Hydrogen transfer, polymerization

Anionic polymerization of unsubstituted acrylamide, catalyzed by strong bases, does not yield typical vinyl polymers. Instead, the product is a 1,3-adduct, poly -alanine). Two alternate reaction paths were originally proposed  

Subsequently, studies of the rate of disappearance of acrylamide in dry sulfolane or pyridine with potassium-r-butoxide initiator led to the following proposed mechanism  

Cis and trans crotonamides can also polymerize by hydrogen transfer polymerization. Sodium r-butoxide in pyridine yields identical polymers from both isomers. Also, hydrogen transfer polymerization of acrylamide with optically active, basic catalysts yields optically active polymers. The reactions can be carried out in toluene, using optically active alcotxolates of amyl alcohol. The initiating ability of the metal ions is in the following order, Na Ba Ca Mg Al. Optically active polymethacrylamide forms with optically active barium and calcium alcoholates, but not with the other cations.In this reaction, however, the asymmetric synthesis takes place 

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Acrylamide readily undergoes polymerization by conventional free radical methods, ionizing radiation, ultrasonic waves, and ultraviolet radiation. The base-cata-lized hydrogen transfer polymerization of acrylamide yields poly-/3-alanine (Nylon 3) a water insoluble polymer that is soluble in certain hot organics. All current industrial production is believed to be by free radical polymerization. 

The catalytic coke produced by the activity of the catalyst and simultaneous reactions of cracking, isomerization, hydrogen transfer, polymerization, and condensation of complex aromatic structures of high molecular weight. This type of coke is more abundant and constitutes around 35-65% of the total deposited coke on the catalyst surface. This coke determines the shape of temperature programmed oxidation (TPO) spectra. The higher the catalyst activity the higher will be the production of such coke [1],... 

Numerous side reactions take place in the reaction zone, some of which are beneficial, but many of which are harmful (4). Some catalysts act to promote olefin isomerization to some extent as well as alkylation. In aviation and motor alkylate production, where more highly branched products are desirable, this isomerization reaction is of considerable benefit. This is especially true when the isomerization of butylene-1 to butylene-2 precedes the alkylation reaction. Harmful side reactions include hydrogen transfer and polymerization. The production of propane from propylene and of normal butane from butylene occurs by hydrogen transfer. Polymerization is very harmful because it not only produces the tar which spends the catalyst, but also reduces the yield of valuable products. 

We have applied this process to the direct polycondensation reaction of 0-alanine to obtain high molecular weight poly(0-alanine) which is difficult to prepare by the NCA method, and has been produced from alternative monomers, e.g. by the ringopening polymerization of 0-propiolactam 2or hydrogen-transfer polymerization of acrylamide 26). 

PREPARATIVE TECHNIQUES Hydrogen transfer polymerization Aciyl amide is polymerized in the presence of a strong base catalyst (e.g., f-BuOK). The polymerization occurs with hydrogen transfer, producing nylon 3. The polymerization is conducted using inactive solvents, such as toluene, pyridine, chlorobenzene, and o-dichlorobenzene from 80 to 200°C. ... 

Discuss and illustrate hydrogen transfer polymerization of acrylamide. 

Nylon 5 can be synthesized by intramolecular hydrogen transfer polymerization of acrylamide" (see chapter 3) ... 

Carbanions bei der anionischen Polymerization des Styrols, Adv. Polym. Sci. 9, I (1972). J. P. Kennedy and T. Otsu, Hydrogen transfer polymerization with anionic catalysts and the problems of anionic isomerization polymerization, J. Macromol. Sci. C (Rev. Macromol. Chem) 6, 237 (1972). 

Method of synthesis hydrogen transfer polymerization of acrylamide in the presence of anionic catalyst vinyl polymerization is side reaction, which can be prevented if tert-BuOK catalyst is finely dispersed in polymerization solvents Masamoto, J, Memoirs of Fukui University of Technology, 3,1,291, 2003. 

A special case is the hydrogen-transfer polymerization of acrylamide or methacrylamide leading to a polyamide. The synthesis of an optically active, "partially stereoregular" poly-methyl-3-alanine by polymerization of methacrylamide with an optically active basic catalyst has been reported (24). 

It is well known that acrylates and methacrylates, a,jS-unsaturated esters, readily undergo vinyl polymerization under radical and anionic conditions. Similar to esters, radical polymerization of a,/l-unsaturated amides, such as acrylamide, methacrylamide, and their /V-monoalkyl-substituted derivatives, proceed in vinyl addition modes, while anionic vinyl polymerization is often accompanied by hydrogen-transfer polymerization due to the highly acidic amide hydrogen of these monomers (Breslow et at, 1957 Kennedy and Otsu, 1972). As described above, a variety of A/,A-diaIkylacrylamides are capable of radical and anionic polymerization to afford vinyl polymers. 

Many studies have been carried out on the anionic polymerization of NIPAM using conventional organometallic catalysts. However, the acidic amide proton of NIPAM inhibited anionic polymerization, instead inducing hydrogen-transfer polymerization imder basic conditions, as shown in Scheme 2. The polymers obtained were insoluble in water and did not show LCST phase separation [14,15]. Recently, the polymerization of monomers in which this active hydrogen was protected by methoxymethyl or trialkylsi-lyl group 9,10 was examined and living anionic polymerization has become possible [60-62]. Ishizone et al. have prepared atactic PNIPAM with a narrow MWD via the anionic polymerization of N-methoxymethyl-NIPAM (9)... 

Breslow et al. reported that nylon-3 ( sometimes described as nylon 3 or poly- p -alanine) is obtained using hydrogen transfer polymerization of acrylamide in the presence of an anionic catalyst ... 

Various methods for the preparation of nylon-3 are reported in references and patents. Among the methods, the hydrogen transfer polymerization of acrylamide is very interesting from both the academic and industrial viewpoints. 

In the base catalyzed polymerization of acrylamide, the vinyl polymerization is reported by Nakayama et al. [7] to occur in addition to the hydrogen transfer polymerization process. 

If we hypothesize that the hydrogen transfer polymerization product of acrylamide is the polymeric structural material of nylon-3, then the following two points arise as potentially serious problems. 

Morgenstem and Berger also reported that a nearly pure nylon- 3 was produced using the hydrogen transfer polymerization of acrylamide [13]. They confirmed these results using an NMR method. 

Morgan, P. M., Condensation Polymers By Interfacial and Solution Methods , Interscience, New York, 1965. A review of the field of condensation, polymerization and hydrogen transfer polymerizations carried out below 100 °C Polym, Rev., vol. 10). 

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