Abstract: A composite material includes a base material and polydopamine adhered to the base material. In an infrared absorption spectrum of the base material to which the polydopamine is adhered, the infrared absorption spectrum being obtained by Fourier transform infrared spectroscopy, a ratio HB/HA satisfies 0.66?HB/HA?1.1, where, in the infrared absorption spectrum, a baseline is defined as a straight line connecting a measured point obtained at 3070 cm?1 to a measured point obtained at 3700 cm?1, HA represents a perpendicular distance from a measured point obtained at 3380 cm?1 of the infrared absorption spectrum to the baseline, and HB represents a perpendicular distance from a measured point obtained at 3630 cm?1 of the infrared absorption spectrum to the baseline.

Abstract: A composite material includes a base material and polydopamine adhered to the base material, the polydopamine containing hydroxy groups. At least one hydrogen atom of the hydroxy groups is substituted with an acyl group.

Abstract: A polyimide includes a non-crosslinked structure including a main chain. The main chain includes a Si—O—C bond. The main chain may include a C—O—Si—O—C bond. The main chain includes, for example, a group denoted by —OSi(R1)(R2)O—. At least one oxygen atom included in the group bonds to, for example, a carbon atom adjacent to the group to form the Si—O—C bond.