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Copolymers of Diketopyrrolopyrrole and Benzothiadiazole: Design and Function from Simulations with Experimental Support
journal contribution
posted on 2019-01-16, 16:05 authored by Deyan Raychev, René Daniel Méndez López, Anton Kiriy, Gotthard Seifert, Jens-Uwe Sommer, Olga GuskovaAlternating
block copolymers consisting of diketopyrrolopyrrole
and benzothiadiazole electron acceptor units linked together via aromatic
five-membered donor heterocycles are studied using a combination of
computer simulation techniques and experiments. Four copolymers are
modeled starting from their monomers to stacked macromolecules: with
two different linkersthiophene or furan, connecting electron-withdrawing
core unitsand two different alkyl substituents at lactam nitrogens
of diketopyrrolopyrrolelinear dodecyl and branched 2-octyldodecyl
chains. In our experiments, we aim at characterization of the optical
and electrochemical properties of two copolymers with branched side
chains differing in the linker, since as the literature survey shows
the data published on these copolymers are very sparse. These properties
can be easily interpreted and later compared with theoretical predictions.
The results of simulations supported by experiments show that monomers
of these polymers have very similar electronic and optical properties,
and the main difference between them consists in various chain curvature
defined by the linker. More curved furan-containing monomers and more
stretched thiophene-linked molecules are characterized by different
energetics of the stack formation and diverse in charge carrier mobilities.
The branching of the side chains affects the planarity of the macromolecules,
leads to longer π–π stacking distance and lamellar
interval in the ordered arrays of polymers, and defines the stacking
patterns of the conjugated backbones. The ambipolar transport is predicted
for the majority of considered copolymer morphologies, and a quantitatively
satisfactory agreement between experiment and computation is achieved.