Polyimides linear

Synthesis and Properties. Several methods have been suggested to synthesize polyimides. The predominant one involves a two-step condensation reaction between aromatic diamines and aromatic dianhydrides in polar aprotic solvents (2,3). In the first step, a soluble, linear poly(amic acid) results, which in the second step undergoes cyclodehydration, leading to an insoluble and infusible PL Overall yields are generally only 70—80%. 

Synthesis and Properties. In 1972, Du Pont marketed a series of linear aromatic polyimides called NR-150 (105) based on... 

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). 

Nonthermoprocessible Condensation Polyimides. These are obtained from condensation of aromatic dianhydrides with aromatic diamines. They are linear noncross-linked resins but their rigid chain stmcture and strongly hydrogen-bonded character leads to systems which do not melt or soften before decomposition. 

The orientation of the polyimide coating by treatment with linearly polarized light is under investigation.34... 

Linear phosphonitrilic chlorides (LPNCs), silicone fluids and, 22 573 Linear photodiode arrays, 19 153 Linear polyesters, 14 116 Linear polyethylene fibers, 20 398 Linear polyimides, synthesis of, 20 273 Linear polymers, 20 391 25 455 high molecular weight, 23 733 zero-shear viscosity of, 19 839 Linear poly(thioarylene)s, 23 705 Linear PPS, 23 704. See also... 

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

The addition to alkenes normally leads to unstable adducts that lose carbon dioxide under the reaction conditions. The intramolecular cycloaddition of the sydnone (30) takes place at room temperature, however (Equation (5)) and the cycloadduct (31) has been characterized <86HCA927>. The unstable species formed by the loss of carbon dioxide are also azomethine ylides. It is therefore possible for a second 1,3-dipolar addition to take place, as illustrated in Scheme 6 for the reaction of 3-phenylsydnone with Al-phenylmaleimide <86TL317,92JA8414>. This 2 1 addition has been used as the basis of a synthesis of polyimides. Imides of the type (32) were used as the dipolarophiles and their reaction with 3-phenylsydnone gave linear polymers <87MM726>. 

Imide passivated linear devices was determined from I-V characteristics of statistically significant numbers of devices following severe PTHB test (i.e., 15 psi, 120°C, 100% relative hvimidity, and 30 V bias). Two coat (3 p) polyimide passivation provided almost twice the mean time to failure of 1 p thick PSG passivation. Polyimide protection against high humidity (13,14) and Na" " diffusion (15) has been reported previously. 

The most important application for bismaleimide resin is multilayer boards. The development in this area requires resins with low dielectric constants. It is well documented in the literature that fluorine containing linear polyimides show lower dielectric constants vis a vis their non-fluorinated counterparts. Recently, Hitachi Research Laboratory, Japan, reported the thermal and dielectric behaviour of fluorine-containing bismaleimides (29). The chemical structures of the fluorinated BMIs investigated are provided in Fig. 6. The non-fluorinated four aromatic rings containing BMI, 4,4 -bis(p-maleimidophenoxyphenyl) propane, was tested in comparison. 

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... 

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

Since this meta-substituted diamine was much more reactive than OFB, a variety of polyimides could be made, aUowing the synthesis of such structures as PMDA-PFMB, a polyimide with a very low thermal expansion coefficient (CTE) that may provide many advantages for microelectronic fabrication. Linear polyimide structures have generally been found to have low CTEs even when bulky groups were attached to the main chain. 

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