Portal de Periódicos da CAPES

Comments on a paper by Axelson and Mandelkern concerning 13 C NMR spectra of polymers

1981; Wiley; Volume: 19; Issue: 1 Linguagem: Inglês

10.1002/pol.1981.180190102

1542-9385

Raymond F. Boyer, Jerry P. Heeschen, J. K. Gillham,

Polymer crystallization and properties

Abstract It is shown that the 13 C NMR spectral collapse temperatures T c reported by Axelson and Mandelkern tend to give a constant ratio of T c / T g averaging 1.21 ± 0.05 and independent of T g or of polymer structure. It is further shown that T c is not a high‐frequency value for T g because this would require T c / T g to decline with increasing T g . T c / T g agrees in numerical value with T u / T g , where T ll is the liquid‐liquid transition lying above T g . Direct comparison of T c and T u for four polymers PIB, PnBA, atactic PP, and isotactic PMMA shows very close agreement. The various results suggest, but do not prove, that T c from 13 C NMR spectroscopy may be a new, direct measure for T ll . A measured T c of 233K for linear PE is compatible with a T g near 195 K (233/195 = 1.19), whereas a T g of 148 K gives the ratio 233/148 = 1.57, which is outside any value shown in tabulated form.