Carbonization of Polyacrylonitrile Composites with Nitrogen-containing Cellulose Derivatives

Thermal carbonization of nitrogen-containing cellulose derivatives (chitin, chitosan, cyanoethyl chitosan, cyanoethyl cellulose, copolymers of allyl carboxymethyl cellulose with polyacrylonitrile) as models of probable products of thermal reaction of cellulose with polyacrylonitrile was studied. The quantitative characteristics of carbonization of the model compounds are influenced by the nitrile group.     

Cocarbonization of polyacrylonitrile with lignin

The boundary and parameters of the thermochemical reaction of lignin and polyacrylonitrile were determined by dynamic and isothermal thermal analysis. The time, temperature, and concentration effects of formation of composites, allowing preparation of new carbonizates with enhanced heat resistance and noticeably higher carbon residue, were studied.     

Structural Features of Carbonization of Copolyimides

The influence of nitrogen-containing heterocycles on the main parameters of carbonization of aromatic copolyimides was considered for aromatic copolyimides containing phenylquinoxaline units as an example. The structural characteristics of intermediates and final products of carbonization were determined.     

Minimizing a Symmetric Quasiconvex Function on a Two-Dimensional Lattice

We consider the minimization problem for a symmetric quasiconvex function defined by an oracle on the set of integer points of a square. We formulate an optimality criterion for the solution, obtain a logarithmic lower bound for the complexity of the problem, and propose an algorithm for which the number of inquiries to the oracle is at most thrice the lower bound.     

Addition homo- and copolymerization of 3-triethoxysilyltricyclo[4.2.1.0<Superscript>2,5</Superscript>]non-7-ene

New norbornene type monomer bearing reactive triethoxysilyl group was synthesized, and its addition homo- and copolymerization with 3-trimethylsilyltricyclonon-7-ene was studied. The target monomer was obtained using regio- and stereospecific [2σ+2σ+2π] cyclo-addition of quadricyclane with vinyltrichlorosilane followed by the reaction of the formed cycloadduct with ethanol in the presence of triethylamine. Addition polymerization was investigated over the three-component Pd-containing catalytic system (Pd complex, Na+[B(3,5-(CF₃)₂C₆H₃)₄]–(cocatalyst) and tricyclohexylphosphine). The N-heterocyclic carbene Pd complex (SIPrPd(cinn)Cl) with high activity and tolerance to the Si—O—C moieties was used as a catalyst. The yields of the homo- and copolymers were 24—68% depending on the monomer (comonomer): Pd: B: PCy₃ ratio. The obtained addition polymers are high-molecular-weight amorphous products, the glass transition temperature of which exceeds 300 °C. The presence of reactive Si(OC₂H₅)₃ groups in the homo- and copolymers made it possible to carry out a hard-to-realize cross-linking involving side substituents and followed by the formation of insoluble polymers.     

Cocarbinization of Blends of Polyacrylonitrile with Chitin and Chitosan

The possibility of thermochemical cocarbonization of polyacrylonitrile with chitin and chitosan by combined heat treatment of their blends was examined. It was concluded that the components form complexes in dimethylformamide and dimethylacetamide at the temperature of polyacrylonitrile cyclization (230–300°C). The main thermal characteristics and the coke numbers of the cocarbonization products were determined.