Nature of Ferroelectric Behavior in Main-Chain Dipolar Glass Nylons: Cooperative Segmental Motion Induced by High Poling Electric Field

Abstract

Main-chain dipolar glass polymers such as aromatic nylons are promising for high energy density and low loss dielectric applications because of the limited, noncooperative oscillation of highly dipolar amide groups. However, quenched aromatic nylons have been reported to exhibit significant ferroelectric switching upon high field poling. It is desirable to suppress ferroelectric switching for electric energy storage application, and this requires a fundamental understanding of the nature of ferroelectric behavior in dipolar glass nylons. In this work, a nearly 100% amorphous aromatic nylon, Selar, was used to investigate the origin of ferroelectricity in glassy nylons. Using Fourier transform infrared spectroscopy, it was found that hydrogen-bonding strength played an important role in the ferroelectric switching of amide dipoles in the loosely packed glassy matrix. When hydrogen bonding was weak such as in the quenched film, significant ferroelectric switching took place. In contrast, quenched and annealed films did not exhibit any ferroelectric switching. High-voltage broadband dielectric spectroscopy was used to study molecular and segmental motions in Selar. It was observed that the primary contribution to ferroelectric switching came from cooperative segmental motions (i.e., a combination of various sub-T g relaxations, where T g is the glass transition temperature) in the main-chain dipolar glass nylon. This understanding will help us design new aromatic nylons with suppressed segmental motions for high energy density and low loss dielectric applications.

High-κ polymers of intrinsic microporosity: a new class of high temperature and low loss dielectrics for printed electronics

“…This result indicated that no significant dielectric nonlinearity was observed up to 71.4 MV m À1 . This was different from main-chain dipolar glass polymers reported recently, 37 where significant dielectric loss was observed as a result of high field-induced cooperative segmental motions. The high-field dielectric property was studied by unipolar D-E loop measurements, and discharged U e and efficiency were obtained from the charge and discharge curves (Fig.…”

“…The high-field dielectric behavior of SO 2 -PIM was further studied using high voltage BDS (HV-BDS). 37 In Fig. S6 (ESI †), all tan d curves under different electric fields largely overlapped, except for slightly enhanced conduction of impurity ions above 50 1C.…”

Dielectric polymers for high-temperature capacitive energy storage

“…12). 170,171 It was found that the presence of the cyano group improves the K from 2.92 of the analogous PI without cyano groups to 3.1-3.5 at room temperature and 1 kHz. In addition, the asymmetric structure of the aromatic diamine monomer can improve the processability and enhance K values of PIs.…”

“…Examples of the main-chain dipolar grafting polymers include but are not limited to aromatic PIs, [167][168][169] PAs, 170 and ArPUs. [171][172][173] The dielectric properties of the main-chain dipolar grafting polymers can be modulated by using different polar chain segments in the polymer backbone, incorporating additional permanent dipoles, varying conjugation length and controlling the degree of crystallinity.…”

“…A systematic study has been conducted regarding the relationship between the monomer structures and dielectric properties of the cyano-containing PIs (PI-CNs), including high-field D-E loops at elevated temperatures. [170][171][172] A series of PIs with a single cyano group per repeating unit were synthesized through a condensation reaction followed by thermal imidization between a diamine, such as the asymmetric 2- 4,4′-oxydiphthalic dianhydride (OPDA), 4,4′benzophenonetetracarboxylic dianhydride (BTDA), PMDA and 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride (DSDA) (Fig. 12).…”