Polymerization of 1,2-butylene oxide initiated by triphenylmethyl salts. I. Kinetics with 1,2-dichloroethane as solvent

1,2-Butylene oxide was polymerized in 1,2-dichloroethane in the temperature range ?20 to + 10°C. Triphenylmethyl salts of hexafluoroantimonate (Ph₃CSbF₆), hexafluoroarsenate (Ph₃CAsF₆), and hexafluorophosphate (Ph₃CPF₆) were employed as initiators. The reactions are characterized by a fast initiation process accompanied by rapid consumption of monomer. This initial stage is followed by a relatively slower polymerization during which the rate of monomer consumption is first-order in respect to monomer. Variation of the counteranion produces very little influence on the rate. The difference between the thermodynamic parameters found for the first and second stages of the reaction are explained on the basis of two different polymerization mechanisms. The linear dependence of rate on initiator concentration indicates that propagation takes place by ion-pairs only within the range investigated here.