Methacrylic acid, stmcture

Acrylics. Acetone is converted via the intermediate acetone cyanohydrin to the monomer methyl methacrylate (MMA) [80-62-6]. The MMA is polymerized to poly(methyl methacrylate) (PMMA) to make the familiar clear acryUc sheet. PMMA is also used in mol ding and extmsion powders. Hydrolysis of acetone cyanohydrin gives methacrylic acid (MAA), a monomer which goes direcdy into acryUc latexes, carboxylated styrene—butadiene polymers, or ethylene—MAA ionomers. As part of the methacrylic stmcture, acetone is found in the following major end use products acryUc sheet mol ding resins, impact modifiers and processing aids, acryUc film, ABS and polyester resin modifiers, surface coatings, acryUc lacquers, emulsion polymers, petroleum chemicals, and various copolymers (see METHACRYLIC ACID AND DERIVATIVES METHACRYLIC POLYMERS). 

Formulations for acryHc copolymers involve monomers such as acryHc acid [79-10-7], methacrylic acid [79-14 ], or esters of these acids. Formation of a copolymer from a methylmethacrylate ester (3), where DVB serves as the cross-linker, gives the stmctures ... 

Third Monomers. In order to achieve certain property improvements, nitrile mbber producers add a third monomer to the emulsion polymerization process. When methacrylic acid is added to the polymer stmcture, a carboxylated nitrile mbber with greatly enhanced abrasion properties is achieved (9). Carboxylated nitrile mbber carries the ASTM designation of XNBR. Cross-linking monomers, eg, divinylbenzene or ethylene glycol dimethacrylate, produce precross-linked mbbers with low nerve and die swell. To avoid extraction losses of antioxidant as a result of contact with fluids duriag service, grades of NBR are available that have utilized a special third monomer that contains an antioxidant moiety (10). FiaaHy, terpolymers prepared from 1,3-butadiene, acrylonitrile, and isoprene are also commercially available. 

In all cases steam is present as the main ballast. The role of steam is to decrease the concentration of isobutane and oxygen in the recycle loop and thus keep the reactant mixture outside the flammability region. Water can be easily separated from the other components of the effluent stream, and also plays a positive role in the catalytic performance of POMs. It is also possible that the presence of water favors the surface reconstruction of the Keggin stmcture, which decomposes during the reaction at high temperature, and also promotes desorption of methacrylic acid, saving it from unselective consecutive reactions. 

Examples of acid modified polyolefins are the copolymers of ethylene with acrylic acid or methacrylic acid. Variations include the partially neutralised acid copolymers with metal ions (ionomers) or terpolymers of ethylene, an acid and an acrylate such as methyl acrylate or isobutyl acrylate. Acid-containing extrudable adhesives are widely used to bond to aluminium foil. Examples of anhydride-modified polyolefins include terpolymers of ethylene, maleic anhydride and acrylates such as ethyl acrylate or butyl acrylate and the anhydride-grafted polyolefins. Some typical applications and stmctures of a variety of multilayer materials with extruded polymer tie-layer adhesives, as described in Du-Pont trade literature, are detailed in Table 16.2. 

Emulsion polymerization requires free-radical polymerizable monomers which form the structure of the polymer. The major monomers used in emulsion polymerization include butadiene, styrene, acrylonitrile, acrylate ester and methacrylate ester monomers, vinyl acetate, acrylic acid and methacrylic acid, and vinyl chloride. All these monomers have a different stmcture and, chemical and physical properties which can be considerable influence on the course of emulsion polymerization. The first classification of emulsion polymerization process is done with respect to the nature of monomers studied up to that time. This classification is based on data for the different solubilities of monomers in water and for the different initial rates of polymerization caused by the monomer solubilities in water. According to this classification, monomers are divided into three groups. The first group includes monomers which have good solubility in water such as acrylonitrile (solubility in water 8%). The second group includes monomers having 1-3 % solubility in water (methyl methacrylate and other acrylates). The third group includes monomers practically insoluble in water (butadiene, isoprene, styrene, vinyl chloride, etc.) [12]. 

Plotted in Figure 13 is the pressure dependence of kp for polymerization of styrene, methyl acrylate (MA), and dodecyl acrylate (DA) as well as for several methacrylic acid esters at 30 °C. The kp value of linear alkyl esters increases in passing from methyl methacrylate (MMA) to dodecyl methacrylate (DMA). The reason behind this trend is seen in the reduced internal friction of the transition state stmcture with DMA, where the dipolar interactions of the carbonyl moieties are better shielded than in case of MMA. ... 

While it is not the focus of this chapter, we wiU provide a brief outline of solvent-mediated stereocontrol for context. Generally, solvent-mediated processes employ bulky fluoroalcohols or other novel solvents to influence the stmcture of the polymer terminus through H-bonding with the pendant side-chains. These processes can enhance the inherent syndiotactic preference of monomers, such as methacrylic acid, JV-vinylpyrroli-... 

Toward this end, the solution behavior of poly(2-(methaciyloyloxy)ethyl phos-phorylcholine)-b-poly(2-(diisopropylamino)ethyl methacrylate) (PMPC-b-PDPA) have been studied by Pearson et al. [7]. The dissociation constant (pKg) for the conjugate acid form of the PDPA block was determined for a number of PMPC-b-PDPA copolymers with varying volume fractions of DPA over a wide range of temperatures. The polymer tends to form aggregates at pH values between 5 and 7.5. However, the size and the stmcture of the aggregates vary with the volume fraction of PDPA and temperature. The obtained data indicate a wide gamut of stmctures which can be formed from a single block copolymer, stmctures that are extended from simple spherical micelles to vesicles and ill-defined supramolecular stmctures (Fig. 2.3). 

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