M. Miyamoto et al., CATIONIC RING-OPENING POLYMERIZATION OF (S)-2-ETHOXY-4-ISOPROPYL-5(4H)-OXAZOLONE TO YIELD POLY(N-ETHOXYCARBONYL-L-VALINE), Macromolecules, 30(7), 1997, pp. 1863-1868
A new polypeptide derivative, poly(N-ethoxycarbonyl-L-valine) (2) was
prepared for the first time by the cationic ring-opening polymerizatio
n of (S)-2-ethoxy-4-isopropyl-5(4H)-oxazolone (1). The polymerization
proceeded with a cationic initiator, methyl trifluoromethanesulfonate,
BF(3)OEt(2), or trifluoromethanesulfonic acid, in an aprotic non-nucl
eophilic solvent such as toluene, chloroform, or nitromethane. The mol
ecular weight of the resulting 2 was independent of the feed ratio of
monomer to initiator but depended on the polymerization temperature. T
he number average molecular weight of 2 prepared at -40 degrees C was
11000. The resulting polymer 2 showed high solubility in organic solve
nts, especially in halogenated hydrocarbons.