Polymeric materials, viii

Since the appearance of the redox [ii, iii] and conducting [iv] polymer-modified electrodes much effort has been made concerning the development and characterization of electrodes modified with electroactive polymeric materials, as well as their application in various fields such as -> sensors, actuators, ion exchangers, -> batteries, -> supercapacitors, -> photovoltaic devices, -> corrosion protection, -> electrocatalysis, -> elec-trochromic devices, electroluminescent devices (- electroluminescence) [i, v-viii]. See also -> electrochemically stimulated conformational relaxation (ESCR) model, and -> surface-modified electrodes. 

With thiyl radicals, intramolecular addition to triple bonds has been observed by Dupuy using high-dilution conditions.In addition to dimeric and polymeric material, cyclized products, e.g., 159, 160, 161, are obtained in yields up to 86% (R = Ph) by photolysis of the thiol 158 (Scheme 72). The cyclization is not selective, as in the case of ethylenic thiols (Section VIII.4.A), products 159 being the major ones when R = H and 160 when R = alkyl, phenyl. The origin of compounds 161 is not clear in some cases it has been demonstrated that compounds 160 isomerize on photolysis into 161, but prior isomerization of the thiols 158 must be considered as a possibility in other cases. ... 

A vapor-phase reaction between butadiene and diborane at 100 C with hydrogen as a diluent produces, in addition to polymeric materials, an appreciable yield of the cyclic 1,2-tetramethylenediborane (VIII) and a smaller amount of l,2-(r-methyltrimethylene)diborane (IX) (95). 

Monomers VII and VIII were designed to provide highly chelating structures for metal ions such as nickel and cobalt. Previous efforts to obtain significant quantities of polymers from similar monomers, such as XIV (2) and its acetyl derivative (16), were unsuccessful. However, the two new compounds polymerized to give a reasonable yield of polypyrrolidine polymer. The 13C NMR spectra of these materials showed a... 

M. R. Buchmeiser, Homogenous metathesis polymerization by well-defined group VI and group VIII transition metal alkylidenes fundamentals and applications in the preparation of advanced materials, Chem. Rev., 100 (2000) 1565-1604. 

Polymers (XLIII-XLV) containing vicinal mercaptan groups were also synthesized from polyfvinyl alcohol) (56,57). The bromoacetal was elaborated with sodium allyloxide, and the allyl ether formed was converted to a dithiol by addition of bromine followed by substitution with KSH. The incorporation of free mercaptan groups was low ( 25 %) (Scheme VIII). These materials are polymeric analogs of 2,3-dithiol-1-propanol (BAL) and would probably be very efficient heavy metal scavengers. 

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