Samples and fractions of a membrane-forming polymer, poly(1-trimethylsilyl- 1-propyne) (PTMSP), were studied by methods of molecular hydrodynamics (velocity sedimentation, translational isothermal diffusion and viscometry) in cyclohexane in the molecular mass range 60<M×10^-3gmol ^-1<430. The following molecular-mass dependencies of the hydrodynamic characteristics (intrinsic viscosity [η] (cm³g ^-1), sedimentation coefficient s₀(s) and translational diffusion coefficient D₀ (cm²s^-1)) were established: [η]=0.198 M^0.50±0.06; s₀=8. 66×10^-16 M^0.50±0.04; D₀=9. 30×10^-5 M^-0.50±0.04. On the basis of the hydrodynamics data the equilibrium rigidity and hydrodynamic diameter of PTMSP chains were evaluated. The equilibrium properties of the different disubstituted polyacetylenes molecules are compared on the base of the normalised scaling plots.