Studies on ionic polymerisation

Abstract

The reaction between anionic polystyrene and cationic polyTHF has been examined and shown to result virtually quantitatively in coupling of the two polymers. The reaction has been exploited to prepare AB, ABA and (AB)n block copolymers and g.p.c. analysis
has shown these materials to be free from contamination by homo­polymer.
The reaction between anionic poly(a-methylstyrene) and living polyTHF has also been examined. The efficiency of the coupling reaction was shown to be about 20%, and this efficiency was rela­tively insensitive to the temperature of the reaction. The com­peting reaction was identified as one of 3-proton transfer resulting in a hydrogen-terminated poly(a-methylstyrene) chain and a polyTHF molecule possessing terminal unsaturation. Transformation of the living poly(a-methylstyrene) into a polymeric Grignardreagent before reaction seemed to have no significant effect on the efficiency of the linking process.
No linking was observed on reaction of living polyTHF and
1,1-diphenylethylene anions.
Reaction of pyridine with living polyTHF was found to be quantitative. Possible synthetic and analytical developments arising from this and similar reactions are discussed.
Six four-membered cyclic sulphones were prepared and tested for polymerisation with anionic, cationic and free-radical initiators. No polymerisation was observed.
Sulpholan was incorporated into an alternating copolymer by (a) generating the aa’dianion on reaction with butyl lithium, and (b) subsequently reacting the dicarbanion with various dihalides such as thionyl chloride and hexamethylene dibromide. The co­polymers were found to be thermally unstable at temperatures above *f20K.
Low molecular weight diadducts (the 2,5-diacetyl-sulpholan
and 2,5-dimethane-sulphonyl sulpholan) were prepared for biological testing.
A cationic to anionic transformation which involved reaction of cinnamyl terminated polyTHF (I) with BuLi was studied with
model compound analogues of I to ascertain if the desired product was produced quantitatively. It was found that a mixture of products was obtained when the reaction was carried out in THF.
A kinetic study of the polymerisation of acenaphthylene in nitrobenzene with propionyl and nitronium hexafluoroantimonate initiators was discovered to be first order with respect to monomer concentration and the same k was recorded for both catalyst systems.
A B-proton transfer reaction from the growing end was found to be operating.