Polyethers with propargyl side chains were synthesized by the acid-catalyzed reaction of dialdehydes 1, alkylene bis(trimethylsilyl) ethers 2, and allenyltrimethylsilane 4. When ethylene glycol bis(trimethylsilyl) ether was used as 2, only oligomer was obtained. However, the use of 2 with longer carbon chains gave the desired polyethers consisting of 1, 2, and 4 in the molar ratio 1:1:2 in good yields in the presence of 10 mol % triphenylmethyl perchlorate (TrClO4) at -20 degrees C. This polyether was treated with organometallic reagents such as Co complex or CuCl to give a cross-linked polymer. This polymer synthesis is unusual in that it concurrently constructs both the polymer backbone and the functional side chains from three starting compounds. (c) 2005 Wiley Periodicals, Inc.