Polyacetaldehyde

Polyacetaldehyde, a rubbery polymer with an acetal poly(oxymethylene) structure, is an unstable solid that depolymerizes to acetaldehyde 

Polyacetaldehyde is formed by cationic polymerization using boron trifluoride (BF3) in liquid ethylene (CH2=CH2). At temperatures below -75°C using anionic initiators, such as metal alkyls in a hydrocarbon solvent, a crystalline isotactic polymer is obtained. Molecular weights of the products fall into the range 800,000 to 3,000,000. 

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Polyacetaldehyde, a mbbery polymer with an acetal stmcture, was first discovered in 1936 (49,50). More recentiy, it has been shown that a white, nontacky, and highly elastic polymer can be formed by cationic polymerization using BF in Hquid ethylene (51). At temperatures below —75° C using anionic initiators, such as metal alkyls in a hydrocarbon solvent, a crystalline, isotactic polymer is obtained (52). This polymer also has an acetal [poly(oxymethylene)] stmcture. Molecular weights in the range of 800,000—3,000,000 have been reported. Polyacetaldehyde is unstable and depolymerizes in a few days to acetaldehyde. The methods used for stabilizing polyformaldehyde have not been successful with poly acetaldehyde and the polymer has no practical significance (see Acetalresins). 

Acetaldehyde is an intermediate for many chemicals such as acetic acid, n-butanol, pentaerithritol, and polyacetaldehyde. 

Poly(4-phenoxybenzoyl-1,4-phenylene) (PPBP), sulfonated, 23 718 Polyacetal, antioxidant applications, 3 121 Polyacetaldehyde, 1 103 Polyacetal fiber, 13 392 Polyacetylene, 7 514-515 26 953 conduction in, 7 527 22 208 molecular structure of, 22 211 optical band gap, 7 529t Peierls distortion in, 22 203, 208 room temperature conductivity, 7 532 synthesis of, 22 213... 

Constitutional (formerly structural) isomerism is encountered when polymers have the same overall chemical composition (i.e., same molecular formula) but differ in connectivity— the order in which the atoms are connected to each other. Polyacetaldehyde, poly(ethylene oxide), and poly(vinyl alcohol) are constitutional isomers. The first two polymers are... 

Polyacetaldehyde Poly(ethylene oxide) Poly(vinyl alcohol)... 

Polyacetaldehyde [IUPAC Poly(oxy[methylmethylene])], like the systems described previously, contains stereocenters that are achirotopic. Both the isotactic and syndiotactic polymers are achiral and do not possess optical activity. 

Amorphous polyacetaldehyde was obtained for the first time in 1936 by Travers (9) and Letort (10) independently by cooling acetaldehyde vapor to liquid air temperature in high vacuum. The polyacetal structure of this polymer was suggested by Staudinger (//). This poly-... 

Poly[o-phthalaldehyde] was reported to be soluble in organic solvents, in contrast with isotactic polyacetaldehyde. This solubility behavior afforded us a good chance to test the stereoregulating capacity of our catalyst in the polymerization process. 

Mathis, P. Effect co-catalytique des traces d eau dans la formation du polyacetaldehyde. Compt Rend. 241, 651 (1955). 

Extreme d un rapport stoechiometrique simple entre initiateur et cocatalyseur dans leur efficacite a former le polyacetaldehyde. Compt. Rend. 242,371 (1956). 

Natta,G Mazzanti,G, Corradini, P, Chini,P, Bassi.I.W. Linear isotactic polymers from aliphatic aldehydes. 1. Polyacetaldehyde. IL Polymers of higher aliphatic aldehydes. Atti Accad. Nazi. Lincei, Classe Set Fis. Mat. Nat. 28,18 (1960). 

Aoyagi,T., Araki,T., Tani,H. Organoaluminum catalysts for polymerization reaction. Synthesis of isotactic polyacetaldehyde by AlR3-alkai metal hydroxide catalysts in situ. J. Polymer Sci. A-l, 10,2325 (1972). 

The polymers had molecular weights of several million, but were completely soluble in water and some organic solvents such as chloroform, acetonitrile, ethylene dichloride and acetic acid. The water solubility results apparently from strong hydrogen bonding between solvent and ether groups but appears to be peculiar to the polyethylene oxides for it is not observed with polyformaldehyde, polyacetaldehyde or poly-... 

Another polymer which is easily peroxidized is polyacetaldehyde it has a polyacetalic structure and is characterized by the presence of some side hydroperoxide groups (1 to 4°/00) due to traces of peracetic acid when the polymer is prepared. The homolytic decomposition of these peroxide groups yields macroradicals to which methyl methacrylate could be grafted [73, 74). 

Delzenne. G et G. Smets Stabilite et degradation du polyacetaldehyde. I. Degradation homolytique du polyacetaldehyde. Makromol. Chem. 18/19, 82 (1956). 

The intramolecular interaction energy was calculated for five isotactic polymers, namely, isotactic polypropylene, poly(U-methyl-l-pentene), poly(3-methyl-1-butene), polyacetaldehyde, and poly(methyl methacrylate) (23). The molecular structures of the first four polymers have already been determined by x-ray analyses as (3/1) (2k), (7/2) (18,25.,26), (U/l) (21), and (U/l) helices (28), respectively. Here (7/2) means seven monomeric units turn twice in the fiber identity period. For isotactic poly(methyl methacrylate) (29), a (5/l) helix was considered reasonable at the time of the energy calculation in 1970, before the discovering of... 

Polypropylene and polyacetaldehyde are the simplest of the above polymers, having only two internal rotation angles, x and Tg, in the main chain. Figure 1 shows the potencial energy contour map for polyacetaldehyde. The crosses indicate the potential minima, and the closed circles the x-ray structure determined by Natta et al. (28). The two minima correspond to the right- and left-hand helices. 

Furukawa et al. [274] and Natta cl al. [275,276] succeeded independently in the preparation of crystalline polyacetaldehyde by using some organometallic compounds, such as diethylzinc or triethylaluminium, for the low-temperature polymerisation of acetaldehyde. Metal alkyls and metal alkoxides, e.g. aluminium isopropoxide, zinc ethoxide or ethyl orthotitanate, have also polymerised other aldehydes such as propionaldehyde and trichloroacetaldehyde to give crystalline polymers (Table 9.3) [270,275,277], A highly crystalline isotactic polymer has been obtained from the polymerisation of w-butyraldehyde with triethylaluminium or titanium tetrachloride-triethylaluminium (1 3) catalysts. Combinations of metal alkyl, e.g. diethylzinc, with water [278] or amine [279] appeared to give very efficient catalysts for aldehyde polymerisations. 

A similar failure of the Onsager model has been reported for polyacetaldehyde by Williams 72), and in epoxy resins by Sheppard73). Williams was able to analyze the polyacetaldehyde data in terms of a temperature dependent correlation between neighboring dipoles based on a conformational model of the polymer chain, and Sheppard has noted 35) that qualitatively similar conformational issues should apply to the epoxide and hydroxyl groups in the epoxy. 

Poly(tetramethylene oxide) Poly(ethylene formal) Poly(tetramethylene formal) Polyacetaldehyde Poly(propylene oxide)... 

By 1951 (29) it had been concluded that polyacetaldehyde is an amorphous polyacetal of very high molecular weight. The polymerization of acetaldehyde is initiated by free radicals assisted by the crystallization of the monomer (crystallization polymerization). 

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