Purification of conjugated polymers using liquid chromatography
Licentiate thesis, 2026
One of the main challenges in the development and commercialisation of organic semiconducting polymers is the batch-to-batch variation that leads to
performance differences in bioelectronic applications such as organic electrochemical transistors (OECTs). The differences in the device performance are
strongly influenced by variations in molecular weight and dispersity inherent to the polymerisation methods. Moreover, polymer purification techniques are often ineffective at removing oligomers and metal residues from the catalysts, which influence the materials’ final properties. Therefore, there is a need for complementary methods that improve the purity of conjugated polymers.
In this work, high-performance liquid chromatography (HPLC) is used as a complementary technique for polymer purification. The method was developed
using poly(3-hexylthiophene) (P3HT), a p-type polymer, to demonstrate how this purification approach effectively narrows polymer dispersity. Furthermore, the role of aggregation behaviour in the separation mechanism is also investigated in two naphthalene diimide-bithiophene (NDI-T2) polymers: one with a hybrid alkyl-glycol side chain that promotes aggregation, and a fully glycolated analogue.
The properties of the synthesized NDI-T2 polymers were compared before and after HPLC fractionation. Oligomer removal from the hybrid-side-chain
polymer resulted in differences in the absorption spectra in solution, higher electrochemical stability of polymer thin films during continuous cycling, and an increase in mobility (μ) in OECT devices (0.012 cm2V−1s−1 vs 0.008 cm2V−1s−1 for the unpurified polymer). Microstructural analysis revealed that increased mobility is likely associated with a higher degree of order in the crystallite domains of the polymer’s higher-molecular-weight fraction. Finally, to test the method’s reproducibility, three batches of the polymer were synthesized and purified. The results showed that oligomers were consistently removed across batches, suggesting that this method can help minimize variation in device performance.
performance differences in bioelectronic applications such as organic electrochemical transistors (OECTs). The differences in the device performance are
strongly influenced by variations in molecular weight and dispersity inherent to the polymerisation methods. Moreover, polymer purification techniques are often ineffective at removing oligomers and metal residues from the catalysts, which influence the materials’ final properties. Therefore, there is a need for complementary methods that improve the purity of conjugated polymers.
In this work, high-performance liquid chromatography (HPLC) is used as a complementary technique for polymer purification. The method was developed
using poly(3-hexylthiophene) (P3HT), a p-type polymer, to demonstrate how this purification approach effectively narrows polymer dispersity. Furthermore, the role of aggregation behaviour in the separation mechanism is also investigated in two naphthalene diimide-bithiophene (NDI-T2) polymers: one with a hybrid alkyl-glycol side chain that promotes aggregation, and a fully glycolated analogue.
The properties of the synthesized NDI-T2 polymers were compared before and after HPLC fractionation. Oligomer removal from the hybrid-side-chain
polymer resulted in differences in the absorption spectra in solution, higher electrochemical stability of polymer thin films during continuous cycling, and an increase in mobility (μ) in OECT devices (0.012 cm2V−1s−1 vs 0.008 cm2V−1s−1 for the unpurified polymer). Microstructural analysis revealed that increased mobility is likely associated with a higher degree of order in the crystallite domains of the polymer’s higher-molecular-weight fraction. Finally, to test the method’s reproducibility, three batches of the polymer were synthesized and purified. The results showed that oligomers were consistently removed across batches, suggesting that this method can help minimize variation in device performance.
conjugated polymers
organic electrochemical transistors
size-exclusion chromatography
10:an, Chemsitry
Opponent: Joost Kimpel, PhD, Chalmers University of Technology
Author
Jessica Itxel Vasquez Matias
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
J.I. Vasquez, R.S. Raju, A. Magni, J. Vanderspikken, J. Pons i Tarres, A. Maxwell, S. Lin, P. Swanson, A. Zhao, M. Jha, W. Maes, C. M¨uller, A. Saleo, B. Cotts, M. Westwood, A. Giovannitti, Aggregation effects benefit purification of conjugated polymers using liquid chromatography
M. Westwood,, R.S. Raju, S. M¨uller, P. Sathirathai, E. Nilsson, M. Denis, J.I. Vasquez, J. Asatryan, J. ¨Ohberg, S.H. Paleti, J. Pons i Tarres, J. Martin, C. M¨uller, A. Giovannitti, Standardizing conjugated polymers through liquid chromatography
Subject Categories (SSIF 2025)
Materials Chemistry
Polymer Chemistry
Publisher
Chalmers
10:an, Chemsitry
Opponent: Joost Kimpel, PhD, Chalmers University of Technology