Melt structure of crystalline polymers as studied by means of magnetic orientation

In a series of papers, we have reported that crystalline polymers including pory(ethylene-2,6-naphthalate) (PEN), isotactic polystyrene (iPS), and poly(ethylene terephthalate) (PET) undergo magnetic orientation in the induction period of isothermal crystallization from the melt However, we have recently found that isotactic polypropylene (iPP) undergoes magnetic orientation in the molten state. Also it was found that PET aligns in the magnetic field even in its molten state. These findings indicate that the ordered structure responsible for the magnetic orientation could be traced back to the melt before the induction period. In this study, the ordered structure existing in the melt is studied by means of magnetic orientation and the crystallization process. A hypothesis describing the structure and formation mechanism of the ordered structure is presented.