Developed optical and fluid mechanical techniques to study the degradation in performance for General Electric’s Talaria projection television system due to electron beam damage to the memory storage material which was a composite polymeric fluid.
Discovery of the oxidative bleaching of irradiation induced free radical color centers in polymers and exploitation of the effect to study diffusion as a function of temperature, gas pressure, tensile and compressive stress by the use of strain induced photoelasticity. Developed simplified mathematical models to explain and quantify the important distinction between moving diffusion boundaries in polymers with and without diffusate swelling.
Extensive experimental investigation involving measurements of ionic conductivity, dielectric permittivity, moisture sorption and diffusion for various classes of polymer membranes. These studies led to the Barker-Sharbaugh weak electrolyte model for ionic conduction in polymers and liquid dielectrics. The model is relevant to fuel cell membranes and high energy density capacitors.
Experimental and theoretical research for the US Airforce involving charge and mass transport and time domain dielectric spectroscopy for extended chain polymers. This work led to the development of a much more detailed theory based on the weak electrolyte model but now applicable to anisotropic conductivity and permittivity and being more explicitly related to molecular superstrucure. The more general version of the theory also includes the case of highly stretched membranes and includes the effects of temperature, tension, compression, and sorption of polar substances.
Pioneer experimental and theoretical investigations of the effects of hydrostatic pressure on the thermal conductivity of polymer membranes and the molecular interpretation . Also measurements of anisotropic thermal conductivity tensor in oriented membranes.
Utilization of mass spectrometer and several other methods to measure the sorption, permeation, and diffusion of small molecules through a wide variety of molecularly related membranes subjected to different states of elastic and plastic strain.
Barker’s most significant contribution is the development and experimental confirmation, with the aid of several of his graduate students, of the Entropy Correlation Theory (ECT). This theory is an extension of classical statistical thermodynamics to cover a broad class of thermally activated rate processes and is based on Barker’s discovery of an unexpected functional correlation between a rate process’ activation entropy and the difference in the configurational entropies of the different states of molecular organization which influence the rate process. The ECT has been useful in explaining certain important aspects of diffusion and permeation in oriented polymer membranes and offers promise for application to other situations where there is a kinetic transformation between different states of molecular order or disorder.
Development of an expanded version of nucleation and growth theories to explain the dependence or polarization switching times in ferroelectric polymer membranes. Coincidental improvements to classical nucleation theory.
Many other contributions: e.g., studies for Xerox Corp. related to charge transfer on multiple collision between quasi-insulating particles; several different microscopic, spectroscopic, and mechanical techniques to ascertain surface damage to polymers by ultraviolet, electron, and gamma irradiation; development of theories to relate parameters such as elastic modulus and Poisson’s ratio to thermal expansivity and other thermodynamic properties and to molecular characteristics (e.g., intermolecular potential functions) ; The use of time domain techniques (impedance spectroscopy) to measure dielectric properties up to the GHz range.
Publication of a series of theoretical papers which interrelated the macroscopic elastic and thermal properties of solid polymers to characteristics of the molecular structure and order, by means of statistical thermodynamical concepts such as Gruneisen parameters and correlated coefficients in intermolecular potential functions.