Chiral nanostructure in polymers under different deposition conditions observed using atomic force microscopy of monolayers: poly(phenylacetylene)s as a case study.

Dynamic poly(phenylacetylene)s (PPAs) adopt helical structures with different elongation or helical senses depending on the types of pendants. Hence, a good knowledge of the parameters that define their structures becomes a key factor in the understanding of their properties and functions. Herein, the techniques used for the study of the secondary structure of PPAs using atomic-force microscopy (AFM) are presented, with special attention directed towards the methods used for the preparation of monolayers, and their consequences in the quality of the AFM images. Thus, monolayers formed by drop casting, spin coating followed by crystallization or annealing, Langmuir-Blodgett and Langmuir-Schaefer methods, onto highly oriented pyrolytic graphite (HOPG) or mica, are described, together with the AFM images and the resulting helical structure obtained for different PPAs. Furthermore, some conclusions are drawn both on the adequacy of the different techniques for the formation of monolayers and on the solid supports utilized to elucidate the secondary structure of different PPAs.