Dioxetanes as mechanoluminescent probes in thermoplastic elastomers

Mechanoluminescent 1,2-dioxetane units, which emit light upon scission of the strained 4-membered ring, were incorporated into the main chain of segmented copolymers with poly(tetramethylene oxide) soft segments and various hard segments. Test samples of the polymers emitted light upon applying strain. Polymers with hydrogen bonding urethane or amide groups in the hard segments showed stronger luminescence than polyester segmented copolymers of similar molecular weight. Increasing strain rate led to stronger luminescence. The positive effect of molecular weight on emission intensity in polyurethanes was interpreted in terms of decreased chain slippage when multiple hard segments anchor the polymer chain in different hard blocks. The results demonstrate that even chains with more than 50 hard segments slippage can be further reduced by increasing the degree of polymerization.