Structure-Property Relationships in Segmented Polyviologen Ionene Rotaxanes

Abstract

Abstract The first structure-property relationships are reported for segmented polyrotaxane ionenes which possess the rotaxane moiety at the hard segment. These ionenes are based on PTMO/MDI (PTMO M n of 650, 1000, or 2000 daltons) as the elastomeric segment and paraquat hard segments with either PF6 − or Br− as the counterion. GPC indicates that these ionenes have a highly variable architecture with respect to the placement of the ionene hard segment. SAXS also supports the notion of a randomly placed hard segment because the interionic domain d spacings are not predictable or consistent. SAXS also shows there are few “lone multiplets” in the PF6 − derivative whereas there are considerable numbers of isolated ion pairs in the Br− ion-exchanged ionenes. Tensile testing shows that the PTMO-1000 and PTMO-2000 materials are elastomeric with good properties, but the PTMO-650 ionene is not elastomeric with the ionic hard segment as a continuous phase. Dynamic mechanical tests also indicate that these segmented ionenes are phase separated with two transitions. TGA indicates that the rotaxane derivative is stable to higher temperatures than the nonrotaxane analog. Although the observed structure-property relationships suggest that these systems are generally varied in the placement of the paraquat hard segments, it is clear that the rotaxane moiety increases the elastic modulus and increases thermal stability.