Thickness and composition dependence of the glass transition temperature in thin random copolymer films

Park, Chul Ho; Kim, Jae Hyun; Ree, Moonhor; Sohn, Byeong‐Hyeok; Jung, Jin Chul; Zin, Wang‐Cheol

doi:10.1016/j.polymer.2004.04.048

Cited by 94 publications

(85 citation statements)

References 26 publications

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“…233,234 ) Depending upon the polymer and the substrate, T g can decrease or increase with decreasing film thickness, with increases of up to 40 K being reported. [237][238][239][240][241][242] T g decreases are generally interpreted in terms of enhanced mobility at the free surface while increases in T g are interpreted as reduced mobility near the substrate interface. Even bigger decreases in T g (up to 70 K) have been reported for freestanding polymer films in the nanometer regime.…”

Section: A Thin Film Propertiesmentioning

confidence: 99%

Perspective: Supercooled liquids and glasses

Ediger

Harrowell

2012

The Journal of Chemical Physics

457

445

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Supercooled liquids and glasses are important for current and developing technologies. Here we provide perspective on recent progress in this field. The interpretation of supercooled liquid and glass properties in terms of the potential energy landscape is discussed. We explore the connections between amorphous structure, high frequency motions, molecular motion, structural relaxation, stability against crystallization, and material properties. Recent developments that may lead to new materials or new applications of existing materials are described.

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Section: A Thin Film Propertiesmentioning

confidence: 99%

Perspective: Supercooled liquids and glasses

Ediger

Harrowell

2012

The Journal of Chemical Physics

457

445

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“…Polymeric materials that experience confinement are influenced by the substrate composition, especially in films with thicknesses less than 100 nm. [55,56] In strongly interacting polymer/substrate systems such as Nafion/gold, the backbone lies parallel to the surface as a result of the sulfonate/substrate interactions driving the side chain to orient perpendicularly to the surface, for films with thicknesses of well beyond 25 nm, as evidenced by the negative birefringence values (n ≈ -0.01) for samples with thickness greater than 200 nm on platinum and gold.…”

Section: Molecular Anisotropymentioning

confidence: 99%

Substrate‐Dependent Molecular and Nanostructural Orientation of Nafion Thin Films

Kushner

Kusoglu

Podraza

et al. 2019

Adv Funct Materials

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The effects of film thickness and substrate composition on the ionomer structure in porous electrodes is critical in understanding pathways towards developing higher performance electrochemical devices, including fuel cells and batteries. Insights are gained into the molecular and nanostructural orientation dependence for thin Nafion films (12 to 300 nm thick) on gold, platinum, and SiO 2 model substrates. Molecular orientation is determined from the birefringence measured using spectroscopic ellipsometry, while the nanostructural orientation of the ionic domains was measured using grazing-incidence smallangle X-ray scattering. Density functional theory calculations for the molecular polarizability of the Nafion backbone and side chain show complimentary contributions to the measured birefringence values for the material. Nafion films prepared on SiO 2 substrates exhibit a nearly isotropic molecular and nanostructural orientation. Films on gold and platinum display parallel backbone orientations, relative to the substrate, with decreasing film thickness. However, a birefringence transition towards molecular isotropy is observed for 30 nm thick films on Au and Pt; while the ionic nanostructured domains continuously align parallel to the substrate. This apparent isotropic molecular orientation with increasing domain orientation highlights the difference between the backbone and side chain orientation, a key finding for elucidating transport in confined films at the interfaces.

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“…The T g of molecular liquids and polymers can deviate substantially from the bulk T g with confinement to the nanometre length-scale. 15,[30][31][32][33][34][35][36] As the confining dimension is decreased below a critical value, e.g., film thickness in polymer films, interparticle spacing in polymer nanocomposites, diameter in molecular glass-former filled controlled pore glass, an increasingly large fraction of material is in direct contact with interfaces. The deviation in T g with confinement can be explained as a result of (or lack of) interfacial interactions between the polymer and the interface.…”

Section: Confinement Effects On the Glass Transition Temperaturementioning

confidence: 99%

Physical aging of confined glasses

Priestley

2009

Soft Matter

103

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The properties of glasses confined to the nanometre length-scale can deviate substantially from those found in bulk samples. Physical aging, the structural relaxation of glasses toward equilibrium, leads to time-dependent mechanical, electrical, optical properties, etc. This article highlights experimental work on the impact of confinement on the physical aging of molecular and polymeric glasses, a topic that is both scientifically interesting and technologically important. Experimental observations, as well as challenges and future work, are discussed.

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Thickness and composition dependence of the glass transition temperature in thin random copolymer films

Cited by 94 publications

References 26 publications

Perspective: Supercooled liquids and glasses

Perspective: Supercooled liquids and glasses

Substrate‐Dependent Molecular and Nanostructural Orientation of Nafion Thin Films

Physical aging of confined glasses

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