Changes of proton-enhanced, magic-angle-spinning 13C-NMR dynamic parameters during cure of tetra(ethylene glycol)dimethacrylate

P. E M Allen, G. P. Simon, D. R G Williams, E. H. Williams

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Dynamic NMR and mechanical properties TSL, T1p(C) at 60 kHz, Tg at ≈1 Hz and its half width, log decrement (Δmax) and compression modulus (E) were measured for poly[tetra(ethylene glycol)dimethacrylate] (PTEGDMA) at different extents of cure. The β, γ and water-induced transitions were also noted. The spin-lock, cross-polarization time-constant, TSL, declined to its limiting value before the vitrification point. T1p(C), relaxation time in the rotating 13C field, increased sharply at or just after vitrification. The change is greatest at quaternary C, decreasing through CH2, CH2O and CH3, being barely significant in the latter. The observed changes affirm that T1p(C) is sufficiently influenced by spin-lattice relaxations to provide a monitor of the damping of mid kHz components during cure. The small change observed at CH3 shows that this group is not the origin of changes in relaxation rates at other groups. Correlations with E and Tg show the importance of mid kHz components of group motion to the cooperative motions determining the response to macroscopic strain at lower frequencies. MAS 13C-NMR showed that PTEGDMA contains residual unsaturation at limiting cure and that two types, constrained and unconstrained, can be distinguished.

Original languageEnglish
Pages (from-to)549-557
Number of pages9
JournalEuropean Polymer Journal
Issue number7
Publication statusPublished - 1 Jan 1986
Externally publishedYes

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