Reactivity activated acrylates/methacrylates

Osman, R., Namboodiri, K., Weinstein, H. and Rabinowitz, J.R. (1988) Reactivities of acrylic and methacrylic adds in a nudeophilic addition model of their biological activity. J. Am. Chem. Soc., 110, 1701-1707. 

ATRP has been widely applied to the polymerization of styrene [2]. Nonetheless, ATRP owes most of its success to the large compatibility with many different monomers [6d], such as acrylates, methacrylates, (meth)acrylamides and acrylonitrile, which readily made this technique available for the production of several new block copolymers (see Table 6.2). Even though the majority of the work has been done with copper as transition metal, styrene ATRP has been carried out using Fe-, Ru-, Ni-, Pd- and Co-based systems [6d]. Note that ATRP does not require the high reaction temperature typical of NMP and this is also part of the success of this polymerization technique. Different ligands have been used to solubilize the copper atom (see Scheme 3) and it has been noticed that they not only make the copper ready for the reaction but can also modify the reactivity of the metal towards both the activation and deactivation reactions. Actually, the presence in the system of a metal, the need for complex ligands to solubilize them and the deep color typically imparted by this... 

Novel iron carbonyl monomer, r)4-(2,4-hexadien-l-yl acrylate)tricarbonyl-iron, 23, was prepared and both homopolymerized and copolymerized with acrylonitrile, vinyl acetate, styrene, and methyl methacrylate using AIBN initiation in benzene.70,71 72 The reactivity ratios obtained demonstrated that 23 was a more active acrylate than ferrocenylmethyl acrylate, 2. The thermal decomposition of the soluble homopolymer in air at 200°C led to the formation of Fe203 particles within a cross-linked matrix. This monomer raised the glass transition temperatures of the copolymers.70 The T)4-(diene)tricarbonyliron functions of 23 in styrene copolymers were converted in high yields to TT-allyltetracarbonyliron cations in the presence of HBF4 and CO.71 Exposure to nucleophiles gave 1,4-addition products of the diene group.71... 

Reactivity ratios of a number of activated acrylates and methacrylates with different structural monomers are given in Table 2. Polymer compositions produced at low conversions from equimolar monomer fe compositions are also indicated in the Table. These values are back calculated from the reactivity ratios, and are hence equivalent to experimental data. The actual copolymeriz-ability patterns of three comonomer pairs are also shown in Fig. 4. These results show that, among the various monomer pairs, AOTcp with styrene, and AOTcp with 7V-vinylpyrrolidone, produce azotropic copolymers at about equimolar monomer feed compositions. The relatively small reactivity ratios of these two monomer pairs indicate that their equimolar copolymerization produces approximately alternating, rather than random or block, copolymers. 

The copolymers obtained by radical copolymerization of maleic anhydride (MA) with acrylic or vinyl comonomers, and the maleic add copolymers, generally obtained by the hydrolysis of the maleic anhydride copolymers (Figure 10.1), can be called maleic copolymers. They were intensively studied from a theoretical perspective, but also for their applications [1-3]. Copolymers ofMA with electron-donating comonomers, such as styrene, vinyl acetate, N-vinyl pyrrolidone, and methyl vinyl ether, have an alternant structure [ 1 ], but when MA is copolymerized with electron-acceptor comonomers like methyl methacrylate, acrylonitrile, statistic copolymers are obtained [1,2]. MA units from the copolymers are very reactive active agents with amine or hydroxyl groups... 

One way of influencing the way in which the added oligomer is distributed in the final cured produce is to provide reactive sites on the oligomer so that it can be incorporated into the acrylic matrix as it forms. For instance, if the added oligomer contains terminal, active, acrylic, or methacrylic unsaturation, it can be easily incorporated into the growing acrylic polymer chains as the adhesive cures. Then it is unable to precipitate as a separate phase and must remain more or less uniformly distributed throughout the matrix. On the other hand, incompatible... 

Alkyl derivatives of the alkaline-earth metals have also been used to initiate anionic polymerization. Organomagnesium compounds are considerably less active than organolithiums, as a result of the much less polarized metal-carbon bond. They can only initiate polymerization of monomers more reactive than styrene and 1,3-dienes, such as 2- and 4-vinylpyridines, and acrylic and methacrylic esters. Organostrontium and organobarium compounds, possessing more polar metal-carbon bonds, are able to polymerize styrene and 1,3-dienes as well as the more reactive monomers. 

Labelled monomers have been used in co-polymerizations for analysis of the resulting co-polymers and consequent determination of monomer reactivity ratios (15, 16). This technique is of particular value when the compositions of the different monomer units are rather similar or when the co-polymer contains only very small amounts of one of the monomers. These points can be appreciated by considering calculations on co-polymers of methyl methacrylate and methyl acrylate summarized in Table 1. The analyses have been calculated ignoring contributions of end-groups it assumed that the acrylate ester is labelled with carbon-14 and that specific activities are expressed in units such as curies/g of carbon. 

A similar mechanism was proposed when 1,5-dithiocin 838g underwent polymerizations with methyl methacrylate (MMA) and styrene (STY). The activated double bound of 838g was found to have a profound affect on reactivity. In fact, co-polymerization of 838g with MMA at 70 °C the 5-terminated sulfanyl radicals preferred to undergo homopropagation, while cross-propagation is favored for MMA-terminated radicals. Both monomers possessed an electron-deficient acrylate double bond with similar possibilities for conjugative stabilization of the adduct radical by the ester functionality, which would explain the apparent equal reactivity of the MMA radical to either monomer. 

Substitution of the proton by methyl in acrylic monomers is not accompanied by reduced reactivity of the methylated derivative. Bolshakov et al. have shown that the low rate of, for example, methacrylate or methacrylamide polymerizations at temperatures of 100-120 K in melting ethanol is caused by the low reactivity of the resulting active centres [129],... 

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