Synthesis And Research Of Novel Negative-Type Photosensitive Polyimides

Photosensitive polyimides (PSPIs) are high performance polymer materials, and they have outstanding electrical and mechanical properties, excellent thermal stability, low thermal expansion coefficient, water and organic solvents-resistant, also can absorb the a-particles. For that reason, PSPIs have been widely applied in the fields of microelectronics, micro machinery manufacturing, paint protection, and so on. Recently, the research of negative-working PSPIs is the hotest spot more than others. So far, most negative-working PSPIs are the poly (amic ester) and poly (amic ion-linkage) types fabricated by thermal treatment (up to 350℃) after UV-cured. Such thermal imidization process would cause volume contraction because of the loss of low-molecular substance during the cyclization process, and it will make the film generate internal stress, even lead to deformation and delamination, that seriously restricted the applications of these kinds of photosensitive materials. Therefore, the research and development of the PSPIs, without post-curing, has a very important theoretical significance and application value.The diamine monomer 4,4'-diamino-4"-hydroxytri-phenylmethane (DHTM) with a pendant phenyl hydroxyl group was firstly synthesized from 4-hydroxybenzaldehyde, aniline and aniline hydrochloride. And then, the resulting DHTM and the other one commercial 4,6-Diaminoresorcinol dihydrochloride (DAR) reacted with pyromellitic acid dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA), respectively, to obtain the hydroxylate polyimides (PI-1 and PI-2). Finally the methacrylic acid glycidyl ester (GMA) was grafted onto the PIs main chain to get the PSPIs (PSPI-1 and PSPI-2). The chemical structure of monomer and polymers were identified by FT-IR spectra and 1H-NMR, and the molecular of PSPIs was detected by the gel permeation chromatography (GPC). The results showed that the DHTM and PSPIs have been successfully synthesized. The molecular weight of PSPI-1 and PSPI-2 are 25400 and 20570, and the polydispersity index (MW/Mn) is 1.52 and 1.71, respectively. Moreover, the optimal condition of the grafting reaction was deliberated, the best grafting reaction conditions are as follows, reaction time:10 hours, reaction temperature:90～100℃, monomer GMA and the hydroxyl molar ratio:1.2:1, the catalyst system:5% tertiary amine and 1% quaternary ammonium salt composite system.Furthermore, the solubility of PSPIs was investigated, the thermal stability and glass transition temperature (Tg) of the polymers were also researched by thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC), respectively. The results show that PSPIs have a better solubility compared to PIs, and PIs has excellent thermal performance as well as PSPIs, heated 10% weight loss temperatures of PI-1, PI-2, PSPI-1 and PSPI-2 were 481℃,425℃,362℃and 355℃, and the Tg were 287℃,268℃,240℃and 223℃, respectively.The photosensitivity and curing hardness of the PSPIs coatings were also researched. The results show that the PSPIs coatings have good photosensitivity as well as the curing hardness is H.