Investigation of the Consequences of Cooperative Motion in Polymers and their Miscible Blends

Ralph H. Colby (Penn State University) DMR-0433079

We apply simple ideas about cooperative motion in glass-forming liquids to dynamics of miscible polymer blends. The segmental (monomer) motion is sensed by dielectric spectroscopy and both experimental data and our model prediction see the main features: (1) Concentration fluctuations broaden the relaxations of each component in the blend and (2) Each component has a distinct temperature dependence.The second feature makes the relaxations involving whole chains (that control the viscosity of the mixture) have a complicated temperature dependence. These features must be understood to process polymer blends into useful items, such as golf balls, plastic toys, automobiles and airplanes. Dielectric Loss (Fig. 1) and Loss Modulus (Fig. 2) of miscible

blends of poly(vinyl ethylene) (PVE) and polyisoprene (PI).The predicted relaxations in the blends are shown as blacksolid curves, obtained by summing the predicted contributionsfor each blend component (shown as colored curves).

Macromolecules, 2004, 37, 6994-7000.Macromolecules, 2005, 38, 4919-4928.

pure PVE

pure PI50% PVE / 50% PI blend

Investigation of the Consequences of Cooperative Motion in Polymers and their Miscible Blends

Ralph H. Colby (Penn State University) DMR-0433079

Education

Under this grant, graduate student Brian Erwin has defended his Ph.D. Thesis and started a job with IBM August 1, 2005. 2nd year graduate student (Wenjuan Liu) has just started to get new experimental results. Two faculty collaborate with RHC on this project: Sanat Kumar (RPI) and Jane Lipson (Dartmouth).

Outreach• To Industry – Our models of polymer blend

dynamics are being exploited to design zero-birefringence plastics for optical storage media. This idea comes from a 1983 Xerox Patent, but to truly accomplish zero birefringence the relaxation times of the component polymers must be precisely matched.

• To Undergraduates – We have had 21 undergraduates participate in our NSF-funded research since 1995. One is in Medical School, one completed Law School, nine went on to Graduate School in Science and Engineering and the other ten are employed by US industry.

• To Minority Students – RHC participates yearly in the FastStart program at PSU designed to help inner-city Freshmen adjust to college and the BEST program (sponsored by Kodak) aimed at getting minority students to attend college in Engineering or Science.

Ralph Colby (right) receives tutoring from Paul Callaghanin Callaghan’s Rheo-NMR lab at the Victoria University ofWellington, New Zealand while on sabbatical in 2005 asa Fulbright Senior Scholar. This 6-month visit exchangedideas about polymer dynamics and NMR imaging in flow.