Large rings structure

The large ring structure in the main chain gives this material a high Tg of +35 °C, and thus it is not rubbery at normal ambient temperatures and requires plasticisation to achieve elastomeric behaviour. 

Amphotericin B (Fungizone), a polyene antifungal drug produced by the actinomycete Streptomyces nodosus, consists of a large ring structure with both hydrophilic... 

It may well be that branched and large ring structures could arise not only from the propagation reaction (scheme (c)), but partly also from the disproportionation reaction (b) which certainly proceeds simultaneously with the propagation. The interaction of a linear amide group with a linear amide anion would generate by disproportionation a branched polymer structure... 

Ring structures of five atoms may occur, or even up to sixteen or more, in which one member of the ring is sometimes oxygen. Large ring structures of this type, such as in cyclohexadecanolide, are de-... 

Isomorphic substitution of cations of a lower valency for Si in the tetrahedral zeolite framework causes large-ring structures to stabilize with respect to dense structures. In small- to medium-pore zeolites, the cations which will have to be introduced in the micropore channels in order to compensate for the negative charge on the zeolite lattice and to maintain charge neutrality will interact with each unfavorably other if the concentration of low-valency cations in the lattice is high. In wide-pore zeolites the repulsion is less moreover, more favorable channel positions may be available than in the more dense zeolites. 

Macrolide A large ring structure with many functional groups. An example is provided... 

Two other antibiotics that destroy membranes, amphotericin B and nystatin, are large ring structures that are used in treating serious systemic fungal infections. These antibiotics... 

Chlorophyll complexes contain porphoryin molecules. These large ring structures have four nitrogen atoms that donate electrons to a metal center and help bind it. For example, take chlorophyll a, illustrated in Figure 17-1. 

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