Polymer anhydride amic acid

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. 

Reaction of 4-nitro-l-benzoyl chloride with benzocyclobutene 1 provided the benzoylated product 15 [36]. The nitro group of 15 was reduced with hydrogen in the presence of palladium on charcoal to afford he amine product 16 [44]. Reaction of the amine with maleic anhydride provided the amic acid which was converted to the maleimide 17 by cyclodehydration with acetic anhydride and sodium acetate at 95 °C [45-47], This monomer and its homo-polymer will be discussed in greater detail in a later section. 

Polysulfobetaines derived from alternating styrene-maleic anhydride copolymers 32 are easily prepared by ring opening of the anhydride moiety with 3-dimethylaminopropylamine, imidizing the resulting poly(amic acid) by heating, and alkylation with propane sultone [70-72]. For investigations of structure-property relationships additionally to 32b, the polymers 33 and 34 were synthesized [71]. The ionene-like polymer 33 was prepared... 

The solubility of the polyimide dictates, to a large extent, the synthetic route employed for the copolymerization. The ODPA/FDA and 3FDA/PMDA polyimides are soluble in the fully imidized form and can be prepared via the poly(amic-ac-id) precursor and subsequently imidized either chemically or thermally. The PMDA/ODA and FDA/PMDA polyimides, on the other hand, are not soluble in the imidized form. Consequently, the poly(amic alkyl ester) precursors to these polymers were used followed by thermal imidization [44]. For comparison purposes, 3FDA/PMDA-based copolymers were prepared via both routes. The synthesis of the poly(amic acid) involved the addition of solid PMDA to a solution of the styrene oligomer and diamine to yield the corresponding poly(amic acids) (Scheme 8). The polymerizations were performed in NMP at room temperature for 24 h at a solids content of -10% (w/v). Chemical imidization of the po-ly(amic-acid) solutions was carried out in situ by reaction with excess acetic anhydride and pyridine at 100 °C for 6-8 h. The copolymers were subjected to repeated toluene rinses in order to remove any unreacted styrene homopolymer. 

The Pis were prepared in the procedures similar to one described in Appendix 1. One of the examples is described as follows. To the stirred solution of 0.6 g (0.883 tmnol) of diamine (4, Appendix 1) in 5 ml of DMAc, 0.382 g (0.883 mmol) of 6FDA was gradually added. The mixture was stirred at room temperature for 4 hr imder nitrogen atmosphere to form poly(amic acid). Chemical cyclodehydration was carried out by adding equal molar mixture of acetic anhydride and pyridine into the above mentioned poly(amic acid) solution with stirring at room temperature for 1 hr, and then treated at lOO C for 4 hr. The polymer solution was poured into methanol. The precipitate was collected by filtration, washed thoroughly with methanol, and then dried at 100°C under vacuum. 

A poly(imide-siloxane)/titania hybrid film was fabricated by a sol-gel process by the in situ formation of titania within the poly(imide-siloxane) matrix [85]. The poly(amic acid siloxane) polymer was prepared from 4,4 -oxydiphthalic anhydride, 2, 2-bis [4-(4-aminophenoxy) phenyl] propane, and a,a>-bis(3-aminopropyl)polydimethylsiloxane. Acetylace-tone was used as chelating agent in order to reduce the rate of hydrolysis of titanium alkoxide in the polymer. The presence of titania on the surface of eventually produced films enhances the adhesive strength at the interface. 

Lee et al. [169] reported the preparation of new soluble and intrinsically photosensitive poly(amide-co-imide)s containing p-phenylenediacryloyl moiety. The copolymers were formed from p-phenylenediacryloyl chloride, aromatic dianhydrides, and two equivalents of aromatic diamines. The products were subsequently imidized by reactions with the poly(amide-co-amic acid), acetic anhydride, and pyridine. The polymers were stable up to 350°C, showed good solubility in polar aprotic solvents, and became insoluble after the irradiation due to the photodimerization of phenylenediacryloyl moiety. The photo-reactivity increases with the irradiation temperature [169]. 

Crystalline thermoplastic polymers made from two or more different monomers, usually ethylene and propylene. A family of polymers based on the combination of trimellitic anhydride with aromatic diamines. In the uncured form (ortho-amic acid), the polymers are soluble in polar organic solvents. The imide linkage is formed by heating, producing an infusible resin with thermal stability up to 290 °C. These resins are used for laminates, prepregs, and electrical components. 

The formation of poly(amic acid), which is the first step in this synthesis, is a fast exothermic reaction which is generally carried out at room temperature or slightly above in a solvent for the polymer. Under these conditions the extent of imidization is negligible. In a typical process, the diamine is dissolved in dimethylformamide, dimethylacetamide or dimethyl sulphoxide and the dianhydride is added portion-wise with cooling. A viscous solution of the poly(amic acid) is formed. The poly(amic acid) contains a mixture of m- and p- diamide units as shown above. The second step in the preparation of the polyimide is cyclization of the poly(amic acid). Aromatic polyimides are usually insoluble and infusible and cannot therefore be fabricated either in solution or in the melt. It is thus necessary to convert the poly(amic acid) to the polyimide in that physical form in which the final polymer is desired. For example, in the preparation of film the poly(amic acid) solution is cast and then heated firstly to about 150°C and finally to 300°C. During imidization, water is formed and may cause scission of the polymer chains, particularly in the casting of thick film. The addition of acetic anhydride and pyridine (catalyst) to the poly(amic acid) solution results in the effective removal of water from the reaction system and prevents molecular weight reduction. 

Poly(amic acids) prepared from diamines and pyromellitic anhydride react with metal acetylacetonates to yield polymers with chelated metal ions (i). These products form tough films, which indicated that the initially high molecular weight of the poly(amic acid) was retained on chelation. Heating these products gave electrically conductive materials containing free metal (i). 

---