The hyperbranched polymers prepared for this study enable us
for the first time to probe the mechanism of chain degradation
under DOD print conditions because of the higher printable concentrations
possible and the higher chain end density. It is well
documented that degradation of linear polymers under sonication
proceeds by a free radical mechanism, whilst it has been shown
that some ladder type polymers degrade by a heterolytic mechanism
[36e38]. Polymer solutions containing the spin trap PBN were
exposed to a series of identified conditions, which were known to
induce polymer degradation. In all cases toluene was chosen for its
low dielectric constant and high boiling point.