biostudies-literatureElter MKlaus Tschira StiftungDeutsche Forschungsgemeinschaft27594-27599https://www.ebi.ac.uk/biostudies/studies/S-EPMC11468784biostudies-literatureUnknown146(40)Stronger chemical bonds withstand higher mechanical forces; thus, the rupture of single bonds is preferred over the rupture of double or triple bonds or aromatic rings. We investigated bond scission in poly(dialkyl-<i>p</i>-phenylene ethynylene)s (PPEs), a fully conjugated polymer. In a scale-bridging approach using electron-paramagnetic resonance spectroscopy and gel permeation chromatography of cryomilled samples, in combination with density functional theory calculations and coarse-grained simulations, we conclude that mechanical force cleaves the sp-sp² bond of PPEs (bond dissociation energy as high as 600 kJ mol^-1). Bond scission primarily occurs in shear bands with locally increased shear stresses. The scission occurs in the middle of the PPE chains. Breaking sp-sp² bonds into free radicals thus is feasible but requires significant mechanical force and an efficient stress concentration.Journal of the American Chemical SocietyBreaking Strong Alkynyl-Phenyl Bonds: Poly(&lt;i&gt;para&lt;/i&gt;-phenylene ethynylene)s under Mechanical Stress.PMC11468784EXC-2082 - 1-390761711Bunz UHFGrater FBrosz MKiesewetter DCFreudenberg JElter MKuzhelev ADreuw ASucerquia DKurth MPrisner TFfalseBreaking Strong Alkynyl-Phenyl Bonds: Poly(&lt;i&gt;para&lt;/i&gt;-phenylene ethynylene)s under Mechanical Stress.Stronger chemical bonds withstand higher mechanical forces; thus, the rupture of single bonds is preferred over the rupture of double or triple bonds or aromatic rings. We investigated bond scission in poly(dialkyl-<i>p</i>-phenylene ethynylene)s (PPEs), a fully conjugated polymer. In a scale-bridging approach using electron-paramagnetic resonance spectroscopy and gel permeation chromatography of cryomilled samples, in combination with density functional theory calculations and coarse-grained simulations, we conclude that mechanical force cleaves the sp-sp² bond of PPEs (bond dissociation energy as high as 600 kJ mol^-1). Bond scission primarily occurs in shear bands with locally increased shear stresses. The scission occurs in the middle of the PPE chains. Breaking sp-sp² bonds into free radicals thus is feasible but requires significant mechanical force and an efficient stress concentration.2024-01-01T00:00:00Z2024 Oct2025-04-18T13:20:41.377Z2025-04-06T22:57:40.455ZS-EPMC114687843933282010.1021/jacs.4c08765