Cardo structure

Banerjee et al. [60] also prepared fluorinated copoly(arylene ether)s by incorporating different molar ratios of A-phenyl-3,3-( w(4-hydroxyphenyl) phthalimidine (Scheme 2.11) in the polymer structure and studied the Tg. It was observed that with an increase in the amount of phthalimidine moiety, the Tg increased because of the rigid cardo structure. The copolymer with highest bisphenol A content had an EB as high as 45% as a result of the increase in flexi-bilizing isopropylidene units. 

The Tgs (253-284°C) of these polyimides were higher than that of PI-(HQDA-4,4 ODA) (Table 7.12). As aromatic bulky fluorene moieties combined short aromatic jc-conjugation with a cardo structure, the e values of the polyimides were lower without decreasing thermal stability. Asymmetric bulky groups such as fluorene disturb the chain packing and enhance the free volume in the polyimides. However, as internal rotation of the ether bonds is suppressed, the thermal stability of the polyimides does not decrease greatly. 

Detroyer, A., VanderHeyden, Y., Cardo-Broch, S., Garda-Alvarez-Coque, M. C., Massart, D. L Quantitative structure-retention and retention-activity relationships of 3-blocking agents by micellar liquid chromatography. 

These are a special sroup of polymeric materials. The name cardo comes from Latin, which means loop. The polymers contain cyclic structures that may be perpendicular to the aromatic backbones. An example would be a cardo polybenzimidazole ... 

Table 2.2 Names, abbreviations and chemical structures of diamines containing cardo group...

Many kinds of AEMs based on quatemized polymers containing a quaternary ammonium group have been developed and tested in ADAFC, such as polyethersulfone cardo (QPES-C) [205], polyetherketone cardo (QPEK-C) [206], poly (phthalazinone ethersulfone ketone) (QPPESK) [207], poly(arylene ethersulfone) (QPAES) [208-210], QPAES cross-linked with tetraphenylolethane glycidyl ether (QPAES/4EP) [210], poly (arylether oxadiazole) (QPAEO) [211], poly styrene-block-poly (e thy lene-ran-butylene)-block-poly styrene (QSEBS) [212], poly(vinyl alcohol) (QPVA) [213], poly(vinyl chloride) (QPVC) [214], and poly (vinylbenzyl chloride) (QPVBC) [215]. The chemical structures of some of these polymers are shown in Fig. 6.13. 

Much of this work has been done in an attempt to understand the principles that govern the relationship between gas permeability and permselectivity with polymer repeat unit structure because of an interest in developing polymeric membranes that exhibit higher permeability and permselectivity simultaneously. The cardo group, bulky pendant groups, kinks, and bends in the polymeric structures inhibit the close packing, which, in turn, increases the FFV and rigidity simultaneously and improves the processability, permeability, and permselectivity. 

Banerjee and group have developed a number of fluorinated PAs for the separation of benzene/cyclohexane by PV [11-13]. Several PAs were prepared from fluorinated bis(ether amine)s with different bulky cardo groups. The backbone of the PAs was systematically altered by changing the acid moiety (terephthalic acid, isophthalic acid, and 5-tert butyl-isophthalic acid), and they studied the effect of these structural changes on the PAs PV properties [72]. The values related to benzene/cyclohexane PV are tabulated in Table 4.9. 

Y.F. Yeonga, H. Wanga, K.P. Pramodab, T.S. Chunga, Thermal induced structural rearrangement of cardo-copolybenzoxazole membranes for enhanced gas transport properties, J. Membr. Sci. 397-398 (2012) 51-65. 

Alkaline Membrane Fuel Cells, Membranes, Fig. 3 Chemical structure of (a) quaternary ammonium polysulfone-based anion exchange membrane and (b) polyethersulfone-cardo-based anion exchange membrane... 

TA1 Tager, A.A., Kolmakova, L.K., Bessonov, Yu.S., Salazkin, S.N., and Trofimova, N.M., Effect of the molecular mass and porous structure of cardo polyarylate on the thermodynamic parameters of dissolution (Russ.), Vysokomol. Soedin., Ser. A, 19, 1475, 1977. 

The wholly aromatic processable PAs is achieved by modifying diamines, diacids, or both structures. The modification of the monomers can be broadly categorized in the four pathways to get the processable aromatic PA (i) incorporation of flexible spacers (ii) incorporation of bulky substructures as side substituent, (iii) incorporation of non-linear rigid alicyclic structures and cardo moieties and (iv) incorporation of fluorine as trifluoromethyl or a mixture of thereof. A short discussion on the monomers for the processable PAs has been described below. 

Figure 5.4 Structure of cardo diacid and diamine monomers (a) (from [8]) and (b) (from [9]).

Figure 5.15 Chemical structure of the PAs based on cardo 2,2 -bis (4-carboxyphenoxy)-9,9 -spirobifluorene (from [45]).

As expected, the presence of the isomeric structures has no effect on properties such as glass transition temperature or solubility (d). Both isomers introduce bends into the polymer chain due to a dihedral angle between the phenyl substituent in the 3-position of the indan group and the aromatic ring within the indan system. Also, the indan group can not be viewed as a classic cardo group as introduced by fluorene or phthalein groups. 

Without the introduction of ladder-like moiety induced from benzodioxane, polyimides derived from distorted backbone units have potentials to retain the intrinsic microporosity because the imide linkage itself is formed as very rigid and flat two-dimensional structure. " Similar to Cardo-PIM, these polymers are based on bifluorene units, which have a 90° kink that prevents space-efficient packing or crystallization of the otherwise stiff polymer chains. Weber and Thomas synthesized bi-, tri- and tetra-functional bifluorene and reacted with dianhydride, di(acid chloride) or trimesoyl chloride for contorted polyimide and polyamide. The most microporous polyimide represents the BET surface area of 982 m g , providing much potential for highly permeable gas separation membranes. 

Figure 22.7 Chemical structures of the cardo-type polyimide.

In comparison with the membranes with common aromatic skeletons such as poly-sulfane (PS), poly(ether ether ketone), poly(phthalazinon ether sulfone ketone), poly(etherimide), poly(benzimidazole), poly(phenylene oxide), polysiloxane, poly(oxyethylene) methacrylate, poly(arylene ether sulfone), and polyethersulfone Cardo, which are generally at high price and of complicated synthesis processes, the most important advantages of the aliphatic polymer materials as PEM membranes are their low cost, easy preparation, and simple structure. These aliphatic PEMs are particularly environmentally friendly (e.g., if the quatemization process is proceeded when these aromatic membranes are used for alkaline PEM fuel cells, the synthesis route uses chloromethyl ether for chloromethylation, which is very toxic and carcinogenic). However, the stability of the aliphatic PEMs is not very good. This is probably the biggest challenge when they are used in electrochemical devices. 

The commercial cardo poly(ether ketones) (PEK-C) were selected by Liu et al. to prepare AEMs by usual three-step postmodilication method (Figure 11.8). The final membranes showed ionic conductivity varied from 1.6 to 5.1 mS/cm over the temperature range of 20°C-60°C. Although its ionic conductivity was quite lower compared with other PEEK-based AEMs, the methanol permeability was less than 10" cm% at 30°C in 4 M methanol solutions. Except this way, Zhang and colleagues successfully introduced benzyl chloromethyl groups to the PEK-C matrix via plasma graft polymerization. This approach enables a well preservation in the structure of... 

FIGURE 11.8 Chemical structure of commercial cardo poly(ether ketone) ionomers. 

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