A Route to Self-Organized Honeycomb Microstructured Polystyrene Films and Their Chemical Characterization by ToF-SIMS Imaging

• Published in: Advanced functional materials 2007-05, Vol.17 (7), p.1079-1084
• Main Authors: Yunus, S., Delcorte, A., Poleunis, C., Bertrand, P., Bolognesi, A., Botta, C.
• Format: Article
• Language: English
• Subjects: Microstructures; Polymers; Self-assembly; Structural characterization; Structure-property relationships; Thin films
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200600470

A new type of polymer compound that allows the formation of highly ordered microstructured films by casting from a volatile solvent in the presence of humidity, and its characterization by ToF‐SIMS (time‐of‐flight secondary‐ion mass spectrometry) are presented. A honeycomb structure is obtained by activation of 2,2,6,6‐tetramethyl‐1‐piperidinyloxyl (TEMPO)‐terminated polystyrene (PS) with p‐toluenesulfonic acid (PTSA). The mechanism of this activation reaction, leading to a more polar PS termination, is deduced from simple experiments and supported by ToF‐SIMS characterization. Positive and negative ToF‐SIMS imaging allows different chemical regions correlating to the film morphology to be distinguished. This new, straightforward activation process, together with ToF‐SIMS chemical imaging, provides a better understanding of the phenomena underlying the formation of these films by directly linking the role of polar terminations to the microscale self‐organization. This new method, transposable to other organic acids, suggests interesting new perspectives in the field of self‐organized chemical and topographical patterning. Breath‐figure imprinted films of p‐toluenesulfonate‐2,2,6,6‐tetramethyl‐1‐piperidinium‐oxyl polystyrene display a chemical patterning in addition to the regular ordering of cavities (see figure and cover). Time‐of‐flight secondary‐ion mass spectrometry (ToF‐SIMS) indicates that the polymer end groups are located on the cavities' surfaces.