Polyimides molecular structure

Fig. 3.5.2 Polyimide molecular structures and syntheses investigated for LB alignment films.

Fig. 6.2.7 Effect of polyimide molecular structure on the driving margin (M).

Molar mass boosting, 89 Molecular composites, polyimide, 269 Molecular structure, of polyurethanes, 209-217... 

Structural steels, tellurium in, 24 425 Structure(s), see also Chain structure Chemical structures Cocontinuous structures Controlled structure Crystal structure Molecular structure Morphology Phase structure of carbon fibers, 26 737-739 detersive systems for, 8 413t HDPE, 20 157-162 LLDPE, 20 182-184, 203-205 polyesterether elastomer, 20 72-73 polyester fiber, 20 21 polyether antibiotics, 20 137-139 polyimide, 20 276-278 polymer, 20 395-405 protein, 20 449 PTT, 20 68t... 

The lack of flexibility of the polymer chain has to be improved by introducing linkage groups into the dianhydride component. Accordingly, continuous and flexible films of perfluorinated polyimides are expected to be obtained by combining diamines, which have high reactivities, with dianhydrides, which have flexible molecular structures. 

Li Y, Wang X, Ding M, Xu J (1996) Effects of molecular structure on the permeability and permselectivity of aromatic polyimides. J Appl Polym Sci 61(5) 741... 

X-ray photoelectron spectroscopy has been used to study the metal polyimide interface formed during room temperature metal deposition. Several mono-layers of Al, Au and Cu were sputter-deposited onto cured polyimide, to a thickness which permitted the observation of both polyimide and metal peaks. Deconvolution of core-level Cls, Nls and Ols polyimide peaks and A12p, Au4f and Cu2p3/2 metal overlayer peaks has demonstrated that chemical reaction occurs at the carbonyl sites for all these metals under the conditions used. In addition, the aromatic nature of the molecular structure at the interface is believed to decrease while the percentage of an isoimide-like component increases. 

The dielectric properties of substrates depend heavily on the chemistry of the constituent raw materials. The presence of polar chemical groups within the molecules increases the dielectric constant. The relatively simple molecular structures of polyethylene (CH2 - CH2) and polytetrafluorethylene (CF2 - CF2) would be expected to have low dielectric constants. Epoxy resins and polyimides have relatively high dielectric constant values since they have complex molecular structures. 

A relatively large quantity (approximately 200 gm) of an aromatic heterocyclic material was available and was used to develop a fracture test method that could be used to characterize materials limited in available quantities. This material is an acetylene-terminated polyimide, known as Thermid 600, which has the molecular structure shown in Figure 1. Although the material is a bit difficult to work with in the 100% solid form, this form was used to fabricate specimens. Cure kinetics and rheological data were measured and used to guide specimen fabrication. 

Recent evidence indicates that the influence of molecular structure on gas permeation through polymers is complex. For example, reports investigating series of structurally varied polyimides (5-7), polyacetylenes (2), polystyrenes (2) and silicone polymers (12) show that gas transport rates within a particular polymer class can vary dramatically depending upon the structure of the monomer present. These observations on materials where the monomer changes while the functional "link" remains constant suggest that structural factors other than the polymer class are significant in determing gas transport properties. 

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