Polymerization of anions

Not all monomers are anionically polymerizable. Nevertheless, one can take advantage of the activity of the living ends to introduce reactive end groups at the extremity of homopolymers and then use such end groups to initiate the polymerization of anionically non polymerizable monomers. This method has been applied to the synthesis of copolymers with polyvinyl and polylactone blocks19 and of copolymers with polyvinyl and polypeptide blocks20-2S). One can at last use both anionic and cationic polymerization to prepare block copolymers of tetrahydrofuran with styrene or methylstyrene2. ... 

The polymerization of anions is a special type of irreversible anodic processes. Of these the oxidation of sulphate to persulphate ions has been studied in the deepest detail. In the production of pcrsulphuric acid the yield is increased to a certain limit by a higher concentration of the initial sulphuric acid and an increased current density at the anode of smooth platinum. In too concentrated sulphuric acid the pcrsulphuric acid is already hydrolysed to a considerable extent to monopersulphuric acid (Caro s acid), which then acts as a depolarizer and lowers the required high potential at the anode. Electrolysis of sulphate solutions also gives persulphates and in this reaction the current efficiency will depend on the nature of the cation the efficiency increasing in the order of Na+, K+ and NHj. 

Taking into consideration the above concept, it is intuitively obvious that the simplest way to assess quantitatively acid-base properties of the anhydrous borates is to estimate the dependence of polymerization of anions in the borate structures on the sizes and valences of cations, and also on the ratio (N) of the total number of B03 triangles and BO4 tetrahedra (NB) to the total amount of cations (NM) contained in the borate structural formula N = Nb/Nm. From the crystallochemical point of view it is clear that the increase of the N-ratio increases the anion polymerization and the ratio Nb3+/No2. It leads to a decrease in the oxygen activity coefficient and simultaneously, to more acid properties of these compounds. Also, the value of n = nA/no (nA - number of triangles, - number of tetrahedra) increases (for N < 1), i.e. the ratio of the number of BO3 triangles to BO4 tetrahedra in the structures of compounds increases. 

Polymerization of Anions.—The conversion of thiosulfate to tetra-thionatc, i.e.,... 

Among the cationic initiators examined, only Mel is active for the polymerization. Et30 F4 and MeOTf produced stable phosphonlum salts 2 which did not Induce the polymerization of Anionic and... 

Reaction 17 shows that carboxylate containing polymers have been used to initiate graft polymerizations of anionically polymerizable monomers such as lactones (54). 

The mechanism of the polymerization of anionic polymerization involves the generation of a cyclopentadienyl centered negative ion. The reaction can be terminated by the addition of Me3SiCl (Fig. 8.22). 

Another example of polymerization in self-assembled spherical complexes is related to polymerization of an anionic monomer within the nanocavity of a highly cationic M12L24 coordination sphere with 24 ammonium cations on its interior surface [60]. The highly cationic nanoenvironment of this nanocage was exploited for controlling radical polymerization of anionic sodium p-styrenesulphonates. It was demonstrated that a cationic sphere can have electrostatic interactions with anionic guests and encapsulate them within its cationic interior. 

---