Anionic Polymerization of a Benzofulvene Monomer Leading to a Thermoreversible π-Stacked Polymer. Studies in Macromolecular and Aggregate Structure

The polymerization of trans-diene BF1 [ethyl 1-methylene-3-(4-methylphenyl) -1/7-indene-2-carboxylate] has been studied in the presence of various amounts of an anionic initiator such as phenyllithium in order to obtain information on the properties of this diene monomer and on its polymers. The anionic polymerization of BF1 produced a mixture of oligomers and a polymer (poly-BF1-AP), the proportion of which is regulated by the amount of the initiator used. Poly-BF1 was separated from lower oligomers on the basis of the solubility in n-hexane, and the soluble material was further fractionated by chromatography to obtain activated monomers and dimers. The structure of dimers and poly-BF1-AP has been investigated by NMR spectroscopy, absorption and emission spectroscopy, and mass spectrometry. The whole set of results is consistent, confirming for poly-BF1 a vinyl (1,2) polymer chaining stabilized by means of aromatic stacking interactions. The thermoreversibility of poly-BF1-AP was characterized by 1H NMR and compared to its DSC features. Remarkably, SEC-MALS analysis showed that the molecular weight of poly-BF1-AP is relatively low (about 10 kg/mol), and SEM studies revealed that the polymer is liable to give nanospheres and microspheres showing favorable shapes and dimensions. These results suggest the potential tuning of the material properties of these π-stacked polymers by means of the regulation of the molecular weight. © 2008 American Chemical Society.