Rectangular thin-channel columns were designed to determine partition and diffusion coefficients of small molecular weight solvents in polymer membranes based on the inverse gas chromatography (IGC) technique. The advantage of using this novel column was analyzed in terms of uniform distribution of polymer thickness, ease of preparation of stationary phase (thin polymer layer), and repeated use of the column. A mathematical model was developed to describe the velocity profile of the carrier gas, and both the time- and location-dependent concentration profiles of solvent in the column. By using the moment analysis method, the partition coefficient and diffusion coefficient were related to the dimensionless first moment and dimensionless second central moment of the elution curve of the solvent, respectively. The first dimensionless moment of the elution curve was found to be independent of the carrier gas velocity, while the second central moment increased with the increase of the carrier gas velocity. Both these behaviors support the theoretical predictions. The diffusion and partition coefficients of ethanol were obtained on polymers of cellulose diacetate (CDA) and sulfonated poly(ether ether ketone) (SPEEK) with a sulfonation degree of 79% over different temperature ranges. Based on the Arrhenius formula, the diffusion activation energies and the solvent dissolution enthalpies in both polymers were also obtained. The diffusion coefficients of 1-propanol were also obtained using two different lengths of columns.