Pyromellitic dianhydride PMDA

There are only two inexpensive dianhydrides 3,3,4,4,-benzophcnonctctracarbox-ylic dianhydride (BTDA) and pyromellitic dianhydride (PMDA). Some other commercially available dianhydrides were used, like 3,3, 4,4 -biphenyltetracarboxylic dianhydride (BPDA), 2,2,-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA), oxydiphthalic anhydride (ODPA), and 3,3/,4,4/-diphenylsulfonetetracarboxylic dianhydride (DSDA) (Fig. 5.29). Many other dianhydrides are reported in the literature (Fig. 5.30) ... 

Hedrick et al. reported imide aryl ether ketone segmented block copolymers.228 The block copolymers were prepared via a two-step process. Both a bisphenol-A-based amorphous block and a semicrystalline block were prepared from a soluble and amorphous ketimine precursor. The blocks of poly(arylene ether ether ketone) oligomers with Mn range of 6000-12,000 g/mol were coreacted with 4,4,-oxydianiline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in NMP in the presence of A - me thy 1 morphi 1 i nc. Clear films with high moduli by solution casting and followed by curing were obtained. Multiphase morphologies were observed in both cases. 

PLA degradation, 43 Planar polymer, synthesis of, 505 PLLA. See Poly(L-lactic acid) (PLLA) PMDA. See Pyromellitic dianhydride (PMDA)... 

The most common chain extenders are the dianhydrides (also known as tetracar-boxylic dianhydrides). The most common of these is pyromellitic dianhydride (PMDA). The latter can be used in synergistic combinations with hindered phenolic aromatic phosphates such as IRGANOX 1425 manufactured by Ciba Geigy [6-8], The hindered phenolic aromatic phosphate is used at levels of 0.1-2.5 wt%. The hindered phenolic aromatic phosphate is an advantageous co-synergist since it... 

Pyromellitic dianhydride (PMDA) is generally used in PET at concentrations ranging from 0.05 to 2%. Reactive extrusion of PET with PMDA has been reported by Incamato et al. [9], These authors used PMDA to increase the molecular weight of PET industrial scraps sourced from a PET processing plant. They found that concentrations of PMDA between 0.50 and 0.75 % promote chain extension reactions that lead to an increase of MW, a broadening of the MWD and branching phenomena which modify the PET scrap in such a way that makes... 

Figure 14.1 Reaction of pyromellitic dianhydride (PMDA) chain extender with PET end groups (hydroxyl and carboxylic acid groups) to give chain extension and branching of PET...

Conditions for low temperature solution polymerizations of pyromellitic dianhydride (PMDA) have been developed for a wide variety of aromatic 1,4-phenylene [54, 55] and 4,4 -biphenylene [56-58] diamine monomers in a number of aprotic solvents to give high molecular weight prepolymers referred to as polyamic acids. Since the imidized structures are insoluble, they must be processed in the form of their polyamic acids which are subsequently imidized thermally or by chemical dehydrating agents. Although this procedure is acceptable for thin film or fibers, the fabrication of thick parts is complicated by the water of imidization. 

Aromatic polyimides have excellent thermal stability in addition to their good electrical properties, light weight, flexibility, and easy processability. The first aromatic polyimide film (Kapton, produced by DuPont) was commercialized in the 1960s and has been developed for various aerospace applications. The structure of a typical polyimide PMDA/ODA prepared from pyromellitic dianhydride (PMDA) and 4,4 -oxydianiline (ODA), which has the same structure as Kapton, is shown in (1). Aromatic polyimides have excellent thermal stability because they consist of aromatic and imide rings. 

Relative to microelectronic applications, the out-of-plane dielectric constant for BPDA-PFMB films measmed after aging at 50% relative humidity for 48 h at 23°C was between 2.8 and 2.9 (0.1 kHz to 1 MHz) (ASTM D-150-81These values are considerably lower than that of commercial polyimides such as PMDA-ODA (pyromellitic dianhydride, PMDA) (s = 3.5 at 1 kHz and 3.3 at 10 MHz). The dielectric constant and tan 8 (dissipation factor) were temperature- and frequency-dependent. The dielectric constant, which was independent of temperature until near 210°C increased above this point until a frequency-dependent maximum was reached at about 290°C. The dissipation factor, which was also independent of temperatme below 200°C, underwent a rapid increase with no maximum between 200 and 400°C owing to ion conductivity. The temperatme at which this increase occurred increased as the frequency increased. The films also... 

In addition to pyromellitic dianhydride (PMDA), three other dianhydrides were used to extend the polyester segments. These anhydrides were prepared by heating trimellitic arihydride (IV) with glycol diacetates (V) (6) ... 

Fig. 21 Crystal structure of the charge-transfer complex pyrene pyromellitic dianhydride (PMDA). The alternate stacking of donors and acceptors. .. DADADA. .. is characteristic of weak charge-transfer complexes. (After Boeyens and Herbstein, 1965b)...

After the primary amines, acid anhydrides are the next most important class of epoxy curing agents, although these are not used as often in adhesive systems as they are in casting compounds, encapsulants, molding compounds, etc. The most common types of anhydrides are hexahydrophthalic anhydride (HHPA), phthalic anhydride (PA), nadic methyl anhydride (NMA), and pyromellitic dianhydride (PMDA), although there are several others. Chemical structures of several anhydrides are illustrated in Fig. 5.6. 

Anhydrides are sometimes used in epoxy adhesives to provide specific properties or to provide improvements in handling strengths. The most important anhydride in epoxy adhesive formulations is pyromellitic dianhydride (PMDA), which provides very high temperature properties. 

Pyromellitic dianhydride (PMDA) is a solid having a melting point of 286°C. It contains two anhydride groups symmetrically attached to a benzene ring. Because of the compactness of the molecule, PMDA achieves very high crosslink densities and, therefore, high heat and chemical resistance. PMDA cured epoxy adhesives have a heat distortion temperature on the order of 280 to 290°C. 

A typical formulation for a metal-to-metal adhesive-sealant that is cured with a combination of phthalic anhydride and pyromellitic anhydride is shown in Table 12.6. Table 15.9 shows the high-temperature properties of another epoxy formulation cured with pyromellitic dianhydride. Epoxy formulations cured with pyromellitic dianhydride (PMDA) show good short-term thermal stability in the temperature range of 150 to 230°C. 

On the other hand, many studies on dynamic mechanical properties at temperatures lower than room temperatures have been reported 5,7 63,64). For example, a small (3 transition near —50 °C has also been observed in epoxy resins. Cuddihy 65,661 observed a (3 transition in resins cuted with different hardeners such as DETA, MPDA, HHPA, pyromellitic dianhydride (PMDA), and tris(dimethylaminomethyl)-phenol (DMP-30) (Fig. 19). The larger the size of the P transition, the higher the impact strength (Table 8). 

Adjacent ladders are cross-linked by strong O—H O hydrogen bonds via the water molecules. Incorporation into 19 of pyromellitic dianhydride (PMDA) 21 produces [DTPO]2[PMDA] which has a similar ladder structure, but in this case the PMDA molecules are also able to associate via C—H O hydrogen bonds (synthon XIII) to form tapes (Fig. 12.1 lb). In the absence of water molecules, adjacent ladders are bound via additional C—H O bonds. The overall structure, therefore, consists of a three-dimensional, C—H O bound DTPO network, threaded by PMDA tapes also bound via C—H O interactions (Fig. 12.1 lc). This fascinating structure represents a solid-state polypseudorotaxane mediated entirely by weak C—H O hydrogen bonds. 

Fig. 5. Back electron transfer rates in photogenerated radical ion pairs in acetonitrile (a) 9,10-Dicyanoanthracene in its excited state served as the acceptor. Aryl, alkyl, methoxy and amino benzene derivatives as well as aliphatic amines served as donors [62] (V = 23 cm-1, 2, = 0.97 eV, Aj = 0.64 eV). (b) Perylene, pyrene, benzperylene, and aromatic amines served as donors. Tetracyanoethylene (TCNE), pyromellitic dianhydride (PMDA), phthalic anhydride (PA), maleic anhydride, pyrene and perylene served as electron acceptors [63], Various combinations of donors or acceptors were excited (V = 20 cm , As = 1.45 eV, A, = 0.07 eV). The parabolas drawn are different from those offered in the original analysis. The parameters that were used were selected to emphasize the similarity to Fig. 4 (in all cases v = 1500 cm-1)...

Polyimides have excellent dielectric strength and a low dielectric constant, but in certain electrolyte solutions they can electrochemically transport electronic and ionic charge. Haushalter and Krause (5) first reported that Kapton polyimide films derived from 1,2,4,5-pyromellitic dianhydride (PMDA) and 4,4 -oxydianiline (ODA) undergo reversible reduction/oxidation (redox) reactions in electrolyte solutions. Mazur et al., (6) presented a detailed study of the electrochemical properties of chemically imidized aromatic PMDA- derived polyimides and model compounds in nonaqueous solutions. Thin films of thermally... 

One commonly used polyimide is poly(N,N -bis(phenoxyphenyl)-pyromellitimide). This may be prepared from the reaction of pyromellitic dianhydride (PMDA) and oxydianiline (ODA) in a two step process (Figure 1). The first step involves a solution reaction forming the poly(amic acid) (PAA). After solvent removal this material can be thermally cyclized to the polyimide (PI). To improve properties, it is often annealed at temperatures up to 400° C. 

Scheme 10 Reaction of OAFS with pyromellitic dianhydride (PMDA) to form a nanocomposite with completely rigid imide tethers between cube vertices [126]...

The well known synthesis of low molecular phthalocyanines Pc, 2) starts from phthalic add derivatives like 1,2-dicyanobenzene, 1,3-diiminoisoindolenine and jAthalic anhydride The yield of metal free or metal containing Pc is often high (80-100%). By starting with a Wfunctional material like 1,2,4,5-tetracyanobenzene (TCB) or pyromellitic dianhydride (PMDA) a polymeric phthalocyanine (polyPc) (86) must be formed under the same conditions (Eq. 40). But the determination of structure and molecular weight is very difficult. Byproducts may be formed and the resulting polymers are often less soluble. But structure investigations are very important to correlate structure and property. 

Generally, synthesis of dianhydrides is somewhat more complex than that of diamines and until recent time pyromellitic dianhydride (PMDA) and benzophenone-3,3, 4,4 -tetracarboxylic dianhydride (BTDA) had been the only commercially produced aromatic dianhydrides. Some of the significant commercial products developed recently, are Upilex by UBE Ind. and Ultem by General Electric. The former is based on biphenyl-3,3, 4,4 -tetracarboxylic dianhydride (BPDA) and the latter on 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride or bisphenol A dianhydride (BPA-DA). BPDA is produced by oxidative coupling of inexpensive phthalic acid esters in the presence of palladium catalyst [23, 24]. 

A procedure similar to that which we have already reported was employed [9,10]. This involves the preparation of a pre-polymer poly(amic acid) (PAA) solution in DMAc, followed by imidization in suspension in paraffin oil. A typical procedure for the preparation of linear functionalized spherical polyimide particulates was as follows. A round-bottomed 3-necked flask was flushed with N2 and charged with a diamine in DMAc. The diamine was completely dissolved in DMAc. While solution was mechanically stirred, finely ground pyromellitic dianhydride (PMDA) was added to the mixture on an ice bath in small portions, and then stirring continued overnight at room temperature. Paraffin oil with poly(maleic anhydride-co-octadec-l-ene)(l l) (O.Swt% in oil) as a suspension stabilizer was added to the flask. The PAA solution was suspended for 2hr at 60T) at the speed of 400rpm. After that, imidization was initiated by dropwise addition of a mixture of acetic anhydride (4.0 molar excess of PMDA used) and pyridine (3.5 molar excess of PMDA used). After 24hr, the polyimide particulates were filtered, washed with dichloromethane and then dried at 80 °C in a vacuum oven. 

Fluorescence spectra of polyimide as a function of thermal history for two of the most common commercially available polyimide precursors, Du Pont PI-2545 and PI-2555, were obtained. These precursors are polyamic acids formed from the polycondensation reaction of pyromellitic dianhydride (PMDA) and oxydianiline (ODA),... 

The polyamic acids were prepared in these laboratories using modifications of a standard preparation (7). Benzophenone tetracarboxylic acid dianhydride (BTDA), benzenetetracarboxylic acid dianhydride (pyromellitic dianhydride PMDA), oxydianiline (ODA), 1,4-phenylenediamine (PDA) and 1,3-phenylenediamine (MPDA) were all obtained from Aldrich Chemical Co. The S -biphenyl tetracarboxylic acid dianhydride (BPDA) was obtained from Ube Chemical Company. The polyamic acids were prepared in N-methylpyrrolidinone (BTDA-ODA, BTDA-MPDA and BTDA with a 1 1 molar ratio of MPDA and ODA) or dimethyl acetamide (BPDA-PDA and PMDA-ODA). 

Two of the additives were also incorporated into a more conventional polyimide system, pyromellitic dianhydride (PMDA)/4,4 -ODA, to see if the diamic acid additives were effective in lowering the dielectric constant of a higher dielectric constant polyimide also. The evaluation was preliminary in that only two additives were screened at one concentration. As is shown in Table IV the dielectric constant was lowered, though not as significantly as in the BDSDA/4-BDAF system. 

---