Rapid Transitions between Defect Configurations in a Block Copolymer Melt

Abstract

With in situ scanning force microscopy, we image the ordering of cylindrical microdomains in a thin film of a diblock copolymer melt. Tracking the evolution of individual defects reveals elementary steps of defect motion via interfacial undulations and repetitive transitions between distinct defect configurations on a time scale of tens of seconds. The velocity of these transitions suggests a cooperative movement of clusters of chains. The activation energy for the opening/closing of a connection between two cylinders is estimated.

Scanning Force Microscopy as Applied to Conformational Studies in Macromolecular Research

“…[201] Wide variety of morphology changes in thin block copolymer films were demonstrate by in situ SFM studies in real time regime at elevated temperatures. [202][203][204] On the other hand, SFM device equipped with a liquid cell allows one to study in real time regime stages of precipitation from solutions for different objects, e.g., proteins [205] or polycationic flocculants. [206] In some cases the dynamic transformations may be induced purposefully by direct influence of the microscope tip.…”

Thermal Fluctuations of Ferroelectric Nanodomains in a Ferroelectric-Dielectric PbTiO3/SrTiO3 Superlattice

“…In other systems, disordered spatial structures give rise to multiple spatial patterns with energy states with small energy separations compared to k B T, leading to spontaneous fluctuations in both 'hard' [5][6][7] and 'soft' materials [8]. However, it is technically challenging to image fluctuating ferroelectric nanodomain patterns directly because of a combination of the nm-scale periodicity of the domain pattern [3] and the pm-scale atomic displacements that distinguish domains with different polarization directions [9].…”

“…The former possibility entails the generation and annihilation of topological defects, as demonstrated in imaging studies of the motion of block copolymer chains [8]. In comparison, fluctuations without changes in the configuration require transitions between striped domains with different orientations.…”

“…On the other hand, the generation and annihilation of topological defects, as observed in block copolymer chains in Ref. [8], occurs via closing of the gaps between the stripes (annihilation of topological defects) and the opening of new gaps (generation of topological defects) in the immediate vicinity (usually a few stripe periods) and requires no net change of system free energy.…”

Effects of Electric Fields on Block Copolymer Nanostructures

“…Performing ex situ sample treatments with the aim of imaging the same spot on the sample prior to and after annealing would require time-consuming repositioning protocols. This might not be feasible because of rather abrupt changes in the structure during the snapshot treatment in the electric field [36]. With the experimental setup used here we managed to overcome these problems [9].…”