Role of the Restricted Geometry on the Morphology of Ultrathin Poly(di-n-hexylsilane) Films

Despotopoulou, M. M.; Frank, Curtis W.; Miller, R. D.; Rabolt, John F.

doi:10.1021/ma00123a042

Cited by 57 publications

(56 citation statements)

References 3 publications

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“…But in case of thin films of low or moderate thickness, the chains are affected by the substrate on a short distance and the main part of the material does not manifest bulk properties. Moreover, if the thickness of films is sufficient and the polymer chains can build a supramolecular structure, then they can be aligned rather than entangled and, thus, in the first place, optoelectrical properties [22,23] and the polymer structure [24,25,26] are influenced. Evidences for thickness threshold of structural ordering in thin poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) films have been already published [27].…”

Section: Introductionmentioning

confidence: 99%

Thickness dependent structural ordering, degradation and metastability in polysilane thin films: A photoluminescence study on representative σ-conjugated polymers

Urbánek

Kuřitka

2015

Journal of Luminescence

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Cite this article as: Pavel Urbánek and Ivo Kuřitka, Thickness dependent structural ordering, degradation and metastability in polysilane thin films: A photoluminescence study on representative σ-conjugated polymers, Journal of Luminescence, http://dx. ABSTRACTWe present a fundamental experimental study based on the fluorescence investigation of thin σ-conjugated polymer films, where the dependence of optoelectrical properties and UV degradation on film thickness ranging from nano-to microscale was studied. Such extensive and detailed study was performed for the first time and observed spectral shifts in emission and excitation spectra and UV degradation retardation point towards the conclusions that there exists a threshold thickness where the material degradation behavior, electron delocalization and structure suddenly change. The development of well aligned polymeric chain structure between the nano-and micrometer thickness (on the mesoscale) was shown responsible for the manifested phenomena. The material thicker than critical 500 nm has extremely small Stokes shift, maximum extended σ-delocalization along the silicon polymer backbone and exhibits remarkable UV degradation slowdown and self-recovery ability. On the contrary, the electronic properties of thin films below 80 nm resemble those of random coils in solutions. The films of moderate thickness show relatively steep transition between these two modes of structural ordering and resulting properties. Altogether, we consider this complex phenomenon as a consequence of the mesoscale effect, which is an only recently introduced concept in polymer thin films.

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Section: Introductionmentioning

confidence: 99%

Thickness dependent structural ordering, degradation and metastability in polysilane thin films: A photoluminescence study on representative σ-conjugated polymers

Urbánek

Kuřitka

2015

Journal of Luminescence

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“…Experimental studies have demonstrated the effect of size on the mechanical and thermodynamic properties of nano-objects, as seen with the elastic moduli of hollow fibers 9 and electrospun nanofibers, [10][11][12][13][14] which sharply increase below a certain fiber diameter, as well as shifts in object melting temperatures. 15,16 Similarly, thickness and surface interactions of ultrathin polymer films (the film thickness is in the order of 2R g of a polymer chain, or less) highly influence their glass transition and melting temperatures, [17][18][19] polymer dynamics in the glassy state, 20 crystallization kinetics and degree of crystallinity, [21][22][23] phase behavior, 24 and morphology. 25,26 For all the above examples, the portion of ''surface material'' is comparable with the bulk, due to extremely small object size, therefore, the ansatz claiming ''nano-object ¼ bulk þ surface'' seems relevant for such systems from a physical point of view.…”

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confidence: 99%

Electrospun polymer nanofibers: Mechanical and thermodynamic perspectives

Arinstein

Zussman

2011

J Polym Sci B Polym Phys

138

103

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This article reviews and discusses some open problems concerning polymer materials of reduced sizes and dimensions. Such objects exhibit exceptional physical properties when compared with their macroscopic counterparts. More specifically, abrupt increases in polymer nanofiber elastic modulus have been observed when diameters drop below a certain value. In addition, temperature dependence of elastic modulus is highly influenced by fiber diameter. Mechanical (macroscopic) analyses have failed to provide satisfactory explanations for the mechanisms ruling such features, calling for detailed microscopic examination of the systems in question. A hypothesis bridging the current knowledge gaps is presented. The key element of this hypothesis is based on confinement of the supermolecular microstructure of polymer nanofibers and its dominant role in the deformation process. This suggestion challenges the commonly held view suggesting that surface effects are the most significant parameters impacting mechanical and thermodynamic nanofiber behaviors. The review will focus on the mechanical and thermodynamic properties of electrospun polymer nanofibers, selected as representatives of nanoscale polymer objects.

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“…This is important because nucleation cannot occur in films thinner than 10 -15 nm. 1,72 These dewetted droplets crystallize first and act as the nuclei for growth in the monolayer.…”

Section: Monolayer Filmsmentioning

confidence: 99%

“…Confining the crystallizable polymer in a thin film will affect its nucleation, growth rate, and kinetics. These issues have been addressed by studies previously discussed; [33][34][35] however, most of the work has been done by Frank et al 1,59,60,72,73 They have taken several approaches to study the crystallization kinetics. They have used different polymers, PEO 59,60 and poly(di-n-hexylsilane) (PDHS).…”

Section: Crystal Growth and Kineticsmentioning

confidence: 99%

“…They have used different polymers, PEO 59,60 and poly(di-n-hexylsilane) (PDHS). 1,72,73 Experimental techniques include AFM, FT-IR spectroscopy, and fluorescence spectroscopy for the PEO samples, and UV spectroscopy for the PDHS sample. For the spectroscopic techniques, a change in the peak associated with the crystalline fraction was correlated to the amount of crystallinity.…”

Section: Crystal Growth and Kineticsmentioning

confidence: 99%

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Crystallization in Polymer Thin Films: Morphology and Growth

Horn¹,

Cheng²

2008

Series in Soft Condensed Matter

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Confinement of semi-crystalline polymers into thin films can affect both the morphology and the growth of the resultant crystals. Several morphologies, including polycrystalline and single crystalline, can be obtained in thin films under certain conditions. In addition, the molecular orientation and kinetics can be affected by the temperature, film thickness, and interfacial energy. This chapter is a review of various reports in thin film crystallization.

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Role of the Restricted Geometry on the Morphology of Ultrathin Poly(di-n-hexylsilane) Films

Cited by 57 publications

References 3 publications

Thickness dependent structural ordering, degradation and metastability in polysilane thin films: A photoluminescence study on representative σ-conjugated polymers

Thickness dependent structural ordering, degradation and metastability in polysilane thin films: A photoluminescence study on representative σ-conjugated polymers

Electrospun polymer nanofibers: Mechanical and thermodynamic perspectives

Crystallization in Polymer Thin Films: Morphology and Growth

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