No abstract

Synthesis and characterization of aromatic main-chain polyesters containing nonlinear optical chromophores derived from disperse red 1 (DR1) and long alkoxy residues in the side chain are described. Polymer solutions were spin cast into optical-quality thin films. The electrooptical properties of the polymer films poled by a n electric field (20-80 V/pm) were measured by the ATR (attenuated total reflection) method at 632.8 nm and 685 nm.Second-order susceptibilities x(2)zzz and x(2)m as well as piezoelectric coefficient were linearly proportional to the applied poling voltage at a given temperature. The maximum values of second-order susceptibilities x(2)zzz were 140 (632.8 nm) and 91 p m N (685 nm) when the poling was carried out a t a voltage of 79 V/pm at 60 "C. The thermal relaxation behavior investigated at various temperatures demonstrated a n enhanced stability of the presented polymers compared to guest-host or side-chain polymer systems with flexible main chains. The relative stability is ascribed to hindering of the local mobility of the chromophores by the stiff main chains and matrix of long alkoxy side groups in which the chromophores are tightly embedded. Dielectric measurement of P-3 shows only the a-relaxation process in the frequency range 10-2-106 Hz. This relaxation process is of a WLF (Williams-LandelFerry) type behavior. The glass transition temperature (T,) obtained from a WLF fit agrees well with that determined by DSC.

We investigate the effects of atomic layer deposition (ALD)-grown Al2O3 buffer layer on the device characteristics of flexible amorphous InGaZnO thin-film transistors (TFTs) fabricated on ultrathin polyimide (PI) films. The TFT with a buffer layer exhibited a saturation mobility of 8.6 cm2 V−1 s−1 and a subthreshold swing of 0.16 V dec−1 after annealing at 150 °C. Under negative bias temperature stress at 40 °C, the turn-on voltage instabilities of TFTs with and without the buffer layer were estimated to be −1.0 and −13.2 V, respectively. This marked difference is mainly due to the adsorption of water molecules on the PI film resulting in a positively charged surface.

A series of aromatic polyesters were prepared from 2‐bromoterephthalic acid and naphthalenediol isomers. Only the polymers obtained from 1,4‐, and 1,5‐ and 2,6‐naphthalenediols were thermotropic nematogens and those from bent naphthalenediols were not liquid crystalline. Only the polyesters derived from 1,4‐, 1,5‐, and 2,6‐naphthalenediols were semicrystalline. The melting temperatures ranged from 319 to 374°C depending on the structure of naphthalenediol moiety. The glass transition temperature, Tg, ranged from 95 to 168°C. TGA studied revealed that the polyesters have fairly good thermal stability