Research Summary: Non-classical mutual diffusion in polymer/penetrant systems is studied by an oscillatory sorption technique. The physical systems used in the study are polystyrene (PS)/ethylbenzene (EB) and polyimide (PI)/n-methyl pyrrolidone (NMP), and they are chosen because they are typical of 2 broad classes of behavior. A series of experiments will be performed varying the important dimensionless parameter governing the polymer diffusion behavior: the diffusion Deborah number (DEB). The researchers aim to observe the transition from non- classical to classical behavior as DEB is decreased. Quantitative comparisons with a new, thermo-rheological theory will be made. Uniqueness/Innovation: The researchers propose to use the oscillatory sorption technique for macromolecular systems advocated by Vrentas and Duda (J> Memb. Sci. 18, 161 (1984)). The method is potentially powerful: its characterization of mutual diffusion resembles that of momentum transport by dynamic mechanical testing. It eliminates uncertainties connected with imprecise initial conditions and allows precise manipulation of the time scale for observation. The proposed design employs a piezoelectric quartz crystal transducer. The theoretical approach combines modern, non-equilibrium thermodynamics and kinetic theory of concentrated polymer solutions; it formalizes the intuitive developmentof Brochard and DeGennes (Phys. Chem. Hyd. 4, 313 (1982)). There are no adjustable constants in this new approach so that a priori, quantitative predictions of the data can be obtained and tested. Technical Impact/Significance: The proposed experiments will clarify the molecular origins of non-classical effects at small driving forces. Successful application of theory will represent the first, rigorous predictions of non-classical transport. The work can then be extended to expose more general laws governing nonlinear transport. The research has also several practical benefits: (a) ultimately the theory will allow engineering predictions of non-classical diffusion rates from standard rheological data and classical diffusion data; (b) the quartz crystal microbalance enables the study of micromolecule transport in polymer thin film and coatings development, (c) careful research of transport in the PI/NMP system is of generic importance to the electronics industry.
