Random growth statistics of long-chain single molecule poly-(p-phenylene vinylene)

Structures of poly-(p-phenylene vinylene) (PPV) were generated using a rand om growth algorithm. The algorithm assumes that the configuration of a part of the polymer (a few monomers length) can be sampled from the configurati on of a PPV trimer. The probabilities of the configurations of the trimer a re taken as the Boltzmann weight of the energies. We constructed several ty pes of polymers with different numbers of cis-defects which were added to t he polymer either uniformly or randomly distributed within the entire polym er. Polymer characteristics, such as conjugation length, end-to-end distanc e, and radius of gyration, were also calculated. The trends of these charac teristics were found to be inversely proportional with the number of cis-de fects in the polymer. Although average conjugation lengths are generally in dependent of the distribution of cis-defects, the morphology of the polymer is dependent on cis-defect distribution. This suggests that conformational disorder rather than cis-defect density is the determining factor in excit on localization and diffusion in these systems. Finally, we derive a simple model similar to the Ising model that relates the energy needed to break c onjugation to the average conjugation length. (C) 2001 American Institute o f Physics.