Preparation of Meldrum's acid-functionalized polyimides exhibiting organo-soluble, reactive, self-crosslinkable, and colorless features

摘要

Functional polyimides (PIs) having some desired properties, for example, organo-solubility, chemical reactivity, crosslinkable feature, and high transparency in visible region, are attractive for specific applications. This work reports an effort to integrate the above-mentioned properties in one polyimide through introduction of Meldrum's acid (MA) moieties to polyimide chains with using a MA-containing diamine (MADA) as a monomer. The polyimide prepared with MADA and 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) (PIMADA-6FDA) has a number-averaged molecular weight of 56,800 g mol(-1), shows good solubility in tetrahydrofuran and aprotic high polar solvents, and exhibits post-reactivity/crosslinkability through MA-mediated ketene chemistry. Crosslinked PI(MADA-6FDA) film shows a glass transition temperature of 289 degrees C, a dielectric constant of about 2.78, and high flexibility bearing a near-180 degrees bending. The MA-mediated ketene chemistry contributes to in situ building up covalent linkages between PI chains and silica nanoparticles (SNPs) in preparation of PI/SNPs nanocomposite films (NCF). Formation of the PI/SNPs NCFs enhances the thermal and mechanical properties, reduces the dielectric constants, and increases the transparency. The properties of the MA-functionalized PI are attractive for further studies on their applications.