Self-Assembly Investigations of Sulfonated Poly(methyl methacrylate-block-styrene) Diblock Copolymer Thin Films

Claudia Piñón-Balderrama,Javier Revilla-Vázquez,José Bonilla-Cruz,César Leyva-Porras,Carlos Guerrero-Sanchez,Ulrich S Schubert,Roberto Olayo-Valles

doi:10.1155/2019/4375838

Abstract

Poly(methyl methacrylate-block-styrene) block copolymers (BCs) of low dispersity were selectively sulfonated on the styrenic segment. Several combinations of degree of polymerization and volume fraction of each block were investigated to access different self-assembled morphologies. Thin films of the sulfonated block copolymers were prepared by spin-coating and exposed to solvent vapor (SVA) or thermal annealing (TA) to reach equilibrium morphologies. Atomic force microscopy (AFM) was employed for characterizing the films, which exhibited a variety of nanometric equilibrium and nonequilibrium morphologies. Highly sulfonated samples revealed the formation of a honeycomb-like morphology obtained in solution rather than by the self-assembly of the BC in the solid state. The described morphologies may be employed in applications such as templates for nanomanufacturing and as cover and binder of catalytic particles in fuel cells.

Highlights

Block copolymers (BCs) have become promising materials in applications where well-defined nanostructures are required such as photonic crystals [1], high-density information storage devices [2] or templates for metals [3], and semiconducting nanowires [4]
poly(methyl methacrylate) (PMMA)-b-PS block copolymers (BCs) can be selectively sulfonated in the PS block, where the SO3H groups react with the aromatic rings of the styrenic segments to form p-substituted products
As reported by the supplier, PMMA-bPS BCs were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization

Summary

Introduction

Block copolymers (BCs) have become promising materials in applications where well-defined nanostructures are required such as photonic crystals [1], high-density information storage devices [2] or templates for metals [3], and semiconducting nanowires [4]. To the best of our knowledge, there are no investigations of self-assembly morphologies of highly sulfonated PMMA-b-sPS BCs (DS >50 %) in thin films, where high levels of DS might induce a more pronounced phase segregation and stronger interactions with the substrate surface. In this contribution, several well-defined PMMAb-PS BCs of different block composition, molar mass, and low dispersity were converted to their analogous ionomer materials by means of a selective sulfonation on the PS block at relatively low temperature. The methodology presented in this work is an alternative to access nanostructured materials without further annealing treatment that may be employed even in bulk state as polyelectrolytes or in the form of thin films for covering and binding catalytic particles and providing conductive pathways for ions and reactant species in fuel cell applications

Experimental Section

Results and Discussion

Conclusions