Converting high modulus water-based elastomeric core–shell nanoparticle films from viscoelastic to predominantly elastic using di-epoxide crosslinking

Abstract

Most elastomers are formed using solvent-based processes which result in an environmental burden. Consequently, elastomers formed using water-based nanoparticle dispersions are highly desirable. Here, we investigate elastomer-like films based on water-dispersible carboxylic acid-containing core–shell (CS) nanoparticles. The nanoparticles contain a poly(n-butylacrylate) (PBA) core and a poly(BA-co-acrylonitrile-co-methacrylic acid) shell. We react the –COOH groups of the shell with a di-epoxide (1,4-butanediol diglycidyl ether, BDDE) which replaces dissipative hydrogen bonds in the nanoparticle elastomer films with covalent bonds. The reaction with BDDE enables the transformation of a stretchable dissipative film (shear modulus of 9.0 MPa with 20% strain energy recovery) into a predominantly elastic film (shear modulus of 0.20 MPa with almost 100% energy recovery). Our optimum system, CS-0.5, has a shear modulus of 0.40 MPa, an impressive strain-at-break of greater than 300% and an energy recovery of 80%. The strain-at-break is increased to more than 450% using a monofunctional epoxide. We further explore the inter- and intra-nanoparticle nature of the di-epoxide reaction and how the mechanical properties can be tuned by varying the method of film formation. The facile approach introduced here enables the tuning of the mechanical properties of elastomeric core–shell nanoparticle films from dissipative to predominantly elastic on demand.