Diffusion of block copolymers

Yokoyama, Haruki

doi:10.1016/j.mser.2006.08.001

Cited by 49 publications

(69 citation statements)

References 173 publications

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“…The predominant mode in this regime, therefore, has the features of that predicted for incompressible block copolymers with some polydispersity, named in the literature as polydispersity or heterogeneity mode 12 and might be related to interdiffusion processes at the interphases. 33 The fact that the diffusive motion does not appear in the disordered region, below the T DOT , it might be explained by considering that, in this region, the dynamics is governed by concentration fluctuations that become more intense as the T DOT is approached. The compositional profile may have a weakly sinusoidal shape that becomes more intense as the T DOT is approached.…”

Section: Resultsmentioning

confidence: 99%

Relaxation processes in a lower disorder order transition diblock copolymer

Sanz

Ezquerra

Hernández

et al. 2015

The Journal of Chemical Physics

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The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition TODT, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.

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Section: Resultsmentioning

confidence: 99%

Relaxation processes in a lower disorder order transition diblock copolymer

Sanz

Ezquerra

Hernández

et al. 2015

The Journal of Chemical Physics

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“…The poor long range order of this thermally annealed PS-PFMA is primarily due to the strong interaction between PS and PFMA, which restricts the reorganization. 31 In Fig. 4͑b͒, the GISAXS pattern from the nanocellular thin film after the CO 2 process is shown.…”

Section: A Gisaxs Experimentsmentioning

confidence: 99%

“…The increasing lattice dimension suggests that, during the CO 2 process, PS-PFMA chains reduce the number of aggregates ͑reduce the number density and increase the lattice dimension͒ to accommodate the absorbed CO 2 . In thermal annealing, the diffusion and reorganization of the structure is strongly restricted by the strong interaction between PS and PFMA, 31 but the reorganization can be enhanced in the CO 2 process since CO 2 reduces the effective interaction between PS and PFMA and accelerates the diffusion of PS-PFMA copolymer molecules.…”

Section: A Gisaxs Experimentsmentioning

confidence: 99%

Grazing incident small angle x-ray scattering study of polymer thin films with embedded ordered nanometer cells

Yokoyama

Dutriez

et al. 2007

The Journal of Chemical Physics

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Analysis of nanostructures is of increasing importance with advances of nanotechnology. Embedded nanostructures in thin films in particular are of recent interest. Grazing incident small angle x-ray scattering (GISAXS) has been recognized to be a powerful method to probe such embedded nanostructures; however, quantitative analysis of scattering pattern is not always trivial due to complex refraction and reflection at surface and interfaces. We prepared nanocellular thin films using block copolymer template with carbon dioxide (CO(2)); CO(2) "bubbles" were formed in the CO(2)-philic block domains. Such nanocellular structures were analyzed by GISAXS and simulated using distorted wave Born approximation (DWBA). Unlike traditional transmission x-ray scattering, GISAXS requires a careful choice of incident angle to analyze the form factor of scatters embedded in a thin film. Nevertheless, the GISAXS measurements under optimized geometry with quantitative calculations using DWBA revealed that the nanocells are spherical and aligned in a single layer of hexagonal lattice and are surrounded by CO(2)-philic block domains.

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“…For high- BCPs, the increased penalty of mixing results in slower diffusion rate and higher kinetic barriers and subsequently leads to significantly longer annealing times. [4][5][6] Microwave assisted microphase separation appears to offer considerable advantages in reducing annealing times in a number of BCP systems and we show that we can overcome long annealing times associated with a relatively high- poly(styrene-b-lactic acid) (PS-b-PLA) (=0.19) system by utilizing microwave energy. Microwave annealing was first demonstrated by Zhang and Buriak.…”

Section: Introductionmentioning

confidence: 97%

Study of the Kinetics and Mechanism of Rapid Self-Assembly in Block Copolymer Thin Films during Solvo-Microwave Annealing

et al. 2014

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Microwave annealing is an emerging technique for achieving ordered patterns of block copolymer films on substrates. Little is understood about the mechanisms of microphase separation during the microwave annealing process and how it promotes the microphase separation of the blocks. Here, we use controlled power microwave irradiation in the presence of tetrahydrofuran (THF) solvent, to achieve lateral microphase separation in high-χ lamellar-forming poly(styrene-b-lactic acid) PS-b-PLA. A highly ordered line pattern was formed within seconds on silicon, germanium and silicon on insulator (SOI) substrates. In-situ temperature measurement of the silicon substrate coupled to condition changes during “solvo-microwave” annealing allowed understanding of the processes to be attained. Our results suggest that the substrate has little effect on the ordering process and is essentially microwave transparent but rather, it is direct heating of the polar THF molecules that causes microphase separation. It is postulated that the rapid interaction of THF with microwaves and the resultant temperature increase to 55 °C within seconds causes an increase of the vapor pressure of the solvent from 19.8 to 70 kPa. This enriched vapor environment increases the plasticity of both PS and PLA chains and leads to the fast self-assembly kinetics. Comparing the patterns formed on silicon, germanium and silicon on insulator (SOI) and also an in situ temperature measurement of silicon in the oven confirms the significance of the solvent over the role of substrate heating during “solvo-microwave” annealing. Besides the short annealing time which has technological importance, the coherence length is on a micron scale and dewetting is not observed after annealing. The etched pattern (PLA was removed by an Ar/O2 reactive ion etch) was transferred to the underlying silicon substrate fabricating sub-20 nm silicon nanowires over large areas demonstrating that the morphology is consistent both across and through the film.

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Diffusion of block copolymers

Cited by 49 publications

References 173 publications

Relaxation processes in a lower disorder order transition diblock copolymer

Relaxation processes in a lower disorder order transition diblock copolymer

Grazing incident small angle x-ray scattering study of polymer thin films with embedded ordered nanometer cells

Study of the Kinetics and Mechanism of Rapid Self-Assembly in Block Copolymer Thin Films during Solvo-Microwave Annealing

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