Pathway and Kinetics of Cylinder-to-Sphere Order−Order Transition in Block Copolymers

Abstract

The pathway and kinetics for the cylinder-to-sphere order−order transition in a mixture of a matched diblock and triblock copolymer of styrene and ethylene−butene-1 is reported. The microstructure transformation was monitored by viscoelastic measurements, and the structural assignments of the intermediate states were performed by electron microscopy. The kinetics of transformation from macroscopically unaligned wormlike cylindrical microdomains to spherical microdomains arranged on a bcc lattice were extremely slow. The wormlike cylinder-to-sphere transition slowed with decreasing quench depth from the order−disorder transition. Additionally, these order−order kinetics were in quantitative agreement with those for the development of spherical microdomains from an initial disordered state. Further, during the initial induction time following a temperature jump from a wormlike cylindrical order to a spherical state, the sample exhibited liquidlike viscoelastic characteristics and structurally showed the absence of long-range order. In contrast, shear-aligned cylinders rapidly transformed to spheres, adopting a viscoelastic pathway distinct from that of the unaligned samples. The cylinder-to-sphere transition is thermotropically reversible, with the viscoelasticity-based kinetics of the sphere-to-cylinder transition being slower than the cylinder-to-sphere transition.

Phase structural formation and oscillation in polystyrene-block-polydimethylsiloxane thin films

“…Thermally induced OOTs between bodycentred cubic spheres and hexagonally packed cylinders have been observed in bulk and solvent swollen melts. [17][18][19][20][21][22][23][24][25] However, in situ rheological and scattering measurements have not shown evidence of cyclic transitions. On the other hand, recent in situ characterization of the morphology development during thermal annealing of block copolymer thin films indicates that local OOTs occur as a mechanism to anneal out defects.…”

Phase Behavior of Complementary Multiply Hydrogen Bonded End-Functional Polymer Blends

“…[8][9][10][11][12][13] Additionally, the phase behavior can be altered by swelling with solvent or homopolymer, [14][15][16] or two polymers with different composition can be blended. 17,18 In contrast to controlling structure through composition or chain architecture, simple thermal tunability in a polymer structure can be introduced through reversible supramolecular interactions. 19 The nature of the interaction varies widely and most commonly consists of either metal-ligand, 20,21 ionic, 22,23 or hydrogen bonding.…”

Kinetic Pathway of the Cylinder-to-Sphere Transition in Block Copolymer Micelles Observed in Situ by Time-Resolved Neutron and Synchrotron Scattering

“…Consequently, kinetic studies of morphological transitions in block copolymer micellar systems are rare and are mostly related to ordering kinetics and morphological transition in melts or concentrated solutions. Examples include disorder to order, lamella-to-cylinder, cylinder-to-sphere, and cylinder-to-gyroid transition kinetics. Eisenberg et al explored the kinetics and mechanisms of various transitions of polystyrene–poly(acrylic acid) (PS–PAA) block copolymers in water/1,4-dioxane mixtures .…”