Synthesis of Photosensitive Polyimides Incorporating Polydimethylsiloxane Segments and Studies on the Properties of their UV-Cured Films

To reduce the limitations of traditional polyimides (PIs), such as poor processability, limited flexibility, and low solubility, a series of siloxane-modified photosensitive PIs (PSPIs, designated as D1∼D6) were designed and synthesized. The cured films of these PSPIs were prepared by UV irradiation. In comparison to conventional PIs, the cured films exhibited good heat tolerance, enhanced flexibility, and a lower glass transition temperature. Some films demonstrated very good mechanical properties, low dielectric characteristics, and excellent hydrophobicity, with a maximum tensile strain of 66%, a low dielectric constant as low as 2.7, a high surface contact angle of 113°, and a minimal moisture absorption as low as 0.02%. These cured films hold great potential for applications in packaging and solder mask protection for high-frequency, high-speed printed circuit boards (PCBs).