Ja. Ressia et al., Influence of polydispersity on the viscoelastic properties of linear polydimethylsiloxanes and their binary blends, POLYMER, 41(18), 2000, pp. 6885-6894
Linear polydimethylsiloxanes of relatively narrow molecular weight distribu
tion (MWD) were synthesized by anionic polymerization and characterized by
different techniques. Binary blends were also prepared with some of the syn
thesized polymers. Linear viscoelastic parameters, such as storage (G') and
loss (G ") moduli, were obtained at different temperatures as functions of
frequency (omega). The time-temperature superposition principle was applie
d in order to increase the frequency range measured. Zero-shear rate viscos
ity (eta(0)), steady state recoverable compliance (J(e)(0)) and zero-shear
rate first normal stress coefficient (psi(1,0)) were calculated from the da
ta corresponding to the terminal relaxation zone. The molecular weight depe
ndence of those parameters shows a good agreement with classical models and
previously reported results, although J(e)(0) and psi(1,0) are strongly af
fected by polydispersity. Different polydispersity factors were applied in
order to fit the experimental values of the viscoelastic properties with th
e theory. (C) 2000 Elsevier Science Ltd. All rights reserved.