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Ao and Li Nanoscale Research Letters 2011, 6:243

Ao and Li Nanoscale Research Letters 2011, 6:243 http://www.nanoscalereslett.com/content/6/1/243 NANO REVIEW Open Access Temperature- and thickness-dependent elastic moduli of polymer thin films Zhimin Ao*, Sean Li 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. | Ao and Li Nanoscale Research Letters 2011 6 243 http www.nanoscalereslett.eom content 6 1 243 o Nanoscale Research Letters a SpringerOpen Journal NANO REVIEW Open Access Temperature- and thickness-dependent elastic moduli of polymer thin films Zhimin Ao Sean Li 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 Ỗ. Introduction As devices are being developed with a view towards making them smaller thinner and lighter in dimension thin polymer films are found to be in more stringent demand in various applications such as diffusion barriers dielectric coatings electronic packing and so on 1 . Therefore understanding the elastic modulus in confined geometries such as in thin films is critical to the stability of the structures of the actual devices. A growing demand exists for the determination of the mechanical properties of thin films and coatings at a rapid pace. Recent researches primarily focusing on the confinement effect of the glass-transition temperature Tg in thin films 2-7 have presented inconsistent results. It is believed that such a phenomenon might be attributed to the