Polyimides repeat unit structure

In order make an effort to bring the polyimide-metal adhesion problem to an even more fundamental level, we have previously proposed that model molecules, chosen as representative of selected parts of the polyimide repeat unit, may be used to predict the chemical and electronic structure of interfaces between polyimides and metals (12). Relatively small model molecules can be vapor deposited in situ under UHV conditions to form monolayer films upon atomically clean metal substrates, and detailed information about chemical bonding, charge transfer and molecular orientation can be determined, and even site-specific interactions may be recognized. The result of such studies can also be expected to be relevant in comparison with the results of studies of metal-polymer interfaces. Another very important advantage with this model molecule approach is the possibility to apply a more reliable theoretical analysis to the data, which is very difficult when studying complex polymers such as polyimide. 

Table 3.4 Fluorinated Polyimides and Their Repeat Unit Structures with the Respective Dielectric Constants Measured at 1 MHz... 

New heterocyclic polymers designed especially for service at elevated temperatures have intriguing properties, some of which are in contrast to properties usually associated with linear noncrystalline polymers. These polymers have sometimes been described as stiff chains because of the long inflexible repeat units of which they are comprised. Relatively few quantitative studies have yet appeared in the dilute solution properties or the viscoelastic behavior of the new heterocyclic polymers—partly because of the difficulties inherent in working with the poorly soluble materials. Some studies on the polyimide with the (idealized) structure ... 

Figure 10.5 Development of the H-bond network in a sulfonated polyimide (homo)polymer made of chains of aromatic and polyaromatic substituted cycles. Three repeat units of a chain are represented. Structure of the dried membrane in the upper drawing, of the membrane in equilibrium with an atmosphere with hygrometry 15% (middle page drawing) and 65% (lower drawing).

Experimental values were obtained from a number of sources. Table 12.1 identifies the structure of repeat units of all the polyimides mentioned in this work. Table 12.2 gives experimental data for dielectric constants obtained with dry... 

The characteristic structural feature of a polyimide is the presence of the phthalimide grouping in the repeat unit, which is represented by the formula... 

The chemistry of polyimides has previously been reported but the repeat unit of polytetrafluoroethylene is based upon the structure... 

The polyester-imides constitute a class of modified polyimide. These are typified by the structure shown in Figure 4.23. Polyether-imides form yet another class of modified polyimide. These are high-performance amorphous thermoplastics based on regular repeating ether and imide linkages. The aromatic imide units provide stiffness, while the ether linkages allow for good melt-flow characteristics and processability. 

Polyimides, Common name of polymers characterized by repeated imide groups in the macromolecule (Fig. 1.4). Their structure corresponds to that of the step-ladder polymers. Thermally stable infusible insoluble thermosets. Their intermediate prepolymers can be shaped. Modified polyimides have repeated, mainly aliphatic, ester or amide groups in the main chain besides the imide units, in order to facilitate processing. Examples of applications high-temperature electric insulating materials... 

As a repeating imide unit, a polyimide has the general structure... 

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