In this article, we revealed the maximum values of pentafluoropropane (PFP) absorbed by acrylate-type monomers and UV-curable resins causing radical photopolymerization and measured the viscosities in a state saturated with PFP. We described the influences of PFP condensable gas effectively used in UV nanoimprinting on the morphologies of resin patterns fabricated by UV nanoimprinting. The weights of the resins and monomers were increased by exposure to a PFP atmosphere, while the viscosities were reduced markedly. The absorption of PFP depended on the chemical structures of the monomers. The solubility parameter calculated by the Hoy method clearly suggested that the monomer with a solubility parameter of 20 (J cm-3)1/2 absorbed the most PFP. The UV-curable resin composed of the monomer absorbing a large amount of PFP resulted in morphological changes in nanoimprinted resin patterns where the height was lowered and the outermost surface became rough. The UV-curable resins having hydroxyl groups play an important role in preserving the size fidelity of UV-nanoimprinted resin patterns.

We investigated reactive fluorinated (meth)acrylate monomers and macromonomers that caused segregation at the cured resin surface of a viscous hydroxy-containing monomer, glycerol 1,3-diglycerolate diacrylate (GDD), and decreased the demolding energy in ultraviolet (UV) nanoimprinting with spin-coated films under a condensable alternative chlorofluorocarbon gas atmosphere. The X-ray photoelectron spectroscopy and contact angle measurements used to determine the surface free energy suggested that a nonvolatile silicone-based methacrylate macromonomer with fluorinated alkyl groups segregated at the GDD-based cured resin surface and decreased the surface free energy, while fluorinated acrylate monomers hardly decreased the surface free energy because of their evaporation during the annealing of the spin-coated films. The average demolding energy of GDD-based cured resins with the macromonomer having fluorinated alkyl groups was smaller than that with the macromonomer having hydrocarbon alkyl groups. The fluorinated alkyl groups were responsible for decreasing the demolding energy rather than the polysiloxane main chains. We demonstrated that the GDD-based UV-curable resin with the fluorinated silicone-based macromonomer was suitable for step-and-repeat UV nanoimprinting with a bare silica mold, in addition to silica molds treated by chemical vapor surface modification with trifluoro-1,1,2,2-tetrahydropropyltrimethoxysilane (FAS3) and tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane (FAS13).

In the UV nanoimprinting process an antisticking layer such as fluorinated self-assembled monolayer (F-SAM) is grafted on the mold surface to diminish the demolding impact. These layers are supposed to deteriorate as the imprint steps mount up, resulting in defects in the cured resist layer. In this work, continuous multiple shots of UV nanoimprint were conducted in the air and in pentafluoropropane (PFP) gas environment and demolding forces in every imprint step were determined. The experiments revealed that the demolding forces for the imprint in PFP atmosphere drastically reduced compared with those in the air. Water contact angles of the mold surface were also determined in every 225 imprint steps to observe the degree of degradation of the antisticking layer. It was found that the antisticking layer was less damaged or contaminated in the PFP environment than it was in the air after a certain number of imprint steps.

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Electrochemical reduction of hexachlorobuta-l,3-diene in aprotic solvents affords mostly graphitized films which can be easily d.oped with anions and also with cations.