[mems-talk] Re: chain length PDMS

[Philip D. Hewes]

Barbara,
The (monomer?) chain length of PDMS is variable. It is possible to 
purchase PDMS of many different monomer lengths via the viscosity of 
the solution. The relationship between viscosity and molecular weight 
is available in the literature:

    Molecular weight dependence of low shear rate viscosity for    
poly(dimethylsiloxanes). UTC =3D Silicon Compounds: Register and 
Review,    5th ed., United Chemical Technologies, Pennsylvania (1993); 
Lee et al =3D    C.L. Lee, K.E. Polmanteer, E.G. King, =93Flow Behavior 
of    Narrow-Distribution Polydimethylsiloxane,=94 J. Polym. Sci., A-2, 
8,    p1909-1916 (1970); Barry =3D A.J. Barry, =93Viscometric 
Investigation of    Dimethylsiloxane Polymers,=94 J. Appl. Phys., 17, 
p1020-1024 (1946);    Mills =3D N.J. Mills, =93The Rheological 
Properties and Molecular Weight    Distribution of 
Polydimethylsiloxane,=94 Eur. Polym. J., 5, p675-695    (1969); 
Rahalkar et al =3D R.R. Rahalkar, J. Lamb, G. Harrison, A.J.    Barlow, 
=93Viscoelastic Studies of Reptational Motion of Linear    
Polydimethylsiloxanes,=94 Faraday Symp. Chem. Soc., 18, p103-114 
(1983);    El Kissi =3D N. El Kissi, J.M. Piau, P. Attan=E9, G. Turrel, 
=93Shear    Rheometry of Polydimethylsiloxanes. Master Curves and 
Testing of    Gleissle and Yamamoto Relations,=94 Rheol. Acta, 32, 
p293-310 (1993); Dow    Corning =3D Dow Corning fluids product 
information.