Hyperbranched Sulfonated Polydiphenylamine as a Novel Self-Doped Conducting Polymer and Its pH Response

A synthesis strategy for a hyperbranched sulfonated polydiphenylamine was developed. First, a hyperbranched polyvinylbenzoxylamine (H-PVBPA) was prepared by controlled atom transfer radical copolymerization of an amino-protected vinylbenzoxylamine (4-VBPA-tBOC) and 4-chloromethyl styrene followed by deprotection. Second, H-PVBPA was reacted with sodium diphenylamine sulfonate under acidic conditions to generate hyperbranched sulfonated polydiphenylamine (H-PSDA). The H-PSDA exhibited conductivities of 3.7 × 10-2 and 1.2 × 10-2 S/cm in HCl-doped and self-doped states, respectively. The microstructure of H-PSDA in aqueous solutions was found to be sensitive to the pH. In the dedoped state (at pH ≥ 7), AFM identified nanoscale particles of uniform size around 40 nm. The self-doped H-PSDA aggregated at pH = 7 via intermolecular doping interaction, generating large and irregular particles (>200 nm). When the pH was decreased below 5, the aggregates could be dispersed as smaller particles of about 120 nm because of the replacement of the intermolecular self-doping by the external-doping interaction caused by the small molecules of HCl.

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