<i>In situ</i> multi-modal monitoring of solvent vapor swelling in polymer thin films

Hoang, Don; Yang, Jaesung; Paeng, Keewook; Kwon, Young-Ah; Kweon, Oh Sang; Kaufman, Laura J.

doi:10.1063/1.4939669

Cited by 24 publications

(28 citation statements)

References 43 publications

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“…Various SVA setups have been designed to precisely control the processing parameters, e.g., the annealing temperature, making the method a reliable way to process block copolymer thin films for applications. [ 19–27 ] In situ experiments [ 28–32 ] and simulation studies [ 33–37 ] have been performed to elucidate the structural changes during SVA and thus to improve the understanding of the annealing process, resulting in more powerful processing protocols.…”

Section: Figurementioning

confidence: 99%

Solvent Vapor Annealing of a Diblock Copolymer Thin Film with a Nonselective and a Selective Solvent: Importance of Pathway for the Morphological Changes

Jung

Berezkin

Tejsner

et al. 2020

Macromol. Rapid Commun.

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Diblock copolymer thin films of polystyrene‐block‐poly(dimethyl siloxane) (PS‐b‐PDMS) featuring PDMS cylinders in a PS matrix are investigated during solvent vapor annealing with mixtures of n‐heptane (which is strongly selective for PDMS) and toluene (which is close to nonselective for both blocks). Swelling in the vapor of one of the pure solvents and exchanging it stepwise by the vapor of the other solvent is compared to swelling in a given binary solvent vapor mixture for a prolonged time. The resulting structural changes, such as ordering of the cylinders on a hexagonal lattice and their transition into lamellae, are followed using in situ, real‐time grazing‐incidence small‐angle X‐ray scattering (GISAXS). In three runs, the sequence of solvent vapor swelling and vapor exchange is varied. Compiling the resulting morphologies in a diagram of states in dependence on the solvent content in the film and in the minority nanodomains allows insight into the role of the glass transition of the PS matrix for the ordering processes and their time scales. Based on these findings, a protocol is suggested to efficiently obtain an order‐to‐order transition from the cylindrical morphology with random domain orientation to the oriented lamellar state.

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Section: Figurementioning

confidence: 99%

Solvent Vapor Annealing of a Diblock Copolymer Thin Film with a Nonselective and a Selective Solvent: Importance of Pathway for the Morphological Changes

Jung

Berezkin

Tejsner

et al. 2020

Macromol. Rapid Commun.

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“…Changing the vapor ratio therefore offers a unique handle to manipulate the intrachain phase while potentially also controlling interchain ordering . However, further exploration of the SVA induced aggregation and its impact on interchain ordering is necessary so that a correlation with the degree and duration of swelling can lead to further handles of morphological control …”

Section: Figurementioning

confidence: 99%

Control of Intrachain Morphology in the Formation of Polyfluorene Aggregates on the Single‐Molecule Level

et al. 2020

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Controlling the morphology of π-conjugated polymers for organic optoelectronic devices has long been a goal in the field of materials science. Since the morphology of a polymer chain is closely intertwined with its photophysical properties, it is desirable to be able to change the arrangement of the polymers at will. We investigate the π-conjugated polymer poly(9,9dioctylfluorene) (PFO), which can exist in three distinctly different structural phases: the α-, β-, and γ-phase. Every phase has a different chain structure and a unique photoluminescence (PL) spectrum. Due to its unique properties and the pronounced spectral structure-property relations, PFO can be used as a model system to study the morphology of π-conjugated polymers. To avoid ensemble averaging, we examine the PL spectrum of single PFO chains embedded in a non-fluorescent matrix. With single-molecule spectroscopy the structural phase of every single chain can be determined, and changes can be monitored very easily. To manipulate the morphology, solvent vapor annealing (SVA) was applied, which leads to a diffusion of the polymer chains in the matrix. The βand γ-phases appear during the self-assembly of single α-phase PFO chains into mesoscopic aggregates. The extent of βand γ-phase formation is directed by the solvent-swelling protocol used for aggregation. Aggregation unequivocally promotes formation of the more planar βand γ-phases. Once these lower-energy more ordered structural phases are formed, SVA cannot return the polymer chain to the less ordered phase by aggregate swelling.

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“…In conventional SVA experiments, the extent of film swelling is such that aggregate diffusion is too fast for adequate localization and characterization of aggregates. To circumvent this problem, we developed an SVA chamber that allows in situ monitoring of film swelling on a quartz crystal microbalance (QCM) while performing optical imaging of an equivalent film on the chamber bottom . This experimental setup allows control and monitoring of the degree of film swelling, allowing control of particle speed for in situ tracking and interrogation of individual aggregates during the growth process.…”

Section: Figurementioning

confidence: 99%

In Situ Optical Imaging of the Growth of Conjugated Polymer Aggregates

2018

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Understanding the mechanisms that contribute to conjugated polymer aggregate formation and growth may yield enhanced control of aggregate morphology and functional properties on the mesoscopic scale. In situ optical imaging of the growth of MEH‐PPV aggregates in real time in controlled swollen films shows that growth occurs through multiple mechanisms and is more complex than previously described. Direct evidence is provided for both Ostwald ripening and aggregate coalescence as operative modes of aggregate growth in solvent swollen films. These growth mechanisms have a distinct and strong impact on the evolution of morphological order of growing aggregates: while Ostwald ripening allows preservation of highly ordered morphology, aggregate coalescence occurs with no preferential orientation, leading to attenuation in degree of ordering.

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In situ multi-modal monitoring of solvent vapor swelling in polymer thin films

Cited by 24 publications

References 43 publications

Solvent Vapor Annealing of a Diblock Copolymer Thin Film with a Nonselective and a Selective Solvent: Importance of Pathway for the Morphological Changes

Solvent Vapor Annealing of a Diblock Copolymer Thin Film with a Nonselective and a Selective Solvent: Importance of Pathway for the Morphological Changes

Control of Intrachain Morphology in the Formation of Polyfluorene Aggregates on the Single‐Molecule Level

In Situ Optical Imaging of the Growth of Conjugated Polymer Aggregates

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