 Society of Chemical Industry