Role of Interfacial Interaction in Orientation of Poly(<i>N</i>-isopropylacrylamide) Chains on Silicon Substrate.

Wang, C.-H.; Mukherjee, Subhrangsu; Islam, A. K. M. Maidul; Yang, Yaw Wen; Mukherjee, M.

doi:10.1021/ma200614w

Cited by 12 publications

(17 citation statements)

References 34 publications

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“…?Ẽ E). This linear extrapolation is valid in the case of uniaxial symmetry and roughly flat conjugation present in these conjugated systems (Pasquali et al, 2008;Wang et al, 2011).…”

Section: Calculating Optical Constants and Scattering Contrasts From mentioning

confidence: 86%

“…This anisotropy originates from conjugated molecular ring structures that create a uniaxial symmetry orthogonal to the ring and characterized by the carbon C 1s ! * transition dipole moment (TDM) (Wang et al, 2011;O'Connor et al, 2011). Molecules commonly stack along this direction, in stacking, both in liquid-crystalline domains and in extended fibril structures.…”

Section: Introductionmentioning

confidence: 99%

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Origins of polarization-dependent anisotropic X-ray scattering from organic thin films

Gann

Collins²,

Tang

et al. 2016

J Synchrotron Radiat

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Organic thin films that have no overall in-plane directional ordering often nonetheless produce anisotropic scattering patterns that rotate with the polarization of incident resonant X-rays. Isotropic symmetry is broken by local correlations between molecular orientation and domain structure. Such examples of molecular alignment at domain interfaces and within the bulk of domains, which are both critical to fields such as organic electronics, are simulated and compared with experimental scattering. Anisotropic scattering patterns are found to allow unambiguous identification of the mechanism of local molecular orientation correlations and, as such, promise to be both distinct and complementary to isotropic scattering intensity as a general measure of thin film microstructure.

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“…?Ẽ E). This linear extrapolation is valid in the case of uniaxial symmetry and roughly flat conjugation present in these conjugated systems (Pasquali et al, 2008;Wang et al, 2011).…”

Section: Calculating Optical Constants and Scattering Contrasts From mentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Origins of polarization-dependent anisotropic X-ray scattering from organic thin films

Gann

Collins²,

Tang

et al. 2016

J Synchrotron Radiat

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show abstract

“…The equilibrium geometry, electronic structure and X-ray absorption spectra of the free molecule were calculated by DFT with the computer code STOBE-deMon [31][32][33] . A gradient corrected RPBE exchange/correlation functional was applied 34,35 .…”

Section: ■ Computational Methodsmentioning

confidence: 99%

Oxidation of Rubrene Thin Films: An Electronic Structure Study

et al. 2014

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The performances of organic semiconductor devices are crucially linked with their stability at the ambient atmosphere. The evolution of electronic structures of 20 nm thick rubrene films exposed to ambient environment with time has been studied by UV and X-ray photoemission spectroscopy (UPS and XPS), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and density functional theory (DFT). XPS, NEXAFS data, and DFT calculated values suggest the formation of rubrene-epoxide and rubrene-endoperoxide through reaction of tetracene backbone with oxygen of ambient environment. Angle dependent XPS measurement indicates that the entire probed depth of the films reacts with oxygen by spending only about 120 min in ambient environment. The HOMO peak of pristine rubrene films almost disappears by exposure of 120 min to ambient environment. The evolution of the valence band (occupied states) and NEXAFS (unoccupied states) spectra indicates that the films become more insulating with exposure as the HOMO-LUMO gap increases on oxidation. Oxygen induced chemical reaction completely destroys the delocalized nature of the electron distribution in the tetracene backbone of rubrene. The results are relevant to the performance and reliability of rubrene based devices in the environment.

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“…Rigorously by denition, the LCST occurs if the isobar passes through the critical point and would require examination of both temperature and pressure as independent variable. 36 However as the volumetric transition at 1 bar is commonly described as the LCST in the hydrogel literature, [37][38][39] we will utilize this more standard convention.…”

Section: Characterization Of Swellingmentioning

confidence: 99%

Overcoming confinement limited swelling in hydrogel thin films using supramolecular interactions

2014

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The thin film behavior of poly(N-isopropylacrylamide-stat-2-(N-ethylperfluorooctane sulfonamido)ethyl acrylate) (NIPAAm-stat-FOSA) based hydrogels containing 5 mol% FOSA was elucidated using quartz crystal microbalance with dissipation (QCM-D) in combination with spectroscopic ellipsometry (SE) through examination of the lower critical solution temperature (LCST) and temperature dependent swelling for (dry) thicknesses ranging from 10 nm to 121 nm. For all thin films measured, the LCST was shown to slightly increase (>3 °C) in comparison to that of the bulk sample. However for these films, the increase in LCST was statistically identical, irrespective of thickness. Surprisingly, the volumetric swelling of the hydrogel in thin films, even at temperatures less than the LCST, was similar (within 20%) to the volumetric swelling of the bulk hydrogel, despite the expected significant decrease associated with the hydrogel being constrained by the substrate as predicted by one dimensional Flory-Rehner theory. We attribute this enhancement in swelling compared to theoretical expectations to the ability of the hydrophobic crosslinks to re-arrange under stress, which provides a mechanism to alleviate the decreased dimensionality imposed by the substrate; this mechanism is consistent with a large hysteresis in the swelling when cycling between 35 °C and 5 °C. Unlike the LCST, the swelling ratio increases with decreasing film thickness. At low temperatures (below the LCST), the volume swelling ratio increased from 3.9 to 4.9, while at temperatures above the LCST the swelling ratio increased from 1.5 to 2.5 when the film thickness decreased from 121 nm to 10 nm. The combination of facile processing through solution casting without the need for additional crosslinking chemistry and limited thickness dependent variation of swelling and LCST behavior in these physically crosslinked hydrogels makes these materials attractive for applications requiring thermoresponsive soft coatings.

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Role of Interfacial Interaction in Orientation of Poly(N-isopropylacrylamide) Chains on Silicon Substrate.

Cited by 12 publications

References 34 publications

Origins of polarization-dependent anisotropic X-ray scattering from organic thin films

Origins of polarization-dependent anisotropic X-ray scattering from organic thin films

Oxidation of Rubrene Thin Films: An Electronic Structure Study

Overcoming confinement limited swelling in hydrogel thin films using supramolecular interactions

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