We herein report the development of crosslinked polyether particles as a reactive platform for the preparation of functional microgels. Thiol–ene crosslinking of poly(allyl glycidyl ether) in miniemulsion droplets – stabilized by a surface active, bio-compatible polyethylene glycol block copolymer – resulted in colloidal gels with a PEG corona and an inner polymeric network containing reactive allyl units. The stability of the allyl groups allows the microgels to be purified and stored before a second, subsequent thiol–ene functionalization step allows a wide variety of pH- and chemically-responsive groups to be introduced into the nanoparticles. The facile nature of this synthetic platform enables the preparation of microgel libraries that are responsive to different triggers but are characterized by the same size distribution, surface functionality, and crosslinking density. In addition, the utilization of a crosslinker containing cleavable ester groups renders the resulting hydrogel particles degradable at elevated pH or in the presence of esterase under physiological conditions.