Observations on single crystals of an isotactic polyolefin: Morphology and chain packing in poly-4-methyl-pentene-1

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Abstract
Single crystals of isotactic poly-4-methyl pentene-1 were prepared from solution. The crystals were mostly flat squares with more or leas regular shapes. They consisted of thin square layers forming spiral terraces centred on screw dislocations. The molecules were found to be perpendicular to these layers. The same polymer could also be obtained in the form of thin fibrils with the molecules perpendicular to the fibril direction. Both these habits require chain folding, further implications of which are discussed. The unit cell was determined and was found to be tetragonal with a= b= 18.66 Å and c = 13.80 Å containing four obains. The pecking of these chains closely approximates a two-dimensional rock-salt type arrangement with one chain surrounded by four nearest neighbours. It is shown that the helical chains can be in gear with this type of pecking engaging most perfectly if half and half are of opposite winding direction.