Polymerizability of cyclic ethers

Strain energy and polymerizability of cyclic ethers and sulfides"... 

Problem 8.18 (a) Consider the cationic polymerizability of vinyl ethers, cyclic ethers (like tetrahydrofuran), cyclic acetals (like trioxane), and N-vinyl car-bazole. (b) Why do these monomers not copolymerize cationically with olefins like styrene or isobutene ... 

It has long been accepted that cyclic ethers with more than four-membered rings are, in contrast to epoxides, only cationically polymerizable due to the high basicities of their ether oxygen atoms. The cationic polymerization involves 0-... 

Virtually all known types of cationically polymerizable monomers are polymerized using onium salt photoinitiators. Included among these monomers are epoxides, cyclic ethers, mono and polyfunc-tional vinyl compounds, spiroesters, spirocarbonates and cyclic... 

The use of supercritical fluids to extract the cyclic ethers from the polymerizate is described. In one example it is related that a charge of THF-ethylene oxide polymerizate containing 8% cyclic ethers is contacted in batch continuous mode with propylene at 100 °C and 83 atm. The residual polymerizate contains 2% cyclic ether content. No gas volume is given in this example or in the three other examples with other polymers and copolymers extracted using supercritical ethylene and propylene. Thus, no distribution coefficients can be calculated to determine the potential industrial value of this patent. 

Copelin, H. B. 1981. Method for reducing oligomeric cyclic ether content of a polymerizate. U.S. Patent 4,306,058. 

Coating compositions for this process can contain cyclic ethers, vinyl ether monomers, organosilicone monomers, and a wide variety of mono-, di-, and polyepoxy functional materials. Further modifications to this process include the addition of free radical polymerizable monomers in combination with the cationic polymerizable monomers so that both curing processes may take place at the same time. The photoinitiator systems that generate acid catalyst intermediates also generate free radical intermediates or can be combined with other photosensitizer materials such that both... 

The thermodynamic polymerizability of oxetanes, in regard of their ring strain, is high for unsubstituted oxetane AHp -80kJ/mol ( -20 kcal/mol) 6). Thus oxetanes like oxiranes may be polymerized to complete conversion ([M]e is very low) and in this respect differ considerably from the next group in the homologous series oxolanes (5-membered cyclic ethers), for which an equilibrium character of polymerization is clearly noticeable. 

Like THF, cyclic acetals (e.g., 1,3-dioxolane and 1,3,5-trioxane) are polymerizable only with cationic initiators. The ring-opening polymerization of 1,3,5-trioxane (cyclic trimer of formaldehyde) leads to polyoxymethylenes (see Example 3.24), which have the same chain structure as polyformaldehyde (see Example 3.22). They are thermally unstable unless the semiacetal hydroxy end groups have been protected in a suitable way (see Example 5.7). Like the cyclic ethers, the polymerization of 1,3,5-trioxane proceeds via the addition of an initiator cation to a ring oxygen atom, with the formation of an oxonium ion which is transformed to... 

Small changes in the physical conditions and chemical structure can have a large effect on the polymerizability of a cyclic monomer. Thus, whereas 5-membered cyclic ethers such as tetrahy-drofuran have negative free-energy change and so are polymerizable, the ve-membered cyclic... 

THF as a five-membered cyclic ether is only weakly strained. Substitution decreases thermodynamic polymerizability of heterocyclic monomers thus substituted THFs do not polymerize... 

In order to understand whether this behavior can be ascribed to a more complex mechanism than formerly assumed, the authors studied the polymerization of other THF derivatives and observed elimination of water in all cases. Bednarek and Kubisa suggested a general reinvestigation of the polymerizability problems of five-membered cyclic ethers containing hydroxyl groups since the mechanistic details must still be evaluated to explain these results. 

This compound is not well known till now it was only mentioned in a patent C58). We managed to prepare it in an analogous way to compound /3/ in good yield (46). After careful purification, colourless crystals witH a melting point of 23,5°C are yielded (b.p. 51°C,lo 3 torr H-NMR CCDCI3) S = 4,70(s 2H) 3,73 (s 8H) 3,63 (s 8H). This cyclic formal is also readily polymerizable by several initiators (as e.g. boron trifluoride etherate, tin tetrachloride, trifluoroacetic acid etc.) (59). At the solution polymerization in methylene cHToride ( [mJ = 2-3 Mole/1) at 0 C with trifluoro-methane sulphonic acid (0,5 mole ) waxlike polymers are obtained (molecular weights 20,000 - 30,000), which are easily soluble in water and in organic solvents. 

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