Synthesis of Phosphorylcholine-Containing Polyimides and the Fabrication of Biocompatible Nanosheets Thereof

The synthesis of aromatic polyimide containing phosphorylcholine (PC) group was carried out by the co-polycondensation of a PC-containing diamine monomer and 3,5-bis(4-aminophenoxy)benzene with 4,4'-hexafluoroisopropylidene diphthalic anhydride (6FDA) followed by chemical imidization. The solubility of the polyimides decreased as the PC content increased, and the polyimides containing less than 50 mol% PC units were soluble in aprotic polar solvents such as N,N-dimethylformamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone. The nanosheets were successfully fabricated from the PC-containing polyimides by spin coating using poly(vinyl alcohol) or Na alginate as a sacrificial layer, which exhibited a high adhesive strength. Large quantities of nanosheets were also fabricated by a laminating method. Fragmented nanosheets were successfully fabricated by homogenizing the nanosheets suspended in water for 10 min at 16000 rpm. Fragmented nanosheets could be dispersed in water and adhered to the surface of various substrates in a patchwork pattern. Good blood compatibility was observed on the polyimide-coated surfaces. Therefore, the nanosheets and fragmented nanosheets can be useful for biocompatible coating materials.