Thermally rearranged polymer

N.A. Belov, Y.A. Nizhegorodova, S. Kim, S.H. Han, Y.P. Yampolskii, Y.M. Lee, Inverse gas chromatographic study of sorption thermodynamics in thermally rearranged polymer based on 2,2-bis(3-amino-4-hydroxyphenyl)-hexa-lluoropropane and 4,4 -hexafluoroisopropyli-dene diphthalic anhydride, Ind. Eng. Chem. Res. 52 (31) (2013) 10467-10475. 

Other organosilicon polymer precursors for ceramics have either been prepared or improved by means of transition metal complex-catalyzed chemistry. For instance, the Nicalon silicon carbide-based ceramic fibers are fabricated from a polycarbosilane that is produced by thermal rearrangement of poly(dimethylsilylene) [18]. The CH3(H)SiCH2 group is the major constituent of this polycarbosilane. 

Imidazole, l,2,5-trimethyl-4-nitro-mass spectra, 5, 359 Imidazole, 1-trimethylsilyl-reactions, 5, 454 with acid chlorides, 5, 391 Imidazole, 1-trimethylstannyl-reactions, 5, 454 Imidazole, 2,4,5-trinitro-reactions, 5, 98 synthesis, 5, 395 Imidazole, 1,2,4-triphenyl-UV spectra, 5, 356 Imidazole, 1,2,5-triphenyl-UV spectra, 5, 356 Imidazole, 2,4,5-triphenyl-chemiluminescence, 5, 381, 406 irradiation, 5, 433 oxidation, 5, 376, 406 photochemical addition reactions, 5, 421 synthesis, 5, 467, 483 UV spectra, 5, 356, 357 Imidazole, 1-trityl-rearrangement, 5, 377 Imidazole, vinyl-Michael addition, 5, 437 polymers, 1, 281 Imidazole, 1-vinyl-reactions, 5, 450 thermal rearrangement, 5, 450 Imidazole, 2-vinyl-oxidation, 5, 437 Imidazole, l-(D-xylofuranosyl)-synthesis, 5, 491 277-Imidazole, 2,2-dialkyl-rearrangement, 5, 422 277-Imidazole, 4,5-dicyano-2,2-dimethyl-synthesis, 5, 472... 

As shown in Fig. 14, PIM-1 and PIM-7 have been found to exhibit substantially higher O /Nj selectivities (a(O2/N2)>3.0) than other polymers of similar permeability [41]. Other thermally rearranged [78] polyimides show excellent CO /CH separation selectivities. These materials were also shown to function as fuel cell membranes when doped with H3PO4 and proton conductivities of 0.15 S cm" were observed at 130°C [78] that is, higher than polybenzimidazole membranes. 

In this coimection, a cryochemical solid-phase synthesis of metal-polymer systems is of special importance. As a result of such a synthesis, metal clusters and organometallic assemblies formed at low temperatures are buried in a polymer environment, which offers possibilities to stabilize and study these products over a large temperature range. This method was first offered and described in reference 10. The thermal rearrangement of the initial low-temperature system is governed by relaxation processes in polymer matrix. In particular, the aggregation of metal atom clusters to form metal nanocrystals in cryochemically produced metal-polymer systems yields new nanocomposite materials with valuable properties. The study of the mechanism of cluster aggregation, which depends on the characteristics of the polymer matrix, will allow the nanocomposite structure to proceed in the needed direction. Thus, it becomes possible to determine the methods of cryochemical synthesis of metal-polymer materials with predetermined properties. 

Cobaltacyclopentadiene polymers undergo thermal rearrangement to the more stable ( /" -cyclobutadiene)cobalt derivatives, and reaction with isocyanates affords new polymers containing 2-pyridone moieties in the polymer backbone (for details, see Chapter 4, Section 4,4.1) [98-100],... 

Figure 15.1 Comparing the CO2/CH4 Robeson upper bound for dense and thermally rearranged (TR) polymer membranes to the carbon membranes/ and the region for industrial applicability was suggested by Hillock et alf (Data for CMS membranes and industrial applicability region added to the original Robeson plot.)...

The thermal rearrangement of a-hydroxyl-PI membranes improves the gas permselectivity properties in comparison to a neat PI. By intro-dueing segments within the polymer that do not undergo thermal rearrangement, the gas separation properties of the thermally rearranged membrane can be modified. PI copolymers based on 4,4 -hexafluoroisopropylidene diphthalic anhydride and diamines 3,3 -dihydroxy-4,4 -diamino-biphenyI with 2,3,5,6-tetramethyI-l,4-phenyIenediamine or 9,9 -bis(4-aminophenyl)fluorene, thermally rearranged into poly(benzoxazole-co-imide), were tested [107]. 

---