Polymers from non-homopolymerizable monomers

Abstract

There are many inorganic and organic compounds known which are not able to homopolymerize either with well-known polymerizable monomers or even with other non-homopolymerizable compounds. The participation of non-homopolymerizable comonomers with reactivity ratios close to 0 results in copolymers with more or less alternating structure, whereas for a strictly alternating copolymer, both reactivity ratios must be 0. Binary copolymerizations of non-homopolymerizable and homopolymerizable monomers can give information on the topochemistry, and also on the kinetics of such processes, as in these cases the number of propagating steps is remarkably reduced. Up to now, very little is known on the terpolymerization of three non-homopolymerizable comonomers. Experimental investigations have shown that only combinations of two monomers with electron donor and one monomer with electron acceptor properties or vice versa yield terpolymers, whereas from three monomers of similar electronic behavior, no terpolymers are obtained. All such terpolymers are of alternating structure where a donor unit is succeeded by an acceptor unit. For copolymerizations of two or three non-homopolymerizable monomers, two different mechanisms must be considered: the so-called complex model postulates the incorporation of donor-acceptor complexes of the monomers into the growing chain, whereas with the terminal or penultimate model the addition of free monomers to growing macroradicals is described. Measurements of the rate of polymerization in combination with determinations of the complex constants of the involved donor and acceptor monomer pairs together with a new kinetic scheme allow us to distinguish between the simultaneous participation of free monomers and complexes in the polymerization process.