1. Characterization of Polymers with the Kerr-Effect Alan E. Tonelli, North Carolina State University, DMR 0966478 A recent NSF Workshop report on Polymers concluded that “recent advances in polymer syntheses leading to elaborate and precise architectures require accompanying advances in microstructural character- ization beyond those currently available, which are collectively inadequate”. Unlike spectroscopic probes that are only sensitive to local polymer microstructures, the birefringence observed in polymer solutions when subjected to high electric fields, ie., the directional dependence of light refracted through them, depends on the microstructural make-up of the entire polymer chain. It is the molecular alignment produced by the net dipole moment and its relation to the direction of maximum polarizability of the entire polymer chain averaged over all conformations in solutions which determine both the magnitude and sign of its Kerr-Effect. This is illustrated in the Figure, for 2 tri-block copolymers with polar para-bromostyrene (p-Br-S) and non-polar styrene (S) blocks located in different positions. Both tri-blocks contain the same numbers of comonomer units (60 mol% p-Br-S). Though the microstructures/architectures of A and B are indist- inguishible by any other means, the Kerr-Effect is not only sensitive to their microstructures, but also to their locations/ positions in the copolymer chain. It would appear that the Kerr-Effect does indeed have the potential to characterize more fully the “elaborate and precise architectures “ (microstructures and their locations or MACROSTRUCTURES) of A B p-Br-S/S/p-Br-S(A) and S/p-Br-S/S (B) Tri-block copolymers, whose molar Kerr constants, m K, are both predicted and observed to have similar magnitudes, but with m K(A) negative and m K(B) positive in sign. polymers, thereby increasing our ability to understand their behaviors and properties.

2. Our preliminary results for S/p-BrS coplymers, including those with random, blocky, and gradient comonomer sequences, and tri-blocks have been published in J. Polym. Sci., Part B: Polym. Phys., 51, 735–741, 2013. We discovered that our RAFT synthesized gradient S/p-BrS copolymers possess a parallel stereosequence gradient, i.e., as p-BrS units increase along the chain backbone, so do syndiotactic diads. We have also examined other polymers with the Kerr effect, including stereoregular i- and s- PMMAs, precise and random ethylene/ vinyl acetate E/Vac copolymers (from Hillmyer et al.) and random and regular alternating styrene/butadiene S/B multi-block copolymers (from Bates et al.). The stereocomplexation of i- and s-PMMAs and the different macro- structures of the E/VAc and S/B copolymer samples were in fact distinguished by their Kerr effects. From left-to-right are photos of Dr. Shauntrece Hardrict (Post-Doc. 1 st year), Rana Gurarslan (grad. student 2 nd & 3 rd years), and Kathleen Dreifus (undergrad. Student 2 nd & 3 rd summers). Attached are photos of the Post-Doctoral, graduate, and undergraduate students who have been and/or are currently supported on this grant. They have been assisting with the syntheses of model polymers and measurement and calculation of their molar Kerr constants. In addition, Prof. Brent Summerlin, at U. of Florida, and his students have become active collaborators in the syntheses of model polymers for Kerr-Effect study. Characterization of Polymers with the Kerr-Effect Alan E. Tonelli, North Carolina State University, DMR 0966478