Synthesis of telechelic polymers through metathesis reactions and borane chemistry.

摘要

This thesis describes novel routes to the synthesis of telechelic polymers, and to triblock copolymers from these telechelic precursors. The approach involves a confluence of metathesis and boron chemistry.;Our approach to this problem has been two-fold. In our first approach, we have employed ring-opening metathesis polymerization of a cyclic olefin, by a commercially available non-living catalyst system, in the presence of a trialkylborane containing acyclic olefin to not only introduce a functional group precursor at the end of a growing polymer chain but also to control the molecular weight of the final product.;In our second approach to this problem, we have employed the cross-metathesis reaction of a polymer containing small amounts of unsaturation in the polymer backbone, with a trialkylborane containing acyclic olefin. By this method, not only is the polymer degraded and the molecular weight of the product controlled by controlling the amounts of the reactants, but a functionalization of the broken chain ends occurs simultaneously. This route allows us to access telechelic forms of polymers that do not innately undergo the metathesis reaction. This approach extends the scope of this chemistry and makes it a general method applicable to a wide range of polymers with very small amounts of unsaturation in the polymer backbone.;Triblock copolymers of different compositions were synthesized by employing the telechelic polymers obtained by the above methods as central blocks. The composition of the products obtained from these block copolymerization reactions were used to evaluate the efficiencies of the methods of generation of these precursor telechelic polymers. The different triblocks exhibited interesting variations in thermal and mechanical properties, based on their compositions.;A brief foray into the field of ring-opening metathesis copolymerization of a cyclic olefin with a trialkylborane containing cyclic olefin involves taking advantage of the unique features of this form of polymerization to introduce functional groups in random fashion along the polymer backbone. In addition, a unique control over bulk properties, viz. melting point of the final product could be attained by this approach. Such materials could have unique applications as specialty elastomers.