Poly(propylene glycol)-based ammonium ionenes as segmented ion-containing block copolymers

The synthesis and characterization of series of segmented poly(propylene glycol) (PPG)-based ammonium ionenes is described. Bromine end-capped oligomers were successfully synthesized using the reaction of 6-bromohexanoyl chloride with 1000, 2000, and 4000 g/mol PPGs.¹H NMR spectroscopy, titration studies, and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry revealed the difunctionality of the oligomers. First, a series of PPG-based ammonium ionenes was synthesized from bromine end-capped PPG oligomers and N,N,N′,N′-tetramethyl-1,6- hexanediamine. For this series, a single glass transition temperature (T _g) of approximately-66 °C was observed through differential scanning calorimetry (DSC); dynamic mechanical analysis (DMA) showed the onset of flow ranged from 20 to 80 °C. In addition, a series of PPG-based ammonium ionenes containing 1,12-dibromododecane was synthesized to increase the aliphatic hard segment (HS) content and enhance the mechanical properties of the resulting materials. For these, two T_g's were observed using DMA; DMA also showed the onset of flow of ionenes containing higher HS content (33 wt %) occurred in the range of 100-140 °C. Tensile analysis for these ionenes demonstrated an average tensile strength at break ranging from 0.2 to 2.4 MPa. Small angle X-ray scattering (SAXS) profiles for these ionenes showed that Bragg distances increase linearly with the molecular weight of PPG soft segment.