A mathematical model is described for surface-initiated photopolymerization of PEG-DA forming crosslinked biofunctional PEG hydrogel membranes based on the NF technique. The model includes an additional monomer with biological functionality, which is a common experimental strategy for the design of ECM mimics in tissue engineering in order to direct signaling pathways, and considers concentration-dependent VP propagation and reaction diffusion termination. The influence of these features on the crosslink density of the soluble and gel phases, the progression through gelation, sol/gel fraction, and molecular weight distribution of biofunctional PEG hydrogel are studied using the NF model. This model may be useful for specific applications of tissue engineering.