We report on the achievement of differential control over adsorption and desorption kinetics of selected vapor phase molecules at ultrathin polymer bilayer interfaces. We synthesize and deposit maleimide-vinyl ether alternating copolymer layers, where each polymer layer contains different pendant side group functionalities and the order of layer deposition is controlled. The adsorption isotherm behavior of these interfacial structures, when exposed to methanol and hexane vapor, shows that the identity of the adsorbates and the order of polymer adlayer deposition both influence the interfacial adsorption characteristics. The absence of hysteresis in the isotherm data indicates that our measurements are made under equilibrium conditions, indicating the achievement of chemical and structural control over the thermodynamics of adsorption at these interfaces.