Double quantum NMR applied to polymer networks with low concentrations of pendant chains

R. H. ACOSTA; G.A. MONTI; D. A. VEGA; M.A. VILLAR; E.M. VALLÉS

Mainz, Alemania

Congreso; 27th Annual Meeting of the Magnetic Resonance Discussion Group of the Society of German Chemists; 2005

Asociación Alemana de Química

Mechanical properties of a polymeric materials can be directly related to its structure. In the particular case of polymer networks, chemical or physical cross-linking points give distinctive characteristics to these materials such as high elongation, better thermal stability and insolubility. Model silicone networks have been extensively studied in order to explain the influence of molecular structure on mechanical properties. Free chains and pendant chains are the more common defects in real networks; in particular, pendant chains have a strong influence on the viscoelastic properties of these networks, changing considerably the spectrum of relaxation times. The influence of pendant chains at low concentrations in silicone networks is studied using double quantum proton nuclear magnetic resonance (DQ-NMR). Changes induced by the defects in the residual dipolar couplings are related to changes in the viscoelastic relaxation times and compared against pendant chain concentration behavior of the elastic modulus.