Crystallization of Polymers Under 1D Confinement
223
towards the topics, but to the limited number of experimental techniques permitting
to characterize the relaxation processes occurring in polymers during crystallization.
In the case of confined geometries (thin films, nanorods, etc), at the state of the
art, only broadband dielectric spectroscopy has been able to provide a microscopic
information on mechanisms of crystallization [4, 14, 18–28].
In this chapter, focusing on 1D confinement (thin films), we will revise the results
of the investigation of the kinetics of crystallization by means of broadband dielectric
spectroscopy. After introducing the methodology to perform such measurements, we
will discuss on a model of the thickness dependence of the crystallization rate and
finally show the first experimental tests supporting its validity. We will conclude this
chapter with a short perspective on future work which could further advance our
understanding of the crystallization at molecular level.
2 Guidelines for Sample Preparation
Samples for the investigation of the crystallization in thin films are commonly
prepared in the geometry of capped films, via a bottom-up approach permitting to
fabricate nanocapacitors by alternating conductive and dielectric layers; see Fig. 1.
Tough lacking a direct optical access, this geometry has several advantages. Its
symmetry [29] (metal/polymer/metal) eases modeling with respect to the case of
supported film (wall/polymer/gas) where the presence of two intrinsically different
interfaces requires a larger number of hypotheses. Capped geometry is also a benchmark system for the investigation of nanocomposites, [30] and is relevant at industrial
level, especially in the case of multilayers, for packaging applications.
Fig. 1 Sketch of the approach currently used to perform crystallization experiments on ultrathin
polymer films via dielectric spectroscopy. The polymer layer, a dielectric medium is capped between
two conductive layers (e.g., thermally evaporated Al)
223
towards the topics, but to the limited number of experimental techniques permitting
to characterize the relaxation processes occurring in polymers during crystallization.
In the case of confined geometries (thin films, nanorods, etc), at the state of the
art, only broadband dielectric spectroscopy has been able to provide a microscopic
information on mechanisms of crystallization [4, 14, 18–28].
In this chapter, focusing on 1D confinement (thin films), we will revise the results
of the investigation of the kinetics of crystallization by means of broadband dielectric
spectroscopy. After introducing the methodology to perform such measurements, we
will discuss on a model of the thickness dependence of the crystallization rate and
finally show the first experimental tests supporting its validity. We will conclude this
chapter with a short perspective on future work which could further advance our
understanding of the crystallization at molecular level.
2 Guidelines for Sample Preparation
Samples for the investigation of the crystallization in thin films are commonly
prepared in the geometry of capped films, via a bottom-up approach permitting to
fabricate nanocapacitors by alternating conductive and dielectric layers; see Fig. 1.
Tough lacking a direct optical access, this geometry has several advantages. Its
symmetry [29] (metal/polymer/metal) eases modeling with respect to the case of
supported film (wall/polymer/gas) where the presence of two intrinsically different
interfaces requires a larger number of hypotheses. Capped geometry is also a benchmark system for the investigation of nanocomposites, [30] and is relevant at industrial
level, especially in the case of multilayers, for packaging applications.
Fig. 1 Sketch of the approach currently used to perform crystallization experiments on ultrathin
polymer films via dielectric spectroscopy. The polymer layer, a dielectric medium is capped between
two conductive layers (e.g., thermally evaporated Al)