Effect of quench depth on grain structure in quiescently ordered block copolymers

Abstract

Grain growth in a polystyrene-polyisoprene block copolymer melt is studied by time-resolved depolarized light scattering after a quiescent quench from the disordered to the ordered state. At shallow quench depths, classical nucleation and growth kinetics are observed. Grains comprising the equilibrated ordered phase nucleate and grow by consuming the surrounding disordered phase. In contrast, deep quenches result in the formation of disorganized grains with an average order parameter that is well below the equilibrium value. Small angle neutron scattering and rheological experiments were conducted to facilitate the interpretation of the light scattering data. We show that the nonequilibrium grain structure formed during deep quenches is due to extremely high nucleation density. Under these circumstances, the space required for the formation of equilibrated grains is unavailable.

Maximizing the grain growth rate during the disorder‐to‐order transition in block copolymer melts

“…9 -11 In contrast, the measured grain growth rate (dv g /dt during the early stages of the disorder-to-order transition) decreased monotonically with decreasing temperature. 18 We argued that these results were obtained because ordering kinetics in our sample were dominated by nucleation effects. 18 The main purpose of this article, which is a continuation of the work described in ref.…”

“…18 We argued that these results were obtained because ordering kinetics in our sample were dominated by nucleation effects. 18 The main purpose of this article, which is a continuation of the work described in ref. 18, is to identify the factors that control grain growth rates in block copolymers.…”

“…18. The weight-average molar masses of the polystyrene and polyisoprene blocks were determined to be 19.8 and 6.0 kg/mol, respectively, and the polydispersity index of the copolymer was 1.07.…”

“…18 The main purpose of this article, which is a continuation of the work described in ref. 18, is to identify the factors that control grain growth rates in block copolymers. This can only be accomplished if growth rates are studied at a fixed nucleation density.…”

“…[13][14][15][16][17][18][19] In a recent article, 18 we used this technique to study grain growth in a quenched polystyrene-block-polyisoprene copolymer melt. The time required for to reach unity increased monotonically with decreasing temperature, a result that is consistent with previous work.…”