Isotactic-specific anionic polymerization of N-isopropylacrylamide with dilithium tetra-tert-butylzincate in the presence of a fluorinated alcohol or Lewis acid

Abstract

The polymerization of N-isopropylacrylamide (NIPAAm) with dilithium tetra-tert-butylzincate (TBZL) has been investigated in toluene at low temperatures in the presence of alkyl and fluorinated alcohols. Of the alcohols examined, 1,1,1,3,3,3-hexafluoro-2-propanol induced isotactic specificity and accelerated the polymerization process, affording the corresponding poly(NIPAAm)s with meso (m) diad contents of 82% in relatively high yields. It is worthy of note that the introduction of a fluorinated alcohol, which is typically used as an inhibitor in conventional anionic polymerization processes, enabled control over the stereospecificity and rate of the anionic polymerization of NIPAAm when TBZL was used as an initiator. Yttrium trifluoromethanesulfonate also induced isotactic specificity in the NIPAAm polymerization process in methanol and gave poly(NIPAAm) with an m diad content of 88% in high yield.