8 research outputs found
Green and Blue Electrochromic Polymers from Processable Siloxane Precursors
Herein
we report the synthesis of a new class of processable siloxane precursor
polymers consisting of aromatic groups and flexible siloxane linkages
and their conversions to green and blue electrochromic polymers in
the solid state. 3,4-Ethylenedioxythiophene (EDOT), 2,2âČ-bisÂ(3,4-ethylenedioxythiophene)
(BiEDOT), and a donorâacceptor moiety 4,7-bisÂ(EDOT)-2,1,3-benzothiadiazole
(BEBTD) were incorporated as aromatic groups to demonstrate the versatility
of the precursor method to different aromatic systems. The utilization
of a siloxane linkage allows for a precursor polymer exhibiting improved
solubility in common organic solvents and accessible glass transition
temperatures (â1 to 132 °C) as compared to a previously
reported silane precursor. A simple method to control the thermal
properties of the precursor was also demonstrated by incorporation
of both siloxane and silane functionalities into the precursor backbone.
The oxidatively converted product from the precursors showed electronic
and optoelectronic properties comparable to the conjugated polymer
prepared by conventional electrochemical polymerization of monomers
in an electrolyte bath. In addition to the dark-blue to sky-blue electrochromic
PEDOT from EDOT and BiEDOT, a dual-band absorbing green to sky-blue
electrochromic polymer was demonstrated using BEBTD. This demonstrates
that the precursor approach is easily applicable and feasible for
the preparation of conjugated polymers from numerable electrochemically
polymerizable aromatic groups
PEDOT:PSS âWiresâ Printed on Textile for Wearable Electronics
Herein, the fabrication of all-organic
conductive wires is demonstrated
by utilizing patterning techniques such as inkjet printing and sponge
stencil to apply polyÂ(3,4-ethylenedioxythiophene) polystyrenesulfonate
(PEDOT:PSS) onto nonwoven polyethylene terephthalate (PET) fabric.
The coating of the conducting polymer is only present on the surface
of the substrate (penetration depth ⌠200 Όm) to retain
the functionality and wearability of the textile. The wires fabricated
by different patterning techniques provide a wide range of resistance,
i.e., tens of kΩ/⥠to less than 2 Ω/⥠that
allows the resistance to be tailored to a specific application. The
sheet resistance is measured to be as low as 1.6 Ω/âĄ,
and the breakdown current is as high as 0.37 A for a 1 mm wide line.
The specific breakdown current exceeds the previously reported values
of macroscopic carbon nanotube based materials. Simple circuits composed
of the printed wires are demonstrated, and resistance of the circuit
from the measurement agrees with the calculated value based on Kirchhoffâs
rules. Additionally, the printed PEDOT:PSS wires show less than 6.2%
change in sheet resistance after three washing and drying cycles using
detergent
Rationally Designed Polyimides for High-Energy Density Capacitor Applications
Development
of new dielectric materials is of great importance
for a wide range of applications for modern electronics and electrical
power systems. The state-of-the-art polymer dielectric is a biaxially
oriented polypropylene (BOPP) film having a maximal energy density
of 5 J<b>/</b>cm<sup>3</sup> and a high breakdown field of 700
MV/m, but with a limited dielectric constant (âŒ2.2) and a reduced
breakdown strength above 85 °C. Great effort has been put into
exploring other materials to fulfill the demand of continuous miniaturization
and improved functionality. In this work, a series of polyimides were
investigated as potential polymer materials for this application.
Polyimide with high dielectric constants of up to 7.8 that exhibits
low dissipation factors (<1%) and high energy density around 15
J<b>/</b>cm<sup>3</sup>, which is 3 times that of BOPP, was
prepared. Our syntheses were guided by high-throughput density functional
theory calculations for rational design in terms of a high dielectric
constant and band gap. Correlations of experimental and theoretical
results through judicious variations of polyimide structures allowed
for a clear demonstration of the relationship between chemical functionalities
and dielectric properties
Screen-Printed PEDOT:PSS Electrodes on Commercial Finished Textiles for Electrocardiography
Electrocardiography
(ECG) is an essential technique for analyzing
and monitoring cardiovascular physiological conditions such as arrhythmia.
This article demonstrates the integration of screen-printed ECG circuitry
from a commercially available conducting polymer, PEDOT:PSS, onto
commercially available finished textiles. ECG signals were recorded
in dry skin conditions due to the ability of PEDOT:PSS to function
as both ionic and electronic conductors. The signal amplifies when
the skin transpires water vapor or by applying a common lotion on
the skin. Finally, PEDOT:PSS wires connected to PEDOT:PSS electrodes
have been shown to record ECG signals comparable to Ag/AgCl connected
to copper wires
Optimization of Organotin Polymers for Dielectric Applications
Recently,
there has been a growing interest in developing wide band gap dielectric
materials as the next generation insulators for capacitors, photovoltaic
devices, and transistors. Organotin polyesters have shown promise
as high dielectric constant, low loss, and high band gap materials.
Guided by first-principles calculations from density functional theory
(DFT), in line with the emerging codesign concept, the polymer polyÂ(dimethyltin
3,3-dimethylglutarate), pÂ(DMTDMG), was identified as a promising candidate
for dielectric applications. Blends and copolymers of polyÂ(dimethyltin
suberate), pÂ(DMTSub), and pÂ(DMTDMG) were compared using increasing
amounts of pÂ(DMTSub) from 10% to 50% to find a balance between electronic
properties and film morphology. DFT calculations were used to gain
further insight into the structural and electronic differences between
pÂ(DMTSub) and pÂ(DMTDMG). Both blend and copolymer systems showed improved
results over the homopolymers with the films having dielectric constants
of 6.8 and 6.7 at 10 kHz with losses of 1% and 2% for the blend and
copolymer systems, respectively. The energy density of the film measured
as a <i>D</i>â<i>E</i> hysteresis loop
was 6 J/cc for the copolymer, showing an improvement compared to 4
J/cc for the blend. This improvement is hypothesized to come from
a more uniform distribution of diacid repeat units in the copolymer
compared to the blend, leading toward improved film quality and subsequently
higher energy density
Acrylated Poly(3,4-propylenedioxythiophene) for Enhancement of Lifetime and Optical Properties for Single-Layer Electrochromic Devices
We utilized our in situ method for
the one-step assembly of single-layer electrochromic devices (ECDs)
with a 3,4-propylenedioxythiophene (ProDOT) acrylate derivative, and
long-term stability was achieved. By coupling the electroactive monomer
to the cross-linkable polymer matrix, preparation of the electrochromic
ProDOT polymer can occur followed by UV cross-linking. Thus, we achieve
immobilization of the unreacted monomer, which prevents any degradative
processes from occurring at the counter electrode. This approach eliminated
spot formation in the device and increased stability to over 10â000
cycles when compared to 500 cycles with conventional ProDOT devices
wherein the monomer is not immobilized. The acrylated electrochromic
polymer exhibits similar electrochromic properties as conventional
ProDOT devices, such as photopic contrast (48% compared to 46%) and
switch speed (both 2 s). This method can be applied to any one-layer
electrochromic system where improved stability is desired
Rational Design of Organotin Polyesters
Large dielectric constant and band
gap are essential for insulating materials used in applications such
as capacitors, transistors and photovoltaics. Of the most common polymers
utilized for these applications, polyvinyldiene fluoride (PVDF) offers
a good balance between dielectric constant, >10, and band gap,
6 eV, but suffers from being a ferroelectric material. Herein, we
investigate a series of aliphatic organotin polymers, pÂ[DMTÂ(CH<sub>2</sub>)<i><sub>n</sub></i>], to increase the dipolar and
ionic part of the dielectric constant while maintaining a large band
gap. We model these polymers by performing first-principles calculations
based on density functional theory (DFT), to predict their structures,
electronic and total dielectric constants and energy band gaps. The
modeling and experimental values show strong correlation, in which
the polymers exhibit both high dielectric constant, â„5.3, and
large band gap, â„4.7 eV with one polymer displaying a dielectric
constant of 6.6 and band gap of 6.7 eV. From our work, we can identify
the ideal amount of tin loading within a polymer chain to optimize
the material for specific applications. We also suggest that the recently
developed modeling methods based on DFT are efficient in studying
and designing new generations of polymeric dielectric materials
Poly(cannabinoid)s: Hemp-Derived Biocompatible Thermoplastic Polyesters with Inherent Antioxidant Properties
The
legalization of hemp cultivation in the United States has caused
the price of hemp-derived cannabinoids to decrease 10-fold within
2 years. Cannabidiol (CBD), one of many naturally occurring diols
found in hemp, can be purified in high yield for low cost, making
it an interesting candidate for polymer feedstock. In this study,
two polyesters were synthesized from the condensation of either CBD
or cannabigerol (CBG) with adipoyl chloride. Poly(CBD-Adipate) was
cast into free-standing films and subjected to thermal, mechanical,
and biological characterization. Poly(CBD-Adipate) films exhibited
a lack of cytotoxicity toward adipose-derived stem cells while displaying
an inherent antioxidant activity compared to poly(lactide) films.
Additionally, this material was found to be semi-crystalline and able
to be melt-processed into a plastic hemp leaf using a silicone baking
mold