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Temperature- and thickness-dependent elastic moduli of polymer thin films.

Ao Z, Li S - Nanoscale Res Lett (2011)

Bottom Line: The mechanical properties of polymer ultrathin films are usually different from those of their counterparts in bulk.Understanding the effect of thickness on the mechanical properties of these films is crucial for their applications.However, it is a great challenge to measure their elastic modulus experimentally with in situ heating.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia. zhimin.ao@unsw.edu.au.

ABSTRACT
The mechanical properties of polymer ultrathin films are usually different from those of their counterparts in bulk. Understanding the effect of thickness on the mechanical properties of these films is crucial for their applications. However, it is a great challenge to measure their elastic modulus experimentally with in situ heating. In this study, a thermodynamic model for temperature- (T) and thickness (h)-dependent elastic moduli of polymer thin films Ef(T,h) is developed with verification by the reported experimental data on polystyrene (PS) thin films. For the PS thin films on a passivated substrate, Ef(T,h) decreases with the decreasing film thickness, when h is less than 60 nm at ambient temperature. However, the onset thickness (h*), at which thickness Ef(T,h) deviates from the bulk value, can be modulated by T. h* becomes larger at higher T because of the depression of the quenching depth, which determines the thickness of the surface layer δ.

No MeSH data available.


Related in: MedlinePlus

The temperature-dependent elastic modulus of PS thin films with h = 10, 30, and 100 nm and bulk obtained from Equation 3.
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Figure 2: The temperature-dependent elastic modulus of PS thin films with h = 10, 30, and 100 nm and bulk obtained from Equation 3.

Mentions: Using Equation 3, the temperature dependence of elastic modulus of PS thin films with h = 10, 30, and 100 nm and bulk are shown in Figure 2. It is noted that the elastic modulus decreases as T increases for all the films. At low temperatures, there is a nearly linear relationship between the elastic modulus and temperature. However, the elastic modulus decreases steeply at the onset of approximately 210, 300, and 350 K for 10, 30, and 100 nm PS thin films, respectively, while the glass-transition temperatures are 275, 347, and 368 K for 10, 30, and 100 nm, respectively, based on Equation 4. The differences between the onset point and Tg are 65, 47, and 18 K, respectively, for the films of three different thicknesses, which imply that the modulus decreases greatly in the glass-transition temperature region, and this region is more extended as the thickness decreases, consistent with the available experimental data in published literatures [19,21,22].


Temperature- and thickness-dependent elastic moduli of polymer thin films.

Ao Z, Li S - Nanoscale Res Lett (2011)

The temperature-dependent elastic modulus of PS thin films with h = 10, 30, and 100 nm and bulk obtained from Equation 3.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211304&req=5

Figure 2: The temperature-dependent elastic modulus of PS thin films with h = 10, 30, and 100 nm and bulk obtained from Equation 3.
Mentions: Using Equation 3, the temperature dependence of elastic modulus of PS thin films with h = 10, 30, and 100 nm and bulk are shown in Figure 2. It is noted that the elastic modulus decreases as T increases for all the films. At low temperatures, there is a nearly linear relationship between the elastic modulus and temperature. However, the elastic modulus decreases steeply at the onset of approximately 210, 300, and 350 K for 10, 30, and 100 nm PS thin films, respectively, while the glass-transition temperatures are 275, 347, and 368 K for 10, 30, and 100 nm, respectively, based on Equation 4. The differences between the onset point and Tg are 65, 47, and 18 K, respectively, for the films of three different thicknesses, which imply that the modulus decreases greatly in the glass-transition temperature region, and this region is more extended as the thickness decreases, consistent with the available experimental data in published literatures [19,21,22].

Bottom Line: The mechanical properties of polymer ultrathin films are usually different from those of their counterparts in bulk.Understanding the effect of thickness on the mechanical properties of these films is crucial for their applications.However, it is a great challenge to measure their elastic modulus experimentally with in situ heating.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia. zhimin.ao@unsw.edu.au.

ABSTRACT
The mechanical properties of polymer ultrathin films are usually different from those of their counterparts in bulk. Understanding the effect of thickness on the mechanical properties of these films is crucial for their applications. However, it is a great challenge to measure their elastic modulus experimentally with in situ heating. In this study, a thermodynamic model for temperature- (T) and thickness (h)-dependent elastic moduli of polymer thin films Ef(T,h) is developed with verification by the reported experimental data on polystyrene (PS) thin films. For the PS thin films on a passivated substrate, Ef(T,h) decreases with the decreasing film thickness, when h is less than 60 nm at ambient temperature. However, the onset thickness (h*), at which thickness Ef(T,h) deviates from the bulk value, can be modulated by T. h* becomes larger at higher T because of the depression of the quenching depth, which determines the thickness of the surface layer δ.

No MeSH data available.


Related in: MedlinePlus