Polyimide and Derivatives

Pis are rigid, high melting point, high glass transition temperature (T ), thermally stable polymers synthesized by the condensation reactions of dianhydrides with diamines (Fig. 4.4) [34]. Normally, Pis are synthesized in lab scale with different types of dianhydrides and diamines in order to tailor its separation properties when being used as membrane material (Fig. 4.4). 

Precursor Configuration Pyrolysis conditions (temperature heating rate soak time atmosphere) Reference 

4 -benzophenone tetracarboxylic dianhydride (BTDA) and 5(6)-amino-1 (4 -aminophenyl)-1,3-trime1hylindane (DAPI) 

4 (hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,3 -4,4 -biphenyl tetracarboxylic acid dianhydride (BPDA) and 2,4,6,-trimethyl-1,3-phenylene diamine (DAM) 

---

Closely related to the polyamides are the polyimides and derivatives such as polyamide-imides and polyether-imides. These are discussed in Sections 18.13 and 18.14. 

Polyimides, and derivative copolymers such as poly(ester-imide)s have been known for decades but none were reported before 1987 to contain lyotropic or thermotropic mesophases, except certain copoly(esterimide)s with three or more monomers [6,7]. 

A direct route to obtain polyimides and polybenzoxazoles without diacid has been explored by using direct carbonylation of an aromatic diiodo compound.100 The reactions were performed in polar aprotic solvent. The cheaper chlorine derivative can be used instead of the iodo one when it is located on a strongly... 

Photosensitive functions are in many cases also heat sensitive, so the preparation of photosensitive polyimides needs smooth conditions for the condensations and imidization reactions. Some chemical reactants, which can be used for polyamide preparation, have been patented for the synthesis of polyimides and polyimide precursors. For example, chemical imidization takes place at room temperature by using phosphonic derivative of a thiabenzothiazoline.102 A mixture of N -hydroxybenzotriazole and dicyclohexylcarbodiimide allows the room temperature condensation of diacid di(photosensitive) ester with a diamine.103 Dimethyl-2-chloro-imidazolinium chloride (Fig. 5.25) has been patented for the cyclization of a maleamic acid in toluene at 90°C.104 The chemistry of imidazolide has been recently investigated for the synthesis of polyimide precursor.105 As shown in Fig. 5.26, a secondary amine reacts with a dianhydride giving meta- and para-diamide diacid. The carbonyldiimidazole... 

Pascal et al. [49-50] studied semi-2-IPN derived from linear thermoplastic polyimides and thermosetting bismaleimides from the same type of starting... 

The variety of ways in which chloral and trinitrotoluene (TNT) derivatives can be used to prepare novel polyimides and polymeric materials is very promising. The use of chloral and TNT derivatives allows for the synthesis of a large number of monomers which, in turn, can impart a variety of useful properties to their respective polymers. The possibility of preparing, from available raw materials, high-molecular-weight compounds with increased heat and thermal resistance in combination with improved solubility and, consequently, easiness of processing is especially attractive and may provide impetus for further work in this field. 

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... 

Starting materials and solvents were purchased from Aldrich Chemical Co. acetonitrile (ACN), N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP) were obtained anhydrous in Sure/Seal bottles and used as received. The polyamic acid of PMDA-ODA (2545 Pyralin) was supplied by DuPont. The soluble polyimide XU-218, derived from 3,3, 4,4 -benzophenone tetracarboxylic dianhydride (BTDA) and diamino-1,1,3-trimethyl-3-phenylindan isomers (DAPI) was purchased from Ciba-Geigy Corp. The acetylene terminated imide oligomer powder (Thermid MC-600) derived from BTDA, aminophenylacetylene, and 1,3-bis (2-aminophenoxy) benzene (APB) was obtained from National Starch and Chemical Company. Kapton Type II (PMDA-ODA) films were obtained from DuPont Co., Apical polyimide films were obtained from Allied Corp., and Upilex Type-S and Type-R polyimide films derived from 3,3, 4,4 -biphenyl tetracarboxylic dianhydride (BPDA) plus p-phenylenediamine (PDA) and ODA, respectively were obtained from ICI Americas Inc. 

A series of novel polyimides were prepared from diaminophthalide 288 and four anhydrides 289 for the investigation of water-permeable membranes. Of the polymer products 290, the best permeability was associated with bulky groups (trifluoromethyls) on the polyimide chains <2005JAPS2047>. There are other variants of diaminophthalide 288 used to prepare polyimides and polyamides. A fluorinated variation 291 has been used for polyimide synthesis <2004MI979> as has 292, derived from o-cresolphthalein 284 <1999PSA455>. 

TABLE 1. Optical alignment of polyimide compositions derived from 1,2,3,4-cyclobntane-tetracarboxylic dianhydride and selected diamines. 

Curing of epoxy resins can be initiated photochemically by release of imidazole from photolabile protected derivatives, such as AT-(2-nitrobenzyloxycarbonyl)imi-dazole. Positive working polyimide resists derived from 2-nitro-p-xylyleneoxy-amine have been synthesized and studied and 2-nitrobenzyloxy derivatives are included in a formulation for submicron imaging. ... 

The reactivity of the maleimide monomer was dependent on the substitution pattern of the phenyl ring, with the substituents in the ortho position tending to lower the molecular weight of the polymer formed. The THP substituent is readily removed either chemically or thermally to yield poly(iV-(hydroxyphenyl)maleimides). All polymers exhibited excellent thermal stability and showed no evidence of degradation below 360 °C. Reaction occurs between the phenolic ring of the polyimide and HMTA, to form benzoxazine-type derivatives. These reactions have been studied comprehensively using the monomeric model systems, Ai-(hydroxyphenyl)succinimides (Figure 8) . 

The polyimide is prepared from 1,5 naphthlene diamine (1,5 ND) and 3,3, 4,4 diphenylhexafluoroisopropylidene tetracarboxylic acid dianhydride (6F). A polyamide acid is obtained initially and this is cyclized to give the polyimide. Because polyimides are derivatives of polyamides, polyimides are often included in reviews of aromatic polyamides. Another reason polyimides are included in this paper is that they illustrate the role of Structure Level II on gas transport properties in a straightforward manner. 

In principle, the aminomethyl derivatives could be made, and these can be cyclised to the isoindolines. Apart from being chemical intermediates, little value can be placed on them, although the diisoindolines can be used to make step-ladder polymers unfortunately the current literature suggests that the resultant polymers have no advantage over polyimides, and, in addition, the starting material is far more difficult to synthesise(52). 

Triazine Ring Cross-linked Polyimides and Refractory Materials Derived from Them... 

It should be noted that both polyimides and ladder polyheteroarylenes derived from bis(phthalic anhydrides) possess relatively low thermal and chemical stability [37, 39, 57,58], which to a great extent, is mainly attributed to the strained five-membered imide moieties presented in the formed heterocycles, large positive charges on the carbonyhc carbons in the systems, comparatively low orders of the bonds C-C(0)- and N-QO). This is illustrated by the molecular diagram of 1,2-benzoylenebenzimidazole, i.e. the simplest individual... 

Since all carbon atoms contribute to the tt system of polyimide, and the vast majority does in polystyrene, knowledge of the (preferential) orientation of the TT orbitals is sufficient to derive the (preferential) orientation of the pol3nmer chains, d vice versa. Therefore, the preferential orientation of the polyimide chains along the rubbing direction results in a preferential orientation of the 7T orbitals perpendicular to the rubbing direction. For polystyrene, on the other hand, the preferential orientation of the tt orbitals is parallel to the rubbing direction. 

In this discussion we deal with the resistance of polymers to various chemicals, (mainly water, acids, bases or organic solvents) as well as with their endurance after being exposed to climatic conditions or to fire. Most polymers show very low water absorbency, except for Nylon and cellulose derivatives that are sensitive to humidity. Most polymers also withstand mild inorganic chemicals at ambient temperatures. Excelling at this are the fluoro compoimds, Noryl, polyimide and polysulfone while polypropylene, PVC and epoxy are considered fair. Polyester and polycarbonate are sensitive to bases, while Nylon is affected by acids. Detailed tables of data exist, describing the resistance of plastics to many chemicals at specific temperatures. Most thermoplastics have a tendency to dissolve in specific organic solvents. 

A suitable polymer material for preparation of carbon membranes should not cause pore holes or any defects after the carbonization. Up to now, various precursor materials such as polyimide, polyacrylonitrile (PAN), poly(phthalazinone ether sulfone ketone) and poly(phenylene oxide) have been used for the fabrication of carbon molecular sieve membranes. Likewise, aromatic polyimide and its derivatives have been extensively used as precursor for carbon membranes due to their rigid structure and high carbon yields. The membrane morphology of polyimide could be well maintained during the high temperature carbonization process. A commercially available and cheap polymeric material is cellulose acetate (CA, MW 100 000, DS = 2.45) this was also used as the precursor material for preparation of carbon membranes by He et al They reported that cellulose acetate can be easily dissolved in many solvents to form the dope solution for spinning the hollow fibers, and the hollow fiber carbon membranes prepared showed good separation performances. 

---