Polyimides, crosslinked

Lastly, the polyimide has some inherent photosensitivity. The use of a photosensitive polymer requires fewer processing steps, which also implies an increased yield for the circuit. Ciba-Geigy announced the formulation of inherently photosensitive polyimides in 1985.(5) The use of an inherently photosensitive polyimide is attractive because no sensitizers are added to contaminate the final resin, no functionality is added which degrades the thermal and chemical resistance, and fewer volatiles are present to contaminate the resin or equipment than in some other approaches to photosensitive polyimides. Recent work has shown that these polyimides crosslink on irradiation through hydrogen abstraction by triplet benzophenone and subsequent coupling of the resultant radicals. ... 

Thermoset polymers like polyimide, crosslinked sulfonated poly(ether ether ketone) and polyacrylate can be used for membrane applications. The presence of nanoparticle nucleates the nanopore formation with the assistance of an agent. The nanopore is responsible for the solvent separation and transportation. Membranes such as solvent filters, filters for bacteria and virus, and membrane for gas separation can be developed using clay-polymer nanocomposites [118-119]. 

V. A. Bershtein, L. M. Egorova, P. N. Yakushev, P. Sysel, R. Hobzova, J. Kotek, P. Pissis, S. Kripotou, P. Maroulas, Hyperbranched polyimides crosslinked with ethylene glycol digly-cidyl ether Glass transition dynamies and permeability. Polymer, 47, 6765-6772 (2006). 

Bershtein V A, Egorova L M, Yakushev P N, Sysel P, Hobzova R, Kotek J, Pissis P, Kripotou S, Maroulas P (2006) H)rperbranched Polyimides Crosslinked with Ethylene Glycol Diglycidyl Ether Glass Transition Dynamics and Permeability. Pol)mer 47 6765-6772. 

Cycloahphatic diamines react with dicarboxyUc acids or their chlorides, dianhydrides, diisocyanates and di- (or poly-)epoxides as comonomers to form high molecular weight polyamides, polyimides, polyureas, and epoxies. Polymer property dependence on diamine stmcture is greater in the linear amorphous thermoplastic polyamides and elastomeric polyureas than in the highly crosslinked thermo set epoxies (2—4). 

Recent work has focused on a variety of thermoplastic elastomers and modified thermoplastic polyimides based on the aminopropyl end functionality present in suitably equilibrated polydimethylsiloxanes. Characteristic of these are the urea linked materials described in references 22-25. The chemistry is summarized in Scheme 7. A characteristic stress-strain curve and dynamic mechanical behavior for the urea linked systems in provided in Figures 3 and 4. It was of interest to note that the ultimate properties of the soluble, processible, urea linked copolymers were equivalent to some of the best silica reinforced, chemically crosslinked, silicone rubber... 

Zeolite/polymer mixed-matrix membranes prepared from crosslinked polymers and surface-modified zeolite particles offered both outstanding separation properties and swelling resistance for some gas and vapor separations such as purification of natural gas. Hillock and coworkers reported that crosslinked mixed-matrix membranes prepared from modified SSZ-13 zeolite and 1,3-propane diol crosslinked polyimide (6FDA-DAM-DABA) synthesized from 2,2 -feis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, p-dimethylaminobenzylamine-and 3,5-diaminobenzoic acid displayed high CO2/CH4 selectivities of up to 47 Barrer and CO2 permeabilities of up to 89 Barrer under mixed gas testing conditions [71]. Additionally, these crosslinked mixed-matrix membranes were resistant to CO2 plasticization up to 450 psia (3100kPa). 

Alkyne end-capped polyimide oligomers are obtained by including an amine or anhydride that contains a triple bond in the polymerization mixture of diamine and dianhydride. Curing to a thermoset product takes place on heating with cyclotrimerization to an aromatic system (Eq. 2-215) as the crosslinking reaction. However, cyclotrimerization is not complete, and the... 

The Diels-Alder reaction can be employed to obtain thermosetting polyimides. If BMI (the bisdienophile) and the bisdiene react nonstoichiometrically, with bismaleimide in excess, a prepolymer carrying maleimide terminations is formed as an intermediate, which can be crosslinked to yield a high temperature resistant network. 

One resin based on the BTDA/ODA backbone and 2-aminobiphenylene as an endcapper was thought to be such a resin (126). High quality laminates could be fabricated, but the Tg of the crosslinked polymer was lower than expected and therefore thermal oxidative stability was poor. The chemical structure of this thermosetting polyimide is given in Fig. 42. 

Throughout this chapter the chemical concepts employed to synthesize and cure addition poly(imides) have been discussed and their use as matrix resins for fiber composites has frequently been mentioned. The most important property of the imide backbone structure is the inherent thermal stability. The target of achieving the temperature performance of linear poly(imide) has not been reached, because of the aliphatic nature of the reactive endgroups, and because of the low molecular weight of the imide backbone required for processing. Future developments of addition polyimides will, as in the past, focus on the requirement of high thermal and thermal oxidative stability of the crosslinked... 

As a radical photoinitiator, we used 2-hydroxyisopropyl phenyl ketone (DAROCUR 1173 Ciba-Geigy), taken in an amount of 3 wt% based on polyimide (Scheme 5.13). The pattern of an exotherm obtained for the 1% solution of the polyimide (-X- = -O-), the high value of polymerisation enthalpy (352.4 J/g) and the short times of attaining the maximum peak (4.4 s) and the induction time (2.4 s) allow us to consider that this polyimide to be rather reactive from the point of view of polymerisation and formation of a crosslinked structure. 

Direct Patterning of Photosensitive Polyimides. Photosensitive polyi-mides (PSPIs) are recently developed materials that can be directly photo-patterned like a negative photoresist (80,85,88,146-148). The most common PSPIs are polyamic acids that have been esterified with photoreactive alcohols and combined with photoinitiators to form a polymer that will crosslink under exposure to UV radiation and become insoluble. The unexposed material is selectively dissolved in a developer solution, and the patterned film is then cured to convert the cross-linked polyamic acid to a polyimide and drive off the cross-linking groups. 

High hydrophilicity Amine crosslinked epoxies of high crosslink density (TGAP, TGMDA) Many polyimides >3%... 

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