  It is now possible to produce graphene nanoribbons (GNRs) with atomically
defined widths. GNRs offer many opportunities for electronic devices and
composites, if it is possible to establish the link between edge structure and
functionalisation, and resultant GNR properties. Switching hydrogen edge
termination to larger more complex functional groups such as hydroxyls or
thiols induces strain at the ribbon edge. However we show that this strain is
then relieved via the formation of static out-of-plane ripples. The resultant
ribbons have a significantly reduced Young's Modulus which varies as a function
of ribbon width, modified band gaps, as well as heterogeneous chemical
reactivity along the edge. Rather than being the exception, such static edge
ripples are likely on the majority of functionalized graphene ribbon edges.
