Acrylate groups, polymerization techniques

Hydrophobic polymers with some hydrophilic groups can be obtained with an emulsion polymerization technique. Suitable monomers are nitrogen-containing acrylics and methacrylics allyl monomers such as dimethylamino-ethyl methacrylate, dimethylaminopropyl methacrylamide, diethylamino-ethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate and nitrogen-containing allyl monomers (e.g., diallylamine and N,N-diallyl-cyclohexylamine) [225,226]. 

Free radical polymerization is a key method used by the polymer chemist to produce a wide range of polymers [21]. It is used for the addition polymerization of vinyl monomers including styrene, vinyl acetate, tetrafluoroethylene, methacrylates, acrylates, (meth)acrylonitrile and (meth)acrylamides, etc. in bulk, solution and aqueous processes. The chemistry is relatively easy to exploit and is tolerant to many fimc-tional groups and impurities. Consequently it is the most studied polymerization technique in ionic liquids. 

Weak-acid, cation exchange resins are prepared by copolymerization of an organic acid or add anhydride and a cross-linking agent. As a rule, acrylic or methacrylic acid is used in combination with divinyl benzene, ethylene dimethacrylate, or similar compounds with at least two vinyl groups. The pearl polymerization technique described above can be used if esters instead of the water-soluble acids are polymerized. The esters are hydrolyzed after polymerization. The final products have ionic contents of 9-10 eq/kg (dry). Resins of this type are Amberlite IRC-50, Duolite CS-101, Permutit H-70, and Wofatit CP-300. 

Acrylic Resins. Low molecular mass acrylic resins (see also Section 2.5) may be obtained by using fairly large amounts of chain-transfer reagents (e.g., thiols). The resultant problems of smell have, however, led to the implementation of new polymerization techniques, such as group-transfer polymerization or dead-end polymerization. Bifunctional (telechelic) polymers [3.38] are obtained and can be used as binders for low-solvent paints. 

Manicurists should be aware of the sensitizing potential of the mono(meth)acrylates and use no-touch techniques for the skin before the acrylates become polymerized (Kanerva et al. 1996). Occupational sensitization has not been commonly reported. Hemmer s group (1996) estimated that only 10-15% of the reported cases of acrylic nail allergy were occupation-ally related, in contrast to dentistry, where most cases are occupational. They postulate that sensitization is not primarily caused by the uncured gel or monomer but by the remaining monomers in the cured plastic nail and the filing dust that is produced when the nail is smoothed or polished . 

In this way, by variation of the length and the composition of the moiety between the (meth)acrylate groups, a large number of linear a,(o diacrylates and dimethacrylates have been synthesized. Crosslinking is achieved by free radical polymerization, by photopolymerization, or by other techniques [72]. 

The use of macromonomers in controlled living polymerization techniques, such as ionic or CRP, is at present the preferred synthesis strategy for the preparation of relatively well-defined graft copolymers. Macromonomers are oligomers fitted with polymerizable end-groups, mainly styrenic or (meth)acrylic, that can copolymerize with monomers to form comb-type graft copolymers with pendent preformed polymer chains. 

One of successfully applied polymerization technique in grafting-from approach is atom transfer radical polymerization ATRP [5]. ATRP can be used for controlled polymerization of many vinyl monomers i.e. acrylates, acrylonitrile or monomers containing different functional groups. Most of them can be polymerized by a traditional radical polymerization, however ATRP allows to obtain polymers with precise value of molecular weight (M ) and polydispersity index (PDI). 

As the main part of the GI-POFs is composed of PMMA, the loss spectrum is nearly the same as that of SI-POF with PMMA core. The attenuation loss of GI-POF with the gel-copolymerization technique at 652 nm is 134 dB/kra Koike s group, Keio University, has used an interfacial-gel-polymerization technique where bro-mobenzene or other chemicals are used as unreactive components instead of vinyl phenyl acetate or vinyl benzoate in the interfacial-gel-copolymerization method. An attenuation loss of 90 dB/km at 572 nm was obtained. MMA-dg was also used as a monomer instead of MMA, and the deuterated polymer core GI-POF was successfully fabricated. Fluorinated acrylate monomer was also used to fabricate moisture-resistant GI-POF. Attenuation losses of 113 and 155 dB/km at 780 nm wavelength were obtained for deuterated and fluorinated POFs, respectively. These POFs are Oj pected to serve as the signal transmission medium with high information capacities in local area network systems. However, this GI-POF has not been commercially available so far because of the fabrication difficulty of the technique in a mass production level with reasonable attenuation loss and fabrication cost. 

Chloride-capped poly(iso-butylene) (PIB) prepared via cationic polymerization was also used as macroinitiator for the copper-catalyzed radical polymerization of acrylates, methacrylates and St [140-143]. The C-Cl moiety at the end of the PIB chain cannot initiate living radical polymerization due to its lower activity for redox reactions, but it can be modified into an active form by inserting several units of St. Since the cross-reaction from the living PIB chain to St is a relatively rapid process, it is possible to add only a few St units to the PIB chain [144]. The resulting 1-chloro-l-phenylethyl end groups are potential initiating sites for ATRP of many vinyl monomers, leading to a variety of new block copolymers, such as CLB-23 (see Scheme 3.33), [140,142] which cannot be prepared by any direct polymerization techniques, because isobutylene can be polymerized only by cationic polymerization. 

Polymerization of methacrylates is also possible via what is known as group-transfer polymerization. Although only limited commercial use has been made of this technique, it does provide a route to block copolymers that is not available from ordinary free-radical polymerizations. In a prototypical group-transfer polymerization the fluoride-ion-catalyzed reaction of a methacrylate (or acrylate) in the presence of a silyl ketene acetal gives a high molecular weight polymer (45—50). 

Group-Transfer Polymerization. Du Pont has patented (29) a technique known as group-transfer polymerization and appHed it primarily to the polymerization of acrylates and methacrylates. It is mechanistically similar to anionic polymerization, giving living chains, except that chain transfer can occur (30). 

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