Application of Solid-State NMR To Characterize the Interaction of Gel Inhibitors with Emeraldine Base Polyaniline

• Published in: Macromolecules 2002-07, Vol.35 (14), p.5565-5569
• Main Authors: Young, Tanya L, Espe, Matthew P, Yang, Dali, Mattes, Benjamin R
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Structure, morphology and analysis
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma020397m

The extent and types of changes occurring to polyaniline (PANI) films cast from solutions containing a gel inhibitor were characterized by solid-state NMR (SSNMR). Two secondary amine gel inhibitors, 2-methylaziridine (2-MA) and pyrrolidine (Py), were studied and observed to have very different reactivities with the polymer. 13C and 15N SSNMR data show that pyrrolidine adds to the quinoid ring of ∼50% of the repeat units, converting these units from the emeraldine base form to the leucoemeraldine form. The presence of the pendant amine group also disrupts chain packing, increasing the amount of kilohertz regime chain motion in the solid state as determined from the magnitude of T 1 ρ(H). In contrast, 2-MA reacted only slightly with PANI, addition to ∼5% of the repeat units, but 0.7 2-MA/repeat unit was physically trapped in the PANI film. The greater reactivity of Py (pK b = 3) relative to 2-MA (pK b = 6) is related to the amine's nucleophilicity and orbital arrangement.