Monte Carlo simulation of tetrahedral chains, 6. Linear and star‐branched polymers near to theta conditions

By use of the pivot algorithm, star‐branched chains with F = 4, 8 and 12 arms of length n and linear chains ( F = 2) are generated on a tetrahedral lattice (120 ⩽ nF ⩽ 3 840). By taking into account non‐bonded nearest‐neighbour interactions (each contact contributes an energy ϕ · kT to the total energy of the configuration) a variation of the thermodynamic quality of the solvent is simulated by a variation of the energy parameter ϕ in the range −0,425 to −0,525. The energy parameter ϕ ⊙ = −0,475, characteristic of theta conditions, was evaluated by use of an intramolecular criterion (proportionality between mean‐square dimensions and total chain‐length) and confirmed by a crossover scaling analysis. Theta dimensions are found to be larger than those of nonreversal random walks, the deviation growing with increasing number of arms.