Atactic polyacetaldehyde

We started our investigation in 1957 and worked out initially reliable methods for preparing amorphous atactic polyacetaldehyde (16). Soon thereafter we discovered crystalline isotactic poly aldehydes (49, 51). Detailed studies of polymerization conditions, polymer structures, and stabilization of the polymers followed. 

Formation of pure isotactic polyacetaldehyde was reported. It forms in small quantities in the presence of an atactic polymer obtained with crystalline BF therate. 

As mentioned earlier, polymers of formaldehyde are described in the next section. Polymers of higher aliphatic aldehydes and ketones have been extensively investigated but, in general, they do not have the stability necessary for commercial development. For example, acetaldehyde may be polymerized using organometallic initiators at low temperatures, e.g., triethylaluminium at —78 C in this case crystalline isotactic polymer is obtained. Also, the polymerization of acetaldehyde may be effected with cationic initiators at low temperatures (e.g., aluminium chloride at —65°C) or with metal oxides at low temperatures (e.g., alumina at —70°C) in these cases amorphous atactic polymer is obtained. The tacticity of polyacetaldehyde arises because the polymer comprises structural units which contain an asymmetric carbon atom ... 

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