5 research outputs found
Light-Switchable Polymers of Intrinsic Microporosity
The
interest in (micro)Āporous systems is greater than ever before
with microporous polymers finding application in areas such as gas
storage/separation and catalysis. In contrast to the vast majority
of publications on microporous polymers seeking ever higher values
for surface area or uptake capacity for a particular gas, this work
presents a means to render a microporous system responsive to electromagnetic
stimuli. The incorporation of a diarylethene (DAE) derivative in the
backbone of a polymer of intrinsic microporosity (PIM) produces a
microporous system that exhibits photochromism as proven by UVāvis
absorption and NMR studies. In the resulting DAE-PIM, surface area
is not a fixed unalterable property but can be influenced by the external
and nondestructive stimulus light in a reversible manner. Furthermore,
in combination with Matrimid, free-standing membranes can be produced
that display light-switchable diffusivity and permeability for carbon
dioxide and oxygen. In this way, material scientists are offered the
potential to employ only one system that can assume several states
with different properties for each
Molecular Mobility and Physical Aging of a Highly Permeable Glassy Polynorbornene as Revealed by Dielectric Spectroscopy
Polymeric
membranes represent a cost- and energy-efficient solution
for gas separation. Recently superglassy polymers with high free volume
outperform many conventional dense polymers in terms of gas permeability
and selectivity. However, such polymers are prone to pronounced physical
aging, resulting in a dramatic reduction in the gas permeability.
Molecular mobility of polymer segments plays an important role in
the physical aging and the gas transport performance of polymeric
membranes. Molecular mobility and physical aging of a representative
superglassy polynorbornene with very high gas permeability, PTCNSi2g,
was monitored by using dielectric spectroscopy with state-of-the-art
high-resolution analyzers. This work helps to shed some light on the
structureāproperty relationship of superglassy polymers on
a molecular level and to provide practical ādesign rulesā
for the development of high performance polymers for gas separation
Molecular Mobility and Gas Transport Properties of Mixed Matrix Membranes Based on PIMā1 and a Phosphinine Containing Covalent Organic Framework
Polymers with intrinsic
microporosity (PIMs) are gaining attention
as gas separation membranes. Nevertheless, they face limitations due
to their pronounced physical aging. In this study, a covalent organic
framework containing Ī»5-phosphinine moieties, CPSF-EtO,
was incorporated as a nanofiller (concentration range 0ā10
wt %) into a PIM-1 matrix forming dense films with a thickness of
ca. 100 Ī¼m. The aim of the investigation was to investigate
possible enhancements of gas transport properties and mitigating effects
on physical aging. The incorporation of the nanofiller occurred on
an nanoaggregate level with domains up to 100 nm, as observed by T-SEM
and confirmed by X-ray scattering. Moreover, the X-ray data show that
the structure of the microporous network of the PIM-1 matrix is changed
by the nanofiller. As molecular mobility is fundamental for gas transport
as well as for physical aging, the study includes dielectric investigations
of pure PIM-1 and PIM-1/CPSF-EtO mixed matrix membranes to establish
a correlation between the molecular mobility and the gas transport
properties. Using the time-lag method, the gas permeability and the
permselectivity were determined for N2, O2,
CH4, and CO2 for samples with variation in filler
content. A significant increase in the permeability of CH4 and CO2 (50% increase compared to pure PIM-1) was observed
for a concentration of 5 wt % of the nanofiller. Furthermore, the
most pronounced change in the permselectivity was found for the gas
pair CO2/N2 at a filler concentration of 7 wt
%
First Clear-Cut Experimental Evidence of a Glass Transition in a Polymer with Intrinsic Microporosity: PIMā1
Polymers
with intrinsic microporosity (PIMs) represent a novel,
innovative class of materials with great potential in various applications
from high-performance gas-separation membranes to electronic devices.
Here, for the first time, for PIM-1, as the archetypal PIM, fast scanning
calorimetry provides definitive evidence of a glass transition (<i>T</i><sub>g</sub> = 715 K, heating rate 3 Ć 10<sup>4</sup> K/s) by decoupling the time scales responsible for glass transition
and decomposition. Because the rigid molecular structure of PIM-1
prevents any conformational changes, small-scale bend and flex fluctuations
must be considered the origin of its glass transition. This result
has strong implications for the fundamental understanding of the glass
transition and for the physical aging of PIMs and other complex polymers,
both topical problems of materials science
First Clear-Cut Experimental Evidence of a Glass Transition in a Polymer with Intrinsic Microporosity: PIMā1
Polymers
with intrinsic microporosity (PIMs) represent a novel,
innovative class of materials with great potential in various applications
from high-performance gas-separation membranes to electronic devices.
Here, for the first time, for PIM-1, as the archetypal PIM, fast scanning
calorimetry provides definitive evidence of a glass transition (<i>T</i><sub>g</sub> = 715 K, heating rate 3 Ć 10<sup>4</sup> K/s) by decoupling the time scales responsible for glass transition
and decomposition. Because the rigid molecular structure of PIM-1
prevents any conformational changes, small-scale bend and flex fluctuations
must be considered the origin of its glass transition. This result
has strong implications for the fundamental understanding of the glass
transition and for the physical aging of PIMs and other complex polymers,
both topical problems of materials science