ABSTRACT:2,3,6,7-naphthalenetetracarboxylic dianhydride (NTDA) showed high reactivity in the polymerization of polyimide precursors [poly(amic acid)s (PAAs)] with various aromatic and cycloaliphatic diamines with an exception of trans-1,4-cyclohexanediamine (CHDA). On the other hand, another isomer 1,4,5,8-NTDA did not allow the formation of high molecular weight PAAs. The poor reactivity of 1,4,5,8-NTDA is probably attributed to the more stable six-membered anhydride structure. The polyimide (PI) films derived from 2,3,6,7-NTDA with some diamines possessing stiff/linear structures, i.e., p-phenylenediamine (PDA), 4-aminophenyl-4 0 -aminobenzoate (APAB), and 2,2 0 -bis(trifluoromethyl)benzidine (TFMB) exhibited no distinct glass transitions on the dynamic mechanical thermal analysis or a considerably high T g exceeding 400 C, extremely low CTE values close to that of silicon wafer or lower, and relatively low degrees of water absorption simultaneously in addition to excellent thermal stability. A polyimide system derived from 2,3,6,7-NTDA and 4,4 0 -oxydianiline (4,4 0 -ODA) achieved a low CTE approximate to that of copper foil (20.0 ppm K À1 ) in spite of the presence of flexible ether linkages in the structure while retaining excellent film toughness (elongation at break > 80%). The low CTE characteristics observed probably results from the longer naphthaldiimide mesogenic unit which acts more effectively for the imidization-induced in-plane orientation. The properties of 2,3,6,7-NTDA-based PIs were compared with those of PIs derived from a fixed diamine with different dianhydrides, i.e., pyromellitic dianhydride (PMDA) and 3,3 0 ,4,4 0 -biphenyltetracarboxylic dianhydride (s-BPDA) to elucidate the merits of the use of 2,3,6,7-NTDA. The results revealed that 2,3,6,7-NTDA is a useful monomer for lowering both CTE and water absorption and enhancing T g . [doi:10.1295/polymj.PJ2006234] KEY WORDS Polyimides / 2,3,6,7-Naphthalenetetracarboxylic Dianhydride / 1,4,5,8-Naphthalenetetracarboxylic Dianhydride / Low Linear Coefficient of Thermal Expansion (CTE) / Low Water Absorption / Polyimides (PIs) have been widely utilized in a variety of micro-and optoelectronic applications such as the substrates for flexible printed circuit (FPC) and tape automated bonding (TAB), buffer-coating films and interlayer dielectrics for LSI chips, high temperature adhesives, light wave guides for their combined excellent properties, i.e., high glass transition temperatures (T g ), high resistance to chemicals and radiation, relatively low dielectric constants (K or "), and good mechanical properties.1-10 The advantages of PI materials are considerably high purity in the resins, simple production processes, and the ease of structural modifications through copolymerization using various commercially available monomers.Recently, the demands of PIs for the FPC applications have been increasing more and more in the world. Particularly, adhesive-free PI film/Cu laminates (flexible copper clad laminates, FCCL) for FPC fabrications, where the ...

Polyimide (PI) derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) with trans-1,4-cyclohexanediamine (CHDA), i.e., s-BPDA/CHDA was investigated from the viewpoint of ordered structure and intermolecular interaction. Thermodynamic parameters of the model compounds for melting behavior suggested significantly restricted conformational changes in the trans-1,4-cyclohexylene unit and the presence of strong BPDI—BPDI interaction in s-BPDA/CHDA. The effect of diamine structure on the fluorescence yield also supported the presence of the BPDI—BPDI interaction or the BPDI dimer in s-BPDA-based semi-cycloaliphatic PIs. The results of the fluorescence depolarization measurements can be rationalized by a proposed mechanism assuming the presence of the BPDI dimer sites, where the fluorescence of s-BPDA/CHDA occurs by excitation of the lower energy trap sites consisting of the BPDI dimer via excitation energy migration or direct excitation of the dimer. The structure-sensitive infrared band around 550 cm-1 gradually shifted toward higher frequency with simultaneous narrowing with increasing cure temperature, suggesting gradual ordered structure formation in s-BPDA/CHDA. Thermal imidization at 400 °C caused splitting of the C—H stretching band around 2940 cm-1, corresponding to the disappearance of distinct glass transition for the s-BPDA/CHDA system.

Heat-resistant polymers with an intense, visible photoluminescence (PL) functionality are presented. A polybenzoxazole (PBO) containing hexafluoroisopropylidene (HFIP) side groups exhibited an intense purple PL with a quantum yield, ΦPL, of 0.22 (22%), owing to the effectively disturbed concentration quenching (CQ) in the fluorophore units by the bulky HFIP side groups. The chain ends of a wholly cycloaliphatic polyimide (PI), derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 4,4′-methylenebis(cyclohexylamine) (MBCHA), were modified with conjugated monoamines. The PI derived from 2,3,6,7-naphthalenetetracarboxylic dianhydride (2,3,6,7-NTDA) and MBCHA exhibited a very high glass transition temperature (Tg = 376 °C) and purple fluorescence from the S1(π,π*) state. However, its ΦPL value was lower than expected. A pronounced effect of fluorophore dilution using CBDA on the PL enhancement was observed. This is closely related to the planar structure of the 2,3,6,7-NTDA-based diimide units. By contrast, the counterpart using an 2,3,6,7-NTDA isomer, 1,4,5,8-NTDA, was virtually non-fluorescent, despite its sufficient dilution using CBDA. The PI film obtained using 3,3″,4,4″-p-terphenyltetracarboxylic dianhydride (TPDA) with a non-coplanar structure and MBCHA exhibited an intense blue fluorescence spectrum (ΦPL = 0.26) peaking at 434 nm. The dilution approach using CBDA enhanced its fluorescence up to a high ΦPL value of 0.41. Even when TPDA was combined with an aromatic diamine, 2,2′-bis(trifluoromethyl)benzidine (TFMB), the intense blue fluorescence was observed without charge-transfer fluorescence. A semi-cycloaliphatic PI derived from TFMB and a novel cycloaliphatic tetracarboxylic dianhydride, which was obtained from a hydrogenated trimellitic anhydride derivative and 4,4′-biphenol, was used as another host polymer for 9,10-bis(4-aminophenyl)anthracene (BAPA). The BAPA-incorporating PI film resulted in a significant PL enhancement with a considerably high ΦPL of 0.48. This PI film also had a relatively high Tg (265 °C). A reactive dye, N,N′-bis[4-(4-amino-3-methylbenzyl)-2-methylphenyl]-3,4,9,10-perylenetetracarboxydiimide, was harnessed as a fluorescence probe to explore transamidation between polyimide precursors in solution.