Nitroxide-mediated controlled/living radical copolymerizations with macromonomers

Shielding effects in polymer-polymer reactions. IV. Intermolecular contact formation between star-branched molecules

Pairs of star-branched molecules--taken from ensembles of athermal five-way cubic lattice chains prepared by Monte Carlo simulation--are analyzed for the relative probability of mutual contact formation between particularly specified segments i and j belonging to different chains within these pairs. These contact probabilities--termed shielding factors K(ij)--are calculated by means of exact enumeration as a function of chain length ranging from n = 8 to 256 bonds per arm, as a function of functionality (i.e., the number of arms) ranging from F = 2 to 6 arms, and as a function of segment position within the arms ranging from central to terminal segments. In addition, changes of properties that characterize the size and shape of the involved molecules while approaching and penetration are evaluated as a function of chain separation.

Where are the End-Groups in a Hyperbranched Polymer?

The location of the end-groups in hyperbranched polymers is modelled by considering two synthetic strategies. The first synthesis is to make linear chains, and then link these chains. The second strategy is to sequentially add multifunctional monomers. The first strategy represents hyperbranched polymers synthesized by living radical methods, whereas the second represents polycondensations at low conversion. The high-conversion case is also considered. The present analysis suggests that sequential addition of monomers places more end-groups at the polymer’s surface than synthesis by linking chains. If the end-groups are catalysts, synthesis by the addition of monomers should give fewer inaccessible catalysts.