Conformational and Motional Characteristics of Trans-1,4-diene Polymers Confined to Channels.

Prompted by the studies of Sozzani and coworkers, who have polymerized diene monomers complexed with perhydrotriphenylene (PHTP) to form inclusion compounds, we have investigated the conformations and mobilities of the resulting isolated trans- 1,4-diene polymer chains confined to the channels of their inclusion compounds with PHTP. This was achieved by a two step procedure: i.) from all the possible conformations available to the free polymer chains, those conformations which fit into the channels of their inclusion compounds with PHTP were defined and ii.) a test was performed to determine whether or not it was possible to interconvert between these channel conformations while the trans-1,4-diene polymers remained inside their channels. This procedure was applied to trans-1,4-polybutadiene, trans- 1,4-polyisoprene, and isotactic trans-1,4-poly (penta-1,3- diene) chains confined to the channels of their inclusion compounds with PHTP. We found the channel conformers of the butadiene and pentadiene polymers able to interconvert while inside their channels. By contrast, the isoprene polymer was not able to interconvert between its channel conformers without significant expansion of its confining PHTP channel (ca. 30% increase in channel diameter, compared to the 0-5% increase observed for interconverting butadiene and pentadiene chains). These results are consistent with the solid state sup 13 C and sup 2 H NMR studies performed by Sozzani et al. to elucidate the conformations and mobilities of the same trans-1,4-diene polymers when restricted by the channels formed in their PHTP inclusion compounds.