In this work, poly[1-(trimethylsilyl)-1-propyne] (PTMSP) has been considered as a new membrane material for non-aqueous nanofiltration applications in ethanol media (SRNF), and compared with other silicone-based commercially available membranes (MPF-50 and Membrane D). Noticeable membrane swelling in ethanol media (66±4%) provides rather high ethanol permeation and the ethanol permeability normalized by the dry membrane thickness (P·d_dry, kgm/(m²h×10⁵Pa) (kgm/(m²hbar))) exceeds those of the two commercially silicone-based membranes. Based on WAXS analysis, it seems that the swollen PTMSP membranes in ethanol still possess some nanoscale order and probably ethanol exists in PTMSP as clusters or even as a liquid phase. It was found that the retention of negatively charged Remazol Brilliant Blue R is higher than 90% (94.2% at 30×10⁵Pa (30bar)). Furthermore, the negative retention of the neutral dye Solvent Blue 35 (MW 350.4; −4.6%) shows that membrane–solute interaction is important and simple sieve mechanism cannot always explain the retention behavior for non-aqueous systems. It was found that higher dye–membrane interaction (distribution coefficient K) leads to lower retention of dyes with low molecular weight (around 350Da).