Vibrational characterization of poly(1-methylpyrrole- co-squaric acid) and poly(1-dodecylpyrrole-co-squaric acid) by enhanced Raman spectroscopy

Poly(1-methylpyrrole-co-squaric acid) (PMPS) and poly(1-dodecylpyrrole-co-squaric acid) (PDPS), copolymers of the class of polysquaraines, were synthesized and their structure determined by UV-VIS-NIR, resonance Raman and surface-enhanced Raman scattering (SERS) and electron paramagnetic resonance (EPR) spectroscopies. The spectroscopic results led to a structure different from that proposed in the literature, having radical units localized in the protonated squarate moieties and polypyrrole dication-like segments. The resonance Raman profiles indicate the presence of two chromospheres that are consistent with the electronic data. The Raman assignment was supported by density functional theory (DFT) calculations. Copyright © 2006 John Wiley & Sons, Ltd.