Molecular weight changes induced in an anionic polydimethylsiloxane by gamma irradiation in vacuum

SATTI, ANGEL J; ANDREUCETTI, NOEMÍ A; CIOLINO, ANDRÉS; VITALE, CRISTIAN; SARMORIA, CLAUDIA; VALLÉS, ENRIQUE M

RADIATION PHYSICS AND CHEMISTRY (OXFORD)

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2010 vol. 79 p. 1137 - 1143

0969-806X

An anionic almost monodisperse linear polydimethylsiloxane (PDMS) was subjected to gammairradiation under vacuum at room temperature. The molecular weight changes induced by theradiation process have been investigated using size exclusion chromatography (SEC) with refraction index (RI) and multi angle laser light scattering (MALLS) detectors, to obtain the number and weight average molecular weights of the irradiated samples.The analysis of the data indicates that crosslinking reactions predominated over scission reactions. The results obtained by SEC-RI have confirmed the presence of small but measurable amounts of scission.A previously developed mathematical model of the irradiation process that accounts for simultaneous scission and crosslinking and allows for both H and Y crosslinks fitted well the measured molecular weight data. This prediction is in accordance with the experimental data obtained by 29Si-Nuclear Magnetic Resonance spectroscopy (NMR) and previously reported data for commercial linear PDMS (Satti et al., 2008).