Monomers as electron acceptors

Every anionically polymerizing monomer has some electrophilic character. 

The ability to accept electrons from donors is particularly pronounced in acrylic acid derivatives [85] its alkyl esters [78, 87, 88], acrylonitrile [88], acrylamide, hydroxylacrylates [85], and further in styrenes substituted with an electronegative atom or group m-nitrostyrene, 2,6-dichlorostyrene [86], / -nitrostyrene [89] bicyclobutane-1-carbonitrile [89] lactones /J-propio-Iactone [85], sulfolactone vinyl ketones [87] unsaturated dicarboxylic acids and their derivatives diethyl fumarate, fumaronitrile [90], ROOC—N— N—COOR [86], cyclic anhydrides of diacids [91 ], particularly maleic anhydride [78, 92] ethylenes substituted with electronegative groups [93, 95] 

These monomers can be copolymerized by a radical mechanism. The unfavourable effect of the 2-substituent is compensated by two 1-substituents strongly stabilizing the electron-deficient transition radical. 

Under certain circumstances, the electron-accepting ability of monomers can be greatly enhanced by their complexation with Lewis acids. 

For example, the reactivity of acrylic and methacrylic acids is considerably changed in the presence of ZnCl2, SnCl4, triethylaluminium, etc. [95, 96] (see Sect. 4.2). 

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