The conformation of lightly branched star polymers in the theta state is investigated. Long-range two- and three-body interactions are assumed to compensate one another exactly, whereas the screened interactions, arising from the finite width of the interatomic potential, do survive. Their repulsive potential dies off with interatomic distance r like (r2) -s/2, so that the mean-square radius of gyration is asymptotically proportional to the number of bonds N. However, the screened interactions expand the polymer above the random-walk conformation and give rise to a further topology-dependent term proportional to N 1/2. The topological index g = (S 2)star/(S2)lin decreases with increasing N for any degree of branching, becoming linear in N -1/2 and tending to the limit 9o~=(3f-2)/f 2 for large N, in agreement with Monte Carlo simulations performed at a vanishing second virial coefficient by Bruns and Carl in 1991. A similar dependence from N-t/2 is also found for the ratio of the hydrodynamic radii h= RH,star/RH,li n.
Посилання на статтю:
The regular star polymer in the theta state / Fabio Ganazzoli*, Monica A. Fontelost and Giuseppe Allegr // Polymer. – 1993. – Vol 34. – P. 2615-2622.