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Hydration of a side-chain-free n-type ladder semiconducting polymer driven by electrochemical doping



Jiajie Guo, Lucas Flagg, Duyen Tran, Shinya Chen, Ruipeng Li, Nagesh Kolhe, Rajiv Giridharagopal, Samson A. Jenekhe, Lee J. Richter, David Ginger


We study the organic electrochemical transistor (OECTs) performance of the ladder polymer, poly(benzimidazobenzophenanthroline) (BBL) in an attempt to better understand how an apparently insoluble side-chain free polymer is able to operate as an OECT with favorable redox kinetics in an aqueous environment. We examine two BBLs of different molecular weights from different sources. Both BBLs show significant film swelling during the initial reduction step. By combining electrochemical quartz crystal microbalance (eQCM) gravimetry, in operando atomic force microscopy (AFM), and both ex situ and in situ and in operando grazing incidence wide-angle x-ray scattering (GIWAXS), we provide a detailed structural picture of the electrochemical charge injection process in BBL in the absence of any hydrophilic sidechains. Compared with ex situ measurements, in operando GIXWSs shows both more swelling upon electrochemical doping than has previously been recognized, as well as less contraction upon dedoping. The data show that BBL films undergo an irreversible hydration driven by the initial electrochemical doping cycle with significant water retention and lamellar expansion that persists across subsequent oxidation/reduction cycles. This swelling creates a hydrophilic environment that facilitates the subsequent fast hydrated ion transport in the absence of the hydrophilic side-chains used in many other polymer systems. Due to its rigid ladder backbone and absence of hydrophilic side-chains, the primary BBL water uptake does not significantly degrade the crystalline order, and the original dehydrated, unswelled, state can be recovered after drying, leading to efficient electronic transport and good stability.
Journal of the American Chemical Society


Organic Electrochemical Transistor


Guo, J. , Flagg, L. , Tran, D. , Chen, S. , Li, R. , Kolhe, N. , Giridharagopal, R. , Jenekhe, S. , Richter, L. and Ginger, D. (2023), Hydration of a side-chain-free n-type ladder semiconducting polymer driven by electrochemical doping, Journal of the American Chemical Society, [online],, (Accessed April 23, 2024)
Created January 11, 2023, Updated January 23, 2023