Microscopic Morphology of Polyfluorene–Poly(ethylene oxide) Block Copolymers: Influence of the Block Ratio

Authors


  • The collaboration between Mons and Mainz is conducted within the framework of the InterUniversity Attraction Pole Program (PAI V/3) of the Belgian Federal Government and the European Science Foundation “Structuring, Manipulation, Analysis and Reactive Transformation of Nanostructures (SMARTON)” program. Research in Mons is supported by the European Commission and the Government of the Région Wallonne (Phasing Out—Hainaut) and the Belgian National Fund for Scientific Research FNRS/FRFC. M. S. acknowledges the F.R.I.A. for a doctoral scholarship.

Abstract

In this paper, we describe the synthesis and characterization of poly(9,9′-dioctylfluorene)–poly(ethylene oxide) (PF-PEO) block copolymers with different block ratio and molecular architectures (diblock or triblock copolymers). Tapping-mode atomic force microscopy is used to investigate the relationship between the molecular structure and the microscopic morphology of thin deposits. Copolymers with a low average volume ratio of PEO (fEO from 0.1 to 0.3) exhibit a well-defined organization into nanoribbons. A model of chain packing is proposed; these structures arise from the interplay of π–π interactions between conjugated PF segments and the interactions of PEO with the mica substrate surface. For copolymers with higher average volume ratio of PEO (fEO > 0.4), the organized structures disappear and lead to untextured aggregates, probably because long-range, regular π–π stacking of the segments can no longer take place. We also observe that the nature of the solvent from which deposits are grown and the substrate polarity have a strong impact on the microscopic morphology.

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