Poly pendant vinyl groups

In analogous fashion, an uncapped polybutadienyllithium or poly-isoprenyllithium anion may attack an unreacted pendant vinyl group of another polymer chain (Reaction 4) to give the alkylbenzyl anion (III). 

The close structural similarities between poly chloroprene and the natural rubber molecule will be noted. However, whilst the methyl group activates the double bond in the polyisoprene molecule the chlorine atom has the opposite effect in polychloroprene. Thus the polymer is less liable to oxygen and ozone attack. At the same time the a-methylene groups are also deactivated so that accelerated sulphur vulcanisation is not a feasible proposition and alternative curing systems, often involving the pendant vinyl groups arising from 1,2-polymerisation modes, are necessary. 

The effect of chemical composition, and dose on a range of different poly(butadiene) samples was also examined by these authors. Similar results were obtained for cis- and trans-l,4-poly(butadiene), however, even larger G-values were measured for 1,2-poly(butadiene), presumably because of the higher reactivity of pendant vinyl groups compared with internal double bonds and the close proximity of side-chains allowing a zipping chain reaction. Among... 

Although KMnO treatment allowed the hydroxylation of about half of the pendant vinyl groups present in the PHA, the reaction performed with 9-borobicyclononane (a hydroboration-oxidation reaction) hydroxylated most of the vinyl groups (almost 100%) present in poly[(/ )-3-undecenoate] (Eroglu et al. 2005). 

Silicone PSAs are blends or reaction products of the combination of a poly-organosiloxane, such as poly(dimethyl siloxane) or its copolymers with diphenyl-siloxane or methylphenyl siloxane, with a polysiloxane resin, which is largely inorganic. Pendant vinyl groups may also be incorporated into silicone PSAs,... 

C-H from vinyl group as (CH2=CH-) C-H pendant vinyl group of the 1,2 unit for liquid carboxylated poly(acrylonitrile-co-butadiene) [or nitrile rubber (NBR)] C-H from vinyl-associated group... 

The effect of polymer composition on secondary reactions is easily seen in rubber mastication. The greater tendency for gelation and branching in styrene rubber is related to the radicals involved. The radicals from styrene rubber have a greater reactivity than allyl radicals [7] toward a-methylenic hydrogen atoms and double bonds. This behavior has been attributed previously to the pendant vinyl groups in certain synthetic rubbers [8,9]. Poly-chloroprene also forms a gel by addition of radicals to double bonds, whose activity is increased by the chlorine substituent [10]. 

The production of styrene-butadiene rubber emulsions is one case where poly-merizabon is deliberately stopped at a low conversion, typically 70-80 %, in order to Hmit the crosslinking reaction from the pendant vinyl groups in the butadiene units. With such large amounts of residual monomer, economics force the recovery and recycling of both butadiene and styrene. After the polymerization stage, residual butadiene is flashed off under vacuum, compressed, cooled and returned to the reactor feed, and styrene is steam stripped in a column stripper, condensed and also returned to the reactor. 

Fig. 4. Chemistry of poly(vinyl cinnamate) negative-acting resist. Initial light absorption by the photosensitizer is followed by energy transfer to produce a pendant cinnamate group in a triplet electronic state. This combines with a second cinnamate on another polymer chain, forming a polymer—polymer...

Poly(vinyl alcohol) (PVA) is a polymer of great interest because of its many desirable characteristics specifically for various pharmaceutical, biomedical, and separation applications. PVA has a relatively simple chemical structure with a pendant hydroxyl group (figure la). The monomer, vinyl alcohol, does not exist in a stable form, rearranging to its tautomer, acetaldehyde. Therefore, PVA is produced by the polymerization of vinyl acetate to poly(vinyl acetate) (PVAc) followed by the hydrolysis to PVA (figure 2). Once the hydrolysis reaction is not complete, there are PVA with different degrees of hydrolysis (figure lb). For practical purposes, PVA is always a co-polymer of vinyl alcohol and vinyl acetate [1]. 

Other halogenated resist systems include partially chlorinated, narrow dispersity poly (vinyl-toluene). The latter differs from the CMS resist above in that chlorine is substituted on the main chain as well as on the pendant methyl group (44). 

Electrochemical doping of insulating polymers has been attempted for polyacetylene, polypyrrole, poly-A/-vinyl carbazole and phthalocyaninato-poly-siloxane. Significantly, Shirota et al. [91] claim to have achieved the first synthesis of electrically conducting poly(vinyl ferrocene) by the method of electrochemical deposition (ECD) [91]. This is based on the insolubilization of doped polymers from a solution of neutral polymers. A typical procedure applied [91] for polyvinyl ferrocene is to dissolve the polymer in dichlorometh-ane and oxidize it anodically with Ag/Ag+ reference electrode under selective conditions. The modified polymer [91] (Fig. 28) is a partially oxidized mixed valence salt containing ferrocene and ferrocenium ion pendant groups with C104 as the counter anion. 

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