Triblock copolyampholytes from 5-(N,N-dimethylamino)isoprene, styrene, andmethacrylic acid: Synthesis and solution properties

ABC triblock copolymers of the type poly[5-(N,N-dimethylamino)isoprene]-blo ck-polystyrene-block-poly(tert-butyl methacrylate) (AiST) were synthesized and hydrolyzed to yield poly[5-(N,N-dimethylamino)isoprene]-block-polystyre ne-block-poly(methacrylic acid) (AiSA) triblock copolyampholytes. Due to a complex solubility behavior the solution properties of these materials had to be investigated in THF/water solvent mixtures. Potentiometric titrations of AiSA triblock copolyampholytes showed two inflection points with the A block being deprotonated prior to the Ai hydrochloride block thus forming a polyzwitterion at the isoelectric point (iep). The aggregation behavior wa s studied by dynamic light scattering (DLS) and freeze-fracture/transmissio n electron microscopy (TEM). Large vesicular structures with almost pH-inde pendent radii were observed.