Methyl oxetane, polymerization

The synthesis of AMO involves treatment of 3,3-bis(chloromethyl) oxetane (BCMO) with sodium azide in the DMF medium at 85 °C for 24 h. Similarly, AMMO which is a monofunctional analog of AMO is synthesized by the azidation of chloro/tosylate product of 3-hydroxymethyl-3-methyl oxetane (HyMMO) with sodium azide in DMF medium at elevated temperatures. These energetic monomers are readily polymerized to liquid curable prepolymers with the help of boron trifluoride etherate/l,4-butanediol initiator system and the outlines of synthesis [147-150] of poly(BAMO) [Structure... 

Oxetane polymers containing perfluorinated substituents are also studied. Cationic polymerization of 3,3-bis[(2,2,2-trifluoroethoxy)methyl]oxetane leads to polymers showing oleophobicity that compare favorably with that of more highly fluorinated acrylates. 

Gationic polymerization of oxetane-containing polymeric precursor obtained by anionic polymerization of 3-ethyl-3-[(oxiranylmethoxy)methyl]oxetane led to ladder polymers containing 15-crown-4 units as shown in Scheme 28. 

A few hyperbranched polymers are known in this category. Ring-opening polymerization of 2-hydroxy methyl oxetane under basic conditions gave only low molecular weight polymer [55]. Most of the work in this category of polymers has been concentrated in polybenzyl ether or polyphenylene ethers. 

By using the aluminum porphyrin-Lewis acid system, we attempted the synthesis of a narrow MWD block copolymer from oxetane and methyl methacrylate (MMA). Methacrylic monomers can be polymerized radically and anioni-cally but not cationically, so a block copolymer of oxetane and methyl methacrylate has never been synthesized. As already reported, methacrylic monomers undergo accelerated living anionic polymerization with the (TPP)AlMe (1, X= Me)-3e system via a (porphinato)aluminum enolate as the growing species. 

The degree and type of substitution has much effect on the properties of the polymer, as well as the rate of polymerization. Increasing methyl substitution at position-3 gives a regular increase in the rate of polymerization, and the most useful properties are observed with polymers of 3,3-dialkyloxetanes, with melting points ranging from 50 to nearly 300 °C. The polymers of 3,3-bis(chloromethyl)oxetane ( BCMO ) have been commercial products for many years, known as Penton and Pentaplast (equation 31). 

THF copolymerizes readily with other cyclic ethers such as oxides and oxetanes. The comonomers used include ethylene oxide (67), propylene oxide (99,100), epichlorohydrin (ECH) (101,102), phenyl glycidyl ether (102), 3.3-bis(chloromethyl) oxetane (BCMO) (25, 98, 101, 103) and 3-methyl-3-chloromethyl oxetane (103). Just as in THF homo-polymerization, a large variety of catalysts have veen used. In many cases the kinetics of copolymerization have been studied. Table 22 summarizes the monomer reactivity ratios, rx (THF), and r2 (comonomer) which have... 

The stereoselective synthesis of unsaturated oxetanes has recently been achieved by Feigenbaum and coworkers.Previous studies have indicated that photochemical cis-trans isomerization of enals is rapid and results in the formation of equivalent amounts of stereoisomeric alkene adducts. " For example, irradiation of rran.r-crotonaldehyde and 2,6-dimethylfuran produced a 1 1 mixture of alkenic isomers (174) and (175) in 64% yield. Irradiation of 4-trimethylsilylbutyn-2-one and furan provided with S 1 stereoselectivity the bicyclic oxetane (176) in which the methyl group occupies the exo position, presumably because of the small steric requirement of the triple bond. Desilyation of the protected al-kyne produced an alkynic oxetane which was hydrogenated under Lindlar conditions to bicyclic vinyl-oxetane (177) attempts to use the unprotected butyn-2-one gave low isolated yields of oxetane because of extensive polymerization. The stereochemical outcome thus broadens previous alkynyloxetane syn-theses and makes possible the preparation of new oxetane structures that may be synthetically useful. 

Rose also derived heats of polymerization. The values he obtained were 20.0 kcalmole for polymerization in methyl chloride solution at —20°C and 19.3 kcalmole" for polymerization in a mixture of ethyl chloride and methyl chloride at —9°C. It is at once a bit unfortunate that this elegant piece of work was carried out as early as 1956 before catalysts leading to less complicated kinetics were discovered, and a tribute to Rose s careful work that he was able to sort out the many complications involved. No other detailed kinetic study of the polymerization of oxetane was made until many years later. In 1971 Saegusa et al. [52], reported a kinetic study of the polymerization of oxacyclobutane initiated by a BF3—THF complex. 

Rose [50] also investigated the polymerization of 2-methyl oxacyclo-butane and of 3,3-dimethyloxacyclobutane enough to learn that they followed a course analogous to that of the parent compound. He also found a heat of polymerization at —9°C of 16.1 kcalmole for 3,3-dimethyloxacyclobutane polymerized in a mixture of ethyl chloride and methyl chloride. Again Saegusa et al. [54] have extended the work to clarify the effect on the propagation rate of a methyl substituent at the 3 position of oxetane. They also examined the solvent effects of CH2CI2 and methylcyclohexane for these two substituted monomers. 

The cationic polymerization of thietane is generally accepted to proceed in the same manner as that of the oxetanes. The most detailed study was carried out by Goethals et al. [42] on thietane and methyl thietanes in CH2CI2 with Et3 0 BF4 as initiator. The initiation reaction was immediate and quantitative [68]. For these monomers propagation also occurred by nucleophilic attack of the monomer on the a-carbon of the cyclic sulphonium ion. For example, the propagation reaction for... 

Using relatively similar systems based on quaternary ammonium and quaternary phosphonium halides in conjunction with sterically hindered methyl(diphenoxy)aluminum, anionic coordination polymerization of the less reactive foiu-membered ring oxetane was shown to occur, giving low-dispeisity poly-oxetanes with M up to 17 000 g mol", owing to sttong monomer aaivation by complexation with the aluminum derivatives. 

In addition to the PU-PVdF blend polymer, the crosslink polymer was also used as a polymer matrix. An oxetane-derived monomer with a vinyl group, 3-acryloyloxy-methyl-3 -methyloxetane (AMO) was prepared and copolymerized with MEMO. The CROP of AMO was first carried out, and then the radical polymerization proceeded to give a crosslinked polymer electrolyte film. The mechanical strength was evidently increased with crosslinking, whereas the ion conductivity was decreased with a maximum ion conductivity of 1.4 x lO S/cm at 30 °C and 1.3 x 10 S/cm at 80°C at the ratio of O Li = 20 (Ye et al., 2007b). Although the crosslink is very efficient to raise the mechanical strength of the polymer matrix, it leads to an unacceptable reduction in the ion conductivity. 

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