Abstract
Mechanoresponsive luminescent (MRL) elastomers, which change their fluorescence color
or intensity upon deformation, can facilitate simple strain detection through optical
signals. Several polymers have been endowed with MRL properties by blending them with
excimer-forming dyes, whose assembly and emission color are affected by deformation
of the blended materials. However, access to elastic MRL polyurethanes based on this
approach has proven difficult and usually requires the covalent incorporation of such
dyes in high concentration. Here, we show that much simpler access to MRL elastomers
is possible by blending thermoplastic polyurethane elastomers with a small weight
fraction of a telechelic sensor macromolecule carrying two excimer-forming oligo(p -phenylene vinylene) dyes at the termini. While the mechanical properties of the two
polyurethanes, which were selected because of their dissimilar mechanical behaviors,
remain unchanged, the additive imparts these materials with MRL characteristics. Notably,
the reliable and reversible detection of strains as low as 5% is possible. The highly
sensitive mechanochromic response mirrors the deformation and relaxation processes
occurring in these model polyurethanes and enabled a detailed analysis of the processes
underlying the shape-memory properties in one of the polyurethanes, in which such
behavior was imparted by a crystallizable soft segment.
Key words mechanochromic materials - stimuli-responsive materials - organic shape-memory polymers
- aggregation
