| Abstract: | Isotropic and oriented thin films of rigid-rod, rigid-rod pseudo-ladder, and ladder polymers were ion-bombarded with 84Kr+ to a dose of 4 × 1016 ions/cm2. The bombardment was conducted at two conditions: one at 190 keV energy with 0.12 μA/cm2 current density and the other at 200 keV energy with 2.0 μA/cm2 current density. With the low current density, the polymers developed a uniform ion-bombarded layer of about 0.35 μm at the surface. This layer showed an electrical conductivity on the order of 10?3s/cm at ambient conditions, an enhancement of 6 to 9 orders of magnitude from the pristine polymers. The enhanced conductivity was found to decrease to 10?6s/cm after the implanted krypton was removed by heating under reduced pressure. It suggests that the enhanced conductivity was due to a synergistic effect of structural change of the polymers and chemical doping by the im-planted ions. With the high current density, most polymer films, except that of rigid-rod pseudo-ladder poly(p-(2,5-dihydroxy) phenylene benzobisthiazole) (DPBT), developed an additional fibrous network structure over the uniform ion-bombarded layer. The comparable conductivity, 53 to 157 s/cm, measured for the various ion-bombarded films in-dicated that neither the molecular structure, rigid-rod or ladder, nor the molecular packing order, isotropic or oriented, constituted significant effect on the conductivity of ion-bombarded polymers. Since krypton could not be detected in the polymers ion-bombarded with high current density, the enhanced conductivity was attributed to the structural change of the polymers. The DPBT films ion-bombarded with high current density showed holes of micron size, probably due to the decomposition of hydroxy pendents from the rigid-rod backbone. © 1993 John Wiley & Sons, Inc. |
