Living metathesis polymerization of several substituted acetylenes by MoOCl4-Et3Al-EtOH

Living polymerization of several substituted acetylenes such as [o-(trimeth ylsilyl)phenyl]acetylene (o-Me3Si-phenylacetylene), 1-chloro-1-octyne, (o-m ethylphenyl)acetylene (o-Me-phenylacetylene) was investigated by using a Mo OCl4-based lcatalyst, MoOCl4-Et3Al-EtOH (1 : 1 : 3-4). It was proved that o -Me3Si-phenylacetylene polymerizes in a living fashion with the MoOCl4-Et3A l-EtOH catalyst in the temperature range 0-30 degrees C. The M-w/M-n was as small as 1.05. The absolute M-n values of poly(o-Me3Si-phenylacetylene) we re determined by vapor pressure osmometry (VPO), and the following relation ship was obtained: M-n (VPO) = 1.28 x M-n (GPC; polystyrene calibration). T he activation parameters for the polymerization of o-Me3Si-phenylacetylene were determined as Delta H-not equal = 73 kJ mol(-1) and Delta S-not equal = -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. Pol ymerization of o-Me-phenylacetylene formed a stereoregular living polymer h aving an M-w/M-n of 1.2 and 90% cis structure. Polymerizations of a few oth er phenylacetylenes having bulky ortho substituents also yielded living pol ymers, which is a tendency similar to those with previous MoOCl4-based cata lysts.