Impact of Nanoscale Confinement on Crystal Orientation of Poly(ethylene oxide)

Wang, Haopeng; Keum, Jong K.; Hiltner, A.; Baer, E.

doi:10.1002/marc.200900653

Cited by 46 publications

(29 citation statements)

References 33 publications

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“…The PEO matrix also shows partial crystallisation after annealing, with two peaks at 19.2 and 23.4 degrees as reported in literature and assigned to the (120) planes and overlapping reflections from the (032), ( 32), 1 (112), ( 12), ( 24), ( 04), and (004) planes. [19][20][21][22] We thus 2 1 2 consider that the soft, polar, PEO environment enables nucleation and growth of CMA crystals to create a thin film of polycrystalline CMA1 embedded in an optically inert PEO matrix. Crystallisation can also be induced in other matrices under harsher experimental conditions and/or over longer times, as detailed in Table S 1.…”

Section: Thin-film Crystallisationmentioning

confidence: 99%

Carbene–Metal–Amide Polycrystalline Materials Feature Blue Shifted Energy yet Unchanged Kinetics of Emission

et al. 2020

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The nature of carbene-metal-amide (CMA) photoluminescence in the solid state is explored through spectroscopic and quantum-chemical investigations on a representative Au-centred molecule. The crystalline phase offers well-defined coplanar geometries-enabling the link between molecular conformations and photophysical properties to be unravelled. We show that a combination of restricted torsional distortion and molecular electronic polarisation blueshift the charge-transfer emission by around 400 meV in the crystalline versus the amorphous phase, through energetically raising the less-dipolar S 1 state relative to S 0 . This blueshift brings the lowest charge-transfer states very close to the localised carbazole triplet state, whose structured emission is observable at low temperature in the polycrystalline phase. Moreover, we discover that the rate of intersystem crossing and emission kinetics are unaffected by the extent of torsional distortion. We conclude that more coplanar triplet equilibrium conformations control the photophysics of CMAs.

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Section: Thin-film Crystallisationmentioning

confidence: 99%

Carbene–Metal–Amide Polycrystalline Materials Feature Blue Shifted Energy yet Unchanged Kinetics of Emission

et al. 2020

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“…A transition from flat-on to edge-on lamellae with the decrease of crystallization temperature has even been identified for a 33 nm poly(bisphenol A hexane ether) film and a nanolayered poly(ethylene oxide) (PEO) system [2,17]. Our experimental observations reveal the occurrence of flat-on lamellar crystals within 50 nm layered PET in a wide range of crystallization temperatures down to 117 C. Moreover, the development of anisotropic SAXS maxima associated to the occurrence of flat-on lamellae has also been observed for the 115 nm layered material crystallized at 117 C (results not shown here).…”

Section: Influence Of Crystallization Temperature On the Development mentioning

confidence: 99%

Confined crystallization of nanolayered poly(ethylene terephthalate) using X-ray diffraction methods

Flores

Ania

Arribas

et al. 2012

Polymer

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a b s t r a c tThe development of crystalline lamellae in ultra-thin layers of poly(ethylene terephthalate) PET confined between polycarbonate (PC) layers in an alternating assembly is investigated as a function of layer thickness by means of X-ray diffraction methods. Isothermal crystallization from the glassy state is insitu followed by means of small-angle X-ray diffraction. It is found that the reduced size of the PET layers influences the lamellar nanostructure and induces a preferential lamellar orientation. Two lamellar populations, flat-on and edge-on, are found to coexist in a wide range of crystallization temperatures (T c ¼ 117e150 C) and within layer thicknesses down to 35 nm. Flat-on lamellae appear at a reduced crystallization rate with respect to bulk PET giving rise to crystals of similar dimensions separated by larger amorphous regions. In addition, a narrower distribution of lamellar orientations develops when the layer thickness is reduced or the crystallization temperature is raised. In case of edgeon lamellae, crystallization conditions also influence the development of lamellar orientation; however, the latter is little affected by the reduced size of the layers. Results suggest that flat-on lamellae arise as a consequence of spatial confinement and edge-on lamellae could be generated due to the interactions with the PC interface.

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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.…”

mentioning

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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Impact of Nanoscale Confinement on Crystal Orientation of Poly(ethylene oxide)

Cited by 46 publications

References 33 publications

Carbene–Metal–Amide Polycrystalline Materials Feature Blue Shifted Energy yet Unchanged Kinetics of Emission

Carbene–Metal–Amide Polycrystalline Materials Feature Blue Shifted Energy yet Unchanged Kinetics of Emission

Confined crystallization of nanolayered poly(ethylene terephthalate) using X-ray diffraction methods

Electrospun polymer nanofibers: Mechanical and thermodynamic perspectives

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