From Notch-Tip Stress to Mechanophore Activation - A Multiscale Study of Mechanochromic PMMA
Year: 2026
Type: preprint
Abstract: Mechanophore-functionalized polymers enable optical readout of molecular-level stress under macroscopic deformation. Spiropyran (SP)-doped poly(methyl methacrylate) (PMMA) provides a well-established platform for mechanochemical stress sensing, yet molecular stress fields around defined geometric stress concentrators remain largely disconnected from continuum mechanics. To bridge this gap, we develop a geometry-matched molecular dynamics (MD) and finite-element (FE) approach for PMMA containing two opposing semi-elliptical notches of systematically varied depth and width. Molecular simulations employ a hybrid coarse-grained/all-atom (CG/AA) PMMA model with atomistically resolved, quantum-chemically (QC) informed SP, while the FE models use the MD-derived stress–strain response of bulk PMMA as input. Under uniaxial tension, both approaches capture notch-tip stress localization, plastic-zone propagation toward the ligament center, and the characteristic butterfly-shaped stress field. FE simulations reproduce MD notch-tip stresses, demonstrating that suitably parameterized continuum models capture key notch mechanics, whereas defect-mediated rearrangements require molecular resolution. Notch geometry strongly enhances SP activation to its merocyanine (MC) form, lowering the onset strain and localizing activation in highly elongated chains and around deformation-induced voids near the notch edges. These results link defect geometry and molecular stress concentration to mechanophore activation and directly connect molecular and continuum notch mechanics.
Source: ChemRxiv
Language: English
Subfield: Polymers and Plastics
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7222441365