Patterned Layers of a Semiconducting Polymer via Imprinting and Microwave-Assisted Grafting

Enhancements in both the rate and extent of grafting of poly(9,9′‐n‐dihexyl fluorene) (PDHF) onto flat and nanopatterned crosslinked photopolymer films are described. Reactivity of the surfaces toward grafting via the Yamamoto‐type Ni(0)‐mediated coupling reaction is increased by synthesizing and incorporating 2,7‐dibromo‐9‐fluorenyl methacrylate (DBFM, 2) as a new grafting agent. Varying the concentration of surface‐embedded DBFM is shown to control both overall graft formation and fluorescence with a maximum thickness of up to 30 nm and peak emission at 407 nm for 40 wt% loading. In addition, microwave irradiation is introduced as an effective means to drive graft formation and thus allows fabrication of PDHF‐functionalized surfaces in as little as 30 min. Both forms of improvement are extended to DBFM‐embedded, nanocontact‐molded features ranging in size from 100 µm to 100 nm in width and 60 nm in height. Microwave‐assisted grafting from these patterned surfaces produces fluorescent features as imaged by optical microscopy and a corresponding increase in feature height as measured by atomic force microscopy. Significant grafting of poly(9,9′‐n‐dihexyl fluorene) of up to 30 nm is achieved from flat and nanopatterned crosslinked photopolymer films (see image). Novel use of microwave‐assisted grafting and synthesis of a new 2,7‐dibromo‐9‐fluorenyl methacrylate grafting agent provides films with peak emission at 407 nm and fluorescent nanocontact‐molded features.