Living Metathesis Polymerization of Several Substituted Acetylenes by MoOCl4–Et3Al–EtOH

Living polymerization of several substituted acetylenes such as [o-(trimethylsilyl)phenyl]acetylene (o-Me3Si- phenylacetylene), 1-chloro-1-octyne, (o-methylphenyl)acetylene (o-Me-phenylacetylene) was investigated by using a MoOCl4-based catalyst, MoOCl4–Et3Al–EtOH (1:1:3—4). It was proved that o-Me3Si-phenylacetylene polymerizes in a living fashion with the MoOCl4–Et3Al–EtOH catalyst in the temperature range 0—30°C. The Mw/Mn was as small as 1.05. The absolute Mn values of poly(o-Me3Si-phenylacetylene) were determined by vapor pressure osmometry (VPO), and the following relationship was obtained; Mn(VPO)=1.28×Mn (GPC; polystyrene calibration). The activation parameters for the polymerization of o-Me3Si-phenylacetylene were determined as ΔH≠=73 kJ mol−1 and ΔS≠=−13 J mol−1 K−1. MoOCl4–Et3Al–EtOH induced the living polymerization of 1-chloro-1-octyne as well to give a polymer with small polydispersity. Polymerization of o-Me-phenylacetylene formed a stereoregular living polymer having an Mw/Mn of 1.2 and 90% cis structure. Polymerizations of a few other phenylacetylenes having bulky ortho substituents also yielded living polymers, which is a tendency similar to those with previous MoOCl4-based catalysts.