Highly Stretchable Polymers: Mechanical Properties Improvement by Balancing Intra‐ and Intermolecular Interactions

Abstract

The mechanical properties of polymers are highly dependent on the mobility of the underlying chains. Changes in polymer architecture can affect inter‐ and intramolecular interactions, resulting in different chain dynamics. Herein, an enhancement in the mechanical properties of poly(butylmethacrylate) is induced by folding the polymer chains through covalent intramolecular crosslinking (CL). Intramolecular CL causes an increase in intramolecular interactions and inhibition of intermolecular interactions. In both the glassy and rubbery states, this molecular rearrangement increases material stiffness. In the glassy state, this molecular rearrangement also leads to reduced failure strain, but surprisingly, in the rubbery state, the large strain elasticity is actually increased. An intermediate intramolecular CL degree, where there is a balance between intra‐ and intermolecular interactions, shows optimal mechanical properties. Molecular dynamics simulations are used to confirm and provide molecular mechanisms to explain the experimental results.

Effect of intramolecular crosslinker properties on the mechanochemical fragmentation of covalently folded polymers

“…More recently, we have also shown that reversible noncovalent interactions used for intramolecular collapse present an additional advantage—due to entropic spring effects, these sacrificial bonds can reform after mechanical unfolding, leading to even longer property lifetimes . In the solid state, we have shown that intramolecular collapse leads to additional advantages—significant improvements in moduli, stretchability, and toughness …”

“…As in our recent studies, 9,23 the chemistry chosen for intramolecular folding is grounded on the Michael addition of poly(MMA) [(PMMA)-co-AEMA], 24 since it offers a simple and reliable crosslinking chemistry which can be easily followed by NMR. 8,10,14 Hence, a large batch of a linear PMMA-co-AEMA SCHEME 1 Synthesis of SCPNs having intramolecular CLs with different lengths.…”

“…Recently, we have been studying the use of covalent intramolecular CLs to tune the mechanical properties and mechanochemical response of polymer chains while maintaining the material thermoplastic . Intramolecular CLs connect between two monomer sites within the same chain, folding the polymer into a more compact, yet still soluble, meltable, and therefore processable, polymer architecture, commonly called single‐chain polymer nanoparticles (SCPNs) .…”

“…6,7 Recently, we have been studying the use of covalent intramolecular CLs to tune the mechanical properties and mechanochemical response of polymer chains while maintaining the material thermoplastic. [8][9][10] Intramolecular CLs connect between two monomer sites within the same chain, folding the polymer into a more compact, yet still soluble, meltable, and therefore processable, polymer architecture, commonly called single-chain polymer nanoparticles (SCPNs). 11,12 In recent studies, we demonstrated that SCPNs folded by covalent bonds, while thermoplastic in nature, respond to mechanical stress in a similar way to thermosets, presenting significantly higher rate of mechanochemistry, but demonstrating a significant slower loss in properties.…”

“…15 In the solid state, we have shown that intramolecular collapse leads to additional advantagessignificant improvements in moduli, stretchability, and toughness. 9 with most work focusing on the chemistry and the challenge to inhibit intermolecular reactions. Given the interest and recent advances in chain folding, in addition to developing new chemistries, the development of different applications for these polymer materials is quite attractive.…”