Analysis of Wetting of Perylene Diimide Thin Films-on-Glass by Water

Abstract

Perylene tetracarboxylic diimide (PTCDI), derivatives have attracted the attention of the scientific community owing to their thermal stability, electron affinity-enabling n-type semiconductor behaviour and useful photophysical properties. Thin films of six new perylene tetracarboxylic diimides were fabricated on glass substrate by spin coating. The contact angles made by water on these six substrates, some with alkyl chain derivatives and the others with polar side chains, were measured using a precision contact angle goniometer. The alignment of these films on glass substrates are inferred from the contact angle data and the results are compared with those of the (self) alignment in liquid state. Derivatives with alkyl chains were seen to interact more with water, causing a lower contact angle compared to the more polar derivatives. This counter-intuitive result is interpreted in terms of molecular alignment of samples on the glass substrates.