Intramolecular Cross-Linking: from Single Chain to Bulk Materials

Or Galant gorr@campus.technion.ac.il 1 Charles E. Diesendruck 1 Meredith Silberstein 2 Maya Pinhas-Davidovich 3
1Shulich Faculty of Chemistry, Technion-Israel institute of Technology, Haifa, Israel
2Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York, USA
3Biotechnology and Food Engineering Faculty, Technion-Israel institute of Technology, Haifa, Israel

Polymeric materials have historically been divided into thermoplastics and thermosets, as a consequence of their thermal processability. Thermoplastics typically present a glass transition temperature (Tg), and a melting temperature (Tm) while in thermosets, covalent cross-links between chains restrict relative movement. While they still present a Tg, thermosets cannot be melted. In this research, we exploit chemistry to produce chains with intramolecular cross-links only, restricting relative movement in the chain, but allowing the chains to flow in relation to each other, making thermoplastics reinforced with covalent cross-links. The synthetic strategy involves a two-step approach; first a linear chain is prepared; then, intramolecular cross-linking is carried out under high dilution to inhibit intermolecular reactions. The obtained polymers are studied for their mechanical and thermomechanical properties at the single molecule level, as well as in bulk materials.

Interestingly, in the solid state, these materials are similar to biological materials cast from proteins, which present high strength and toughness, two properties which tend to be mutually exclusive in synthetic materials.[1],[2] However, intramolecular cross-linking physically limits entanglement between chains, and therefore, toughness is initially lost. To better mimic the superior mechanical properties of protein-derived materials, additional non-covalent interactions between chains is necessary. By functionalizing the nanoparticles’ surfaces with hydrogen-bonding motifs we aim to receive a material in which chains are untangled and still present high toughness, similar to biological materials. In these type of materials, mechanical properties are controlled by structure and not monomer chemistry.

[1] Wegst, U. G. K. et al. Bioinspired structural materials. Nat. Mater. 14, 23–36 (2014).

[2] Egan, P., Sinko, R., LeDuc, P. R. & Keten, S. The role of mechanics in biological and bio-inspired systems. Nat. Commun. 6, 7418 (2015).









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