SEGMENT ORIENTATION IN A QUIESCENT BLOCK-COPOLYMER MELT STUDIED BY RAMAN-SCATTERING

Segment orientation of a poly(styrene)-poly(butadiene) star diblock copolymer melt is investigated using polarization-modulated laser Raman scattering (PMLRS). The PMLRS technique is based on Raman spectroscopy and allows for the simultaneous measurement of statistical segment orientation and birefringence. It is found that at temperatures below the glass transition temperature of poly(styrene), segments in both poly(styrene) and poly(butadiene) blocks preferentially align normal to the interface separating microdomains. However, at temperatures greater than the glass transition temperature of poly(styrene), segment orientation disappears. At this temperature, a dramatic decrease in birefringence is also observed. The implications of these findings on the existence of copolymer chain extension in the so-called strong segregation limit are discussed.