Journal
JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS
Volume 48, Issue 10, Pages 1009-1015Publisher
WILEY
DOI: 10.1002/polb.21989
Keywords
amorphous; amorphous polymers; C-13 CP/MAS rotor-synchronized NMR; diamagnetism; macromolecular order; magnetic levitation; NMR; orientation
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Funding
- Ministerio de Sanidad y Consumo, Institut de Salud Carlos III [FIS PI05/2087, PI08/1677]
- Consejo Superior de Investigaciones Cientificas
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Molecular order in an amorphous polymer with anisotropic magnetic susceptibility is altered by applying external magnetic fields. Disks of atactic polystyrene (a-PS) are prepared by solvent casting outside or inside a magnet. The effect of the magnetic field on the polymer samples is investigated by magnetic levitation and solid state NMR spectroscopy. Magnetic levitation of the a-PS disks shows that the orientation of disk symmetry axis with respect to the magnetic field gradient depends on the magnitude and direction of the applied field during casting. Similarly, carbon-13 two-dimensional cross-polarization/magic angle spinning rotor-synchronized NMR measurements in these samples show modulation patterns of the spinning side bands only on disks prepared in the presence of a magnetic field. These findings suggest that macromolecular order could be induced in a fluid or fluid-solid phase transition with cooperative segmental motions reorienting the diamagnetic susceptibility tensor to minimize the magnetic contribution to free energy of the sample. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1009-1015, 2010
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