Conformation and segmental mobility of a diluted single polymer chain simulated with bond fluctuation model

The conformation of a single long polymer chain has been modelled using the Bond Fluctuation Model. The interaction between non-bonded segments has been introduced in the model by means of a Lennard-Jones potential while two energy potentials depending on bond length and bond angle took into account intramolecular interactions. The effect on chain configuration of varying bond angle potential, which tends to extend the polymer chain, was studied. The chain was allowed to equilibrate at high temperature, adopting a random coil conformation. When the system was subjected to a cooling ramp, its energy and dynamically accessible volume decreased but the system maintained the liquid conditions up to a temperature range in which the glass transition yielded a glassy coil with very restricted but not null segmental mobility. The remaining mobility in the glassy state, as well as its conformation, characterised through correlation functions, also depended significantly on the strength of bond angle potential. Further isothermal annealing yielded very compact structures, always amorphous with particular shapes depending on annealing temperature.