Thickness-dependence of block copolymer coarsening kinetics

Abstract

Despite active research, many fundamental aspects of block copolymer ordering remain unresolved. We studied the thickness-dependence of block copolymer grain coarsening kinetics, and find that thinner films order more rapidly than thicker films. Bilayer films, or monolayers with partial layers of islands, order more slowly than monolayers because of the greater amount of material that must rearrange in a coordinated fashion. Sub-monolayer films order much more rapidly than monolayers, exhibiting considerably smaller activation energies, as well as larger exponents for the time-growth power-law. Using molecular dynamics simulations, we directly study the motion of defects in these film regimes. We attribute the enhanced grain growth in sub-monolayers to the film boundaries, where defects can be spontaneously eliminated. The boundaries thus act as efficient sinks for morphological defects, pointing towards methods for engineering rapid ordering of self-assembling thin films.

Self-assembly of block copolymers under non-isothermal annealing conditions as revealed by grazing-incidence small-angle X-ray scattering

“…As expected, the A T value increases following an Arrhenius behaviour, the activation energy of the polymer being 29.7 kJ mol À1 . Additionally, the values are within the range of previously reported values (Black et al, 2017;Perego et al, 2014;Majewski & Yager, 2015;Ferrarese Lupi et al, 2017). It is worth mentioning the existence of a temperature dependence revealed by our experiments (Fig.…”

“…Table 1 compiles the experimental A T and values extracted from the in situ data recorded during the annealing experiments. The extracted values (Table 2) were consistent with previously reported investigations for this polymer using SEM defectivity analysis (Claveau, 2018) and for similar polymers (Ji et al, 2011;Majewski & Yager, 2015;Black et al, 2017). As expected, the A T value increases following an Arrhenius behaviour, the activation energy of the polymer being 29.7 kJ mol À1 .…”

“…An understanding of the parameters governing the kinetics of the BCP self-assembly process is of key importance to model the evolution of the system as it can be crucial to predict the final order and determine the processing conditions to obtain defect-free patterned areas (Harrison et al, 2002;Murphy et al, 2015;Kim et al, 2014). Both the selfassembly kinetics and obtained morphology have been widely investigated as a function of different physical/experimental parameters (Ji et al, 2011) such as annealing conditions (Berry et al, 2007;Sanz et al, 2011;Majewski & Yager, 2015;Gu et al, 2014), BCP thickness (Black et al, 2017) and BCP/substrate interaction . Typically, the characterization of BCP thin films is addressed by using microscopy techniques.…”

Photothermally Directed Assembly of Block Copolymers

“…Generally, thicker films order more rapidly, owing to reduced confinement and substrate effects. However, one can also observe enhancement in kinetics in thinner films, for instance due to defect annihilation or morphology alignment at film edges.…”

Self-assembly of a silicon-containing side-chain liquid crystalline block copolymer in bulk and in thin films: kinetic pathway of a cylinder to sphere transition

“…15,[18][19][20]38,39 Furthermore, although extensive studies of the equilibrium morphologies in the thin films of various block copolymers have been widely reported, the structural evolution processes of the BCP thin films are still poorly understood. Knowledge of the ordering pathways and transition process is a prerequisite both for eliminating kineticallytrapped defects in BCP thin films [40][41][42][43] and for understanding how LC phase transitions could induce order-order transitions. [44][45][46] Here, we present the self-assembly behavior in bulk and in thin films of a silicon-containing side-chain liquid crystalline block copolymer poly(dimethylsiloxane-b-11-(4′-cyanobiphenyl-4-yloxy)undecylmethacrylate) or PDMS-b-P(4CNB11C)MA, where the molecular weights M n of PDMS and P(4CNB11C)MA are 5.0 and 14.5 kg mol −1 , respectively (Fig.…”