Supramolecular Networks Obtained by Block Copolymer Self-Assembly in an Epoxy Matrix: Preparation and Shape Memory Behavior

MATEOS, A.; SCHMARSOW, R.N.; CASADO, U.; ZUCCHI, I.A.; SCHROEDER, W.F.

Buenos

Congreso; WCCE11 - 11th World Congress Of Chemical Engineering; 2023

World Chemical Engineering Council

In recent years, there has been a growing interest in the study of supramolecular networks obtained by self-assembly of amphiphilic molecules due to their responsive behavior to different external stimuli. Supramolecular gels are obtained from amphiphilic molecules that self-assemble in a suitable solvent forming elongated structures, such as fibers, strands or ribbons. These structures are connected by multiple non-covalent interactions generating 3D networks that encapsulate the solvent and prevent its flow. The possibility of embedding supramolecular networks into polymer matrices opens access to a new generation of functional polymers with great potential for various applications. In this work, we investigate the effect of supramolecular networks on the mechanical properties and shape memory behavior of a thermosetting matrix.Crystallization-driven self-assembly of a poly(ethylene-block-ethylene oxide) (PE-b-PEO) diblock copolymer (Mn 1400; 50 wt% PEO, Aldrich Chemical Co.) was used to generate supramolecular networks in epoxy monomers (DGEBA, DER 332, Aldrich Chemical Co.). PE-b-PEO self-assembles into nanoribbons with a semicrystalline PE core bordered by coronal chains of PEO, and the nanoribbons, in turn, bundle into lamellar aggregates with an average stacking period of 16.5 nm (for 20 wt% PE-b-PEO). The nanoribbons are interconnected forming a crystalline 3D network structure (Figure 1). Supramolecular gels were characterized by oscillatory rheology. At 98 ºC, a crossover of the storage (G’) and loss (G’’) moduli occurs indicating a transition from gel to liquid, produced by the disintegration of the supramolecular network in DGEBA monomer. The crossover temperature agrees with the melting peak of PE blocks. The obtained gels were irradiated at room temperature to photopolymerize the DGEBA monomer. SAXS experiments show that the polymer matrix preserves the structure of the supramolecular network and avoids its disintegration when the material is heated above the melting temperature of PE cores. Furthermore, the matrix does not influence the crystallization-melting processes of PE. Shape memory cyclic tests show that the maximum deformed strain of these materials can be precisely tuned by programming the temperature within the melting range of the supramolecular network.