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Nanostructured Conducting Polymers for Applications in Water Treatment and Aerospace Coatings

  • Author(s): Farrell, Thomas Potapenko
  • Advisor(s): Kaner, Richard B
  • et al.
Abstract

Nanostructured conducting polymers have been synthesized by chemical oxidative polymerization, where the nucleation conditions have been intentionally modified to produce materials with high processability. These materials have been blended with conventional polymers and incorporated into polymer membranes via nonsolvent-induced phase separation. The membranes produced show tunable hydrophilicity, pore structure, and separation properties. Pure polyaniline membranes are super hydrophilic and have unusually high permeability.

The pore structure and resultant separation properties of polyaniline ultrafiltration membranes have been modified by the use of 4-methylpiperidine (4MP) as a gel-inhibiting agent. Bovine serum albumin (BSA) rejection for polyaniline membranes is improved from 0% to over 90% when 4MP is included in membrane casting solutions. Membranes cast with 4MP are hydrophobic until an appropriate post-treatment method is applied. Treatment with camphorsulfonic acid recovers the hydrophilicity in these membranes through induction of the expanded coil conformation of polyaniline, where hydrophobic 4MP molecules can now diffuse out of the polymer matrix.

Polypyrrole nanospheres have been produced by rapidly initiated chemical oxidative polymerization and used to produce nanocomposite membranes with polysulfone. The nanocomposite membranes have high BSA rejection (>80%) and have permeabilities up to 5 times greater than pure polysulfone. Fouling experiments were performed on these membranes by monitoring the flux upon introduction of BSA and subsequent washing steps. Membranes containing as little as 2% PPy nanospheres were resistant to both reversible and irreversible fouling by BSA proteins.

Copolymer nanofibers of poly(aniline-co-ethylaniline) have been produced by rapidly-initiated chemical oxidative polymerization using the initiators p-phenylenediamine and N-phenyl-1,4-phenylenediamine. Copolymer nanofibers are formed in all stoichiometries as determined by electron microscopy. Resulting copolymer compositions are enriched in ethylaniline due to the higher reactivity ratio of ethylaniline in comparison to aniline. All copolymers possess lower conductivity than the parent polyaniline nanofibers. Conductivity is highest in copolymer samples where p-phenylenediamine is used as an initiator.

Carbon nanotube/polyurethane composites have been produced as static dissipative coating materials by using polyaniline/dodecylbenzenesulfonate (DBSA) as a matrix and dispersant. While chloroform and DBSA were unable to disperse non-functionalized carbon nanotubes, the introduction of polyaniline produced homogeneous dispersions with carbon nanotubes. These materials were combined with solvent-based polyurethane to produce composite coatings. With as little as 20% loading of these polyaniline-based conducting materials, the composites fall within the static dissipative regime and maintain a high transparency.

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