Film Properties of Polyazomethines (1). Effect of Incorporation of Intramolecular Cyclodehydrating Units

Abstract

Polyazomethines (PAzMs) were polycondensed from terephthalaldehyde (TPAL) with 2,2′bis(trifluoromethyl)benzidine (TFMB) and 2,2-bis[4-(4-aminophenoxy)phenyl] hexafluoropropane (HFBAPP). The PAzMs showed high solubility in N -methyl-2-pyrrolidone (NMP) ( > 15 wt.%) at room temperature and good film-formability. The film properties of the TPAL/TFMB-based PAzM copolymers were evaluated in the present study. In spite of their rod-like backbone structures, the PAzM films showed much higher coefficients of thermal expansion (CTE) in comparison with initial expectation. The results suggest that the simple casting process from the NMP solutions can not be a trigger for inducing pronounced chain orientation toward the direction parallel to the film plane (in-plane orientation). On the other hand, the incorporation of intramolecular cyclodehydrating (thermally imidizable) sites into the rigid TPAL/TFMB-based PAzM backbone by using pyromellitic dianhydride (PMDA) or 4,4′ -oxydiphthalic anhydride (ODPA) allowed the formation of low-CTE films upon imidization even for rather low reactive site contents. A possible mechanism to explain the present results is proposed. The TPAL/TFMB-based poly(imide-azomethine)s (PIAzMs) achieved excellent combined film properties in addition to low CTE (= 6.7-25.5 ppm K-1); namely, they have relatively high Tg values exceeding 300 °C, very low water absorption ( < 0.17%), sufficient toughness, high tensile modulus, and good thermal stability. Accordingly, the PIAzM systems investigated in the present study could be promising candidates for a new type of heat-resistant dielectric material for use in microelectronic applications.

Colorless polyimides with low coefficient of thermal expansion derived from alkyl-substituted cyclobutanetetracarboxylic dianhydrides

“…Indeed, we have previously observed that a polyazomethine (PAzM) copolymer film prepared by casting its NMP solution showed a very high CTE of 97 ppm K −1 in spite of its rigid chain structure, as depicted in Fig. . A comparison between the PAzM and the present copolyimides suggests that strong intermolecular forces (e.g.…”

Ultra‐low modulus polyazomethines and enhanced adhesion strength with copper foils

“…Accordingly, the gradual modulus decrease cannot be directly explained from a decrease in the crystallinity. Most likely, it is also not related to orientational relaxation with an increase in T a because PAzMs including flexible units essentially possess no practical chain alignment along the film plane ( X–Y ) direction (called in‐plane orientation) by solution casting . As a possible explanation, the modulus decrease tendency observed in Fig.…”

“…We have previously investigated polyazomethine (PAzM) systems and obtained sufficiently flexible films with high T g. Poor attention has been paid so far to PAzM films for electronic applications, although main interests have been directed to PAzM fibers . The present work focused again on PAzM systems to investigate their potentiality as cover layer materials of FPCs.…”

Film Properties of Polyazomethines (2). Poly(imide-azomethine)s Derived from Ester-containing Dialdehydes, Tetracarboxylic Dianhydrides, and a Fluorinated Diamine

“…In a previous study [19] it was shown that highly stiff/linear structures of PAzM systems prepared from terephthalaldehyde (TPAL) with 2,2 1 -bis(trifluoromethyl)benzidine (TFMB) and minor fractions of 2,2-bis(4-aminophenoxypheny)hexafluoropropane (HFBAPP) possessed excellent solubility in N-methyl-2-pyrrolidone (NMP) and led to the production of good films by solution casting. However, the PAzM films did not display low CTE characteristics which went against initial expectations.…”

“…An alternative approach was to partially incorporate some intramolecular reactive sites (amic acid units) into the rod-like TPAL/TFMB-based PAzM backbone by using minor fractions of some tetracarboxylic dianhydride comonomers. The intramolecular thermal cyclodehydration (imidization) at the reactive sites induced a pronounced in-plane chain orientation phenomenon that was responsible for the low CTE characteristics, even when the reactive sites were introduced with a rather low content and/or a bent/flexible structure was formed after the reaction [19].…”