Mechanochromic Microfibers Stabilized by Polymer Blending

Abstract

Stimuli-responsive polymers processed into microfibers bear the potential to be fabricated as systems detecting stress-induced failures. Microfiber processing of spiropyran (SP)-functionalized polymer poly(methyl acrylate) (PMA), in pristine form and as a blend with poly(methyl methacrylate) (PMMA), was studied. Material inhomogeneities such as bead formation and fiber–fiber fusion affected the durability of the microfibers which were aimed to be applied as self-reporting materials. The present study investigates the effect of polymer blending to improve the structural stability, i.e., the shape of the fibers compared to the nonblended PMA fibers (NBF). Blended microfibers (BF) with <4 wt % PMMA could overcome the structural malfunctions observed in NBF. Rheological analyses confirmed that there were no drastic alterations in the mechanical properties due to blending with a low amount of PMMA. We report the mechanoactivation in the structurally stable and durable BF processed via centrifugal force spinning (CFS). These fibers detected high strain deformations and retained the mechanochromic response after unloading. The color change in the BF confirms strain-induced isomerization of SP which will further assist in the visual inspection of damage before failure. The microfibers also showed reversible photochromism upon irradiation with ultraviolet (UV) light (360–370 nm) and green light (520–530 nm). The outstanding benefit of processing microfibers from polymer blends is the ease of obtaining structurally stable, self-reporting material with longer durability.