Structure-mechanochemical activity relationships for cyclobutane mechanophores.

Ultrasound activation of mechanophores embedded in polymer backbones has been extensively studied of late as a method for realizing chemical reactions using force. To date, however, there have been few attempts at systematically investigating the effects of mechanophore structure upon rates of activation by an acoustic field. Herein, we develop a method for comparing the relative reactivities of various cyclobutane mechanophores.

Masked cyanoacrylates unveiled by mechanical force.

Mechanical damage of polymers is often a destructive and irreversible process. However, desirable outcomes may be achieved by controlling the location of chain cleavage events through careful design and incorporation of mechanically active chemical moieties known as mechanophores. It is possible that mechanophores can be used to generate reactive intermediates that can autopolymerize or cross-link, thus healing mechanically induced damage.

Mechanical reconfiguration of stereoisomers.

Poly(methyl acrylate) of varying molecular weight was grown from the enantiopure ditopic initiator (R)- or (S)-1,1'-binaphthyl-2,2'-bis-(2-bromoisobutyrate). Subjecting CH(3)CN solutions of high-molecular-weight derivatives (M(N) > 25 kDa) to sonication at 0 degrees C resulted in >95% racemization after 24 h, as determined by circular dichroism; no appreciable racemization was observed in low-molecular-weight derivatives. Control experiments excluded the possibility of a thermal racemization mechanism.