فهرست مطالب molavian

Carbon backbone polymers are prepared by the polymerization of olefins. The carbon backbone is built two carbon atoms at a time. The reaction is fundamentally different from conventional olefin polymerizations in that the carbon backbone is built one carbon atom at a time (C1 polymerization). The general reaction involves the polymerization of ylide (a neutral dipolar molecule containing an anionic site attached directly to a heteroatom carrying a formal positive charge) or ylide like monomers via a Lewis acidic borane initiator or catalyst. Living polyhomologation allows for the production of extremely low molecular weight PEs and PE mimics with the best molecular weight distribution control out with relatively mild conditions. The greatest challenge for living polyhomologation is the availability of raw materials. Not only is their
a limited selection of suitable monomers and catalysts, but these materials also are not commercially available and must be synthesized. Here in, a new one-pot boron-catalyzed polymerization of tetrahydrotiophenium methylide which was synthesized in situ has been used to prepare polymethylenes. The living polymerization via the intermediacy of sulfur ylides was initiated and catalyzed by the organoborane as a one-pot procedure. Termination of the resulting tris(polymethylene) organoborane with acetic acid produced polymethylenes. One-pot synthesis of polymethylene was easily achieved under mild conditions in high yields and purity through sulfur ylide mediated homologation. The reactions were used to produce polymethylenes with molecular weights in the range of 17000-260000 (based on GPC) with low polydispersities between 1.07-1.18.