Polyimide oligomers

The process known as transimidization has been employed to functionalize polyimide oligomers, which were subsequentiy used to produce polyimide—titania hybrids (59). This technique resulted in the successhil synthesis of transparent hybrids composed of 18, 37, and 54% titania. The effect of metal alkoxide quantity, as well as the oligomer molecular weight and cure temperature, were evaluated using differential scanning calorimetry (dsc), thermogravimetric analysis (tga) and saxs. 

The thermal polymerization of reactive polyimide oligomers is a critical part of a number of currently important polymers. Both the system in which we are interested, PMR-15, and others like it (LARC-13, HR-600), are useful high temperature resins. They also share the feature that, while the basic structure and chemistry of their imide portions is well defined, the mode of reaction and ultimately the structures that result from their thermally activated end-groups is not clear. Since an understanding of this thermal cure would be an important step towards the improvement of both the cure process and the properties of such systems, we have approached our study of PMR-15 with a focus only on this higher temperature thermal curing process. To this end, we have used small molecule model compounds with pre-formed imide moieties and have concentrated on the chemistry of the norbornenyl end-cap (1). 

Ethynyl End-Capped Polyimide Oligomers Containing Oxyethylene Linkages... 

Oligomers of BTDA and Linear Diamines. A series of ethynyl end-capped polyimide oligomers was synthesized by the following route. 

Norbomene end-capped polyimide oligomers (trade name LARC) are obtained by including 5-norbomene-2,3-dicarboxylic anhydride (nadic anhydride) (XLVII) in the polymerization reaction between a dianhydride and diamine [de Abajo, 1988 Hergenrother, 1987]. Heating the oligomer at 270-320°C results in a thermoset product. The main reaction... 

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... 

Table 12. Cure onset temperatures of phenylethynyl-terminated polyimide oligomers Endcaps Polymerisation onset Temp., °C ...

US 5,028,681 (American) 1991 Novel poly(imide siloxane) block copolymers and process for their preparation General Electric EN Peters Injection moldable block copolymers with high IV and excellent chemical/physical properties. Blends useful for impact modification Novel siloxane-imide block copolymers and a process for their preparation are covered. The method involves reacting a hydroxy-terminated polyimide oligomer with a siloxane oligomer with dimethylamino, acetyl or chlorine end-groups... 

In the presence of aromatic polymers, it reacts to form biphenylated aromatics as major products. Biphenylene end-capped polyimide oligomers were prepared using PMR technique and its curing poperties were investigated [88]. 

X. Rao, H. Zhou, G. Dang, C. Chen, andZ. Wu. New kinds of phenyleth-ynyl-terminated polyimide oligomers with low viscosity and good hydrolytic stability. Polymer, 47(17) 6091-6098, August 2006. 

The imidization was conducted as previously described.(8) A reverse Dean Stark trap with a condenser filled with DCB was fitted to the flask. An additional amount of DCB was added to the reaction mixture to bring the. solvent ratio to 80%NMP/20%DCB. The reaction mixture was heated to 165 C by immersion in a hot silicone oil bath. The reaction was allowed to heat for a total of 24 hours to ensure complete imidization. The solution was cooled to ambient temperatures, and precipitated in methanol in a high speed blender. Upon cooling, the ODPA-Bis P solutions became turbid. The polyimide oligomers were collected and dried in a vacuum oven for 18 hours at 200 C and for 1 hour at 300 C. 

The copolymer synthesis was carried out in a three neck round bottom flask equipped with a mechanical stirrer, nitrogen inlet, thermometer and a condenser with drying tube. The stoichiometry was offset by using an excess of the polyimide oligomer. In every case, the calculated was 40,000 g/mole. The polyimide oligomer was dissolved in chlorobenzene and heated to -125 C. The amine terminated oligomer was added slowly and rinsed with chlorobenzene to bring the final reaction solids content to 15 percent. The reaction was stirred at -125 C for 2 hours. The solution was cooled to ambient temperatures and cast into films. The films were heated slowly in a vacuum oven and dried for at least 3 hours at 250°C. 

Proton NMR Analysis All proton spectra were measured on a Varian Unity 400 MHz NMR. Samples were dissolved in deuterated chloroform. TMS was used as an internal reference standard for the polyimide oligomers. Chloroform was used as a reference for the polyimide-siloxane copolymers. 

A major goal of the research in proton exchange membrane fuel cells is the development of high-temperature membranes that may operate at 120 °C and low humidity. One route are multi-block copolymers with completely disulfonated PAES and naphthalene polyimide oligomers [107]. 

N. Bilow, A. L. Landis, L. J. Miller, Copolymer of polyimide oligomers and terephthalonitrile N,N-dioxide and their methods of preparation, 1975 US Patent 3864309. 

Phenylethynyl end-capping of polyimide oligomers (Fig. 3.54) has shown promise for high-temperature plastics and adhesives, with Tg > 300°C and high adhesive strength, hot strength, and oil resistance (Table 3.55). 

Paracyclophane. The strained rings of paracyclophane (Fig. 3.58) open and polymerize on heating. When paracyclophane end-groups are attached to polyimide oligomers and thermally cross-hnked, cured composites have excellent heat-resistance (Table 3.56). 

M., and Cook, R.C. (2003) Characterization of the imidization of poly(amic acid) to an insoluble polyimide oligomer by matrix assisted laser desorption ionization time-of-flight mass spectrometry. PMSE Preprints, 89, 392. 

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