Cyclic compounds polymerization

The kinetics of this type of polymerization are the same as for simple condensation for this reason, the use of the term polycondensation is perhaps more appropriate. Unless kinetic evidence suggests otherwise, polymerizations involving the formation of chain polymers from cyclic compounds, following ring scission, are classed as condensation polymerizations. Some important con-... 

Cyclic and Polymeric Substances Containing Antimony-Antimony Bonds. A number of oiganoantimony compounds containing rings of four, five, or six antimony atoms have been prepared. The first such compound to be adequately characterized, tetrakis-l,2,3,4-/f i-butyltetrastibetane [47191 -73-5], Cj H Sb, was obtained by the interaction of a dialkylstibide and iodine (70) ... 

Acyclic diene molecules are capable of undergoing intramolecular and intermolec-ular reactions in the presence of certain transition metal catalysts molybdenum alkylidene and ruthenium carbene complexes, for example [50, 51]. The intramolecular reaction, called ring-closing olefin metathesis (RCM), affords cyclic compounds, while the intermolecular reaction, called acyclic diene metathesis (ADMET) polymerization, provides oligomers and polymers. Alteration of the dilution of the reaction mixture can to some extent control the intrinsic competition between RCM and ADMET. 

In order to account for the nonvolatility, infusibility, and limited solubility, Leuchs postulated polymerization of the ground type cyclic compound, as indicated by the subscript x in his formula given above. It is now well established that linear polypeptides are produced on decarboxylation of the N-carboxyanhydrides of a-amino acids, and under favorable conditions the chain length may be fairly large. Leuchs favored the view that strained rings, i.e., those of other than five or six... 

The process proceeds through the reaction of pairs of functional groups which combine to yield the urethane interunit linkage. From the standpoint of both the mechanism and the structure type produced, inclusion of this example with the condensation class clearly is desirable. Later in this chapter other examples will be cited of polymers formed by processes which must be regarded as addition polymerizations, but which possess within the polymer chain recurrent functional groups susceptible to hydrolysis. This situation arises most frequently where a cyclic compound consisting of one or more structural units may be converted to a polymer which is nominally identical with one obtained by intermolecular condensation of a bifunctional monomer e.g., lactide may be converted to a linear polymer... 

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... 

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 ... 

A corresponding anionic mechanism in the presence of a strong base (or electron donor) is plausible. Other cyclic compounds may be susceptible to polymerization by similar ionic mechanisms. Inasmuch as the growth step must be extremely rapid, a chain reaction is indicated and classification with vinyl-type addition polymerizations should be appropriate in such cases. 

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

Other cyclic compounds such as the N-carboxyanhydrides of a-amino acids,and lactams may be polymerized similarly with regeneration of an amino group at each step. According to the mechanism postulated, the number of polymer molecules formed should equal the number of initiator molecules (e.g., ROH) introduced, and the average number of monomers per polymer molecule should equal the ratio of monomer consumed to initiator. 

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)... 

Allcock, H. R. (1972). Phosphorus-Nitrogen Compounds. Academic Press, New York. A useful treatment of linear, cyclic, and polymeric phosphorus-nitrogen compounds. 

Our interest in such compounds stems mainly from the possibility that they might be useful precursors to new classes of phosphorus-containing polymers or cyclic oligomers. Functional linkages such as E = NSiMe3 or CR SiMe3 could serve as sites for condensation-polymerization reactions, leading to novel cyclic or polymeric sys terns, ... 

The reaction of C—Li reagents with carbon-carbon double bonds has great technological relevance because it is the basis of the anionic polymerization processes. This reaction also affords convenient synthetic routes to cyclic compounds, when internal addition to an olefinic double bond present in the metallated molecule takes place (e.g. equations 68, 83 and 84). 

Lapienis, G. andS. Penczek, Cyclic Compounds Containing Phosphorus Atoms in the Ring, Chap. 13 in Ring-Opening Polymerization, Vol. 2, K. J. Ivin and T. Saegusa, eds., Elsevier, London, 1984. 

Fluorinated Cyclic Compound, Polymerizable Fluommonomer, Fluoropolymer Polymeric florinated norbomane - and terpolymers are illustrated below. 

Tricoordinated boron compounds (boranes) are coordinatively unsaturated and their chemistry is dominated by reactions in which complexes are formed. These complexes are either neutral molecules (borane complexes), anions (borates) or boron cations. Space limitations mean that little or no attention will be paid to complexes containing several boron atoms and to species of the type L-BH3, [BH,]- and [L2BH2]+ (L = neutral ligand), discussed in detail in several books and reviews. Similarly, little attention will be paid to the plethora of metal borates and the cyclic and polymeric amino- and phosphino-boranes. 

A very important field of polymerization, stereospecific polymerization, was opened in 1955. In this year, Natta and his coworkers (1—3) polymerized a-olefins to crystalline isotactic poly-a-olefins with the Ziegler catalyst, and Pruitt and Baggett (4,5) polymerized dl-propylene oxide to crystalline polypropylene oxide, which was later identified as an isotactic polymer by Price and his coworkers (6,7). Since then, a large number of compounds including both unsaturated and cyclic compounds were polymerized stereospecifically and asymmetrically. Development of the stereospecific polymerization stimulated... 

Cyclic and polymeric phosphazenes will form water-soluble platinum(II) complexes. The compounds contain square planar platinum bonded to the phosphazene via nitrogen.1503-1506... 

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