title: Critical viscoelastic behavior of polydimethylsiloxane networks around the sol-gel threshold.
abstract: Seven model polydimethylsiloxane (PDMS) networks were obtained by hydrosilation of a difunctional vinyl-terminated PDMS prepolymer with a SiH-containing cross-linker. Viscoelastic experiments, completed by size exclusion chromatography and static light scattering experiments, were performed in order to study the influence of molecular parameters on the dynamic properties around the sol-gel threshold. The dynamic critical parameter u was determined from experiments close to and above the sol-gel threshold. Our results show that the growth mechanism of PDMS clusters and the viscoelastic behavior are a function of the ratio NN_{e} , where N and N_{e} are, respectively, the numbers of Kuhn monomers between branch points and between entanglements. For NN_{e}<1 , the growth mechanism of clusters is the critical percolation and u=0.69 , and for NN_{e}>1 , the growth mechanim of clusters is the diffusion-limited cluster aggregation and u=0.76 .
authors.affiliation: Laboratoire d'Analyse des Interfaces et de Nanophysique, UMR-5011, Universite Montpellier II, CC082, Place E. Bataillon, 34095 Montpellier Cedex 5, France.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Gasparoux
authors.forename: Thomas
authors.initials: T
authors.lastname: Tixier
authors.forename: Philippe
authors.initials: P
authors.lastname: Tordjeman