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In Situ Probing the Relaxation Properties of Ultrathin Polystyrene Films by Using Electric Force Microscopy

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ABSTRACT

The rapid development of nanoscience and nanotechnology involves polymer films with thickness down to nanometer scale. However, the properties of ultrathin polymer films are extremely different from that of bulk matrix or thin films. It is challenging to distinguish the changes of physical properties in ultrathin films using conventional techniques especially when it locates near the glass transition temperature (Tg). In this work, we successfully evaluated a series of physical properties of ultrathin polystyrene (PS) films by in situ characterizing the discharging behavior of the patterned charges using electric force microscopy. By monitoring the surface potential in real time, we found that the Tg of ultrathin PS films is clearly independent of film thickness, which are greatly different from that of thin PS films (film thickness larger than 10 nm).

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Temperature-dependent SPD curves of a ultrathin PS films with different thickness of 6, 9, and 10 nm and b normal thin PS films with thicknesses of 21, 43, and 78 nm
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Fig5: Temperature-dependent SPD curves of a ultrathin PS films with different thickness of 6, 9, and 10 nm and b normal thin PS films with thicknesses of 21, 43, and 78 nm

Mentions: The temperature-dependent SPD curves for ultrathin PS films with different film thicknesses are illustrated in Fig. 5a. The discharging behaviors are quite similar when ultrathin PS film thickness reduces from 10 to 6 nm. Both linear and very sharp decay tendencies are obtained when the temperature increases from room temperature (298 K) to 328 K. With temperature continuously increasing, the sharp discharging behaviors tend to be gentle until patterned charges are nearly exhausted. According to the previous studies, the interface layer which is near the substrate could be negligible [11, 18], while the top layer and middle layer are regarded as the free surface layer and bulk layer [42], respectively. Polymer chains on the top surface layer have larger free space and higher mobility, which is much more active and independent of the bulk-like layer [10, 35, 39, 43, 44]. Hence, there is fast dynamics near the free surface compared to normal thin films and bulk matrix [13, 23, 45, 46], and most charges dissipate very quickly at the beginning stages. However, with the continuous dissipation of patterned charges, a reduction in the driving forces for the segmental relaxation could lead to a reduced discharging behavior, which conversely weakens the discharging behavior.Fig. 5


In Situ Probing the Relaxation Properties of Ultrathin Polystyrene Films by Using Electric Force Microscopy
Temperature-dependent SPD curves of a ultrathin PS films with different thickness of 6, 9, and 10 nm and b normal thin PS films with thicknesses of 21, 43, and 78 nm
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383798&req=5

Fig5: Temperature-dependent SPD curves of a ultrathin PS films with different thickness of 6, 9, and 10 nm and b normal thin PS films with thicknesses of 21, 43, and 78 nm
Mentions: The temperature-dependent SPD curves for ultrathin PS films with different film thicknesses are illustrated in Fig. 5a. The discharging behaviors are quite similar when ultrathin PS film thickness reduces from 10 to 6 nm. Both linear and very sharp decay tendencies are obtained when the temperature increases from room temperature (298 K) to 328 K. With temperature continuously increasing, the sharp discharging behaviors tend to be gentle until patterned charges are nearly exhausted. According to the previous studies, the interface layer which is near the substrate could be negligible [11, 18], while the top layer and middle layer are regarded as the free surface layer and bulk layer [42], respectively. Polymer chains on the top surface layer have larger free space and higher mobility, which is much more active and independent of the bulk-like layer [10, 35, 39, 43, 44]. Hence, there is fast dynamics near the free surface compared to normal thin films and bulk matrix [13, 23, 45, 46], and most charges dissipate very quickly at the beginning stages. However, with the continuous dissipation of patterned charges, a reduction in the driving forces for the segmental relaxation could lead to a reduced discharging behavior, which conversely weakens the discharging behavior.Fig. 5

View Article: PubMed Central - PubMed

ABSTRACT

The rapid development of nanoscience and nanotechnology involves polymer films with thickness down to nanometer scale. However, the properties of ultrathin polymer films are extremely different from that of bulk matrix or thin films. It is challenging to distinguish the changes of physical properties in ultrathin films using conventional techniques especially when it locates near the glass transition temperature (Tg). In this work, we successfully evaluated a series of physical properties of ultrathin polystyrene (PS) films by in situ characterizing the discharging behavior of the patterned charges using electric force microscopy. By monitoring the surface potential in real time, we found that the Tg of ultrathin PS films is clearly independent of film thickness, which are greatly different from that of thin PS films (film thickness larger than 10 nm).

No MeSH data available.