Study of the Diamagnetic Properties of Liquid Polydimethylsiloxane (PDMS) with the Moses Effect

The relationship between the magnetic susceptibility and degree of polymerization of liquid polydimethylsiloxane (PDMS) was studied experimentally. The magnetic susceptibility of the liquid PDMS was established with the Moses effect, i.e., study of the shape of the near-surface well (the well created near the surface-vapor interface) created in the liquid by a permanent magnetic field. The study of the shape of the near-surface well was carried out under experimental registration of the laser beam reflected from the PDMS/air interface. The broad range of available molecular weights of PDMS made it suitable for the study. The diamagnetic susceptibility, (Formula presented.) of PDMS was measured for a broad range of molecular weights. The plot of magnetic susceptibility, χ, against the number of repeating units in the chain, n, was linear. The result was compared with the magnetic susceptibility predicted by the Pascal law. The volume magnetic susceptibility (Formula presented.) of the liquid PDMS was established as (Formula presented.) = (−7.77 ± 0.06) · 10⁻⁶. The magnetic susceptibility of the PDMS monomer was established as χ_exp (n = 1) = (60.3 ± 0.32) · 10⁻¹¹, which is in a satisfactory agreement with the Pascal empirical rule.