914
I. Bacosca et al. / Reactive & Functional Polymers 71 (2011) 905–915
maximum profile valley depth, Rv, which represents the lowest
point in the region relative to the zero level, was ꢀ0.37 m. The to-
tal roughness height, Rt, which is the height difference between the
highest point and the lowest point in the region, was 1.83 m. The
maximum profile peak height, Rp, which represents the highest
the domain of 445–520 °C. The polymers containing a more rigid
structure have one step of decomposition compared to related
polymers with more flexible linkages and exhibit two steps of
decomposition. The glass transition temperature of poly(amide
imide)s was in the range of 193–220 °C: the lowest value was
found for polymer which had more flexible ether bridges, while
the highest value was found for polymer which contained nitrile
groups in both monomer segments and more para catenations.
The molecular relaxations were determined by dynamic mechani-
cal analyses and dielectric spectroscopy. The data evidenced three
l
l
point in the region relative to the zero level, was 1.45
cally we have an interesting needle geometry).
lm (practi-
The nano-actuation of polymer film was determined using an
interferometric AGILENT 5529A system, an instrument which
investigates and measures the linear micro and nano-displacement
with a remarkable resolution of 2 nm. The experiments were per-
formed using a manual switch to control the dc electric field.
Fig. 10 presents the nanometric displacement of polymer film 4a
with flexible thin electrodes, at 70, 100, 130 and 150 V. A plane
thin electrode can ensure a good electric contact with the polymer
membrane and good mechanical roughness at the contact with the
retroreflector of the measuring equipment. The signals which are
visualized represent the film actuation response to an electric dc
field at different voltage.
secondary relaxations (c, b1, b2) and a primary relaxation (a) attrib-
uted to glass transition temperature. For a poly(amide imide) film,
the nanometric displacement showed a value of ꢀ140 nm and a
sensibility of 0.933 nm Vꢀ1 at 150 V. All these properties make
the present polymers potential candidates for high performance
applications as position nanoelectromechanical actuators.
Acknowledgements
An electrostrictive effect of the polymer film appears: the mi-
cro-actuation or deformation of the polymer film is proportional
to the square of the field [47]. The nano-actuation is characterized
by the following parameters: the electric field, E (V mꢀ1) = U/g,
where U is the dc voltage and g is the thickness of the film (for
polymer film 4a the thickness is about 0.18 mm); the maximum
value of nano-actuation or nano-displacement, d (nm); the sensi-
tivity of nano-actuation, S (nm Vꢀ1) = d/U. The specific actuation
parameters of the experiments performed on polymer film 4a are
summarized in Table 3.
This work was supported by CNCSIS–UEFISCDI, Project number
PNII–IDEI code ID_997/2008. We thank Dr. M. Cristea and V.
Musteata at ‘‘Petru Poni’’ Institute of Macromolecular Chemistry,
Iasi, Romania, for DMA and BDS measurements.
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