We have synthesized a polyacetylene derivative, poly(dipropargyl-16-crown-5), through the cyclopolymerization of the corresponding monomer by metathesis catalysts. The polymer containing crown-ether units was characterized by spectroscopic and thermal techniques. The polymer structure is believed to be a cyclized form with both five- and six-membered rings. The polymer exhibits high cation-binding properties and ionochromic effects. The order of the selectivity of alkali- metal cations for both the monomer and the polymer was found to be Na+ > K+ > Li+ and the polymer shows the largest red shift by approximately 40 nm in lambda(max) for Na+.