Solid State NMR of Nylon 7
Abstract
Nylon 7 obtained from Du Pont was treated to give samples with very different histories. As-obtained flakes were melt-pressed above the T(m) into films, quenched in ice-water or annealed at 220 deg C. Polymer flakes were dissolved in 2,2,2-trifluoroethanol:methylene chloride to give a 3 w.v % dope which was cast onto glass or precipitated into diethyl ether. A sample of the cast film was annealed at 160 deg C. Differences were observed in both the 13C and 15N solid state NMR spectra of the samples. Most strikingly, the 13C spectrum of the sample cast onto glass showed multiple peaks consistent with the presence of both alpha and gamma crystallites, while the DSC thermogram showed a single melting endotherm. Annealing this film at 160 deg C converted the gamma crystallites into alpha crystallites without sample melting or degradation. 13 C T(1) values increase with annealing. That is, the annealed sample had the longest T(1)s followed by the cast-annealed film cast film, quenched film and precipitated sample. The 12C chemical shift of the carbon immediately adjacent to the nitrogen atom consistently move downfield in the same order as the T(1) increase. Crystallite size and perfection can account for these trends. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 29, 1992
- Accession Number
- ADA251719
Entities
People
- C. G. Johnson
- Lon J. Mathias
Organizations
- University of Southern Mississippi