1,3-Dioxolane, polymers

Andrews JM, Semiyen JA. Equilibrium ring concentrations and the statistical conformations of polymer chains part 7. CycHcs in poly(1,3-dioxolane). Polymer. 1972 13 142-144. 

The most remarkable observation in the series of dioxolane polymers is that some derivatives with relatively bulky substituents show excellent values of up to 185 °C. Considering that the operating temperature of CYTOP-based GI POFs... 

Y, and Okamoto, Y. (2011) Characterization and properties of semicrystalline and amorphous perfluoropolymer poly(perfluoro-2-methylene-l,3-dioxolane). Polym. Adv. Technol, 22 (8), 1272-1277. 

Alamo R, Eaton JG, Guzman J. Crystallization of polyformals. 2. Influence of molecular weight on the morphology and growth rate in poly(l,3-dioxolane). Polymer 1982 23 379. 

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. 

The PGS obtained by Wang and coworkers was a kind of thermoset elastomer with the Young s modulus of 0.282 0.025 MPa, a tensile strain of at least 267 zE 59.4%, and a tensUe strength was at least 0.5 MPa. The mechanical properties of PGS were well consisted with that of some common soft tissues. Although PGS is a thermoset polymer, its prepolymer can be processed into various shapes by solving it in common organic solvents such as 1,3-dioxolane, tetrahydrofuran, isopropanol, ethanol, and iV,M-dimethylformamide. Porous scaffolds can be fabricated by salt leaching. 

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 ... 

A closely related method was used by Jaacks and his collaborators [22] to determine the concentration of tertiary oxonium ions (IV) in the polymerisation of dioxolan. They did this by killing the reaction with EtONa, hydrolysing the polymer and determining the EtOH derived from the killing agent by gas-chromatography ... 

Studies of the kinetics of the polymerisation of 1,3 dioxolan and of the depolymerisation of its polymer by perchloric acid in methylene dichloride have been accompanied by measurements of the electrical conductivity of the reaction mixtures [23]. These have shown that ions are present during the reactions and the evidence strongly suggests that they are essentially concerned in these. This is one of the very few direct demonstrations of the participation of ions. 

Keele Polymer Group, and their PMR-spectrum agreed with that in the literature. What puzzled us was that he could find no end-groups by any of the conventional methods. We were encouraged, however, by a DuPont patent for the preparation of poly-1,3-dioxolan, in which the inventor had recorded that no end-groups could be found in the polymers. This absence of end-groups in our polymers was the principal problem that determined the direction of our researches 70, 72, 73. ... 

The next structural study of polydioxolans of DP ranging from 7 to 70 by Plesch and Westermann [6] confirmed the regular structure of the polymer. It was also shown that when a polydioxolan was formed and then depolymerised in solution by perchloric acid, the only product was monomer. This is apparently in conflict with the findings of Miki, Higashimura, and Okamura [7] who reported that a reaction mixture, in which dioxolan had been polymerised for 3 hours at 35 °C by BF3-Et20, contained 1,3,5-trioxepan, 1,4-dioxane, trioxane, and other compounds. Most probably the difference is at least partly due to the long reaction time and the use of boronfluoride, which is well known to produce more side-reactions than protonic acids. 

The ring expansion mechanism is of course only a special case of the well-known mechanism by which dioxolan reacts with non-cyclic formals e.g., (I) and CH2-(OMe)2 give (MeOCH2OCH2-)2 in this way. It also accounts in a simple manner for the cleanness of the monomer-polymer equilibrium and for the high yields of cyclic dimer (without any detectable linear fragments) which are obtainable from 1,3-dioxane and 1,3-dioxepan [8]. 

The object of the work described was to discriminate between the two principal rival theories concerning the polymerisation of 1,3-dioxacycloalkanes by anhydrous perchloric acid, the Mainz theory and the Keele theory . By means of Jaaks s method for determining tertiary oxonium ions we found that in polymerisations under the driest conditions the concentration of these is negligibly small. This was done with 1,3-dioxolane (1), 4-methyl-l,3-dioxolane (4), and 1,3-dioxepane (5), and the findings are supported by determinations of the content of hydroxy groups of polymers prepared and killed under different conditions. 

Table 2 The content of fert-oxonium ions in polymers of 4-methyl-1,3-dioxolane and 1,3-dioxepane (5) ...

The Polymerisation of 1,3-Dioxolan, Part I, Structure of the Polymer and Thermodynamics of its Formation, P.H. Plesch and P.H. Westermann, Journal of Polymer Science, Part C, 1968, 16, 3837-3843. 

Oligomers from 2-Methyl-l,3-dioxolan, Y. Firat and P.H. Plesch, Journal of Polymer Science, Polymer Letters, 1975,13,135-136. 

Cyclic ketene acetals, which have utility as co-polymers with functional groups capable of cross-linking, etc., have been prepared by the elimination of HX from 2-halomethyl-l,3-dioxolanes. Milder conditions are used under phase-transfer conditions, compared with traditional procedures, which require a strong base and high temperatures. Solid liquid elimination reactions frequently use potassium f-butoxide [27], but acceptable yields have been achieved with potassium hydroxide and without loss of any chiral centres. The added dimension of sonication reduces reaction times and improves the yields [28, 29]. Microwave irradiation has also been used in the synthesis of methyleneacetals and dithioacetals [30] and yields are superior to those obtained with sonofication. 

---