Poly linear, cyclic

The chromatographic conditions specified produced a chromatogram in which, for Uni-dyme-18-dimer acid, there are four broad peaks corresponding to neutrals, monobasic, dibasic, and poly basic components. Each peak represents the elution of many isomers for example, the dibasic peak is composed of linear, cyclic, and aromatic dimer, each in various geometric, structural, and conformational isomeric forms (the peaks are very broad as a result of the presence of these isomers). 

INTRODUCTTON Polymer molecules may have a variety of architectural structures such as linear, ring, star, branched, and ladder chains as well as three-dimensional network structures. The first synthetic cychc jxjlymers to be prepared and characterized were the poly(dimethylsiloxanes) (PDMS), which were reported in 1977. Since that time a number of other cychc pwlymers have been synthesized including cyclic polystyrene, cyclic poly(phenyhnethylsiloxane), cyclic poly(2-vinylpyridine), cyclic polybutadiene, and cychc poly(vinyhnethylsiloxane). ... 

Depending on the polyol used, linear, cyclic, or spiro polyacetals are produced. Mixtures of diols may be used to yield random copoly meric poly acetals. 

Structure of Poly-Diox (cyclic vs linear) and Mechanism of Polymerization 45. ... 

The reported molar masses of polyesters obtained by enzymatic catalysis are relatively low, generally below 8000, except for polymers recovered by precipitation.336 This procedure results in the elimination of a soluble fraction consisting of low-molar-mass linear and cyclic oligomers.336 An Mw as high as 46,400 has thus been reported for a poly(tetramethylene decanedioate) obtained... 

The cohesive energy per carbon atom in a poly-yne ring is only 99.1 kcal/mol, clearly lower than the value in Cc. Anticipating a long and complicated route of formation when starting from graphite, in does not seem likely that any of the larger clusters observed experimentally would have a linear or cyclic chain structure. 

Cyclophosphazenes are a fascinating group of inorganic heterocyclic compounds whose chemistry is multi-faceted, well developed and reasonably well understood. They are closely related to the linear poly-phosphazenes this relationship is unlike any other existing between ring-polymer systems. Although cyclic siloxanes and polysiloxanes have a close interrelationship, the number and types of cyclophospha-zene derivatives that are known, together with their exact counterparts in polyphosphazenes, underscore the utility of cyclophosphazenes as models for the more complex polyphosphazenes. The literature on cyclophosphazenes has appeared earlier in the form of books (1,2), chapters of books (3-5), authoritative compilations of data (6,7), and several reviews (8-21). The current literature on this subject is reported annually in the Specialist Periodic Reports published by the Royal Society of chemistry (22). This review deals mostly with chlorocyclo-... 

Quite often in the ring-opening polymerization, the polymer is only the kinetic product and later is transformed to thermodynamically stable cycles. The cationic polymerization of ethylene oxide leads to a mixture of poly(ethylene oxide) and 1,4-dioxane. In the presence of a cationic initiator poly(ethylene oxide) can be almost quantitatively transformed to this cyclic dimer. On the other hand, anionic polymerization is not accompanied by cyclization due to the lower affinity of the alkoxide anion towards linear ethers only strained (and more electrophilic) monomers can react with the anion. 

The broad emission and low-fluorescence quantum yield of PPS suggested a distribution of trapping sites in the Si skeleton, which were also considered responsible for the lower-than-expected conductivity. The far-IR spectrum of PPS suggested the existence of cyclohexasilane rings connected by linear chains.361,362 Subsequent investigations by Irie et al. on the electronic absorption spectra of radical ions of poly(alkylsilyne)s were taken to indicate the presence of various cyclic silicon species, in corroboration of this conclusion.363 The large Stokes shift and broadness of the fluorescence emission indicate a range of fluorophore structures, different from the chromophore structures. This is... 

Synonyms metaphosphoric acid glacial phosphoric acid. Long chain linear or cyclic metaphosphoric acids of formula (HP03)n are also called poly-metaphosporic acids. 

Fig. 7.141. Cyclic voltammogram (semi-infinite-linear diffusion conditions) in the system Ag(poly)/5 x 10 2 M Pb(CI04)2 + 5 x 10 1 M NaCI04+5x10-3 M HCI04 with dEdft = 10 mV s-1 at T = 298 K. (Reprinted from E. Budevski, G Staikov, and W. J. Lorenz, Electrochemical Phase Formation and Growth, p. 49, copyright 1996 John Wiley Sons. Reproduced by permission of John Wiley Sons, Ltd.)...

COCs that contain cyclic poly(ene)s can be functionalized with maleic anhydride. These polymers do not have any gel particles and are completely soluble in decalin at 135°C., indicating that they are of substantially linear form and thus not crosslinked (4). 

---