Polymers from non-homopolymerizable monomers

There are many inorganic and organic compounds known which are not able to homopolymerize either with well-known polymerizable monomers or even with o ther non-homopolymerizable compounds. The participation of non-homopolymeri zable comonomers with reactivity ratios close to 0 results in copolymers wi th more or less alternating structure, whereas for a strictly alternating c opolymer, both reactivity ratios must be 0. Binary copolymerizations of non -homopolymerizable and homopolymerizable monomers can give information on t he topochemistry, and also on the kinetics of such processes, as in these c ases the number of propagating steps is remarkably reduced. Up to now, very little is known on the terpolymerization of three non-homop olymerizable comonomers. Experimental investigations have shown that only c ombinations of two monomers with electron donor and one monomer with electr on acceptor properties or vice versa yield terpolymers, whereas from three monomers of similar electronic behavior, no terpolymers are obtained. All s uch terpolyrners are of alternating structure where a donor unit is succeed ed by an acceptor unit. For copolymerizations of two or three non-homopolymerizable monomers, two d ifferent mechanisms must be considered: the so-called complex model postula tes 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 c onstants of the involved donor and acceptor monomer pairs together with a n ew kinetic scheme allow us to distinguish between the simultaneous particip ation of free monomers and complexes in the polymerization process.