S. N. Filatov

Preliminary silylation for structure determination of oligomeric silsesquioxanes by matrix- assisted laser desorption/ionisation mass spectrometry.

The potential of preliminary silylation for the determination of numbers of hydroxyl groups in separate molecules of oligomeric silsesquioxanes by matrix-assisted laser desorption/ionisation mass spectrometry has been demonstrated for the first time. Derivatisations allowing the introduction of trimethylsilyl, tert-butyldimethylsilyl and pentafluorophenyldimethylsilyl groups were tested. It was shown that more reliable structure elucidation of individual oligomers can be achieved knowing the number of hydroxyl groups thus determined.

Synthesis and modification of oligo(aryloxycyclotriphosphazenes) based on 4,4′-dihydroxydiphenyl-2,2-propane

Oligo(aryloxyphosphazenes) are synthesized on the basis of diphenylolpropane and hexachlorocyclotriphosphazene via the phenolate method. Corresponding functional derivatives are obtained through treatment of the oligomers with methacryloyl chloride, glycidyl methacrylate, and epichlorohydrin. GPC data indicate that modification is accompanied by an increase in the molecular mass of the oligomers. Epoxidation of a specially synthesized hexaallyloxy derivative of oligo(aryloxycyclotriphosphazene) with m-chloroperbenzoic acid proceeds incompletely to yield an oligomer with a content of epoxy groups below 6%. All of the compounds are characterized with the use of 31P and 1H NMR spectroscopy.

Halogenated hydroxy-aryloxy phosphazenes and epoxy oligomers based on them

By partial substitution of the chlorine atoms in hexachlorocyclotriphosphazene for halophenols and subsequent reaction of the resulting halogenated phenoxy phosphazene and 2,2-di(4-hydroxyphenyl)propane monophenolate hydtoxy-aryloxy phosphazenes were synthesized with a molecular weight of 1100–1400 g mol−1. Epoxide oligomers (epoxy number of 6–8%), which are cured with the formation of non-combustible compositions [PV-0 class of resistance to combustion according to State Standard (GOST 28157-89)], were obtained by reaction of these compounds with epichlorohydrin. Introduction of 5–50 wt% halogenated epoxyphophazene oligomers in industrial resin ED-20 can significantly improve the flame resistance of compositions based on these compounds.

Methacrylate-containing oligoorganosilsesquioxanes

Methacrylate-containing organosilsesquioxanes with M n = (1.5−5.0) × 103 were synthesized via hydrolytic polycondensation of γ-methacryloxypropyltrimethoxysilane under different conditions. On the basis of comparison of 29Si NMR data and the molecular masses of the oligomers, it was concluded that oligomer molecules contain 8–12-membered siloxane cycles.

Polymeric dental composites modified with carboxy phosphazene methacrylates

Oligophosphazenes containing carboxy and polymerizable methacrylate groups were prepared by the reaction of hexa-p-carboxyphenoxycyclotriphosphazene with glycidyl methacrylate. Introduction of these oligomers in an amount of up to 10 wt % into methacrylate filling dental composites enhances their adhesion to tooth tissues and metals by a factor of 5–7 and the compression strength by 20–30%.

Rheokinetics of the curing of epoxy oligomer ED-20 modified with epoxy phosphazenes

The effect of epoxy phosphazene on the curing parameters of an epoxy amine composition containing epoxy phosphazene was studied via rotational viscometry. The presence of epoxy phosphazene accelerates the process and changes the pattern of polymer-network formation. As a result, the dynamics of the increase in viscosity changes.

Methacrylate composites containing maleic derivatives of cyclotriphosphazene

Oligophosphazenes containing carboxyl groups and copolymerizable double bonds are synthesized through the interaction between hexa-p-hydroxymethylphenoxycyclotriphosphazene and maleic anhydride. The synthesized compounds with a controlled ratio of carboxyl groups and double bonds are used as modifiers of methacrylate dental composites that exhibit high adhesion to hard dental tissues and metals.

Thermal polycondensation of hexa-p-hydroxymethylphenoxycyclotriphosphazene

A procedure for the synthesis of hexa-p-hydroxymethylphenoxycyclotriphosphazene is optimized. The thermal characteristics of this compound are studied, and its capability for thermal self-con-densation is demonstrated. The main steps of polycondensation of hexa-p-hydroxymethylphenoxycyclotriphosphazene involve the formation of methylene ether bonds accompanied by the evolution of water and their further scission without formation of formaldehyde. The resulting polymer is thermally stable up to 470°C.

Rheological and rheokinetic properties of phosphazene-containing epoxy oligomers

The rheological and rheokinetic properties of a two-component binder consisting of epoxy-diane oligomers and the oligoepoxyphosphazenes PEO-1 (30 wt %) and PEO-2 (40 wt %) are studied. The viscosities of the initial oligomers at 40°C are 130 (PEO-1) and 270 (PEO-2) Pa s; the activation energies of viscous flow in the range 40–70°C are from 122 to 128 kJ/mol. The addition of equivalent amounts of curing agents, such as triethylenetetramine or iso-methyltetrahydrophthalic anhydride, reduces the initial viscosity of a composition, most strongly in the presence of the second curing agent (by a factor of 50–100). The activation energies of the cure process with triethylenetetramine in the range 45–95°C are 89 (PEO-1) and 125 (PEO-2) kJ/mol, and the gelation time at 55°C is 6 min for both oligomers. The time of gelation for the system PEO–iso-methyltetrahydrophthalic anhydride at 90°C is 475 min, and the glass-transition temperatures of the cured compositions are 238 (PEO-1) and 250°C (PEO-2), as evidenced by thermomechanical studies.

Polymerization of methyl methacrylate and vinyl acetate initiated by the manganese carbonyl-1,2-epoxy-4,4,4-trichlorobutane system

Polymers containing epoxy groups at the ends of macromolecules and in side radicals are prepared through polymerization of methyl methacrylate and vinyl acetate in the presence of the manganese carbonyl-1,2-epoxy-4,4,4-trichlorobutane system. The presence of reinitiation is revealed; it leads to an appreciable increase in the molecular masses of poly(methyl methacrylate) and poly(vinyl acetate) as compared to polymers synthesized in the presence of 2,2′-azo-bis(isobutyronitrile) and 1,2-epoxy-4,4,4-trichlorobutane.