Polymerization of Dioxolane

The unexpected variety found in cationic polymerizations is well illustrated by recent findings concerning the polymerization of dioxolan by perchloric acid. Gresham91 had been unable to find end-groups in polydioxolans made under anhydrous conditions and concluded that they were cyclic. His result has been confirmed by studies made with anhydrous perchloric acid as catalyst [92]. Since it is extremely unlikely that complete absence of chain ends can be achieved by a cyclization of long chains, and from other evidence, we concluded that the polymerization takes place without formation of chain ends, i.e. by a ring expansion mechanism ... 

The formation of cyclic oligomers in the polymerization of tetrahydrofuran has not been observed (23). In the case of 1,3-dioxolane small amounts of oligomers going from dimer to nonamer have been isolated (24). Under the influence of borontrifluo-ride etherate in methylene chloride at 35 °C small amounts of 1,3,5-trioxepane are formed (25). Miki, Higashimura and Okamura (25) ascribed the formation of this substance to a backbiting reaction in the polymerization of dioxolane ... 

The polymerization of dioxolane remains tire.subject of discussion. Most authors believe that its propagation does not differ from the common model, which in a simple form can be written as (without ilv o umer-ion) [313]... 

W., Mikes, F., Guo, Y, Koike, Y, and Okamoto, Y. (2004) Free-radical polymerization of dioxolane and dioxane derivatives effect of fluorine substituents on the ring opening polymerization. J. Polym. Sci., Part A Polym. Chem., 42, 5180. 

Kubisa and Penczek measured the ratio of secondary and tertiary oxonium ions in the polymerization of dioxolane by CF3SO3H and found that it varied with both the concentration of reagents and with conversion. The use of the kinetic isotope effect to determine the structure of active centres in the polymerization of heterocycles was described. " Bucquoye and Goethals discuss the mechan- D. J. Sikkema and H. AngadOaur, Makmmol. Chern-, 1980,181,22S9. 

In the previous paragraph we discussed polymerization of 1,3-dioxolans substituted at and C, Information on the polymerization of dioxolans substituted at C2 is very limited we shall confine ourselves to the polymerization of 2-vinyl-dioxolans and 2-vinyl--dioxans. 

Tabic 4.5 Extent of Ring-opening During Polymerizations of 2-Methylene-l,3-dioxolane and Related Species... 

If, however, radicals add preferentially to the vinyl group of 48, ring-opening polymerization w-ould give the polymer with in-chain double bonds specifically via resonance structure 49 (Scheme 4.31). Thus, the two pathways are readily distinguishable. No other ring-opening polymerizations of vinyl dioxolane derivatives appear to have been reported to date. 

Table 4.6 Extent of Ring-Opening During Polymerizations of 4-Methylene-1,3-dioxolane and 2-Methylene-1,4-dioxane Derivatives...

The monomer 2 can be regarded as a 2,4-disubstituted-1,3-dioxolane, and the thermodynamic parameters for the polymerization may be compared with those for the polymerization of 1,3-dioxolane in methylene chloride21. ... 

The bicyclic acetals 43 and 45 can be regarded as 4,5-disubstituted-l,3-dioxolanes. In connection with their pdymerizabilities, it is interesting to note here that cis-4,5-dimethyl-l,3-dioxolane has a slightly greater tendency to polymerize than its trans-counterpart22, 37. The polymerization of 45 is an equilibrium reaction and the system is completely reversible. From the temperature dependence of the equilibrium... 

Fig. 56. Dependence of Mwof the microgels on the polymer yield in the anionic polymerization of EDMA in toluene by n-BuLi [254] (see Figure 53 caption for the reaction conditions). Reduced viscosity vs concentration of microgels a) Composition (mol %) N,N -methyl-enebisacrylamide (55%), methacrylamide (33%), methacrylic acid (2%), methacrylamido acetaldehyd-dimethylacetal (10%),measured at 20 °C in water, b) Composition (mol %) 1,4-DVB (35%), propenic acid amide-2-methyl-N-(4-methyl-2-butyl-l,3-dioxolane prepared by emulsion copolymerization and measured in dimethylformamide.

Studies on the polymerization of various 4-methylene-l,3-dioxolans [94] by BF3Et20 or A1C13 showed that 4-methylene-l,3-dioxolan itself polymerises mainly through the double bond the 2-methyl and 2,2-dimethyl compounds gave polymers with a variable carbonyl content. This arises from a co-polymerization in which units of type (VII) and (VIII) are incorporated in the chain in different proportions, according to the reaction conditions ... 

Co-polymerizations and homo-polymerizations of monomers such as dienes or 4-methylene dioxolan, in which two or more types of ion may propagate simultaneously, are further examples of enieidic polymerizations. These dienes, of course, also provide examples of eniedic radical and anionic polymerizations. Indeed the idea of dieidic polymerization has been suggested by several authors in relation to anionic polymerizations it arose from the aggregation in solution of the lithium alkyls [135], and similar phenomena. 

Polymerization of 1,3,5-trioxepane involves more complicated propagation-depropagation equilibria. The initially formed oxycarbocation XX loses formaldehyde to yield oxycarbocation XXI, which in turn loses 1,3-dioxolane to regenerate XX ... 

Polyoxymethylene, also referred to as acetal resin or POM, is obtained either by anionic polymerization of formaldehyde or cationic ring-opening copolymerization of trioxane with a small amount of a cyclic ether or acetal (e.g., ethylene oxide or 1,3-dioxolane) [Cherdron et al., 1988 Dolce and Grates, 1985 Yamasaki et al., 2001]. The properties and uses of POM have been discussed in Sec. 5-6d. 

Finally, it should be mentioned that there exist two other routes for the synthesis of copolymers. First the partial chemical conversion of homopolymers (see Sect. 5.1), for example, the partial hydrolysis of poly(vinyl acetate). Secondly, by homopolymerization of correspondingly built monomers. An example for these macromolecular compounds, sometimes called pseudo-copolymers, is the alternating copolymer of formaldehyde and ethylene oxide synthesized by ringopening polymerization of 1,3-dioxolane. 

A very special type of template polymerization was presented by a group of Japanese scientists. The method used was based on the observation that during radical polymerization of 2,2-diphenyl-4-methylene-l,3-dioxolane, elimination of benzophe-none occurs according to reaction ... 

Research Focus Method for preparing polylactic acid derivatives through the polymerization of o-carboxy anhydrides including (l,3-dioxolane-2,4-diones) using of 4-diaminomethylpyridine as catalyst. 

The polymerization of vinyl-1,3-dioxanes and the properties of polymers derived from them are analogous to what has been observed with the dioxolane monomers (Section... 

Chemicals responsible for odor in some PUR foams were synthesized by polymerization of PO in CH2CL, with BF3(C2H5)20 catalyst (114). The yield was 25% volatile material and 75% polymeric material. The 25% fraction consisted of dimethyidioxane isomers, dioxolane isomers, DPG, TPG, crown ethers, tetramers, pentamers, etc, and 2-ethyl-4,7-dimethyl-1,3,6-trioxacane (acetal of DPG and propionaldehyde). The latter compound is mainly responsible for the musty odor found in some PUR foams. This material is not formed under basic conditions but probably arises during the workup when... 

Benzoic ethers, dioxolane, and sulfur derivatives are photoinitiators which undergo photochemical dissociation reactions into pairs of radicals. The polymerization of vinyl (monomer) into the polymers of the polyvinyl series can be photoinitiated by an ammonium salt of a benzoin ether derivative. In this case the active species is the benzoyl radical (Figure 6.11). 

Solvent effects including 2-methyl-l,3-dioxepane (MDOP), as a solvent, on the propagation kinetics of methyl acrylate (MMA) have been investigated using the PLP-SEC technique (PLP = pulse laser polymerization) <2005MI267>, and the composition of dioxolane-dioxepane copolymers has been studied by IR and differential scanning calorimetry (DSC) <2004PB349>. 

Ring opening polymerization of monocyclic acetals such as 1,3-dioxolane and 1,3-dioxepane has been extensively investigated by several research groups for many years. [6] However, there still remains something to be clarified as to the polymerization mechanisms, particularly the structure of growing species. One of the several reasons that have prevented the elucidation of the polymerization... 

On the basis of kinetic studies on the polymerization of 80 with 1,3-dioxolan-2-ylium ion, an Ac2 mechanism (bimolecular addition on a carbenium ion) has been proposed for this polymerization. This mechanism assumes the bimolecular reaction of the cyclic dioxacarbenium ion with the monomer as the rate-determining step and predicts the preparation step to be nonstereospecific, that is, the formation of a polymer consisting of cis- and frans-2,4-linked 1,3-dioxolane rings. 

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