Toughening Vitrimers Based on Dioxaborolane Metathesis through Introducing a Reversible Secondary Interaction

Area of Science:

• Polymer Science
• Materials Science
• Mechanics of Materials

Background:

• Achieving high toughness in materials often involves a trade-off between hardness and stretchability.
• Dual-cross-linked networks offer a promising strategy to overcome this limitation by incorporating weaker and stronger cross-links.
• The precise molecular mechanisms governing the toughness enhancement in these systems require further elucidation.

Purpose of the Study:

• To investigate the molecular mechanism of energy dissipation in dual-cross-linked networks.
• To prepare and characterize novel dual-cross-linked networks with tunable mechanical properties.
• To understand the role of hydrogen bonding in enhancing material toughness and stretchability.

Main Methods:

• Copolymerization of hexyl methacrylate with hydrogen-bonding n-isopropyl methacrylamide and vitrimeric cross-linkers.
• Tensile testing to evaluate stress-strain behavior and energy dissipation.
• Application of modified Dobrynin theory to model material softening during elongation.

Main Results:

• Increased hydrogen bond density significantly enhanced energy dissipation and initial modulus, bridging the gap between elastomers and glassy materials.
• Material softening during elongation, evidenced by stress overshoot, was effectively captured by a modified theoretical model.
• Deviations at high hydrogen bond densities were attributed to the coupled motion of closely spaced hydrogen bonds.

Conclusions:

• Dual-cross-linked networks with strategically incorporated hydrogen bonds can achieve high toughness.
• The interplay between hydrogen bond dynamics and network architecture dictates material response under tensile load.
• This work provides molecular insights into designing advanced tough and stretchable polymeric materials.