Polymerization of aldehydes

The products consist exclusively of poly( 1 -olefin) units. Polymerizations of 2,3 and 4 octenes with TiCl3/Al(C2H5)3 at 80°C for instance, result in the same high molecular weight homopolymer, poly (1-octene) [319], 

Aldehyde polymers were probably known well over 100 years ago [322-324]. In spite of that, polyoxymethylene is the only product from aldehyde polymerization that is produced in large commercial quantities. Formaldehyde polymerizes by both cationic and anionic mechanisms. An oxonium ion acts as the propagating species in cationic polymerizations [322, 323]. In the anionic ones, the propagation is via an alkoxide ion. 

As stated above, the propagation reaction continues after polymer precipitation. That is due to the fact that the precipitated macromolecules are highly swollen by the monomers. This was shown in polymerizations of n-butyraldehyde in heptane [326]. The physical state of the polymers and the surface areas of their crystalline domains, therefore, influence the paths of the polymerizations. 

The solubility of the initiators in the solvents can affect strongly the molecular weights of the resultant products and their bulk densities [323]. The whole reaction can even be affected by small changes in the chemical structures of the initiators or by changes in the counterions [323]. Chain transferring is the most important termination step in aldehyde polymerizations. 

The cationic polymerizations of formaldehyde can be carried out in anhydrous media with typical cationic initiators. Initiation takes place by an electrophilic action of the initiating species to the carbonyl oxygens. This results in formations of oxonium ions  

The oxonium ions may react as oxygen-carbon cations. The propagation steps consist of attacks by the electrophilic carbon atoms upon the carbonyl oxygens of the highly polar formaldehyde molecules  

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In the author s laboratories the polymerization of aldehydes, ketones, and alcohols by liquid hydrogen fluoride has been repeatedly noted. Acetaldehyde polymerizes and acetone forms polymeric substances on standing for a period of time in solution in hydrogen fluoride. If the solution is separated shortly after mixing, the acetone may be recovered. The same is true of tertiary alcohols. The peculiar action of tertiary chlorides (Simons et al., 35) probably results at least in part from polymerization. The products obtained most likely come from destruction of the polymers in the process of distillation. Benzaldehyde forms a shellac like resin when treated with hydrogen fluoride. A rather interesting polymerization reaction occurs upon treating aralkyl ketones with... 

Furukawa, J. andT. Saegusa, Polymerization of Aldehydes and Oxides, Wiley-Interscience, New York, 1963. Gandini, A. and H. Cheradame, Adv. Polym. Sci., 34/35, 1 (1980). 

Furukawa, J. and T. Saegusa, Polymerization of Aldehydes and Oxides, Wiley-Interscience, New York, 1963. 

Porri,L. and A. Giarruso, Conjugated Diene Polymerization, Chap. 5 in Comprehensive Polymer Science, Vol. 4, G. C. Eastmond, A. Ledwith, S. Russo, and P. Sigwalt, eds., Pergamon Press, Oxford, 1989. Prabhu, P, A. Shindler, M. H. Theil, and R. D. Gilbert, J. Polym. Sci. Polym. Lett. Ed., 18, 389 (1980). Pregaglia, G. F. andM. Binaghi, Ionic Polymerization of Aldehydes, Ketones, andKetenes, Chap. 3 in The Stereochemistry of Macromolecules, Vol. 2, Marcel Dekker, New York, 1967. 

Boron phosphate is used as an acid catalyst for dehydration of alcohols to olefins isomemization of olefins nitration of aromatic hydrocarbons polymerization of aldehydes and other synthetic reactions. It also is used as a flux in silica-based porcelain and ceramics special glasses and acid cleaners. 

Polymerization of aldehyde by typical cationic catalysts such as sulfuric acid and titanium tetrachloride is considered to reflect the steric factor. Acetaldehyde gave an isotactic-rich amorphous polymer whereas propionaldehyde and higher aldehydes gave isotactic crystalline ones. The yield of polymer and the stereospecificity of polymerization increased with the increase in the bulkiness of the alkyl group of the aldehyde (Table 7). 

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