Polyethylene oxide crystallisation

Other polymers which have been subjected to a study of crystallisation kinetics include amorphous cellulose [45], PE and chlorinated polyethylene [46-48], aliphatic polyesters [49], Nylon 8 [50], Nylon 6.6 and 6.10 [51] and perfluorocyclobutyl networks [52], polyethylene oxide-PS star polymers [53] and poly(e-caprolactone) [54]. 

Branching can to some extent reduce the ability to crystallise. The frequent, but irregular, presence of side groups will interfere with the ability to pack. Branched polyethylenes, such as are made by high-pressure processes, are less crystalline and of lower density than less branched structures prepared using metal oxide catalysts. In extreme cases crystallisation could be almost completely inhibited. (Crystallisation in high-pressure polyethylenes is restricted more by the frequent short branches rather than by the occasional long branch.)... 

Membrane formation is generally a fast process and only polymers that are capable of crystallising rapidly fe.g.polyethylene, polypropylene, aliphatic polyamides) will exhibit an appreciable amount of crystallinity. Other semi-ciystalline polymers contain a low to veiy low crystalline content after membrane formation. For example, PPO (2, dimethylphenylene oxide) shows a broad melting endotherm at 245 C[24]. Ultrafiltration membranes derived from this polymer, prepared by phase inversion, hardly contain any crystalline material indicating that membrane formation was too fast to allow crystallisation. 

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