Summary: Novel well‐defined block copolymers composed of polystyrene, poly(2‐vinylpyridine), poly(ethylene oxide), or poly(tert‐butyl methacrylate) as the first block and poly(N,N‐dialkylacrylamide) (PDAlAAm) as the second block were synthesized by ligated anionic polymerization. The latter was carried out in tetrahydrofuran (THF) initiated by 1,1‐diphenyloligostyryllithium in the presence of ZnEt2 and LiCl. At first the role of the additives LiCl and ZnEt2 on the mode of the anionic homopolymerization of N,N‐dialkylacrylamide was investigated. Polymerization in the presence of ZnEt2 resulted in syndiotactic polymers with narrow molecular weight distribution only. In the presence of both additives, the reaction mixture became heterogeneous with a high degree of isotacticity of the polymers. Despite the fact that the polymerizations were performed in heterogeneous phase, the DAlAAm monomers were polymerized in a quantitative yield. The efficiency of the first block of active sites was always higher than 0.71. Preliminary studies using dynamic light scattering of aqueous hydrochloric acid solutions of poly[(2‐vinylpyridine)‐block‐(N,N‐diethylacrylamide)] block copolymers at different temperatures and at pH 2 showed that above 45 °C, micelle‐like aggregates were formed. The heating and cooling cycles were reversible but showed hysteresis, which was obviously due to the isotactic structure of the poly(N,N‐diethylacrylamide) block.Temperature dependence of the scattering intensity of various poly[(2‐vinylpyridine)‐block‐(N,N‐diethylacrylamide)] block copolymers.imageTemperature dependence of the scattering intensity of various poly[(2‐vinylpyridine)‐block‐(N,N‐diethylacrylamide)] block copolymers.

Electroless plating of niobium on a nickel surface is investigated in NaCl-K 2 NbF 7 halide melt containing 10-30 wt % K 2 NbF 7 in the presence of metallic niobium powder. At a temperature of 750°C , a nickel surface is covered by Nb-Ni coatings to a thickness of 20 μm, which include NbNi 3 and NbNi inter metallic compounds. They are characterized by low roughness and the lack of penetration defects. They pro tect nickel from corrosive dissolution in halide salt melts. The microhardness of the coatings is 8370 ± 350 MPa and does not change over the layer thickness within the measurement error.

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Acta Polymerica 39 (1988) Nr. 12 667 Structural specificity of the initiators for the anionic polymerization of acrylonitrile derived from allyl compounds of molybdenum and tungsten €3. L. ERUSSALIMSKY and L. A. FEDOROVA Academy of Sciences of the USSR, Institute for High Molecular Weight Compounds, Leningrad 199004/IJSSRThe interaction of molybdcnum and tungsten chlorides with ally1 magnesium chloride in the Et,O-THF solvent leads to the formation of (C,H,),Mt. zT1IF complexes, where M t is Mo or W and x is 1 or 2. Moderate heating of toluene solutions of these complexes results in the irreversible loss of THF. Tlic initial complexes and, particularly, t h e products of their interaction with 2,2'-dipyridyl induce a n effective low temperature polymerization of acrylonitrile. The corresponding allyl compounds free from t he THP ligands arc completely passive with respect to this monomer. The causc of this phenomenon is discussed on tlic basis of tlic lH-NMR spectra of tlic investigated active and passive agents. Strukturelle Besonderheiten der auf Allyluerbiindungen des Molybduns oder Wolfrarns basierenden Initiatoren fur die anivnisclie Polynierisat ion des AcrylnitrilsDie Wccliselwirkung von Molybtliinund ~~o l f r a n~c l i l o r i d e n mil Allylmagnesiumchlorid im Losungsmittel Et,O-THF fiihrt zur Bildung von Komplexen der Form (C,II,),Mt . zTHV, wo M t fur itlo bzw. W steht und x = 1 oder 2 ist. MaBige ErwHrmung der Toluenlosungeii dicser Komplcxc bcwirkt ciiie irreversible hbspaltung von THF. Die Ausgangskomplcxe und insbesonderc die Produkte ilirer Wccliselwirkung mit 2,2'-Dipyridyl initiiercn effektiv die Ticftemperaturpolymerisation des Acrylnitrils. Die entspreclicnden voii THF-Iiganden freien Allylvcrbindungen verhalten sich gegcniibcr diescm Monomer vollstiindig passiv. Dic IJrsache diesel. Erscheinung wird an Hand von 1H-NMR-Spektrcn der aktiven und passiven Species diskutiert. CmpyEmypnbie oco6ennocmu uicuyuanzopoc noau~epu3ayuu aqmaouumpuaa ua OCHOBQ aaambmix coedunenuii M O -su6dena u eoab$pa&a B3aHMOAefiCTBHe XJIOPMROB ~o n a 6~e r r a H BOJILapaMa C aJIJIMJIMaI'HMfiXJIOpHAOM B CMeIUaHHOM paCTBOpMTeJIe AM-3THJIOBbTfi B@MP-TI'@ IIpHBORAT K 06pa30BatI€TIO KOMIIJIeKCOB (C,&)4Mt -ZTHF, rne Mt-MO MmEf W M J: -1 MJIH 2. YMepeHHbIB IIpOrpeB TOJIyOJILHbIX PaCTBOpOB 3TMX KOMIIJIeKCOB BLI3bIRaeT He06paTMMOe OTIqeIIneHHe T r @ . BCXOAHbIe KOMIIJIeKCbI M B o c o 6 e a~o c~~ IIpOAyKTLI MX B3aMMOgefiCTBMR C 2,2'-gMIIHpHgHJIOM FIBJIRKITCFI 3$@KTHB-HbIMM HHHqHaTOPaMH HM3KOTeMIIepaTypHOfi IIOJIHMepM3a~MM aKpMJIOHMTpMJIa. Te ECe aJIJIMJIbHbIe CO€!gHHeHMR, CBO-60gHbIe OT Tr@-JIHraHROB, MHePTHbI IIO OTHOLUeHMKI K 3TOMy MOHOMepy. n P H q M H b 1 06HaPyW€!HHOI'O FIBJIeHMR o6cyx-AeHbI Ha OCHOBe IIOJIyYeIIHbIX CIIeKTpOn 'H RMP aKTMBHLIX PI UaCCHBHLIX (POPM YIEa3aHHbIX COe~HHeHMB.