Ben Shaughnessy

Courses Taught

Profile

(Research Interests) Theory of soft matter (``complex fluids') with emphasis on polymers. Analytical methods of statistical physics are employed plus some computational analysis. Current research areas include: reacting polymer systems such as free radical polymerization; polymer interfacial phenomena; colloidal suspensions and surfactant aggregates; biophysics. A major research effort concerns reacting polymer systems. We have obtained universal scaling laws for reaction kinetics involving reactive groups attached to high molecular weight polymers. For example, molecular weight dependencies of rate constants are independent of chemical details of the reactive species. Theory has established two classes of behavior: mean field reaction kinetics (intrinsic to dilute solutions) and diffusion-controlled kinetics (intrinsic to melts). Recently we have generalized these ideas to interfacial polymer reactions, technologically important in the reinforcement of polymer-polymer interfaces. Currently we are investigating the kinetics of formation of complex bridging structures at these reactive interfaces. The most important application of polymer reaction kinetics is free radical polymerization (FRP). We have developed ``first principles' theories of FRP, for example of the celebrated autoacceleration or gel effect. Particularly interesting are FRP dynamics, i.e. the behavior under time-dependent driving forces. Our theories appear to explain experiments where virtually infinite polymer radical lifetimes are observed. Theory has also been developed to design and predict new experiments now being performed in collaboration with Prof. Turro in Chemistry. If successful, these highly controlled studies (exploiting precise laser-production of polymer radicals) will allow measurements of fundamental properties of FRP, and polymer reaction kinetics generally, which have hitherto proved impossible. Other polymer interfacial research includes: (a) fracture toughness of reinforced polymer-polymer interfaces (how do surface density and length of reinforcing polymer bridges determine interfacial strength and rupture mechanisms?) and (b) kinetics of polymer attachment to ``sticky' solid surfaces and the configurations of the polymer layers which result. A new focus of research in our group is the physics of biological polymers. We are particularly interested in the statistical mechanics of DNA.

Education

B.S. Bristol (England) Ph.D. Cambridge (England)

Contact Information

bo8@columbia.edu