Micron-patterning of polydiacetylene liposomes by micro-contact printing and Langmuir-Blodgett deposition

Abstract

Polydiacetylenes (PDAs), a family of conjugated polymers that have alternating ene-yne backbone structures, are intriguing substances in several respects. First, PDAs are produced by radiation (UV or γ-ray)-induced polymerization of molecularly-assembled diacetylene monomers in the absence of chemical initiators or catalysts. Second, in general the resultant polymer displays an intense blue color which has a maximum absorption wavelength at around 640 nm. Lastly, the blue-colored PDAs undergo a color transition to form a red phase in response to a variety of environmental stimulations, such as heat, solvent, mechanical stress, and molecular recognition. Owing to the blue-to-red chromic transition and nonlinear optical properties, PDAs have been extensively investigated as potential chemosensors and photonic materials. Recently, fabrication of patterned images on solid substrates using functionalized PDAs has gained much attention. Crooks and his coworkers reported photolithographic creation of micron-sized patterns on Au films using thiol derived self-assembled diacetylenes. Direct generation of nanoscale PDA images using a scanning tunneling microscopy (STM) is also an elegant example of patterned imaging. In addition, patterned fluorescence images have been generated by photolithographic polymerization of solid-supported diacetylenic lipid bilayers. More recently, we described a technique for producing patterned fluorescence images of PDA vesicles on functionalized glass substrates by using a conventional microarray spotter. In this research, micron-sized patterns of polydiacetylene liposomes are fabricated on silicon substrate using micro-contact printing in conjunction with Langmuir-Blodgett deposition. SEM and AFM revealed the morphology of the patterned PDA liposomes. Fluorescence microscopy demonstrated the capability of the PDA liposomes for sensor materials. This investigation has led to the development of a new strategy for the fabrication of conjugated polymer patterns on solid substrates. When combined with the novel optical properties of polydiacetylene, this methodology should enhance the versatility of conjugated polymers in sensor and optical applications.