Spontaneous doping and magnetic properties of polyacetylene and polypropyne synthesized in situ in Ni-exchanged mordenite and mesoporous MCM-41

Abstract

Upon polymerisation of acetylene and propyne inside the channels of Ni²⁺-exchanged mordenite and mesoporous MCM-41 spontaneous doping and formation of antiferromagnetic NiO clusters are observed to various extents. The population of polarons present in the final polymer/zeolite composite: (i) is higher for polyacetylene than for polypropyne; (ii) increases with polymerisation temperature in the range 100 to 335 °C; (iii) increases with the C content; and (iv) is higher for mordenite than for MCM-41 under the same conditions. The use of Ni(0),H⁺-mordenite for polymer formation enhances the polaron population of the resulting polymer by over one order of magnitude. Doped polyacetylene encapsulated in mordenite or MCM-41 was found to be persistent for periods of over three months after its preparation.