Synthesis and pH-responsive assembly of methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) with pendant carboxyl groups

ABSTRACT pH‐responsive methoxy poly(ethylene glycol)‐b‐poly(ε‐caprolactone) bearing pendant carboxyl groups mPEG‐b‐P(2‐CCL‐co‐6‐CCL) was synthesized based on our newly monomer benzyloxycarbonylmethly functionalized ε‐caprolactone. Their structure was confirmed by 1H NMR, 13C NMR, and Fourier transform infrared spectrum spectra. In addition, SEC results indicated that the copolymers had a relatively narrow polydispersity. WXRD and DSC demonstrated that the introduction of carboxymethyl groups had significant effect on the crystallinity of the copolymers. Furthermore, the solution behavior of mPEG‐b‐P(2‐CCL‐co‐6‐CCL) has been studied by various methods. The results indicated that mPEG‐b‐P(2‐CCL‐co‐6‐CCL) had a rich pH‐responsive behavior and the micelles could be formed by pH induction, and the mPEG‐b‐P(2‐CCL‐co‐6‐CCL) could existed as unimers, micelles or large aggregates in different pH range accordingly. The mechanism of which was supposed to depend on the counteraction between the hydrophobic interaction from PCL and the ionization of the carboxyl groups along the polymer chain. Moreover, the mPEG‐b‐P(2‐CCL‐co‐6‐CCL) copolymers displayed good biocompatibility according to the preliminary cytotoxicity study. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 188–199 The water‐soluble copolymer methoxy poly(ethylene glycol)‐b‐poly(ε‐caprolactone) bearing pendant carboxyl groups was prepared based on the new benzyloxycarbonylmethyl‐functionalized ε‐caprolactone monomers. The copolymers self‐assembled by pH induction, and existed as unimers, micelles, or large aggregates in a different pH environment due to the counteraction between the hydrophobic interaction from poly‐(ε‐caprolactone) (PCL) and the ionization of the carboxyl groups along the polymer chain. Therefore, carboxyl group‐functionalized mPEG‐b‐PCL may be a promising candidate as a pH‐sensitive drug carrier.