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Orientation studies in polyacrylonitrile films uniaxially drawn in the solid state
Author(s) -
Bashir Zahir,
Tipping Alison R.,
Church Stephen P.
Publication year - 1994
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.1994.210330102
Subject(s) - polyacrylonitrile , materials science , molecule , dichroism , polymer , context (archaeology) , crystallography , infrared spectroscopy , solvent , chemistry , optics , organic chemistry , composite material , physics , paleontology , biology
Polyacrylonitrile (PAN) films were made by casting a dimethyl sulphoxide (DMSO) solution. After drying, the films were uniaxially drawn by an essentially solid‐state drawing procedure. Using polarised‐infrared (IR) spectroscopy, the dichroism of the nitrile‐stretching vibration was monitored as a function of draw ratio. The dichroism results were converted to plots of chain‐orientation factor versus draw ratio. For this, α, the transition‐moment angle of the vibration, has to be known. Though a value of 68–73° has been suggested in the literature, for the present samples α cannot be 70° or less, and 73° is the most appropriate. The meaning and nature of the transition‐moment angle in the context of a flexible‐chain polymer molecule is discussed. The IR spectrum also showed dichroism in the SO stretch and the CH 3 rocking vibrations from the (residual) DMSO present in the film, indicating that the solvent molecules were also orientated. It is proposed that this occurred due to dipolar interactions between the SO and the CN groups, which led to solvent molecules being bound to the polymer chains. X‐ray diffraction studies indicated ‘lateral‐ordering’ consisting of hexagonally packed, rod‐like chains with no c ‐axis order. The diffraction patterns obtained here were the ‘standard’ ones for PAN, in contrast to those observed previously in solvent‐containing PAN gels.