A polymer patterning technology based on photografting polymerization mediated by photoiniferter chemistry is presented as a simple microlithographic technique that affords flexibility in fabricating and subsequently modifying polymer substrates with various chemistries. In principle, the technique relies upon the design and synthesis of a methacrylated photoiniferter, (methacryloyl ethylenedioxycarbonyl) benzyl N,N-diethyldithiocarbamate (HEMA-E-In). This photoiniferter allows the production of micropatterned polymer substrates with surface or internally grafted chemical modifications. The ability to modify surfaces with covalently bound polymer is demonstrated where the thickness of the layer depends on the exposure time. Furthermore, patterning chemical surface modifications was achieved by combining this process with photomasks to produce micron-sized features (approximately 20 Pro). The method is quite diverse and enables spatially controlled internal modification of polymer networks as demonstrated herein. The developed techniques should be very useful for the facile development of 2-D and 3-D patterned and surface-modified polymers for microfluidic and biomaterial applications.