Electroactive materials with tunable response based on block copolymer self-assembly

Abstract

Ferroelectric polymers represent one of the key building blocks for the preparation of flexible electronic devices. However, their lack of functionality and ability to simply tune their ferroelectric response significantly diminishes the number of fields in which they can be applied. Here we report an effective way to introduce functionality in the structure of ferroelectric polymers while preserving ferroelectricity and to further tune the ferroelectric response by incorporating functional insulating polymer chains at the chain ends of ferroelectric polymer in the form of block copolymers. The block copolymer self-assembly into lamellar nanodomains allows confined crystallization of the ferroelectric polymer without hindering the crystallinity or chain conformation. The simple adjustment of block polarity leads to a significantly different switching behavior, from ferroelectric to antiferroelectric-like and linear dielectric. Given the simplicity and wide flexibility in designing molecular structure of incorporated blocks, this approach shows the vast potential for application in numerous fields.

Tuning the dielectric behavior of poly(vinylidene fluoride-co-vinyl alcohol) using a facile urethane-based crosslinking method

“…via block copolymer self-assembly). 34,[37][38][39][40][41][42][43][44][45] As already shown in eqn (1), the dielectric performance is largely determined by the electric field that is applied. To demonstrate the increased dielectric strength and improved reliability of the crosslinked fluorinated networks compared to pristine poly(VDF-co-VA), a two-parameter Weibull analysis is performed using eqn (2):…”

“…Similarly, this effect of polarizability at the nanocrystal interface on electroactive properties is also observed in the poly(VDF-co-CTFE) terpolymers grafted with low dielectric constant polystyrene (PS) and in the PS-b-poly(VDF-co-TrFE)-b-PS triblock copolymers. 33,34 In both cases, the nanosized crystals also have an insulating (PS) layer destabilizing the polarization induced by the electric field, resulting in a DHL behavior and for the block copolymer even a linear dielectric behavior, severely reducing the effect of macroscopic polarization. Interestingly, this change in the electroactive behavior of the crosslinked samples is completely different from those observed for the other chemically crosslinking methods (via irradiation or using amines).…”

Physical pinning and chemical crosslinking-induced relaxor ferroelectric behavior in P(VDF-ter-TrFE-ter-VA) terpolymers

“…To mitigate these concerns and to consequently enhance the charge-discharge efficiency, while maintaining the large discharge energy densities, ferroelectric crystals are required to be well isolated. 5,14 The crosslinking method of relaxor ferroelectric polymers introduced in this work appears to be very promising. Even though the reduction in crystallinity and increase in the amount of crystals in the disordered paraelectric phase lower the maximum polarization of the crosslinked uorinated terpolymers, the remanent polarization is also reduced signicantly due to better isolation of ferroelectric domains by chemical crosslinking.…”

“…relaxor or double hysteresis loop (DHL) behavior) while still having large polarizations. 5,[7][8][9][10][11][12][13][14][15] As such, co-and terpolymerizations of VDF with other uorinated comonomers, like triuoroethylene (TrFE), chlorotri-uoroethylene (CTFE) and chlorouoroethylene (CFE), have been employed to gradually increase the crystal lattice spacing. 16,17 Dependent on the processing conditions, incorporating these comonomers with a lower dipole moment leads to the formation of physical pinning spots, destabilizing the ferroelectric phase and enhancing the dipole reversibility, which results in relaxor ferroelectric behavior.…”

Introducing Functionality to Fluorinated Electroactive Polymers

“…Due to the difficulty in controlling the synthesis of such polymers adding further functionality, although essential to broaden their application still remains an open challenge [6][7] . Some efforts towards this direction have been recently demonstrated by the preparation of block copolymers of P(VDF-co-TrFE) with polystyrene or poly(2-vinyl-pyridine) in order to tailor the electroactive response from ferroelectric to relaxorferroelectric and linear dielectric 6 . Despite the very interesting findings though, large increase in leakage current was observed for the prepared polymers, creating a main bottleneck for their potential application.…”