Cage structure polymers

CLASS Cage structure polymers Dp-carborane siloxanes... 

Hydrophobic interactions of this kind have been assumed to originate because the attempt to dissolve the hydrocarbon component causes the development of cage structures of hydrogen-bonded water molecules around the non-polar solute. This increase in the regularity of the solvent would result in an overall reduction in entropy of the system, and therefore is not favoured. Hydrophobic effects of this kind are significant in solutions of all water-soluble polymers except poly(acrylic acid) and poly(acrylamide), where large heats of solution of the polar groups swamp the effect. 

The decabome cage structure has also been used with some comonomers, specifically diamines, to give relatively high molecular weight polymers. Fibers formed from these chains can be pyrolyzed to give products that consist largely of boron nitride, BN. 

The pentaborane cage structure -B5H9- has been used as a side group in the preparation of vinyl-type polymers, but only of relatively low molecular weight. Pyrolysis of this material gives primarily boron carbide, B4C. 

FIGURE 3. Conversion of a 1D polymer to a cage structure by simple recrystallization. 

Hexamethylenetetramine is a co-polymer (oligomer really such as those we met in Chapter 52) of formaldehyde and ammonia containing six formaldehyde and four ammonia molecules. It has a beautifully symmetrical cage structure belonging to the adamantane series. 

Compared to other carriers and particularly functionalized polymers the stability of the rhodium catalyst in the zeolite medium is far superior presumably due to the stronger Rh-0 bond compared to P-Rh bond in phosphine bound rhodiumCI)dicarbonyl. Also the cage structure of the zeolite almost precluded inner interaction of the active species and therefore their association into inactive compounds. 

Polysilsesquioxanes of general formula R-[SiOj ] n=l are generally prepared by hydrolysis/polycondensation of the corresponding precursors RSiX (X=Q, OR, H). Four basic structures can be envisaged molecular compound with a cage stmcture, polymer with a regular ladder stmcture, polymer with a 3-D disordered structure and lamellar sohd. 

A comparison of similar substitution products such as the methyl and phenyl compounds shows that the four-membered ring seems to be a stronger chromophore than the five- and six-membered rings. In our present knowledge only cyclic systems (and probably also cage structures) seem to be able to form fluorescent polymers in a matrix of oxygen. 

The end product of the MIP production process, in the vast majority of cases, is a fine powder containing a population of vacant binding sites with a small proportion of non-recoverable template trapped deep within the particle matrix. For monolithic polymers binding sites are of two basic types internal and external. External sites are the product of random cleavage of the cage structure of the total 3-dimensional site. Their geometry depends upon the orientation of the cavity constituents relative to the fracture plane. These are believed to contribute only a small amount of the total binding... 

Another type of group studied as a relacement for some of the oxygen backbone atoms is the carborane cage structure [e.g., meta-CBjoHioC-]. Papitti (16) et.al. reported the synthesis of meta S1B2 polymers ... 

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