Interface dynamics in a block copolymer melt and the effect of noise

The role of fluctuations in the disorder-lamellar transition in a block copolymer melt is investigated using a cell dynamical system simulation by measuring the propagation velocity of the interface between ordered and disordered regions. Our results strongly suggest that near the transition temperature, in the absence of noise, the velocity increases with quench depth as v∼√τ [τ=(Tc−T)Tc is the reduced temperature measured from the transition temperature Tc], while in the presence of noise, the velocity increases as v∼τ. These results lead us to conclude that the addition of noise causes the disorder-lamellar transition to change from second order to first order. This conclusion is consistent with the prediction of Brazovskii [Sov. Phys. JETP 41, 85 (1975)].