The dynamics of order parameter fluctuations has been investigated nea
r the maximum of the static structure factor for semidilute solutions
in a neutral good solvent of a very high molecular weight diblock copo
lymer. The effect of the proximity to the disorder-to-order transition
(ODT) was evident both in the static light scattering intensity and i
n the internal relaxation by increasing the copolymer concentration up
to phi(ODT). All extra relaxation was also observed which can be attr
ibuted to curvilinear Rouse motion of the blocks between entanglements
inside their tubes.