Fluorescent EDOT-Functionalized Poly-E-Caprolactone: Synthesis, Photophysical and Self-Assembling Properties in Organic Solvents and Its Serendipitously Noticed Behaviour in Protonated Media

In the last few years several fluorescent poly-e- caprolactones [1-3] were designed, synthesized and subsequently used as nanoparticles [1], nanofibers [2] or scaffolds [3] in various prospective bioapplications. Meanwhile, our interest was directed toward electro - and photoactive moieties - functionalized poly/or oligo-e- caprolactone, that worked as key building blocks (macromonomers) for new grafted conjugated polymers or hybrid systems successfully used as biosensors [4,5] or regenerative medicine [6]. In the same line, the present report is aimed to extend the investigations and to highlight the properties in solution (photophysical, self-assembling) of 3, 4-ethylenedioxythiophene-functionalized poly-e- caprolactone (EDOT-PCL) synthesized by ring-opening polymerization (ROP). The results of the studies in two organic solvents (chloroform and acetonitrile), having different selectivity in relation with the constitutive parts of EDOT-PCL, revealed its propensity for self-assembling, proved by Dynamic Light Scattering (DLS) measurements, while fluorescent emission maxima in the range 310-430 nm, depending on the solvent were evidenced, as well. Moreover, its capability for spontaneous oxidant-free oligomerization, presumably due to and under the action of acidic character of CDCl₃, serendipitously noticed during ¹³C-NMR registration, was subsequently validated by experiments performed in chloroform in the presence of hydrochloric acid. This is an interesting and applications-oriented useful observation which supports that recently demonstration of oxidant-free polymerization of common EDOT in the only presence of some organic acids [7] could also be extended to EDOT-containing more complex structure.

1. Huang,S., Liu, S., Wang, K., Yang,C. Luo, Y., Zhang,Y., Cao, B., Kang, Y., Wang, M., Nanoscale, 2015,7, 889-895.
2. H .J. Diao, K.Wang, H. Y. Long, M. Wang, S.Y. Chew, Adv. Healthcare Mater., 2016, 5, 529–533.
3. S. Huang, K. Wang, S. Wang, Y. Wang, M. Wang, Adv. Mater. Interfaces, 2016, 1600259.
4. B. G. Molina, A. D. Bendrea, L. Cianga, E. Armelin, Luis J. del Valle, I. Cianga, C. Alemán, Polym. Chem., 2017, 8, 6112–6122.
5. B. G. Molina, L. Cianga, A.D. Bendrea, I. Cianga, C. Alemán, E. Armelin, Polym. Chem., 2019, 10, 5010–5022.
6. B. G. Molina, A. D. Bendrea, S. Lanzalaco, L. Franco, L. Cianga, L. J. del Valle, J. Puiggali, P. Turon, E. Armelin, I. Cianga, C. Aleman, J. Mater Chem B, 2020, doi.org/10.1039/D0TB01259A
7. E. Tomšík, I. Ivanko, J. Svoboda, I.Šeděnková, A. Zhigunov, J. Hromádková, J. Pánek, M. Lukešová, N. Velychkivska, L. Janisová, Macromol. Chem. Phys. 2020, 2000219.