Cyclic polymers poly

Figure 4 compares cyclic voltammograms for a redox polymer (poly-[Fe(5-amino-1,10-phenanthroline)3]3+/2+)91 and p-doping and undoping of a conducting polymer (polypyrrole).92 The voltammogram for the redox... 

Figure 4. (A) Cyclic voltammograms over a range of scan rates for a redox polymer (poly-[Fe 5-amino-1,10-phenanthrotme)3]3+/>)91 and (B) p-doping and undoping of a conducting polymer (polypyrrole) (B). [(A) Reprinted from X. Ren and P. O. Pickup, Strong dependence of the election hopping rate in poly-tris(5-amino-1,10-phenan-throline)iron(HI/II) on the nature of the counter-anion J. Electroanal. Chem. 365, 289-292,1994, with kind permission from Elsevier Sciences S.A.]...

The ruthenium catalyst can be used to catalyze the synthesis of a cyclic poly(octenamer). The catalyst is added to ris-cyclooctene in CH2CI2 solution at 45° C. The intermediate macrocyclic complex undergoes an intramolecular chain transfer to yield the cyclic polymer and regenerate the catalyst. 

Figure 2 shows a d.c. recorder retracing of a typical set of dry air/saturated vapor cycling responses of the optical waveguide coated with the polymer, poly-epichlorohydrin (PEH) and exposed cyclically to benzene vapors. Aside from the clearly detected electrical signals above the dry air baseline reference, their amplitudes appear to show apparent reversibility over the four exposure cycles indicated in the figure. Also, the rise time and decay of these signals are rather symmetric and indicate a film response time of less than one minute. 

Other things that are particularly controlled in condensation polymerization are chain topology and cascade reactivity of monomers. In general condensation polymerization, not only linear polymers but also cyclic polymers can be produced because both ends of the polymer are reactive during polymerization. When cascade reactions selectively occur on a monomer, condensation polymerization proceeds in a way different from general polymerization behavior based on the principle of Carothers and Flory. Thus, in condensation polymerization of AA and BB monomers, if AA monomers successively react with both the functional groups on a BB monomer, a poly-... 

Although rigid-rod poly(p-phenyleneterephthalamide) analogues having alkyl side chains did not contain cyclic polymers, the polycondensation of silylated m-phenylenediamine and aliphatic dicarboxyhc acid chloride afforded cyclic polyamides predominantly (Scheme 49) [187]. Furthermore, cyclic polymers were also produced in polycondensations for polyesters, poly(ether ketone)s, polyimides, and polyurethanes [183]. These examples are the products in polycondensation of AB monomers or in A2 + B2 polycondensations, but cyclization of oligomer and polymer was also confirmed in polycondensation of AB2 monomers [ 188-195] and in A2 + B3 [ 196-202] and A2 + B4 polycondensations [203-206], which afford hyperbranched polymers. 

MALDI-TOF mass spectrometry analysis of poly(methyl acrylate) prepared by the free-radical polymerization of methyl acrylate (MA) in the presence of a cyclic dixanthate under y-ray irradiation revealed that there are at least three distributions, i.e., molecular mass for [ 1-(MA) -H]+ of cyclic polymers, [1-(MA) -THF-H]+, and [1-(MA) -(THF)2-H]+ of linear polymers were observed. The relative content of the cyclic polymers markedly increases at a lower temperature, which may be related to the reduced diffusion rate and the suppressed chain-transfer reaction at the low reaction temperature [39]. 

A cyclic polymer of methyl methacrylate was also synthesized using a het-erotelechelic polymer precursor, although the formation of living polymer of methyl methacrylate is more difficult than that of styrene. Mizawa et al. described the synthesis of heterotelechelic poly(methyl methacrylate) containing a-maleimide-tw-dienyl end groups and its intramolecular cyclization... 

Alternatively, ring closure metathesis reaction is applied to the formation of cyclic polymers, although the main chain does not consist of hydrocarbon. Such a method was reported in the preparation of cyclic poly(THF) as shown in Fig. 33 [112]. Such ring-close metathesis was also applied for a preparation of catenane [113]. 

Fig. 35 Formation of cyclic polymers for the synthesis of cyclic poly(THF)...

Many works on the synthesis of cyclic polymers and block copolymers using kinetically controlled ring-expansion polymerizations of cyclic monomers, such as lactones and lactides with various types of cyclic tin initiators, were reviewed by Kricheldorf [147,148]. Kricheldorfs group continued the synthesis of cyclic polymers, and their recent works have focused on the following. Polycondensations of 4,4/-difluorodiphenylsulfone with tris(4-hydroxy phenyl)ethane were performed in DMSO to give multi-cyclic poly(ether sulfone)s derived from tris(4-hydroxyphenyl)ethane [149]. 

Moreover, lipase-catalyzed reactions of linear and cyclic poly(3-hydroxy-butanoates) were subjected to hydrolysis, transesterification, and intramolecular esterification. A cyclic polymer along with linear polymers was pro-... 

From the analyses of NMR and electron-spray ionization mass (ESI-MS) spectroscopy, the polymers obtained from the polymerization of cyclic disulfides were found to be a cyclic structure [202], The cyclic structure consisting of poly(DT) is assumed to be formed by a backbiting reaction of propagating species [203]. Thermal and mechanical properties of the polymers, and decomposition behaviors of the polymers demonstrate that the polymers obtained from thermal polymerization of cyclic disulfides include a polycatenane structure. From polymerization of cyclic disulfides in the presence of cyclic polyethylene oxide), a polycatenane consisting of two different cyclic polymers was obtained [199]. Thus, poly(DT) contains spatial entanglements of cyclic polymers with each other (a polycatenane structure was presumed) (Fig. 61). 

The five membered cydic 1,3-dioxolane (CHjOCHjCHjO) can be polymerised by a variety of catalysts including sulphuric acid (P7), perchloric acid (98), phosphorus pentachloride (PP) and alkyl aluminium compounds with water as a co-catalyst (100). The effect of the catalyst boron trifluoride diethyl etherate on the polymerisation of 1,3-dioxolane has also been studied and it has been found that equilibrium between monomeric 1,3-dioxolane and poly(l, 3-dioxolane) is set up in both the undiluted polymer and in solution (101-104). Controverf has arisen as to whether the equilibrium is between cyclic monomer and cyclic polymer (98) or between cyclic monomer and chain polymer (104). 

Hogen-Esch et al.172 synthesized a,a -dilithium poly(2-vinylpyridine) by anionic polymerization of 2-vinylpyridine with 1,4-dilithio-l, 1,4,4-tetraphenyl-butane, in THF at —78 °C under inert atmosphere. The cyclization reaction was performed in high dilution by adding 1,4-bis(bromomethyl)benzene (Scheme 83). The main indication for the formation of the cyclic polymers was the significant difference in the Tg value between the cyclic and the linear precursor. 

Kobayashi prepared a novel germanium-containing polymer, poly(germanium enolate), by reaction of a divalent germanium compound, germylene, with a cyclic a, -unsaturated ketone in the presence of a catalytic amount of a lithium compound (Scheme 11.65) [91[. 

An interesting contrast to these results is provided by the Kx values for small cyclics in poly(dimethylsiloxane) equilibrated in solution in diglyme (16,20). In this case, the magnitude of the solvent effect is much smaller than in toluene and, in fact, Kx values for x - 4 and x > 6 are identical within experimental error for an undiluted equilibrate and a diglyme equilibrate containing 134 g dm 3 cyclics and 55 g dm-3 chain polymer (16,20). 

Cooper, D. R. and Semiyen, J. A., Equilibrium ring concentrations and the statistical conformations of polymer chains part 11. Cyclics in poly(etliylene terephtlialate). Polymer, 14, 185 (1973). 

Vasilieva et al. synthesized redox polymers poly[M(SchifQ] (M = Ni, Pd Schiff = tetradentate Schiff bases) with nanowire diameters in the range 20-200 nm using cyclic voltammetry [52]. They demonstrated that nanostructures based on redox polymers have conductivities that are more than an order of magnitude greater than bulk samples of the same polymers. 

In poly(ether sulfone)s that are prepared by polycondensation of silyl-ated 4-terf-butylcatechol and 4,4 -difluorodiphenyl sulfone, macrocyclic polymers were obtained to some extent. The cyclic polymers were detected by means of matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry. 

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