Cyclic homo- and diblock copolymers with different topologies were synthesized using a combination of "living" radical polymerization and "click" coupling reactions. The topologies included 2- and 3-arm stars, with the arms consisting of either cyclic or linear polystyrene. In addition, a diblock consisting of a cyclic polystyrene and a cyclic poly(acrylic acid) was also made. The topologies by imposing topological constraints due to the presence of cyclic polymers and branch points had a marked influence on the glass transition temperature (Tg). It was found that for the polystyrene topology series, the Tg increased above the glass transition temperature at infinite molecular weight for a linear chain (i.e., Tg∞) and correlated to the more compact nature of cyclic polymers. For the cyclic diblock of polystyrene and poly(acrylic acid), the Tg increased significantly due to separation of the blocks into their pure phases. This resulted in significant stretching of the chains and thus loss of conformation entropy. (Graph Presented).
- cyclic stars
- cyclic polystyrene