A convenient synthesis of α,α′- homo- and α,α′-hetero-bifunctionalized poly(ε-caprolactone)s by ring opening polymerization: The potentially valuable precursors for miktoarm star copolymers

Article abstract of DOI:10.1002/pola.27924

Two new ring opening polymerization (ROP) initiators, namely, (3-allyl-2-(allyloxy)phenyl)methanol and (3-allyl-2-(prop-2-yn-1-yloxy)phenyl)methanol each containing two reactive functionalities viz. allyl, allyloxy and allyl, propargyloxy, respectively, were synthesized from 3-allylsalicyaldehyde as a starting material. Well defined α-allyl, α′-allyloxy and α-allyl, α′-propargyloxy bifunctionalized poly(ε-caprolactone)s with molecular weights in the range 4200-9500 and 3600-10,900 g/mol and molecular weight distributions in the range 1.16-1.18 and 1.15-1.16, respectively, were synthesized by ROP of ε-caprolactone employing these initiators. The presence of α-allyl, α′-allyloxy and α-allyl, α′-propargyloxy functionalities on poly(ε-caprolactone)s was confirmed by FT-IR, ¹H, ¹³C NMR spectroscopy, and MALDI-TOF analysis. The kinetic study of ROP of ε-caprolactone with both the initiators revealed the pseudo first order kinetics with respect to ε-caprolactone consumption and controlled behavior of polymerization reactions. The usefulness of α-allyl, α′-allyloxy functionalities on poly(ε-caprolactone) was demonstrated by performing the thiol-ene reaction with poly(ethylene glycol) thiol to obtain (mPEG)₂-PCL miktoarm star copolymer. α-Allyl, α′-propargyloxy functionalities on poly(ε-caprolactone) were utilized in orthogonal reactions i.e copper catalyzed alkyne-azide click (CuAAC) with azido functionalized poly(N-isopropylacrylamide) followed by thiol-ene reaction with poly(ethylene glycol) thiol to synthesize PCL-PNIPAAm-mPEG miktoarm star terpolymer. The preliminary characterization of A₂B and ABC miktoarm star copolymers was carried out by ¹H NMR spectroscopy and gel permeation chromatography (GPC).