Polymerization of Cyclic Compounds

In Section 3 of this chapter it was mentioned that polymers obtained by intermolecular condensation of bifunctional monomers may often be prepared alternatively by an addition polymerization of a cyclic compound having the same composition as the structural unit. Typical examples are shown in Table III. The processes indicated are appropriately regarded as addition polymerizations. Each of these polymers may also be prepared through the condensation of suitable bifunctional monomers. The dimethylsiloxane polymer, for example, may be prepared, as indicated in Table I (p. 45), through the condensation of dimethyl dihydroxysilane formed by hydrolysis of the di-chlorosilane 

The chemical and physical properties of the polymers obtained by these alternate methods are identical, except insofar as they are affected by differences in molecular weight. In order to avoid the confusion which would result if classification of the products were to be based on the method of synthesis actually employed in each case, it has been proposed that the substance be referred to as a condensation polymer in such instances, irrespective of whether a condensation or an addition polymerization process was used in its preparation. The cyclic compound is after all a condensation product of one or more bifunctional compounds, and in this sense the linear polymer obtained from the cyclic intermediate can be regarded as the polymeric derivative of the bifunctional monomer(s). Furthermore, each of the polymers listed in Table III may be degraded to bifunctional monomers differing in composition from the structural unit, although such degradation of polyethylene oxide and the polythioether may be difficult. Apart from the demands of any particular definition, it is clearly desirable to include all of these substances among the condensation 

Monomer type Example Reaction conditions Properties of polymer 

Cyclic anhydride C0(CH2)8C0 [—C0(CH2)sC00—] Heating and/or presence of traces of water Crystalline, m.p. 82°C 

Cyclic thioether (CH2)3=S [ (CH2)3S-]. In dry hexane containing HCl at room temperature Crystalline, m.p. 80-100°C 

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Polymerization of cyclic compounds may also occur by ionic mechanisms under the influence of strong acids or bases and in the absence of water and alcohols. Thus, in the presence of a strong acid or electron acceptor (BF3), ethylene oxide may polymerize violently. The mechanism may be the following, where the electron acceptor is represented by the hydrogen ion ... 

Polymerizations of cyclic compounds, particularly those involving six- or seven-membered rings, frequently are reversible (see Chap. III). 

Here, lipase-catalyzed ring-opening polymerization of cyclic compounds giving polymers other than polyesters is described. l,3-Dioxan-2-one, six-membered cyclic carbonate, was polymerized in the presence of lipase catalysts (Fig. 13)... 

Cationic polymerization of cyclic compounds containing trivalent phosphorus atom has also been reported. Monomers include cyclic phoshites (a) [223,224], phosphonites (b) [225-227], and deoxophosphones (c) [228] ... 

Tsonis and Farona found Re(CO)sCl/EtAlCl2 active at 110°C for homo-polymerization of cyclic compounds containing 5-, 6-, 7-, and 8-membered rings to low-molecular-weight totally saturated materials (ring systems preserved). The initial active form of the catalyst is [(CO)4Re=CHEt ], the same as for the metathesis of internal and terminal olefins." ... 

The overall process of ring-opening polymerization of cyclic compounds can be schematically represented by the reaction ... 

Ring-opening polymerization (ROP) encompasses polymerization of cyclic compounds (monomers) with at least one heteroatom or a double bond in the molecules. Polymerization of the latter proceeds by the metathesis mechanism and is called ring-opening metathesis polymerization (ROMP). It has become customary to use the expression ROP mostly for heterocyclic monomers. Both processes belong to the larger family of chain polymerizations. In this volume of Polymer Science A Comprehensive Reference there are a few chapters that do not entirely belong to ROP. 

Steady-State-Living Chain Polymerization of Cyclic Compounds Identical Reactivities of Ions and Ion Pairs 13... 

Anionic polymerization of cyclic compounds may also belong to the first category of the steady state, namely, with invariant concentration of the active species and sufficiently high rate of initiation. The polymerization of ethylene oxide has already been known for a long time, and similar approaches (and... 

The key initiation step in cationic polymerization of alkenes is the formation of a carbocationic intermediate, which can then interact with excess monomer to start propagation. We studied in some detail the initiation of cationic polymerization under superacidic, stable ion conditions. Carbocations also play a key role, as I found not only in the acid-catalyzed polymerization of alkenes but also in the polycondensation of arenes as well as in the ring opening polymerization of cyclic ethers, sulfides, and nitrogen compounds. Superacidic oxidative condensation of alkanes can even be achieved, including that of methane, as can the co-condensation of alkanes and alkenes. 

Consequently, many reports on pyrazolylborate-zinc compounds have dealt with the modification of the classical tris(pyrazolyl)borate design to better mimic specific enzyme sites,161 or to improve the performance parameters of organozinc catalysts for the polymerization of cyclic esters. This was done by ... 

Studies on the cationic polymerization of cyclic ethers, cyclic formals, lactones and other heterocyclic compounds have proliferated so greatly in the last few years that a detailed review of the evidence concerning participation of oxonium and analogous ions in these reactions cannot be given here. Suffice it to say that there is firm evidence for a few, and circumstantial evidence for many such systems, that the reactive species are indeed ions and there appears to be no evidence to the contrary. A few systems will be discussed in sub-sections 3.2 and 4.4. 

In their papers Rodionov and coworkers described the polymerization of organolithium compounds in terms of the formation of lithium bonds (Scheme 1), analogous to hydrogen bonds, which brought about cyclic or linear association of these compounds in solution . However, the strong association of alkyllithium compounds, persisting even in the vapour phase, indicates that their association takes place through the formation of... 

In polymerizations of unsaturated compounds with Lewis acids the required reaction temperatures are below room temperature, down to -100 °C or even lower (see Example 3-16). On the other hand, cyclic monomers (see Sect. 3.2.3) frequently require higher temperatures. 

Cesium hydroxide is used as electrolyte in alkahne storage batteries. Other apphcations of this compound involve catalytic use in polymerization of cyclic siloxane and treatment of hazardous wastes. 

Y.C. Jang and H.K. Sung, Method for preparing a homo-and co-poly-mers by polymerization of cyclic olefin compounds using fluorine-containing aromatic hydrocarbon compound as catalyst activator, US Patent 6998450, assigned to Korea Kumho Petrochemical Co., Ltd. (Seoul, KR), February 14,2006. 

Heinze et al. found that DMSO in combination with tetrabutylammonium fluoride trihydrate dissolved cellulose (degree of polymerization < 650) within 15 min at room temperature [38]. They also demonstrated that homogeneous esterification of cellulose is possible in this solvent system. The applicability of this new solvent system to cellulose grafting has recently been proved by adoption of cyclic compounds such as lactones and N-carboxy a-amino acid anhydrides (NCAs) [39]. e-Caprolactone was facilely graft-polymerized on cellulose at a graft rate of 65% (per trunk weight of 100), and NCAs at over 100%, in the respective homogeneous reaction systems at < 60 °C. 

LPEI is obtained by cationic polymerization of cyclic iminoethers as oxazoline and oxazine derivatives producing a linear low-molecular compound with a high crystallinity [6-20]. 

Table 5-3. Examples of cyclic compounds that undergo ring-opening polymerization.

It is well known that cyano derivatives of anthracene form charge transfer (CT) complexes with certain aromatic compounds. It was reported [67] that the radical cations formed upon irradiation of these complexes played an important role in initiation of cationic polymerization of cyclic ethers. Pyridinium salts were also found [68] to form CT complexes with hexamethyl benzene and trimethoxy benzene which result in the formation of a new absorption band at longer wavelengths where both donor and acceptor molecules have no absorption. This way the light sensitivity of the pyridinium salts may be extended towards the visible range. According to the results obtained from the... 

Covalent compounds, which are strong alkylating or acylating agents may initiate the cationic polymerization of heterocycles. Again, as in the case of acids, classification of these agents is relative for example, alkyl bromide will efficiently alkylate strongly nucleophilic monomers like cyclic amines or oxazolines and thus initiate their polymerization whereas it will be uneffective in the polymerization of cyclic ethers. 

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