An activatable functionalised Nth generation dendrimer having: a core comprising a first monomer having at least two carboxylic acid functional groups; and N successive generations, where N=0 to 10, wherein each generation comprises: a second monomer having at least two alcohol functional groups, wherein at least one alcohol group is bonded to a carboxylic acid group of the first monomer of the prior generation, and an additional first monomer attached to a second alcohol function group of said second monomer of that generation; and the final generation having attached thereto at said second alcohol functional group of said second monomer, a moiety having a dicarboxylic acid functional group, activatable by treatment with a carboxylic acid activating reagent such that reactivity of the carboxylic acid functional group is increased. The dendrimer, when activated, may be used in applications such as polymer crosslinking and/or nanoshell production.