Molecular miscible blend of poly(2-cyano-1,4-phenyleneterephthalamide) and polyvinylpyrrolidone characterized by two-dimensional correlation FTIR and solid state <SUP>13</SUP>C NMR spectroscopy

초록

Miscibility of blends of poly(2-cyano-1,4-phenyleneterephthalamide/polyvinylpyrrolidone) (CN-PPTA/PVP) was investigated by dilute Solution viscometry, two-dimensional (2D) correlation Fourier transformed infrared (FTIR) spectroscopy and solid state C-13 NMR spectroscopy. It was shown that a large proportion of the PVP, the water-soluble component, could not be removed from CN-PPTA by extraction with water, and even with boiling water for blend films, Suggesting that the flexible aliphatic PVP chain forms a blend with the rigid aromatic CN-PPTA chain through strong intermolecular interaction making it too difficult to dissolve even in boiling water. Viscometry oil a polymer mixture Of dilute Solution showed that [eta](exp) exhibited larger value than [eta](theo) all mixtures used in this experiment, Suggesting occurrence of a strong attractive interaction between the two polymers. 2D correlation FTIR spectroscopy revealed that the carbonyl absorption band of PVP at 1675 cm(-1) shifted to a new low frequency absorption band at 1640 cm(-1) with a change of 35 cm(-1), suggesting strong hydrogen bonding with NH (amide 11) proton of CN-PPTA. Another new absorption band at 1685 cm(-1) was due to the carbonyl absorption band of CN-PPTA shifting to a higher frequency than that at 1662 cm(-1), indicating that some of the carbonyl groups in the CN-PPTA components of the blends were ill a free state or in a non-hydrogen bonded state as a consequence of the participation of NH proton of CN-PPTA in hydrogen bonding, resulting in the absorption bands of NH bend deformation of CN-PPTA at 1542 and 1313 cm(-1) being shifted to higher wavenumber of 1556 and 1324 cm(-1), respectively. Solid state C-13 NMR spectroscopy revealed a chemical shift for C=O of the PVP component in the blend fiber changing down-field (shift to left) at 177.346 ppm with a difference of 1.812 ppm; this was due to a lower electron density around the carbon atom of C=O of lactam via hydrogen bonding with NH proton of amide in the CN-PPTA component, Suggesting that a homogeneous blend of the CN-PPTA and PVP was produced oil a molecular scale via hydrogen bonding. (C) 2008 Elsevier B.V. All rights reserved.

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