Act8 Polyrnoric8 a2 (1991) Nr. 6 2 f O RIJMYNSKAYA, ROMANOVA r t al. : 'lhiisfornia tinns of poly(tnctliacr~lo~iit.rilc) in soliitions number of bobbins or a different construction of the tcmpering surface.The schemc for calculations of nielt relaxation process described here permits to evaluate t h e degree of relaxation of the macromolecules during the tempering of the melt under different technological conditions or, conversely, t o find tempering conditions required for the complete relaxation of the system. Lcliingl;itl/USSR The kinetics of cliangcs of electronic spectra of poly(metliacrylo~iitrilc) in DMSO on aclilition of alkali was studied. The spectral picture depends on ttic amount of a k i l i corresponding to nnc chain unit, the amount of wntcr in the solutiun, and tlic alkali/watcr ratio. Bcsidcs, the inasimal attainablc effective length of conjugation of cyclic scquences is all tlic niore the lower is the rate of initiation of cyclization. -4 slow and unsubstantial decreasc of the intrinsic viscosity csclritles the occurrence of a sharp coil-globule transition on alkaline hydrolysis of poly(mctliacrylonitrilc). Urnwandlungen von Pol~(rne1liacnjlnilril) in LG8urzg bei zugahe oon AlltaliDie Kinetik dcr Andcrungen dcr clcktronischcn Spektrcn von Poly(mctIlacryloitril) in DMSO bei Zugabc vnn Alkali wurdc itntcrsucht. Das Ausschcn dcs Spcktrums hiingt von dcr Mcngc an Alkali bczogC.cn auf einc Einlieit der Polymerkettc nb, sowie vom Wassergchalt tler Liisung und vom Alkali/Wasser-VcrliaItnis. Die maximal erreichbare effcktivc Liingc dcr Konjugat,ion cyclischer Sequenzcn ist urn so griiRcr, je nicdrigcr die Initiierungsgcschwindigkcit der Cyclisicrung ist. Die beobachtcte gcringc Abnaliinc dcr Grcnzviskositat schlicDt dns Auftreten eincs scliarfen Ifbergangs vom Kniiuel xur kompaktcll Kugel bei dcr alkalisclien Hydrolysc des Poly(mctliacryliiitril)s aus.
This work describes a novel heterogeneous oxidation catalyst which is analogous to the homogeneous-phase Fentons reagent for the successful destruction of a range of organic pollutants. The catalyst is a polyacrylonitrile fibre which was modified to incorporate ligating groups, resulting in a transition metal cation being firmly fixed onto the fibre. The novelty of the catalyst resides in its open-knit mesh structure. In the presence of hydrogen peroxide, the catalyst containing ferric ions (as the active site) is shown to rapidly decompose phenol in addition to (a) the anthraquinone dyes: acid blue 45, carminic acid and reactive blue 19, and (b) the azo-dye drimarine red K&. The decomposition reaction was followed by ultraviolet spectroscop): and the distribution of ferric ions on the external surface of the fibre was examined by a scanning electron microscope. The mechanical properties of the fibre were found to have decreased on modification but were still sufficient for the manufacture and commercial exploitation of the fibre.
The course of chemical transformations and of conformational transitions in poly(acrylonitrile) solutions on addition of alkali are compared. The comparison of the changes in electronic structure with the abrupt decrease of intrinsic viscosity allows to correlate the coil‐globule transition with the initial stages of formation of cyclic structures. Most probably the observed irreversibility of the coil‐globule conformational transition is due only to intramacromolecular crosslinking, the scheme of which is presented.
It was found that creation of structured cells for metal particles can be regulated by varying the modification parameters and optimum functioning of catalytic systems can be ensured with them. Mechanisms of formation and the possible structure of variable-ligand Fe 3+ -containing complexes localized on the surface of the fibre support were investigated.A number of problems arise in creating fibrous catalysts with high activity, and the quality and area of the catalyst are dependent on solving these problems. They primarily concern the catalytic activity of the metal and the strength of its attachment to the fibre, the mechanical strength of the fibre itself, and the stability of the catalyst formed.All of these problems are related to selection of the conditions of modification of the initial polymer used as the fibrous support and the technology of attaching the metal to it. Copolymeric polyacrylonitrile (PAN) fibre is the almost irreplaceable initial material for fibrous catalysts [1][2][3][4][5]. This polymer, due to the presence of reactive nitrile groups, allows deliberate structural modification in the course of polymer-analog transformations [3] and thus makes it possible to obtain a polydentate ligand which can be used to coordinate the metal atom during subsequent transformations.Iron-containing fibrous catalysts are relatively universal [1,5,6]. The main process questions in formation of active sites of trivalent iron ions on PAN fibre have been solved. However, more detailed studies are required on formation of functional group complexing agents, realized by treating the initial fibre with an aqueous solution of a mixture of hydroxylamine hydrochloride and hydrazine hydrochloride followed by treatment in aqueous solutions of NaOH and FeCl 3 ⋅6H 2 O.The purpose of our studies was to search for parameters for creating a Fe 3+ -containing catalyst which would ensure the optimum (from a practical point of view) activity and stability of the catalyst while preserving acceptable strength of the PAN fibre.We conducted the studies of the structural transformations of polyacrylonitrile during modification on industrially manufactured PAN complex fibre made with the thiocyanate method from the ternary copolymer of acrylonitrile (92.3%), methyl acrylate (6.2%), and itaconic acid (1.5%) and modeled on PAN films.The ratio of the concentrations of hydrazine and hydroxylamine hydrochlorides (0.5-1), modifying solution pH (2-10), holding time (0.25-2 h), and treatment temperature (100-150°C) were varied in preliminary studies. The treatment temperature in the aqueous solution of NaOH was 95-100°C and the duration was 30-120 sec.We note that by varying the conditions of modification, these groups -ligands -can be contained in the constructed polymer support with different statistical weight. The strength of attachment of Fe 3+ and the stability of the catalyst are essentially a function of their ratio [5]. The optimum parameters for modification of PAN fibre that most completely satisfy the above requirements were sel...
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