Poly(oxypropylene) (I) segments were either covalently or phys. introduced into poly(tetrahydrofuran) (II) ionene to study the phys. properties of modified II. I-II block ionene (III) was prepared from Me2N-terminated II, Me2N-terminated I, and α,α'-dichloro-p-xylene. The tensile strength of III decreased with increasing content of Me2N-terminated I. This is due to possible inhibition of the strain-induced crystallization of the I segments. The addition of polypropylene glycol [25322-69-4] as a plasticizer decreased the peel strength on II ionene, due to a relative decrease in the cationic concentration of II ionene. Exchange of the counteranion in quaternary ammonium groups of II ionene, i.e. the Cl anion for various fatty acid anions, also varied the phys. properties of II ionene.