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, p­[DMT­(CH₂)<i>_n</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 poly­(dimethyltin 3,3-dimethylglutarate), p­(DMTDMG), was identified as a promising candidate for dielectric applications. Blends and copolymers of poly­(dimethyltin suberate), p­(DMTSub), and p­(DMTDMG) were compared using increasing amounts of p­(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 p­(DMTSub) and p­(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