A-Cyanoacrylates

Cyanoacrylate adhesives (Super-Glues) are materials which rapidly polymerize at room temperature. The standard monomer for a cyanoacrylate adhesive is ethyl 2-cyanoacrylate [7085-85-0], which readily undergoes anionic polymerization. Very rapid cure of these materials has made them widely used in the electronics industry for speaker magnet mounting, as weU as for wire tacking and other apphcations requiring rapid assembly. Anionic polymerization of a cyanoacrylate adhesive is normally initiated by water. Therefore, atmospheric humidity or the surface moisture content must be at a certain level for polymerization to take place. These adhesives are not cross-linked as are the surface-activated acryhcs. Rather, the cyanoacrylate material is a thermoplastic, and thus, the adhesives typically have poor temperature resistance. 

Only small amounts of nitromethane are used as solvent, but it is used in specialized appHcations such as the solublization of a-cyanoacrylate glue and acryhc polymers. Also, nitromethane is useflil as solvent for single-phase Friedel-Crafts reactions (115). 

Among Michael acceptors that have been shown to react with ketone and ester enolates under kinetic conditions are methyl a-trimethylsilylvinyl ketone,295 methyl a-methylthioacrylate,296 methyl methylthiovinyl sulfoxide,297 and ethyl a-cyanoacrylate.298 Each of these acceptors benefits from a second anion-stabilizing substituent. The latter class of acceptors has been found to be capable of generating contiguous quaternary carbon centers. 

The adhesive marketed under the tradename Superglue contains the monomer methyl a-cyanoacrylate (Fig. 14.5.1). A variety of cyanoacrylates are commercially sold as contact adhesives with the alkyl group -R denoted in Fig. 14.5.2 varying from a methyl group to produce ethyl, isopropyl, allyl, butyl, isobutyl,... 

Figure 14.5.1 The monomer methyl a-cyanoacrylate found in the adhesive marketed under the trademark Superglue. ...

Surprisingly, a-cyanoacrylic acid is reported to react spontaneously with triethylsilane in the absence of any additional acid to give a quantitative yield of the triethylsilyl ester of a-cyanopropionic acid.236 Ethyl a-cyanoacrylate requires the presence of trifluoroacetic acid to undergo reduction to ethyl 2-cyanopropionate.236 Many of these reductions are highly stereoselective. For example, treatment of... 

Michael addition in the absence of any catalytic agent has been reported for dialkyl and diaryl phosphites and thiophosphites with a-cyanoacrylate esters and a-cyanoacrylic acid.444 Yields of the conjugate addition products were moderate to good. The regiochemistry of this process is the opposite of that previously reported for similar additions to ketene acetals, the latter presumably proceeding by initial protonation of the distal olefinic carbon site.445... 

Kolomnikova, G.D., Prichodchenko, D.Y., Petrovskii, P.V., and Gololobov, Y.G., Interaction of a-cyanoacrylic acid and a-cyanoacrylates with dialkyl and diaryl phosphites, Izv. Akad. Nauk, Ser. Khim., 1913, 1992. 

The adhesion was measured by fastening a lead anchor of known area (2,84 cm ) to the coating with a cyanoacrylate adhesive (Loctite 414) and after curing, pulling it off normal to the surface with a Dillon tensile tester. The force to remove the coating was divided by the area of attachment to convert it to a normalized tensile adhesion value. 

Key ingredient Concentration Share of price L-Lysine >95% -5% Diethyl toiuamide 19% -4% Ethanol 27% -3% a-Cyanoacrylate >95% -4%... 

POLY (ETHYL a - CYANOACRYLATE -CO-ETHYL a -CARBOXAMIDO ACRYLATE) (9 1) (FMR-E101 (FUJI CHEMICAL)) CN CONH- I I CH c-CH.-C-2 I I COOC2H5 COOC2H5 2 X 1 05 1.5 54... 

Woodward et al. 20) also investigated the shear strength of animal skin sections glued with a cyanoacrylate adhesive and cut off by a dermatome. Unfortunately, their method is complicated and it is impossible to perform a comparative estimation of the strength of glueing with different cyanoacrylates. 

Vezin, W., and Florence, A. In vitro heterogeneous degradation of poly(re-alkyl a-cyanoacrylates). J. Biomed. Mater. Res. 14 93—106, 1980. 

Different aromatic residues have been substituted for the pyrazine and phenyl groups in 9 in order to undertake a systematic investigation of this type of compound. Nakanishi et al. have examined the solid-state photochemistry of l,4-bis[p-pyridyl-(2)-vinyl]benzene (10), p-phenylenediacrylic acid dimethyl ester (11), diethyl ester (12) and diphenyl ester (13), and p-phenylenedi[a-cyanoacrylic... 

Similarly, zwitterionic tetramethylenes as initiators of anionic polymerization were also observed. For example, methyl a-cyanoacrylate polymerizes via an anionic mechanism in the presence of n-butyl vinyl ether [90]. A Diels-Alder adduct is also formed. In another example, the reaction of isobutyl vinyl ether and nitroethylene leads to an unstable adduct [91], which is capable of initiating the anionic polymerization of excess nitroethylene, and also the cationic polymerization of added VCZ. 

The products essentially are esters of a-cyanoacrylic acid, predominantly methyl and ethyl ... 

The application of UV absorbers, i.e. compounds absorbing the harmful solar radiation, represents an effective solution of the problem (Rabek, 1990). The absorbed radiation is deactivated by intramolecular radiative and radiationless processes. The ideal UV absorber is expected to absorb all terrestrial UV-A and UV-B radiation but no radiation having wavelengths higher than 400 nm. Different classes of commercialized UV absorbers fulfil requirements on effective plastics protection. A group of UV absorbers acting by excited state intramolecular proton transfer (ESIPT) mechanism (Pospfsil and Nespurek, 1997) includes phenolic derivatives of benzophenone (37), various benzotriazoles, such as 38 or 39, and 1,3,5-triazine 40. Non-phenolic UV absorbers are represented by oxamide 41 and a-cyanoacrylate 42. 

Super glue, that instant adhesive used for so many jobs around the house, illustrates ionic chain polymerization beautifully. The glue contains a cyanoacrylate monomer that polymerizes by an anionic mechanism. Even a trace of water or OH group (for example, that found on your skin) causes an extremely rapid polymerization forming a rigid plastic bonded to the surface(s) on which it polymerized. 

More detailed electrostatic interaction in aqueous media between two surfaces grafted with ionic polymer chains was measured with the use of AFM [100]. The AFM tip surface was modified by graft polymerization of a cationic monomer after being coated with a cyanoacrylate polymer. Figure 41 illustrates the plausible scheme employed in the experiment. A... 

Spontaneous 1 1 copolymerization has been noted when sulfur dioxide was bubbled through bicycloheptene at —40°C. (88), when isobutylene was bubbled through methyl a-cyanoacrylate (54), when 1,3-dioxole was mixed with maleic anhydride (17), and when vinylidene cyanide was mixed with styrene (20), the latter reactions at room temperature. None of these monomers undergoes homopolymerization under the same experi-... 

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