18-Crown methyl methacrylate

In 1981 we reported (2, 3) the first examples of free radical polymerizations under phase transfer conditions. Utilizing potassium persulfate and a phase transfer catalyst (e.g. a crown ether or quaternary ammonium salt), we found the solution polymerization of acrylic monomers to be much more facile than when common organic-soluble initiators were used. Somewhat earlier, Voronkov and coworkers had reported (4) that the 1 2 potassium persulfate/18-crown-6 complex could be used to polymerize styrene and methyl methacrylate in methanol. These relatively inefficient polymerizations were apparently conducted under homogeneous conditions, although exact details were somewhat unclear. We subsequently described (5) the... 

Takeishi, et. al, have described the redox polymerization of methyl methacrylate in the absence of solvent (6). With 18-crown-6 as the phase transfer catalyst and potassium persulfate/sodiurn bisulfite as the redox couple, polymerization was observed at temperatures <50 C whereas little or no polymerization occurred under these conditions in the absence of bisulfite. Above 55 C, however, polymerization occurred even in the absence of bisulfite. From the limited kinetic data reported (6), one can estimate (13) that the rate of polymerization (Rp) is approximately proportional to the square root of crown concentration (Equation 1) ... 

Racemic modifications may be resolved. There are very few examples of this approach having been employed successfully. The racemic cylic ether (RS)-36, which contains two CH2OCH2CO2H arms attached to the 3 and 3 positions on the axially chiral binaphthyl units, has been resolved (48-50, 93, 94) to optical purity in both its enantiomers by liquid-liquid chromatography using a chiral stationary phase of either (R)- or (S)-valine adsorbed on diatomaceous eaitii. Very recently, the optical resolution of crown ethers (/ S)-37 and (/ 5)-38, incorporating the elements of planar chirality in the form of a rron -doubly bridged ethylene unit, has been achieved (95) by HPLC on (+)-poly(triphenyl-methyl methacrylate). 

Bulk polymerization was also studied briefly (Table II), adapting a technique useful in production of impact styrene (I). Solid polybuta-diene was dissolved in styrene, mixed with acrylonitrile and/or methyl methacrylate, charged into a 12-ounce crown-cap bottle, flushed with nitrogen, and tumbled end-over-end at 42 rpm in a constant-temperature water bath for 16 hours at room temperature, 48 hours at 80 °C, and 48 hours at 90°C, then heated in an oven 24 hours at 110°C and 24 hours at 150°C. ABS polymerization produced a grainy, inhomogeneous, light-... 

Methyl methacrylate phosphonate (24 mmol) and 18-crown-6 (57 mmol) dissolved in 300 ml THF were cooled to -78°C, then treated with 50 ml 0.5 M in toluene potassium hexamethyldisilazide, and stirred 30 minutes. The Step 8 product was added as powder to this mixture and stirred 6 hours at -78°C and then overnight at ambient temperature. The mixture was then diluted with 1.21 EtOAc, washed four times with 500 ml water, dried, and concentrated. The residue consisted of a mixture of 10 g of E/7, 1 10, respectively, isomer mixture, and the Z-isomer isolated after recrystallization in EtOAc. 

Several attempts at the free-radical (benzene, 1% AIBN, 100 h, 55 °C) and anionic (1 4 THF-benzene, n-butyllithium-18-crown-6 complex [16, 17], -78 °C) polymerization of IPTMSK afforded only traces (<2 %) of a viscous product. Free-radical copolymerization of IPTMSK with methyl methacrylate (MM A) (50 mol % MM A, benzene, 0.5% AIBN, 100 h, 45 °C) resulted in a low yield (<10 %) of a copolymer composed mainly of MMA units and, as indicated by the IR (Figure 1C) and NMR data, of largely decomposed IPTMSK units. The presence of IPTMSK during copolymerization with MMA significantly decreased the molecular weight of the resulting copolymer. These results suggest that IPTMSK is incapable of homopolymerization by either a free-radical or an anionic mechanism. 

Figure 1. Index of refraction versus dispersion and optical classification of glasses shaded area indicates region of glass formation M. Plexiglas is a methyl methacrylate Lucite is an acrylic resin. BaF, barium flint BaK, Barium crown Balf, light barium flint BaSF, heavy barium flint BK, borosilicate crown F, flint FK, fluorcrown K, crown KF, crown flint LaF, lanthanum flint LaSF, heavy lanthanum flint LaK, lanthanum crown LF, light flint LLF, very light flint PK, phosphate crown PSK, heavy phosphate crown SF, heavy flint SK, heavy crown, SSK, very heavy crown, TiF, titanium flint.

Zilkha s group also reported a series of papers describing the synthesis of mechanically crosslinked polymer through vinyl polymerization [223-225]. They employed the radical copolymerization of a 32-membered crown ether derivatives having one polymerizable double bond with styrene or methyl methacrylate (Scheme 49). Sufficient chain threading repeatedly took place... 

Alkali metals can dissolve in solvating media such as ethers and amines to form blue solutions of solvated electrons. In the presence of strongly complexing ligands such as crown ethers or cryptands, electrides (complexed alkali cation and electron), or nuclides (complexed alkali cation and alkali metal anion) can be formed as shown in Scheme 7.3 [50]. Nuclides have been shown to react with monomers such as styrene and methyl methacrylate... 

The polymerization of acrylate esters by organomagnesium reagents is best described as pseudo-anionic monomer is complexed to a magnesium atom covalently bonded to carbon. The anionic polymerization of methyl methacrylate in benzene yields the syndiotactic polymer when the initiator is an alkali metal complexed with 18-dicyclohexyl-6-crown. When a solution of methyl methacrylate in toluene is placed below a solution of butyl-lithium in the same solvent at —78 °C so as to avoid any mechanical mixing, the polymer obtained has a higher isotacticity than that observed if the solutions are stirred. ... 

A novel generation of carbanions by two-electron transfer reactions has been extended to reaction of methyl methacrylate with an alkali metal supramolecular complex (K+, crown, K ). Methylenedifluorocyclopropanes (112) have been obtained from (110) via intermediate cyclopropyl anion (111) formed by TBAF-induced C-Si bond cleavage. ... 

Although the reactivity increase caused by crown ethers and cryptands in anionic polymerizations has already found a wide range of application, more details have been reported and a number of questions concerning the type and the behavior of the different species present, both in the initiation and in the propagation steps, have been clarified by, for example, kinetic studies [235], Special polymerization reactions that were effected in the presence of crown compounds are those starting with butadiene, propene, styrene, 2-vinyl pyridine, ethylene oxide, propylene sulfide, isobutylene sulfide, methyl methacrylate, p-propyllactone, or e-caprolactone as monomers and alkali metals as initiators [238-246],... 

Boileau, Kaempf, Schue and coworkers have studied the cryptate mediated anionic addition polymerization of several systems including ethylene oxide [38], propylene sulfide [39-40], isobutylene sulfide [40], isoprene [38], methyl methacrylate [38], hexamethyl trisiloxane [40], e-caprolactone [41], styrene [38, 40, 41], ct-methylstyrene [41], 1,1-diphenylethylene [41] and /3-propiolactone [42]. The polymerization of the latter compound induced by dibenzo-18-crown-6 complexed sodium acetate has also been reported [43]. In general, it was found that the polymer-... 

Morita, M., Tanaka, H., Ishikawa, M., and Matsuda, Y. (1996) Effects of crown ethers on the electrochemical properties of polymeric solid electrolytes consisting of poly (ethylene oxide)-grafted poly (methyl methacrylates). Solid State Ionics, 86-88. 401-+05. 

A number of other chemical modifications of polymers have been performed under phase transfer conditions Including the cleavage of peptides from a solid support in a Merrlfield solid phase synthesis (Ref. 65), and the hydrolysis of methyl methacrylate in the presence of catalysts such as polyethylene glycol or 18-crown-6 (Ref. 66). Hradil and Svec (Ref. 67) have very recently completed a study of the reaction of hydrolyzed copoly(glycldyl methacrylate ethylene dimethacrylate) with propane sultone in the presence of tetrabutyl ammonium hydroxide. While the reaction gave only 25% yield in the absence of catalyst, a drastic improvement to 68% conversion was observed when a phase transfer catalyst was added. 

In an independent study, Voronkov and coworkers have reported the preparation of a 1 2 K2S208/18-crown -6 complex characterized as being soluble in methanol, dimethyl sulfoxide, and dimethylformamide. Results obtained using this complex for the polymerization of styrene and methyl methacrylate (MMA) in methanol at 60 C are listed in Table 6. The obviously reduced efficiency of this sytem as compared with results obtained under our conditions certainly can be traced in part to the use of less reactive monomers. However, we can speculate that the choice of solvent, protic vs aprotic, may play a major role as well. 

With the object to obtain an effective and selective extracting material and also to investigate the dependence of the selectivity in the cation binding on the copolymer composition, we have prepared the methacrylamide derivatives of 15-crown-5 Q) and 18-crown-6 U) and their homopol3nners and copolymers with methyl methacrylate (MMA) with various crown monomer compositions. Cation binding properties of these polymers were evaluated by the extraction of alkali metal picrates into methylene chloride. 

Poly(methyl methacrylate) Polystyrene Polycarbonate Poly(4-methyl-1-pentene) Allyl diglycol carbonate (CR-39 ) Crown glass... 

Long chain alcohol esters have lower softening temperature and lower shrinkage on moulding. Polycyclohexyl methacrylate has refractor index similar to crown glass. The esters are prepared by alcoholysis of methyl ester. 

Some of the polymers slowly change their helicity in solution. A chiral crown ether-potassium ferf-butoxide combined system was reported to cause polymerization of methyl, tert-butyl, and benzyl methacrylate to form isotactic polymers that had high rotation values (164). Detailed scrutiny, however, raised questions about the result (135, 165). At first, in the presence of the initiator, the oligomers exhibit considerable activity, but after removal of the catalyst, the optical activity decreases. This decrease may be attributed to unwinding of the helixes in the chain the helicity could be caused by the anchored catalyst. 

Helix-sense-selective polymerization of methyl, benzyl, and f-butyl methacrylates was attempted by using the complexes of chiral crown ethers, 91 and 92, and that of a chiral diamine 93 with n-BuLi however, these esters seem to be too small to form and maintain helical conformation [138,139], The complexes of BuLi with 58a and 59 failed in producing an optically active, helical polymer in the polymerization of methyl and benzyl methacrylates [104b]. 

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