Polybenzoxazoles

Polybenzoxazoles (4.75) are thermally stable polymers, whose possible use under space conditions as a transparent coating aboard spacecraft is restricted by their photodegradability [577]. 

This photodegradability, which results in a loss of optical properties (strong yellow coloration) is due to structural features of benzoxazoles as well to the presence of residual impurities from their synthesis (ketones, esters and amides). 

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Polybenzaylene benzimidazoles (pyrrones) Polybenzoxazoles Thermally stable to 600°C (1112°F) insoluble in common solvents good mechanical properties. Stable in air to 500°C (932°F) insoluble in common solvents except sulfuric acid nonflammable chemical resistant film. 

A direct route to obtain polyimides and polybenzoxazoles without diacid has been explored by using direct carbonylation of an aromatic diiodo compound.100 The reactions were performed in polar aprotic solvent. The cheaper chlorine derivative can be used instead of the iodo one when it is located on a strongly... 

Figure 5.23 Synthesis of polybenzoxazoles by catalytic carbonylation of 4,4 -diiododi-phenylether.

Polybenzoxazole and Polybenzothiazole 5.4.4.1 Formation without Intermediate Isolation... 

Figure 5.47 Synthesis of polybenzoxazole with isolation of polyamide phenol intermediate.

Hydroxyphenylimide, polybenzoxazole synthesis via, 318 Hydroxy-terminated hyperbranched polyesters, 32... 

Poly(2,5-benzophenone), synthesis of, 492 Polybenzothiazole, synthesis of, 314-319 Polybenzoxazoles, synthesis of, 292, 314-319... 

The polymeric intermediate 2209a, derived, e.g., from substituted N,0-bissilyl-ated 4-aminobenzoic acids 2206 b or 2206 c and free or silylated terephthalic acid, affords, on heating to 180-200°C, the fire resistant polybenzoxazole (PBO) 2210 and H2O [20, 21] (Scheme 14.7). O-Silylated 2209b should, likewise, cyclize on heating to give the polymer PBO 2210 with formation of the volatile trimethylsila-... 

Zylon is the registered trademark of Toyobo Corporation for a special polymer of extraordinary strength and thermal stability. Chemically it is polybenzoxazole, consisting of diamino resorcinol and dicatboxylic acids, as terephthalic acid (Scheme 14.1). 

As shown in Figure 1, the onset of decomposition temperature was in this order polybenzoxazole ) 2,4-DIF-PMTAI> 2,4-DIF-PMI. The char yield of these polymers followed the same sequence. It showed that the introduction of more fused heterocyclic rings into the backbone of the polymers enhanced the thermal stability and flame resistance of polymeric materials. 

It was interesting that 2,4-DIF-PMTAI and 2,4-DIF-PMI showed a two-step decomposition. The onset of decomposition at the second step of these two polymers were close to each other. More interesting, they were also close to the onset of decomposition of polybenzoxazole. We have confirmed that the decomposition of these two polymers at 400-550°C resulted in the formation of benzoxazole units on the backbone. ... 

The high thermal stability and flame resistance of polybenzoxazole were due to the resonance stabilization of the aromatic and the heterocyclic structures, were contributed substantially to high bond strength. 

The solubilities of 2,4-DIF-PMI and 2,4-DIF-PMTAI were fairly good in N,N-dimethyl acetamide and N,N-dimethyl foramide. The polybenzoxazole could not be dissolved in any organic solvent and concentrated sulfuric acid could dissolve it. 

Lee JK, Lee TS (2005) Newly synthesized polybenzoxazole derivative with an adjacent hydroxyphenyl ring for optical sensing. J Polym Sci A Polym Chem 43 1397-1403... 

Brian Einsla was born in Wilkes-Barre, PA, in 1978. He earned his Bachelor of Science degree in 2000 in Chemistry at Virginia Polytechnic Institute and State University. He is currently a fourth-year Ph.D. candidate in the Macromolecular Science and Engineering program at VPI SU. His research interests have centered around sulfonated heterocyclic copolymers for fuel cell applications, including polyimides, polybenzoxazoles, and polybenzimidazoles. 

Title Polybenzoxazole Precursor, Photosensitive Resin Composition Using the Same, and Manufacturing Method of Semiconductor Device... 

Research Focus Synthesis of perfluoro polybenzoxazole derivatives for use in semiconductor devices. 

Originality Although the preparation of polybenzoxazole precursors has been an... 

Observations Photosensitive compositions containing polybenzoxazole precursors are... 

TABLE 1. Physical Properties of Selected Polybenzoxazole Films after Curing for 60 minutes at 350°C... 

Additional polybenzoxazole photosensitizers, (I), were prepared by Yamanaka et al. (1) and are discussed. 

Other photosensitive polybenzoxazole resins, (II), were prepared by the authors... 

Nonconjugated polyazomethines, ( ), were prepared by Udea et al. (2) and then converted into polybenzoxazoles by heating from 250 to 400°C for 25 minutes as illustrated in Eq. (1). Polybenzoxazoles were effective as high-performance resins. 

Conjugated polymers incorporated with different heterocyclic moieties were reported. Examples of these conjugated main chains are poly(phenylene vinylene) (10)60 and polybenzoxazole/polybenzthiazole (ll)64 (Scheme 7). In... 

Furthermore, we have extended the high-pressure polycondensation to the synthesis of condensation polymers other than polyimides. A successful example was the high-pressure synthesis of polybenzoxazoles starting from the bis-o-aminophenol (or its hydrochloride) and aliphatic dinitriles (Eq. 8) [35]. The polycondensation readily proceeded under high pressure in a closed reaction vessel with the elimination of the by-product of ammonia (or ammonium chloride). 

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