1 -Substituted polymers from

The improvement in the solubility of the polyimides showed a similar tendency to that of the corresponding polyamides. For example, 2,5-di-f-butyl substituent in polymer backbone was too symmetrical for the solubility to be superior to that of /-butyl-substituted polymers From the solubility behaviors of the polyimides, therefore, it could be concluded that the incorporation of bulky pendant groups along the polymer chain gave the most effective enhancement in the solubility of polymers. (Fig. 2.8)... 

Acetylene-substituted Si-N-P compounds, synthesis, 236-237 Activated aluminas, description, 165 Aerogels, definition, 127 Aggregation of fractals, 104,106 Alcohol-substituted polymers from aldehydes and ketones, deprotonation-substitution reactions, 249-250 Alkenylborazine copolymers, quantitative reactivity studies of copolymerization reactions, 394... 

Applications. Among the P—O- and P—N-substituted polymers, the fluoroalkoxy- and aryloxy-substituted polymers have so far shown the greatest commercial promise (14—16). Both poly[bis(2,2,2-trifluoroethoxy)phosphazene] [27290-40-0] and poly(diphenoxyphosphazene) [28212-48-8] are microcrystalline, thermoplastic polymers. However, when the substituent symmetry is dismpted with a randomly placed second substituent of different length, the polymers become amorphous and serve as good elastomers. Following initial development of the fluorophosphazene elastomers by the Firestone Tire and Rubber Co., both the fluoroalkoxy (EYPEL-F) and aryloxy (EYPEL-A) elastomers were manufactured by the Ethyl Corp. in the United States from the mid-1980s until 1993 (see ELASTOLffiRS,SYNTHETic-PHOSPHAZENEs). 

The bulk polycondensation of (10) is normally carried out in evacuated, sealed vessels such as glass ampules or stainless steel Parr reactors, at temperatures between 160 and 220°C for 2—12 d (67). Two monomers with different substituents on each can be cocondensed to yield random copolymers. The by-product sdyl ether is readily removed under reduced pressure, and the polymer purified by precipitation from appropriate solvents. Catalysis of the polycondensation of (10) by phenoxide ion in particular, as well as by other species, has been reported to bring about complete polymerisation in 24—48 h at 150°C (68). Catalysis of the polycondensation of phosphoranimines that are similar to (10), but which yield P—O-substituted polymers (1), has also been described and appears promising for the synthesis of (1) with controlled stmctures (69,70). 

The presence of the L-form of mannose is unusual. The side-chain substitution is randomly distributed (242) approximately two-thirds of the side chains ate rhamnose. The repeat unit may also contain an 0-acyl group, but the distribution of these units has not been completely determined. The polymer is moderately soluble in water but is insoluble in isopropanol solutions, which are used to obtain the polymer from the culture medium. A method for producing a rapidly hydrating form of welan is avaUable (243). 

A number of publications have discussed the characterization of the substituted polymers (4.5,7,8,9). However, because of the poor hydrolytic stability of the chloropolymer, characterization of it has been rather difficult and slow to develop, and the literature is rather scant in this regard (10,ip. Conclusions about the struct are and polymerization mechanism of the chloropolymer have sometimes been drawn from the analysis of the substituted polymers. These conclusions, of course, assume that there is very little, if any, change of the chloropol pier chain structure during the substitution reaction. It was felt that a direct analysis of the chloropolymer may lead to a more accurate understanding of both the polymer structure and the polymerization mechanism. 

All of the soluble polymers (1 and 3-6) give high resolution NMR spectra (1H, 13C, and 31P) that are completely consistent with their proposed structures. As observed for other types of poly(phosphazenes), the 31P chemical shifts of these alkyl/aryl substituted polymers are consistently ca. 15-30 ppm upfield from those of the analogous cyclic trimers and tetramers. Some important structural information is provided by 13C NMR spectroscopy, particularly for the phenyl/alkyl derivatives 3 and 4. These polymers are rare examples of phos-phazenes that contain two different substituents at each phosphorus atom in the chain. Thus, they have the possibility of being stereoregular. The fact that the structures are completely atactic, however, is confirmed by the observation of three doublets in the P-Me region of the 13C NMR spectrum (ca. 22 ppm) in a 1 2 1 intensity ratio. 

The synthesis of luminescent organoboron quinolate polymers (21) (Fig. 15) via a three-step procedure starting from a silylated polystyrene has been communicated. The synthesis was initiated by the highly selective borylation of poly (4-trimethylsilylstyrene) (PS-Si), followed by the replacement of the bromine substituents in poly(4-dibromoborylstyrene) (PS-BBr) with substituted thienyl groups (R = H, 3-hexyl, 5-hexyl). In the final step, the 8-hydroxyquinolato moiety was introduced. The hexyl-substituted polymers efficiently emitted light at 513-514nm upon excitation at 395 nm.40... 

C. Moreau, M. N. Belgacem, and A. Gandini, Recent catalytic advances in the chemistry of substituted furans from carbohydrates and in the ensuing polymers, Top. Catal, 27 (2004) 11-30. 

The interest in using saccharide-substituted polymers to bind and cluster cell surface proteins arises from studies of L-selectin, a protein involved in inflammation. L-selectin binds glycoproteins that display complex carbohydrates, and... 

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