Novel Langmuir-Blodgett Films of Electrically Conducting Polyion Complexes and Diblock Copolymers

ABSTRACTThe Langmuir-Blodgett (LB) technique has been used to form two different types of multilayer films with novel molecular organizations. In the first case, a new method of fabricating superlattices of conducting polymers has been devised and studied. This method involves forming polyion complexes of acid derivatized conducting polymers with stearylamine (StNH2) and subsequently manipulating them into AB type superlattices by the LB technique. To date, superlattices consisting of isolated alternating monolayers of poly(thiophene acetic acid) (PTAA) and sulfonated polyaniline (PAn) have been studied. The layered structure of these films was found to be very similar to that of their respective homopolymer LB films, as evidenced by X-ray diffraction patterns. The conductivity of these superlattices was in the range of 10−1 S/cm, which is approximately one order of magnitude higher than that obtained with the homopolymer LB films (about 10−2 S/cm). In the second case, LB films of a novel diblock copolymer have been made, where one of the blocks is a water-insoluble polyacetylene precursor and the other block a non-conjugated, water-soluble poly(norbornene) derivative. The precursor block of the LB films could be converted to trans-polyacetylene by heating, and doped to a conductivity of 10−3 S/cm, which was significantly higher than that of cast (10−7 S/cm) or spin-coated (10−5 S/cm) films of the same material. Thus, in both cases, the unique molecular organization created by the LB technique has resulted in films with higher conductivities than those obtained by traditional casting techniques.