Methyl vinyl ether, polymerization

Health and Safety Factors. Because of their high vapor pressures (methyl vinyl ether is a gas at ambient conditions), the lower vinyl ethers represent a severe fire hazard and must be handled accordingly. Contact with acids can initiate violent polymerization and must be avoided. Although vinyl ethers form peroxides more slowly than saturated ethers, distillation residues must be handled with caution. 

Syn- and anti-orientations are possible and there is evidence that the anti-orientation does not favor orbital overlap such an orientation is favored with larger branched-chain substituents. A C-nmr study found that the TT-electron density on the vinyl P-carbon is lower as the reactivity of the monomer increases (20). Methyl vinyl ether exists almost entirely ia the syn-stmcture, a favorable orbital overlap situation, and MVE for this reason is less reactive to both polymerization and hydrolysis (21). 

Stereoregular Polymerization. Chemists at GAF Corporation were first to suggest that stereoregularity or the lack thereof is responsible for both nontacky and crystalline or tacky and amorphous polymers generated from IBVE with BF2 0(C2H )2, depending on the reaction conditions (22,23). In addition, it was shown that the crystalline polymer is actually isotactic (24). Subsequentiy, the reaction conditions necessary to form such polymers have not only been demonstrated, but the stereoregular polymerization has been extended to other monomers, such as methyl vinyl ether (25,26). 

An alternative technique to NMR spectroscopy is chromatography. The partially functionalized sample is completely fimctionahzed with a group different from the one present, the product carefully de-polymerized, its structure examined with a chromatographic technique. For example, partially substituted CA was further derivatized with methyl vinyl ether, the product hydrolyzed, the monomers produced examined with gas chromatography [241]. HPLC has been advantageously applied for the determination of substitution pattern for CAs with DS 0.8 to 3.0, by employing the same approach, i.e., further derivatization of the partially derivatized polymer with methyl trifluoroacetate, followed by de-polymerization. The results obtained by this technique compared favorably with those obtained by NMR [242]. 

A polymeric composition for reducing fluid loss in drilling muds and well cement compositions is obtained by the free radical-initiated polymerization of a water-soluble vinyl monomer in an aqueous suspension of lignin, modified lignins, lignite, brown coal, and modified brown coal [705,1847]. The vinyl monomers can be methacrylic acid, methacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, vinylacetate, methyl vinyl ether, ethyl vinyl ether, N-methylmethacrylamide, N,N-dimethylmethacrylamide, vinyl sulfonate, and additional AMPS. In this process a grafting process to the coals by chain transfer may occur. 

Quasiliving Polymerization of Methyl Vinyl Ether. Similarly to IBVE polymerization, MVE was polymerized with premixed p-DCC/AgSbF initiating systems in CH2CI2 solvent at -70°C by slow and continuous monomer addition. Polymer yields were vL00% at every reaction time. ... 

Some obscurities. Each of the reactions mentioned has been identified in at least one system, but there are very many obscurities to be cleared up. For example, transfer by methyl vinyl ether, phenyl vinyl ether, vinyl acetate and some of the corresponding polymers in the polymerization of styrene by stannic chloride has been studied, but the mechanism is not at all clear [124]. 

Thus monomers such as isobutylene, styrene, methyl vinyl ether, and isoprene undergo polymerization by cationic initiators. The effect of alkyl groups in facilitating cationic polymerization is weak, and it is only the 1,1-dialkyl alkenes that undergo cationic polymerization. 

Various block copolymers have been synthesized by cationic living polymerization [Kennedy and Ivan, 1992 Kennedy, 1999 Kennedy and Marechal, 1982 Puskas et al., 2001 Sawamoto, 1991, 1996]. AB and ABA block copolymers, where A and B are different vinyl ethers, have been synthesized using HI with either I2 or Znl2. Sequencing is not a problem unless one of the vinyl ethers has a substituent that makes its reactivity quite different. Styrene-methyl vinyl ether block copolymer synthesis requires a specific sequencing and manipulation of the reaction conditions because styrene is less reactive than methyl vinyl ether (MVE) [Ohmura et al., 1994]. Both monomers are polymerized by HCl/SnCLj in the presence of (n-CrikjtiNCI in methylene chloride, but different temperatures are needed. The... 

The relative reactivities of alkyl vinyl ethers have been assessed in a number of chemical reactions and structure/activity correlations made via several NMR studies [for bibliography see Ref. (80)]. From the polymerisation data it appears that steric interaction between the incoming polymeric electrophile and monomer is the major factor controlling reactivity, rather than electronic effects. Vinyl ethers are known to exist in either a planar s-cis or a planar s-trans (or gauche) conformation. Infra-red absorption spectroscopy shows that methyl vinyl ether almost certainly exists largely in the s-cis form at room temperature (106), and it seems most likely that /(-chloroethyl vinyl ether also has an energetically favourable planar s-cis form as a result of a favourable gauche interaction of Cl and O atoms. The other alkyl vinyl ethers studied exist predominantly in either planar... 

In a similar way, methyl 3,3-dimethoxypropanoate can be prepared using trichloroacetyl chloride and methyl vinyl ether as starting materials. However, in this case, using methyl vinyl ether without a stabilizer, it is necessary to perform the reaction in the presence of pyridine otherwise extensive polymerization of the vinyl ether takes place. 

Several polymers were found to fit all or most of the above criteria and were used to prepare the carrier films. Many polymers have been used for this purpose, viz., ethyl cellulose, poly(y-benzyl glutamate), poly(vinyl acetate), cellulose acetate phthalate, and the copolymer of methyl vinyl ether with maleic anhydride. In addition to the base polymers, plasticizers were often needed to impart a suitable degree of flexibility. Plasticizers, which are found to be compatible with polymeric materials include, acetylated monoglycerides, esters of phthalic acid such as dibutyl tartarate, etc. An excipient was usually incorporated into the matrix of the carrier films. The excipients used were water-soluble materials, which are capable of creating channels in the polymer matrix and facilitate diffusion of the drug. PEGs of different molecular weights were used for this purpose. 

The major commercial fluoropolymers are made by homopolymerization of tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE),vinyhdene fluoride (VF2), and vinyl fluoride (VF), or by co-polymerization of these monomers with hexafluoropropylene (HFP), perfluoro(propyl vinyl ether) (PPVE), per-fluoro(methyl vinyl ether) (PMVE), or ethylene. The polymers are formed by free-radical polymerization in water or fluorinated solvents. 

In a synthesis of 3-methylpentane-l, 5-diol (5), a mixture of 4.08 moles of croton-aldehyde, 5.06 moles of methyl vinyl ether, and 1.1 g. of hydroquinone (to inhibit polymerization) is heated in an autoclave at 200° for 12 hrs. to produce the methyl-methoxydihydropyrane (3). This is hydrolyzed to /8-methylgIutaraldehyde (4) by... 

Electron-transfer Initiation. Highly electron-rich monomers like A-vinylcarbazole can be polymerized readily by powerful electron acceptors such as chloranil, tetracyanoethylene, and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ). Recently the killing of polymerizations at low conversion by addition of methanol has shown that the ion radicals initially formed combine to give a zwitterion in the case of DDQ with methyl vinyl ether (Scheme 6), although to what extent this structure is maintained throughout polymerization is not certain. 

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