Ordering kinetics in a symmetric diblock copolymer

Abstract

Small angle X-ray scattering (SAXS) and rheology are employed to study the microphase separation transition in a symmetric poly(styrene-b-isoprene) diblock copolymer. The order-disorder transition temperature Toor has been identified with a good precision ( ToDT =359 K) and the interaction parameter is extracted using mean field theory at temperatures well above TODT. The kinetics of microphase separation have been studied by means of rheology in a small temperature range below the order-disorder transition, following a quench from the disordered state.The time evolution of the storage and loss moduli exhibited shapes which are reminiscent of the crystallization isotherms of semicrystalline materials (of the Avrami type). For shallow quenches, we find a temperature range of 3 K below To,, where the ordering proceeds by heterogeneous nucleation and growth of three-dimensional objects with lamellar microstructure. At higher undercooling, the kinetic curves change in form, indicating a different mechanism of structure formation. Our results are compared with theoretical predictions for the ordering kinetics of symmetric diblocks.

Block Copolymers in External Fields: Rheology, Flow‐Induced Phenomena, and Applications

“…The linear complex moduli of polycrystalline lamellar phases are nearly equal with a weak power law dependence, G 0 B G 00 B ω 1/2 , which has been observed experimentally [63,68,79] and predicted theoretically [80][81][82]. This peculiar response is believed to be a consequence of a distribution of domain orientations, which yields a macroscopic response intermediate between that of a liquid (G 0 B ω 2 and G 00 B ω) and a solid (G 0 B ω 0 ) [80].…”

“…In this respect, the true ODT is the so-called equilibrium ODT [67]. The kinetics of ordering of block copolymers has been studied in great detail using combination of shear rheology and time-resolved small-angle X-ray scattering (SAXS) experiments [66,[68][69][70][71]. In general, the results are well described by the Avrami equation that also applies to the kinetics of crystallization.…”

Order–disorder transition and ordering kinetics in binary diblock copolymer mixtures of styrene and isoprene

“…7͑a͒ for SI-C and for quenches to different final temperatures below the T ODT ͑ϭ371 K͒. The GЈ(t) and GЉ(t) curves exhibit the familiar ''S'' shape, as with the SI-85/65 sample studied earlier, 6 with the long-time plateau corresponding to the equilibrium shear moduli of the lamellar morphology. The ordering kinetics-which in contrast to the mechanism of spinodal decomposition depend strongly on the undercooling ͑T ODT ϪT͒-have been analyzed in terms of a nucleation and growth model of the Avrami class.…”

“…The scattering intensity, after correcting for the density fluctuations, 6 was radially averaged and the result is shown in Fig. 1 as a function of the scattering angle for one orientation ͑radial͒.…”

End-functionalized polymers: Versatile building blocks for soft materials

“…In Ref. [49], the effect of zwitterionic substitution on diblock and triblock copolymers has been studied with rheological and dielectric spectroscopy and SAXS experiments to explore the aggregation of the terminal groups and the dynamics. The aggregation processes strongly influence the electron density profile.…”