Addition polymers hydrogen halides

Their physieal properties are essentially those of the alkanes. It is the unsaturated linkages that dominate the ehemistry and the main reaetion is one of addition (e.g. hydrogen, halogen, and hydrogen halides) aeross the double bond to produee saturated eompounds. This reaetivity is utilized in the manufaeture of long-ehain polymers, e.g. polyethylene and polypropylene. 

Polymer Modification. The introduction of functional groups on polysilanes using the alkali metal coupling of dichlorosilanes is extremely difficult to achieve. Some polymers and copolymers with 2-(3-cyclohexenyl)ethyl substituents on silicon have been made, and these undergo hydrogen halide addition to the carbon—carbon double bond (94,98). 

The halogen functional polymer can react with a thiol by nucleophilic reaction, resulting in a polymeric thioether and a hydrogen halide. The latter is trapped by a basic additive, preventing a reverse reaction. Snijder et al. [135] used this technique to modify the end group of poly( -butyl acrylate) into a hydroxy-functional polymer. With 2-mercaptoethanol, the yield of functionalization was higher with the addition of 1,4-diazabicyclo[2,2,2]octane (DABCO) to the reaction mixture. The addition of DABCO allows for the formation of a sulfide anion, which is a stronger nucleophile. They studied this... 

Among the classical (summarized in [11]) reactions of cyanoacetylenes (salt and n-complex formation, nucleophilic addition of, inter alia, amines and alcohols, Diels-Alder additions with 2 (see Section 2.22.2), addition of halogens and hydrogen halides, etc.) their polymerization might deserve a second look since the products formed - polyacetylenes - have attracted much attention during the last two decades. Thus 1, several of its derivatives, and 2 have been polymerized with anionic initiators (triethylamine, sodiiun cyanide, butyllithium) to give black, low-molecular-weight polymers claimed to have structures like 33 [38-40], which is obtained from 2 by treatment with butyllithium. 

In contrast, the reaction of decamethylsilicocene with protic substrates follows three different pathways (Schemes 2 and 3) [6]. Oxidative addition is observed with the hydrogen halides HX, and the protonated silicocene is formed in the reaction with two equivalents of trifluorosulfonic acid. In the reaction with HBF4, the wanted MesCsSr cation might be present together with the BF4" anion as a highly reactive intermediate which easily eliminates BF3 under formation of the polymer (Me5C5SiF) in a final step. 

Vapors of two different monomers (A and B) together with a hot inert gas are fed to a mixer (such as a jet mixer, a simple short tube, or a combination of both) and then to the reactor inlet. Additional inert gas can be introduced as needed. The reactor effluent stream consisting of some polymer, possible oligomers, and by-product acid, is conducted through a quench chamber where the stream is cooled by a flow of relatively cold inert gas. The cooled stream is then led through a separator such as combination of a cyclone separator and filters to remove solid material. The filtered stream is then passed through a water scrubber to remove hydrogen halide and vented to the atmosphere or recycled. 

It is also believed that the large heat capacity of hydrogen halides and their dilution of the flame results in a decrease in the mass concentration of combustible gases and the temperature of the flame. The physical effect of halogen halides is comparable to that of inert gases, CO2, and water. There is no contradiction between the radical trap theory and the physical theory apparently, they complement each other. The contribution of each mechanism depends on the temperature of decomposition of the flame retardant additive and the polymer. 

In adding hydrogen halides and halogens to the >C=C< double bond of 1,2-PB, the functionalization degree of the polymer is mostly determined by the reactivity of the electrophilic agent. Relatively low degree of polydiene hydrochlorination (10-15%) at interaction of HCl and syndiotactic 1,2-PB [16, 39, 40] is caused by insufficient reactivity of hydrogen chloride in the electrophilic addition reaction by the double bond (Table 3.2). Due to this, more electron-saturated >C=C< bonds in 1,4 units of butadiene polymerization are subjected to modification. 

The metal halide thus functions in similar manner to the proton and may be considered to be an acidic catalyst (cf. Luder and Zuffanti, 19). The catalyst-olefin complex differs in one significant respect from the product formed by the addition of the proton (or the corresponding acid) to the olefin the halide catalyst is a neutral but electronically deficient molecule and combines with the pi electrons of the double bond to form a coordinate bond between the carbon atom and the aluminum or boron. On the other hand, the addition of the positive proton to the double bond results in the formation of a true (covalent) link between carbon and hydrogen. In other words, the complex, while it contains an electron-deficient (hence, positive) carbon atom, is in itself electronically neutral the product of the addition of a proton to the alkene contains a similar carbon atom but is itself electrically positive. It has been suggested (Whitmore and Meunier, 20) that this difference is related to the fact that metal halide catalysts tend to yield much higher polymers than do the acid (proton) catalysts. 

The observation that the metal carbene complex, (CO)5W = C(Ph)2 [22], catalyzed the polymerization of cyclic olefins to ring opened polymers containing the diphenylmethylene unit of the catalyst provided additional evidence that carbenes were involved in the catalytic cycle. The formation of the initiating metal carbenes in the classic systems that consist of transition metal halides and alkylating agents was proposed to involve metal alkylation followed by oc-hydrogen loss, Eq. (6). Methane and propene were detected in the early stages of these reactions [23]. 

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