Synthesis and thermal properties of poly[N-(monomethoxypolyethylene oxide)-4-vinylpyridinium salt]s

A new type of cationic polyelectrolyte with poly(ethylene oxide) (PEO) side-chains has been prepared by the spontaneous polymerization of 4-vinylpyridine in the presence of PEO monotosylates or bromides. This very easy anionic polymerization method gives fully PEO-grafted poly(vinylpyridinium) salts of high molecular weight which are soluble in water and many organic solvents. The synthesis, characterization, and thermal properties of a series of polysalts are presented. Five monomethoxypolyethylene glycols of different molecular weights and functionalized by tosylation or bromination were used in the quaternization-polymerization of 4-vinylpyridine. These polymers present good thermal stability up to 260°C in air and decomposition takes place in two steps with the first dequaternization reaction. The effects of the PEO length and the nature of the counter-ion on the melting and glass transition temperatures have been studied. It is shown that the pyridinium structure reduces the tendency of the grafted PEO chains to crystallize. Moreover, all of these polysalts have low T g's in spite of the rigid backbone and the presence of ionic charges.