Conducting diblock copolymers with lonic complex/insulator lamellar microdomains

Abstract

SYNOPSISPoly ( styrene-b-2-vinylpyridine) diblock copolymer films with horizontally oriented lamellar microdomains were obtained by the casting method. Poly (2-vinylpyridine) (P2VP) microdomains were not only quaternized, but were also crosslinked with 1,4-diiodobutane vapor. Subsequently, ionic complex phases were constructed by an ion-exchange reaction of quaternized PPVP phases with lithium perchlorate. The element (chlorine and iodine atoms) distributions on the vertical section of the modified films were measured by means of an energy dispersive X-ray spectrometer. These materials had highly anisotropic conductivity with approximately 6 orders of magnitude. INTRODUCTIONThere have been reports of attempts to measure the electrical conductivity of diblock copolymers in which one of the blocks consisted of poly (2-vinylpyridine ) ( P2VP ) .1-3 However, these materials have never shown electrical anisotropy with conductivities, because the orientation of microphase-separated structures, formed by block copolymers, was not controlled.We have subsequently shown t h a t poly-polymer formed horizontally oriented lamellar microdomains, by means of the air-copolymer and the substrate-copolymer interaction^.^ Following this, semiconducting materials were obtained upon the exposure of film with alkyl dihalide vapor.5 The quaternized PBVP domains exhibited the nature of ionic conduction. This film had a n anisotropic conductivity with about 8 orders of magnitude (conductivity parallel to the film plane ull = and conductivity perpendicular to the film plane a l = s/cm) . Colloidal silver was also introduced into quaternized P2VP layers by reduction of silver iodine.6 This film showed the 100-fold ull value, as compared with that observed in diblock copolymer films with the quaternized P2VP layers. According to our results, high electrical anisotropy originates in the orientation of microphase-separated structures. Thus, it is important that the morphological structure of diblock copolymer films is not disturbed during the modification process. In this article, the ionic complex was introduced into the quaternized P2VP layers by an ion-exchange reaction with lithium perchlorate ( LiC104) in various reaction conditions. The element (chlorine and iodine) distributions, on the vertical section of the modified films, were measured by means of an energy dispersive X-ray spectrometer (EDX) .We studied the anisotropic conductivity of these materials.