Dianhydride structure modifications

All the polyimides derived from synthesized diamines with common dianhydrides such as DSDA and 6FDA exhibited excellent solubilityThe high solubility was possibly due to the structural modification through the incorporation of flexi-... 

It was observed that the TBAPP-based polyimides derived from dianhydrides BPDA and BTDA were soluble in polar aprotic solvents. The high solubility of TBAPP-based polyimides was possibly governed by the structural modification through the incorporation of the flexible isopropylidene, increasing the overall chain flexibility, and methyl substituted arylene ether groups into the polyimide structure. It has been verified that polyimide derived from diamine DAM3 (Table 2.4) had less solubility than that derived from diamine TBAPP. This result clearly demonstrated that the tetramethyl substituents on the phenylene unit effectively improved the polymer solubility. It has been reported that methyl... 

Most of the polyimides were amorphous in nature. This was because of the various structural modifications onto the polymer backbone. In general, polyimides derived from dianhydrides such as PMDA, BPDA and BTDA exhibited higher crystallinity than the other dianhydrides such as OPDA, DSDA and 6FDA. The higher crystallinity reflected on their poor solubility. 

Structural modifications to attain soluble aromatic polyimides have been also carried out by introducing side substituents, alkyl, aryl or heterocyclic rings. One of the first references of this approach described the synthesis of soluble aromatic polyimides containing side phthalimide groups [84,85]. Since then, many attempts have been made to prepare new monomers, diamines and dianhydrides, with pendent groups for novel processable polyimides. Table 7 shows some of these monomers. 

Pol5dmides are known as reliable high temperature polymers with superior mechanical and electrical properties. Polyimides can be easily prepared by reactions between dianhydrides and diamines, and many types of polyimides have been prepared by structural modification of the monomers to obtain the polyimides having desirable... 

Sotoyama et al. [119] reported a side-chain polyimide synthesized by the reaction of a dianhydride-containing azobenzene dye with 4,4 -diaminodi-phenyl ether. The poled polyimide. Structure (14), shows a large EO coefficient (rvi = 10.8 pm V at 1.3 xm) and good thermal stability, even at 120 C. The EO efficiency and thermal stability can be further improved by structural modification. 

As in all thermosetting polyimides, the diamine and the tetracarboxylic dianhydride employed to build the backbone can be varied. Alteration of the diamine, tetraacid or both, allow the modification of the polyimide s melting point and solubility. Of interest to the end user is the influence of chemical structure on the melting transition of the prepolymer and the Tg of the fully cured product. Lowering the uncured Tg means increasing flow and, in most... 

Polyimide surface modification by a wet chemical process is described. Poly(pyromellitic dianhydride-oxydianiline) (PMDA-ODA) and poly(bisphenyl dianhydride-para-phenylenediamine) (BPDA-PDA) polyimide film surfaces are initially modified with KOH aqueous solution. These modified surfaces are further treated with aqueous HC1 solution to protonate the ionic molecules. Modified surfaces are identified with X-ray photoelectron spectroscopy (XPS), external reflectance infrared (ER IR) spectroscopy, gravimetric analysis, contact angle and thickness measurement. Initial reaction with KOH transforms the polyimide surface to a potassium polyamate surface. The reaction of the polyamate surface with HC1 yields a polyamic acid surface. Upon curing the modified surface, the starting polyimide surface is produced. The depth of modification, which is measured by a method using an absorbance-thickness relationship established with ellipsometry and ER IR, is controlled by the KOH reaction temperature and the reaction time. Surface topography and film thickness can be maintained while a strong polyimide-polyimide adhesion is achieved. Relationship between surface structure and adhesion is discussed. 

Here we report a wet surface modification of PMDA-ODA and poly-(bisphenyl dianhydride-para-phenylenediamine) (BPDA-PDA) with KOH or NaOH solution. The modified surfaces are identified with contact angles, XPS spectra and ER IR spectra. Polymer thickness and weight changes are also studied. The depth of modified layer is measured by a non-destructive technique using ER IR and ellipsometry. Relationship between surface structure and adhesion strength is discussed. 

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