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.

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The authors investigated the types of additive nonreactive fluorinated surfactants that effectively decrease the release energy of a certain ultraviolet-cured base resin for radical photopolymerization. The release energies of resins containing various surfactants were compared in two atmospheres, namely air and 1,1,1,3,3-pentafluoropropane (PFP, HFC-245fa). Tridecafluoro-1,1,2,2-tetrahydrooctan-1-ol functioned as the most effective surfactant under an air atmosphere, for detachment of a silica surface modified with tridecafluoro-1,1,2,2-tetrahydrotrimethoxysilane from the cured resins. Under a PFP atmosphere, heptadecafluoro-1,1,2,2-tetrahydrodecan-1-ol with a longer fluoroalkyl chain was necessary to effectively decrease the release energy. It was indicated that the segregation of liquid fluoroalkyl alcohols between the cured resin and modified mold was effective in decreasing the release energy of cured resins.