The synthesis and memory device characteristics of two new poly[2,7-bis(phenylenesulfanyl) thianthrene-hexafluoroisopropylidenediphthalimide] (APTT-6FDA) and poly[4,4 0 -thiobis(p-phenylenesulfanyl)-hexafluoroisopropylidenediphthalimide] (3SDA-6FDA) are reported. The sulfur-containing APTT and 3SDA as electron donor were designed to enhance electron-donating and charge-transporting characteristics for the device application. The optical band gaps of APTT-6FDA and 3SDA-6FDA estimated from the absorption edges were 3.51 and 3.46 eV, which probably resulted from the difference in the structural coplanarity. The estimated energy levels (HOMO, LUMO) of APTT-6FDA and 3SDA-6FDA were (-5.55, -2.04) and (-5.71, -2.25) eV, respectively. The memory device with the configuration of ITO/polymers/Al showed nonvolatile memory characteristics with the low turn-on threshold voltages of 1.5 V(APTT-6FDA) and 2.5 V(3SDA-6FDA), probably resulting from the difference in the HOMO energy level. Also, the memory devices could be repeatedly written, read, and erased. The on/off current ratios of the devices were all around 10 4 in ambient atmosphere. The relatively higher dipole moments of the sulfur-containing polyimides compared to the triphenylamine-based polyimide provided a stable CT complex for the flash memory device. The above electronic properties were further confirmed by the density functional theory (DFT) method at the B3LYP level with the 6-31G(d) basis set. The present study suggested that the new sulfur-containing polyimides would have potential applications for memory devices.

A powerful strategy to enhance the thermal conductivity of liquid crystalline epoxy resin (LCER) by simply replacing the conventional amine cross-linker with a cationic initiator was developed. The cationic initiator linearly wove the epoxy groups tethered on the microscopically aligned liquid crystal mesogens, resulting in freezing of the ordered LC microstructures even after curing. Owing to the reduced phonon scattering during heat transport through the ordered LC structure, a dramatic improvement in the thermal conductivity of neat cation-cured LCER was achieved to give a value ∼141% (i.e., 0.48 W/mK) higher than that of the amorphous amine-cured LCER. In addition, at the same composite volume fraction in the presence of a 2-D boron nitride filler, an approximately 130% higher thermal conductivity (maximum ∼23 W/mK at 60 vol %) was observed. The nanoarchitecture effect of the ordered LCER on the thermal conductivity was then examined by a systematic investigation using differential scanning calorimetry, polarized optical microscopy, X-ray diffraction, and thermal conductivity measurements. The linear polymerization of LCER can therefore be considered a practical strategy to enable the cost-efficient mass production of heat-dissipating materials, due to its high efficiency and simple process without the requirement for complex equipment.

Highly refractive and transparent polyimides (PIs) containing a 3,4,8,9-tetrahydro-2,5,7,10tetrathiaanthracene moiety in their main chains have been developed. These PIs were prepared from several dianhydrides such as 4,4′-[p-thiobis(phenylsulfanyl)]diphthalic anhydride (3SDEA), 4,4′-[(9H-fluorene-9ylidene)bis(p-phenylsulfanyl)]diphthalic anhydride (FPSP), 4,4′-oxidiphthalic anhydride (ODPA), and a new sulfurcontaining aromatic diamine, 1,6-bis(p-aminophenylsulfanyl)-3,4,8,9-tetrahydro-2,5,7,10-tetrathiaanthracene (BTTA), by a two-step polycondensation procedure. The PIs exhibit good thermal and optical properties such as glass transition temperatures higher than 213 °C, thermal decomposition temperatures (T 10% ) in the range of 390-443 °C, and optical transparency higher than 80% at 500 nm for a thickness of ca. 10 µm. Because of the very high sulfur content (28.4%) in the polymer main chain, the PI derived from BTTA and 3SDEA exhibits the highest refractive index, i.e., 1.769 at 633 nm.

We report the nonvolatile memory characteristics of n-type N,N ′-bis(2-phenylethyl)perylene-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI) based organic field-effect transistors (OFET) using the polyimide electrets of poly[2,5-bis(4-aminophenylenesulfanyl)selenophene–hexafluoroisopropylidenediphthalimide] (PI(APSP-6FDA)), poly[2,5-bis(4-aminophenylenesulfanyl)thiophene–hexafluoroisopropylidenediphthalimide] (PI(APST-6FDA)), and poly(4,4′-oxidianiline-4,4′-hexafluoroisopropylidenediphthalic anhydride) (PI(ODA-6FDA)). Among those polymer electrets, the OFET memory device based on PI(APSP-6FDA) with a strong electron-rich selenophene moiety exhibited the highest field-effect mobility and Ion/Ioff current ratio of 105 due to the formation of the large grain size of the BPE-PTCDI film. Furthermore, the device with PI(APSP-6FDA) exhibited the largest memory window of 63 V because the highest HOMO energy level and largest electric filed facilitated the charges transferring from BPE-PTCDI and trapping in the PI electret. Moreover, the charge transfer from BPE-PTCDI to the PI(APSP-6FDA) or PI(APST-6FDA) electrets was more efficient than that of PI(ODA-6FDA) due to the electron-donating heterocyclic ring. The nanowire device with PI(APSP-6FDA) showed a relatively larger memory window of 82 V, compared to the thin film device. The present study suggested that the donor–acceptor polyimide electrets could enhance the capabilities for transferring and store the charges and have potential applications for advanced OFET memory devices.

Epoxy nanocomposites are fabricated by using diamine-functionalized GO and exhibit high Tg, tensile strength, and crosslink density.