Synthesis of Stereoregular Living Polymers from Substituted Acetylenes and Design of Polymerization Catalysts

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The molecular weight distribution (MWD) and steric structure of a polymer should be well defined so that the polymer would exhibit excellent properties and functions. The present study deals with the synthesis of stereoregular living polymers from substituted acetylenes and development of novel catalysts useful for such purposes.1. Stereospecific living polymerization of tert-butylacetylene (tBA) by Mo-based catalysts-The polymerization of tBA by the MoOCl_4-n-Bu_4Sn-EtOH (1 : 1 : 1) catalyst led to living and stereoregular polymers with narrow MWDs (Mw/Mn=1.12 ; cis 97%) . The living nature of this polymerization was confirmed by the fact that, in toluene at 0 and -30ﾟC,the Mn of the polymer increases in direct proportion to monomer consumption, while the MWD remains narrow. The cis content of polymer was evaluated by ^<13>C NMR spectroscopy. Similar but somewhat inferior results were obtained with the MoCl_5-n-Bu_4Sn-EtOH (1 : 1 : 1) system (Mw/Mn=1.24 ; cis 90%) .2. Synthesis of a cis-rich, living poly [ (o-methylphenyl) acetylene] (oMePA) -Polymerization of oMePA by MoOCl_4-n-Bu_4Sn-EtOH catalyst in toluene at 0ﾟC provided a cis-rich living polymer ; cis 77%, Mw/Mn=1,21. The polymerization at-30ﾟC gave results similar to those for 0ﾟC,whereas the polymer obtained at 30ﾟC exhibited a broader MWD and a lower cis content.3. Development of MoOCl_4-based new catalyst systems for living polymerization-In this study, we tried to develop new catalyst systems for the living metathesis polymerization using Et_3Al as cocatalyst. [o- (Trifluoromethyl) phenyl] acetylene was used as monomer, and polymerizations were carried out in anisole at 30ﾟC.Eventually, a polymer with very narrow MWD (Mw/Mn=1.02) could be obtained by use of MoOCl_4-Et_3Al-EtOH at 1 : 1 : 4 ratio.