Polymerizability oxiranes

A very recent paper by Saegusa, 7) describes a method of synthesizing polyoxyethylene macromonomers bearing a polymerizable heterocycle at the chain end. Here again the method involves initiation of the oxirane polymerization by means of an alcoholate (derived from 2-p-hydroxyphenyl)-oxazoline). As metalation agent butyllithium, was used since lithium alcoholates are not very reactive towards oxirane. Indeed, the macromonomers obtained exhibit very low degrees of polymerization. Deactivation was performed with methyl iodide ... 

The enthalpy of polymerization of 3- and 4-membered rings is so much higher than the entropy factor that substitution does not significantly reduce their polymerizability. Disubstituted oxiranes (e.g., isobutylene oxide) or oxetanes (3,3-dimethyloxetane) still polymerize practically irreversibly. Substitution may prohibit polymerization of 5-membered monomers, however. 

All cationically polymerizable monomers can be potentially used in this process however, the main study has been focused so far on the most reactive oxirane and vinyl ethers [4], Alkoxysilane derivatives - the most common acid-sensitive monomers for the synthesis of siloxane materials through the use of sol-gel methods - were not used extensively. Only a few examples of their application in photo-activated cross-linking can be noted, mainly in co-reaction with oxirane sites [5]. Typically, alkoxysilanes are subjected to an acid- or base-catalyzed process involving hydrolysis of an =SiOR group and then condensation of the formed silanol with another molecule bearing an =SiOH or =SiOR function to give a siloxane linkage [6]. It was of interest to combine the properties of cross-linked silicone materials with the ones provided by sterically overloaded... 

CHLOROMETHYL OXIRANE (106-89-8) C3H5CIO Highly flammable, polymerizable liquid. Forms explosive mixture with air [explosion limits in air (vol %) 3.8 to 21.0 flash point 69°F/21°C 88°F/31 °C autoignition temp 772 F/411 °C Fire Rating 3]. Reacts violently with water. Contact with elevated temperatures, contamination, strong acids, strong bases, metallic halides, aluminum, aluminum chloride iron(III) chloride and other chlorides of iron or zinc can cause explosive polymerization. Violent reaction with aniline, hypochlorite, isopropylamine, potassium ieri-butoxide (ignition), sulfuric acid. Mixtures with trichloroethylene forms explosive dichloroacetylene. Incompatible with aliphatic amines, alkaline earths, alkali... 

The high thermodynamic polymerizability of oxiranes (due to the relatively large ring strain) and the availability of monomers such as ethylene oxide (EO), propylene oxide (PO) or epichlorohydrin (ECH) led to considerable efforts directed toward the preparation of high molecular weight polymers. Both cationic and anionic polymerizations were explored and it soon became clear that for several monomers only anionic polymerization gives high polymers. 

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. 

J.4.2.3 Heterocyclic Monomers A variety of heterocyclic monomers can be polymerized by anionic ring-opening polymerizations. The types of anionically polymerizable heterocyclic monomers include oxiranes (epoxides), thiacyclopropanes, thiacyclobutanes, lactones, lactides, lactams, anhydrides, carbonates, and silicones... 

Both free radical and ionic polymerizations are restricted to certain types of monomers. Many olefinic and acrylic monomers are readily polymerizable by a free radical mechanism, whereas other compounds such as oxiranes (epoxides)... 

Polymerizable nonionic surfactants can be obtained by reacting the poly-oxyethylated oxirane with A. A -diallylamine, acrylic acid, or methacrylic acid as the nucleophile [250]. 

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