M. Bednarek et P. Kubisa, COPOLYETHERS WITH CONTROLLED STRUCTURE - MECHANISM OF FORMATION AND MICROSTRUCTURE, Macromolecular symposia, 132, 1998, pp. 349-358
Cationic copolymerization of 3-membered cyclic ethers (oxiranes) with
5-membered cyclic ether (tetrahydrofuran) leads to linear copolyethers
containing significant amount of cyclic fraction. When the copolymeri
zation is conducted in the presence of diols, telechelic copolymers ar
e formed by the process in which oxirane is incorporated into copolyme
r irreversibly by Activated Monomer mechanism, while tetrahydrofuran i
s incorporated reversibly by Active Chain End mechanism. Thus both kin
etic and thermodynamic factors can be used to control the rate of the
incorporation of comonomers. Studies of the kinetics of the competing
reactions leading to formation of copolymer, studies of copolymer micr
ostructure by C-13-NMR and analysis of the composition of the cyclic f
raction, led to the correlation between the copolymer microstructure a
nd the amount of cyclic faction formed. The dependence of the cyclic f
action content on the reaction conditions was therefore explained.