Methods and materials for controlled release of desired chemistries

A delivery system comprising a plurality of particles that each comprise a vehicle and a cargo that is retained by the vehicle, the plurality of particles being configured to controllably release at least a portion of the cargo in response to one or more conditions at a delivery site, wherein the vehicle comprises a polymeric material including one or more labile crosslinking groups that degrade or are otherwise broken in response to the one or more conditions at the delivery site, and wherein one or more of the following conditions are met:

• the vehicle is in the form of a shell defining an interior space in which the cargo is retained;
• the vehicle is substantially in the form of a monolith;
• the particles have an average size of about 5 μm or less.