J. Tao et al., DEPOLARIZED DYNAMIC LIGHT-SCATTERING FROM DIBLOCK COPOLYMER SOLUTIONSNEAR THE ORDER-DISORDER TRANSITION, Macromolecules, 26(17), 1993, pp. 4706-4711
Dynamic light scattering in the depolarized geometry has been used to
investigate the behavior of solutions of an asymmetric diblock copolym
er in a nonselective good solvent near the order-disorder transition (
ODT), as a function of concentration, temperature, and scattering vect
or, q. A new q2-dependent relaxation with q-dependent amplitude and de
polarized intensity appears in the correlation function when the solut
ion crosses from the disordered into the ordered state, which is accom
panied by a significant increase in the depolarized intensity. This is
attributed to the formation of grains of coherently-ordered long cyli
nders in the ordered state, with estimated coherence length of O (mum)
, that gives rise to a large form anisotropy in the microstructured so
lution. The coupled translational/rotational motion of these orientati
onally uncorrelated grains explains the observed diffusive relaxationa
l dynamics.