Impact of the spatial structure of alkyl chains on properties of thiophene-substituted diketopyrrolopyrroles: Part I – Langmuir layer study

•Despite similarities in the molecular structures of the investigated DPP dyes, they behave differently in thin films.•Langmuir layer molecule area is one-third  of DFT-optimized dye structure calculations.•The presence of dimeric and tetrameric forms of the dyes in thin layers are postulated.•Branching of alkyl side chain leads to lowering of Langmuir layer stability.