Super-soft, firm, and strong elastomers toward replication of tissue viscoelastic response

Abstract

Brush-like thermoplastic elastomers combine softness, firmness, strength, and damping on par with soft tissues, which is vital for biomedical device and adhesive applications.

Sticky Architecture: Encoding Pressure Sensitive Adhesion in Polymer Networks

“…The architectural control over adhesion through [n sc , n g , n x ] is maintained, while the additional levers of n bb , n A , and ϕ A are used to improve bulk firmness and cohesive strength (Figure 5b inset, Table S3). 35 Even at higher modulus, E 0 ≅ 130 kPa, brush HM-PSAs demonstrate viscoelastic debonding at ε̇= 1 s −1 , where both tack and fibrillation are witnessed, suggesting their potential implementation as high shear adhesives (Figure 5b, Figure S18). This contrasts with brush elastomers, where greater stiffness results in a Rouse time shift constituting elastic debonding at the same strain rate.…”

“…The moldability was introduced by replacing covalent cross-links with microphase separation in brush-like graft block copolymers denoted as A- g -B, where a controlled fraction of long A blocks were grafted along a bottlebrush B block of a different chemical composition (Figure a, Figures S8–S10). Specifically, A- g -B’s with polystyrene (PS) grafts (A blocks) of DP n A and bottlebrush blocks with PIB side chains of DP n sc undergo microphase separation to produce a physical network linked by A-block domains. Phase separation in block copolymers is dependent on dimensions of the constituting blocks, creating a narrow window for the desired viscoelastic response of PSAs.…”

Magnetoactive Thermoplastic Elastomers with Bottlebrush Strands: Switching and Programming of Mechanical Properties by a Magnetic Field

“…37 The modulus of brush networks exhibits an exponential increase with deformation due to the proximity of the pre-extended backbones to full extention. 27,35,38 In particular, strainstiffening for A-g-B elastomers increases with ϕ A from β = 0.02 to β = 0.07 (Table 1).…”

“…The n bb was regulated by the initiator concentration in FR polymerization, but greater control may be achieved by controlled radical polymerization methods. 27 Note n bb is vital for strength enhancement.…”

“…Herein, we present an advanced platform for the design of magnetoactive thermoplastic elastomers (MATEs) that possess a unique combination of (i) tissue-mimetic softness for magnetic response, (ii) strain-stiffening for strength, (iii) solvent-free molding for MATE fabrication, and (iv) structural reconfiguration to re-program properties on demand. At room temperature (RT), A- g -B bottlebrush graft copolymers form thermoplastic elastomers where chemically distinct block microphases separate into network nodes interconnected by brush strands (Figure a) . Given the μm-sized particles, the brush-like matrix is considered as a continuous medium, where viscoelastic properties are controlled by the A- g -B architectural parameters due to magneto-mechanical coupling being introduced on a micron scale .…”