Pyromellitic acid dianhydride

Nespurek (1984) and Nespurek et al. (1985) measured photogeneration efficiencies of vapor-deposited a-H c. Samples prepared with a surface layer of an acceptor compound, pyromellitic acid dianhydride or tetracyanoquinodimethane, were also studied. In the absence of an acceptor, the efficiencies were in the range of 0.01 to 0.02 at fields of KP V/cm. Nespurek and coworkers... 

Ea, above and below Tg. Three case studies illustrate the range of applicability of the bending beam setup and factors contributing to the stress state. The first is a comparison of two polymers for interlayer dielectrics PMDA-ODA (pyromellitic acid dianhydride - oxydiamine) and a bis-benzocyclobutene. The second is of a neat epoxy resin commonly used for microelectronics encapsulation (epoxidized ortho-cresol novolac cured with a phenolic novolac). The third is a screen-printable polyimide coating used for protection of the integrated-circuit chip. An outline of our stress model is sketched, and example results are presented. 

PMDA-QDA and BCB. Stresses induced during processing of a PMDA-ODA polyimide (pyromellitic acid dianhydride -oxydiamine, Dupont Pyralin 2545) and a bis-benzocyclobutene (BCB, Dow proprietary) were studied using the bending beam apparatus. Both materials were used as supplied by the manufacturer the PMDA-ODA solvated in n-methyl pyrrolidinone and the BCB in xylene. Final coating thicknesses, as measured by profilometry, were 2.8 xm for the PMDA-ODA and 3.2 xm for the BCB on fused quartz strips. 

Fig. 6.14 The anthracene-pyromellitic acid dianhydride (A-PMDA) mixed-crystal system as an example of a weak donor-acceptor crystal with mixed stacks. The ground state is neutral, nearly without charge transfer. The lowest CT state Is formed by a transition of an electron...

In crystals which are composed of two different partner molecules, CT excitations and with them CT excitons are frequently the predominant lowest excitation states and are thus responsible for the lowest-energy transitions in the singlet system. We will illustrate this using the example of the weak donor-acceptor complex anthracene/pyromellitic acid dianhydride, (A/PMDA) (Fig. 6.14). The ground state is neutral and nonpolar, with only a small charge-transfer fraction. The lowest optical excitation starts from the ground state of the donor D, anthracene, (from its highest occupied orbital or HOMO) and leads to the lowest unoccupied orbital (LUMO) of the acceptors A, PMDA, within the mixed stack DADADA. A polar ex-... 

Tetraamino-9,9 -spirobifluorene was taken for the synthesis of polyamide (PA) and polyimide (PI) networks having an intrinsic microporosity, because the crosslike spatial orientation of spirobifluorene units provides loose packing of polymeric chains in final networks [263]. By reacting the tetraamine with terephthalic acid or pyromellitic acid dianhydride dissolved in A/-methylpyrrolidone or o-cresol, respectively, microporous materials were obtained as depicted in the following scheme ... 

The polyether-ester polyamic acid imidization process in a solid state under microwave irradiation was studied by Yu et al. [73]. The prepolymer, polyether-ester polyamic acid, was prepared by the polycondensation of poly(tetramethylene ether)glycol di-p-aminobenzoate (Polyamine-650, Polaroid, Co.) and pyromellitic acid dianhydride (PMDA) at room temperature in DMF solution. Later, the prepolymer solution was cast on polytetrafiuoroethylene plates to form 200 pm thin films that were imidized under microwave irradiation in a household microwave oven at 60 °C. The temperature was measured by means of a thermocouple applied to the film surface immediately after the intervals of microwave turn off It was found that microwave irradiation reduced both the reaction temperature and time. For example, during the solid phase thermal polymerization 68.3% polyamic acid was converted to polyimide at 155 °C, while under microwave irradiation 65 % of polyamic acid was reacted at 60 °C within 3 h [73]. 

C10H2O6, Pyromellitic acid dianhydride, 45B, 320 C10H5CI7O, racemic-1-exo-4,5,6,7,8,8-Heptachloro-exo-2,3-epoxy-3a,4,7,7a-tetrahydro-4,7-methanoindane, 44B, 280 Cl0H6CI6O3, 1,3,7,8,8a,9-Hexachloro-4a,5,6,8a-tetrahydro-1,3-epidi-oxy-4,6-methanoisochroman, 44B, 281 CioHb03, 4-Methylumbelliferone, 41B, 362 CioHsO, Anemonin, 31B, 142... 

Polyimides are manufactured from diamines and dianhydrides. The created polymer structure causes differences in hydrolysis resistance, while thermal resistances are comparable. Thus, polyimides made from pyromellitic acid-dianhydride (PMDA) and diaminodiphenyl ether (ODA) or diaminodiphenyl thioether (SDA), respectively exhibit excellent hydrolysis resistance, while polyimides made from PMDA and m-phenylenediamine (MPD), p-phenylenediamine (PPD), or benzidine have very poor resistance and were therefore not developed further [723]. 

Czuppon AB, Kaplan V, Speich R, Baur X (1994) Acute autoimmune response in a case of pyromellitic acid dianhydride-induced hemorrhagic alveolitis. Allergy 49 337-341 Dalphin JC, Debieuvre D, Pernet D, Maheu MF, Polio JC, Toson B (1993) Prevalence and risk factors for chronic bronchitis and former s lung in French dairy farmers. Br J Ind Med 50 941-944... 

The electron-phonon coupling parameters in Table I correspond to a reorganization energy of 360 cm" which corresponds to the accurately determined value for the CT absorption of the anthracene pyromellitic acid dianhydride 7C-molecular complex. It might be argued that this value is too small for the problem at hand. However, increasing this value would only strengthen the conclusions of ref. 18, vide supra. 

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