20 research outputs found
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, ≥5.3, and
large band gap, ≥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
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>–<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