Geomagnetic variation anomaly and electric conductivity structure beneath Yunnan, China

A novel side-chain liquid-crystalline polyimide (SLCPI) was prepared via copolycondensation from 3,5-diamino-benzonic-4Ј-biphenyl ester, 4,4Ј-diamino-biphenyl ether, and 3,3Ј,4,4Ј-oxydiphthalic dianhydride. The energy-minimized structure and liquid crystallinity of SLCPI were investigated by molecular modeling, differential scanning calorimetry (DSC), wide-angle X-ray scattering, and polarized optical microscopy, respectively. The results indicated that this polyimide (PI) with side-chain mesogenic units exhibited a nematic NI phase. Because of the in situ self-reinforcement of side-chain mesogenic units, the improved tensile strength and modulus of PI films reached 270% and 300%, respectively. The coefficient of thermal expansion of films decreased by 40%. DSC and thermogravimetric analyses indicated that the phasetransition temperature of SLCPI was above 240°C, and the 5% weight-loss temperature was above 520°C. Moreover, copolycondensation of two diamines with dianhydride and incorporation of pendent mesogenic units diminished the regularity and symmetry of main chains; as a result, SLCPI exhibits good film processability.

show abstract

“…DABBE was prepared as described in the literature 7. The synthesis of SCLPI is outlined in Figure 1.…”

Section: Synthesis and Instrumentsmentioning

confidence: 99%