The present disclosure relates to a polymeric system for release of an active agent, comprising a first polymeric phase containing the active agent, the first polymeric phase forming discrete regions of a set size range and being dispersed within a second polymeric phase comprising a cross-linked polymer-phenol conjugate for release of the active agent therein. The present disclosure further provides an injectable hydrogel comprising the disclosed polymeric system, a carrier for delivering a biologically active substance or a drug comprising the injectable hydrogel, and a method for producing the disclosed polymeric system.