Synthethic polymers can be prepared with features that combine many of the advantageous properties of natural materials, including environmental response. This research news article considers the different types of reponse that can be 'programmed in' to polymers and the applications that are developing as a consequence of the designed responses. In particular, we focus on two key applications at the biology/materials science interfaces; responsive drug delivery systems and 'smart' surfaces for cell culture and regenerative medicine.