Measurements on polyaniline using dielectric analysis (DEA, -50°C to 240°C 0,4 Hz to 10' Hz), differential scanning calorimetry (DSC, 30 "C to 240 "C) and infrared spectroscopy (IR) after heat treatment from 25 "C to 300°C are carried out. After conversion of DEA results to complex electric modulus, the conductivity relaxation time distribution can be obtained, which remains unchanged for temperatures below 160°C and becomes narrower in the temperature range from 180°C to 240°C due to the occurrence of crosslinking reactions, as is confirmed by the exothermic behavior above 160°C and by the decrease of the relative intensity of quinoid absorption with respect to that of the aromatic ring. The crosslinking reaction causes a decrease in dc conductivity, a narrowing in conductivity relaxation time distribution and an increase in activation energies for conductivity and conductivity relaxation. 0 1993, Hilthig & Wepf Verlag, Basel CCC 0025-1 16X/93/%05.00

This study successfully incorporated a short‐segment fluorine‐containing chain extender (2,2,3,3‐tetrafluoro‐1,4‐butanediol [TF]) into castor oil‐based polyurethane (COPU) to synthesize TF/COPUs. The interactions between TF and COPU components were identified by Fourier transform infrared and X‐ray photoelectron spectroscopies, the results revealed that the increase in the TF content increased the van der Waals forces in CF…CO and the hydrogen bonding force in CF…HN. Atomic force microscopy indicated that the addition of more TF contributed to a higher level of microphase separation in the TF/COPUs. Thermogravimetric analysis showed that the TF component can enhance the thermal resistance of TF/COPUs. Differential scanning calorimetry and dynamic mechanical analysis indicated that the glass transition temperature (Tg) of TF/COPUs increased with the TF content. The stress–strain testing showed that the tensile strength and elongation at break values decreased with the TF content. This tensile behavior may be due to the molecular weight of a TF/COPU decreased with the TF content as evidenced by the gel permeation chromatography results. The hydrolytic degradation tests of dipping TF/COPUs in 3 wt% NaOH solution indicated that TF could lower the surface free energy and enhance the degradation stability of TF/COPUs.

In this study, a new electroluminescent poly(2-decyloxy-5-(4 0 -tert-butylphenyl)-1,4-phenylene-vinylene) (designated as DBP-PPV) with no tolane-bis -benzyl (TBB) structure defect was prepared by dehydrohalogenation of 1,4-bisbromomethyl-2-decyloxy-5-(4 0 -tert-butylphenyl) benzene (as monomer). The monomer bearing decyloxy and 4 0 -tert-butylphenyl substituents was synthesized via alkylation, bromination and Suzuki coupling reactions. The two asymmetric substituents of the monomer can suppress the formation of TBB defect during polymerization process and make the resultant polymer be soluble in common organic solvents. The structure and properties of DBP-PPV were examined by 1 H-NMR, FT-IR, UV/Vis, TGA and photoluminescence (PL) analyses. Moreover, with the DBP-PPV acting as a lightemitting polymer, a device with sequential lamination of ITO/PEDOT/DBP-PPV/Ca/Ag was fabricated. The electroluminescence (EL) spectrum of the device showed a maximum emission at around 546 nm, corresponding to a yellowish-green light. The device showed a turn-on voltage of about 8.4 V and a maximum luminescence efficiency of 0.11 cd/A at an applied voltage of 12 V.