Abstract
A series of soluble aromatic poly(amide-imide)s (PAIs) was prepared from a new diamide–diamine monomer having biphenyl units with two CF3 groups. The diamide–diamine monomer was polymerized with 2,2′-bis(trifluoromethyl)benzidine and pyromelltic dianhydride through an imidization reaction to prepare PAIs with a controlled imide/amide bond ratio in the main chains. While the PAIs with the highest imide bond content showed a limited solubility, other PAIs were soluble in polar organic solvents and can be solution-cast into flexible freestanding films. All PAIs exhibited high thermal stability with 5% weight loss temperature (Td5) from 464 to 497 °C in air, and no appearance of glass transition up to 400 °C. Notably, the linear coefficient of thermal expansion (CTE) value of the PAI films was linearly decreased with the imide bond content and varied from 44.8 to 7.8 ppm/°C.
Highlights
Soluble Poly(amide-imide)s fromCurrent rapid technological developments in display and microelectronic devices demand processable high-performance materials which have thermo-dimensional stability
PAI-3 was only soluble in hot organic solvents its rigid character
The PAIs described here follow this general structure–property relationship, and the coefficient of thermal expansion (CTE) of the polymer was sharply decreased with the increasing portion of rigid and linear TFMB/PMDA imide segments (Figure 7a)
Summary
Current rapid technological developments in display and microelectronic devices demand processable high-performance materials which have thermo-dimensional stability. Though polyimides possess many attractive features, most of the wholly aromatic polyimides with rigid structures for thermo-dimensional stability generally suffer poor solubility in organic solvents, which often frustrates their diverse application [2]. Most aromatic PAIs are prepared via two synthetic routes: one is direct polycondensation between diamine and trimellitic anhydride or trimellitic anhydride chloride, and the other is the imidization/amidation of amide-/imide-containing monomers While the former route is usually employed in commercial production of PAIs [16,17], the majority of laboratory studies utilize the latter route because polymerization can be readily conducted through conventional synthetic techniques used for polyimides or polyamides [18,19]. The incorporation of amide bonds together with multiple CF3 groups would impart good organosolubility and thermal properties to the corresponding PAIs
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