Comparison of mean field theory and 1H-NMR transversal relaxation of poly(dimethylsiloxane) networks.

D. A. VEGA; M. A. VILLAR; E. M. VALLES; C. A. STEREN; G. A. MONTI

MACROMOLECULES

American Chemical Society

Año: 2001 vol. 34 p. 283 - 283

0024-9297

p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: justify; mso-layout-grid-align: none">We have estimated the mass fraction of elastic and pendant chains of model poly-(dimethylsiloxane) (PDMS) networks using transverse proton relaxation in nuclear magnetic resonance (1H NMR). These experiments were compared with theoretical estimations of the mass fraction of pendant chains predicted by mean-field calculations (MFC). A recursive approach, originally postulated by Miller and Macosko and extended by the authors to obtain information on several molecular parameters related to the molecular structure of the pendant chains, was employed for the theoretical calculations. A preliminary inspection of the results showed that proton relaxation measurements underestimate the mass fraction of pendant material. We speculate that trapped entanglements, in which long pendant chains are involved, may act as temporary cross-linking points in the time scale of the 1H NMR experiments. In this