A new series of fluorinated alicyclic-functionalized polyimides derivated from natural-(D)-camphor: Synthesis, structure–properties relationships and dynamic dielectric analyses

A series of novel fluorinated alicyclic-functionalized polyimides (FPI-x) were prepared from a new alicyclic-functionalized diamine, 1,3-bis ((4-amino-2-(trifluoromethyl)phenoxylmethylene)-1,2,2-trimethyl cyclopentane (BAFMT), which was derivated from natural-(D)-camphor via multi-step process. The influence of the presence of the alicyclic and fluorinated structure on the general properties of the polymers was systematically investigated in terms of optical, thermal and mechanical properties, solubility and hydrophobicity, rendering the general structure–properties relationships for the FPI-x. Compared with the analogous control aromatic polyimide NPI-x, FPI-x shows better solubility, improved optical transparency, lower moisture absorption and surface energy, owing to the presence of the fluorine-containing group and alicyclic structure in the polymer chain. Although presenting a slight decrease as compared with NPI-x, the good thermal stability of polyimide was retained on the large in the fluorinated alicyclic-functionalized polymer FPI-x, with Tg ranging in 197–233 °C and Td5 ranging in 374–420 °C. A particular research emphasis were placed on employing the dielectric relaxation technique to study the dielectric constant (ε′), dielectric loss (ε″) and electric modulus (M″) of the fluorinated alicyclic-functionalized polyimide film FPI-4 and its control sample NPI-4. The observed dielectric relaxations have been fully studied by integrating the contributions of the specific structure and functional groups. It is revealed that the presence of fluorinated alicyclic-functionalized group endows FPI-4 with lower dielectric constant ε′ (2.88 at 1 MHz and 25 °C) and dielectric loss ε″ (0.0058 at 1 Hz and 25 °C) than NPI-4 (3.49 and 0.0084) and commercial Kapton HN (3.19 and 0.006) with the same measurement frequency and temperature.