268
M. Tress et al.
amorphous state. This signature is typical for spatial confinement and a decomposition of the respective relaxation time distribution yields three fractions of different
dynamics. These are assigned to a rigid amorphous fraction around the crystallites, a mobile amorphous fraction, and a confined amorphous fraction of enhanced
dynamics presumably located around the POSS centers. In complementary FTIR
measurements, crystalline and amorphous moieties can be addressed individually
and their evolution upon crystallization can be traced. The better time resolution
of the FTIR data reveals a multi-step process with a particular lag time; firstly, a
fast mechanism initializes the crystallization, secondly, a tenfold slower process is
present, which matches the BDS results. This suggests a complex interplay between
the crystallization of the iPS arms and conformational changes due to the complex
architecture and structural constraints.
Keywords Star-polymer · Confinement · Enhanced dynamics · POSS
Abbreviations
BDS Broadband Dielectric Spectroscopy
CAF Confined Amorphous Fraction
DSC Differential Scanning Calorimetry
FTIR Fourier Transform Infrared Spectroscopy
HN
Havriliak-Negami
iPS
Isotactic Polystyrene
MAF Mobile Amorphous Fraction
RAF Rigid Amorphous Fraction
POSS Polyhedral Oligomeric Silesquioxane
RTD Relaxation Time Distribution
1 Introduction
Crystallization in polymers can tremendously alter their material properties and is
therefore of great interest in fundamental and applied research [1, 2]. Thereby, not
only the properties of the crystalline structure itself are relevant. Due to the fact
that polymers basically never crystallize entirely, the implications for the remaining
amorphous fraction are of similar or even bigger importance. In most cases, the
material becomes macroscopically more rigid while its toughness is reduced after
(partial) crystallization [3, 4]. On the molecular scale this can be comprehended by
the smaller number of chains which can relax and dissipate mechanical stress. In the
crystalline domains the chains are arranged in lamellar structures which do not allow
for stress release (except for mobility along the chain axis in certain polymers [5]).
M. Tress et al.
amorphous state. This signature is typical for spatial confinement and a decomposition of the respective relaxation time distribution yields three fractions of different
dynamics. These are assigned to a rigid amorphous fraction around the crystallites, a mobile amorphous fraction, and a confined amorphous fraction of enhanced
dynamics presumably located around the POSS centers. In complementary FTIR
measurements, crystalline and amorphous moieties can be addressed individually
and their evolution upon crystallization can be traced. The better time resolution
of the FTIR data reveals a multi-step process with a particular lag time; firstly, a
fast mechanism initializes the crystallization, secondly, a tenfold slower process is
present, which matches the BDS results. This suggests a complex interplay between
the crystallization of the iPS arms and conformational changes due to the complex
architecture and structural constraints.
Keywords Star-polymer · Confinement · Enhanced dynamics · POSS
Abbreviations
BDS Broadband Dielectric Spectroscopy
CAF Confined Amorphous Fraction
DSC Differential Scanning Calorimetry
FTIR Fourier Transform Infrared Spectroscopy
HN
Havriliak-Negami
iPS
Isotactic Polystyrene
MAF Mobile Amorphous Fraction
RAF Rigid Amorphous Fraction
POSS Polyhedral Oligomeric Silesquioxane
RTD Relaxation Time Distribution
1 Introduction
Crystallization in polymers can tremendously alter their material properties and is
therefore of great interest in fundamental and applied research [1, 2]. Thereby, not
only the properties of the crystalline structure itself are relevant. Due to the fact
that polymers basically never crystallize entirely, the implications for the remaining
amorphous fraction are of similar or even bigger importance. In most cases, the
material becomes macroscopically more rigid while its toughness is reduced after
(partial) crystallization [3, 4]. On the molecular scale this can be comprehended by
the smaller number of chains which can relax and dissipate mechanical stress. In the
crystalline domains the chains are arranged in lamellar structures which do not allow
for stress release (except for mobility along the chain axis in certain polymers [5]).