Polymer, Vol.41, No.12, 4429-4436, 2000
Selective synthesis of various di- and triblock copolymers from substituted acetylenes through sequential living polymerization by MoOCl4-based catalysts in anisole
Block copolymerization of substituted acetylenes through the sequential addition process was studied by use of three MoOCl4-based living polymerization catalysts in anisole solvent. In the case of the MoOCl4-n-Bu4Sn-EtOH catalyst system, diblock copolymers with very narrow molecular weight distributions were selectively formed from any combinations of two monomers among 1-chloro-1-octyne (ClOc), [o-(trimethylsilyl)phenyl]acetylene (o-Me(3)SiPA), and [o-(trifluoromethyl)phenyl]acetylene (o-CF(3)PA) irrespective of the order of monomer addition. When the MoOCl4-Et3Al-EtOH and MoOCl4-n-BuLi catalysts were employed, several diblock copolymers with higher molecular weights were obtained owing to lower initiation efficiencies. With these catalysts, however, the order of monomer addition affected the block copolymerization, and reversing the orders that selectively gave block copolymers resulted in contamination by the homopolymers from the first monomers. The use of MoOCl4-n-Bu4Sn-EtOH enabled to produce ABC- and ABA-type triblock copolymers composed of ClOc, o- Me(3)SiPA, and o-CF(3)PA regardless of the order of monomer addition. ABC-type triblock copolymers with very high molecular weights could be synthesized using MoOCl4-Et3Al-EtOH and MoOCl4-n-BuLi, when the monomers were successively polymerized in the order of ClOc, o-Me(3)SiPA, and o-CF(3)PA. (C) 2000 Elsevier Science Ltd. All rights reserved.
Keywords:RING-OPENING METATHESIS;PI-ALLYLNICKEL CATALYST;EARTH-METALCOMPLEXES;BLOCK-COPOLYMERS;COORDINATION POLYMERIZATION;ALKYLIDENE COMPLEXES;DIBLOCK COPOLYMER;DERIVATIVES;INITIATOR;PHENYLACETYLENES