Polymeric Nanofibers from Rapid Expansion of Supercritical Solution

The use of the supercritical fluid technique, rapid expansion of a supercritical solution into a liquid solvent (RESOLV), to process polymers into nanofibers (less than 100 nm in diameter) is reported. It is found that the polymer concentration in the preexpansion supercritical solution plays a critical role in determining the dominating product morphology between nanoparticles and nanofibers. For the CO2-soluble poly(heptadecafluorodecyl acrylate) (PHDFDA), as an example, the rapid expansion of the polymer solutions in supercritical CO2 with low and high PHDFDA concentrations into an ambient aqueous NaCl solution produces exclusively nanoparticles and nanofibers, respectively. The RESOLV processing of poly(methyl methacrylate) (PMMA) and biodegradable polymer poly(L-lactic acid) (PLA) in supercritical CO2-cosolvent system into nanofibers is also described and discussed.