pH-Responsive diblock copolymers prepared by the dual initiator strategy

Diblock copolymers poly(tetrahydrofuran-b-tert-butyl acrylate) (PTHF-b-PtBA) and poly(tetrahydrofuranb- 1-ethoxyethyl acrylate) (PTHF-b-PEEA) were successfully synthesized by the dual initiator 4-hydroxybutyl-2- bromoisobutyrate (HBBIB). The isobutyrate and alcohol function of HBBIB were used for the atom transfer radical polymerization of tBA ( or EEA) and the living cationic ring-opening polymerization of THF, respectively. Hydrolysis or thermolysis of the aforementioned diblock copolymers results in amphiphilic pH-responsive copolymers PTHF-b-poly( acrylic acid) ( PTHF-b-PAA). Matrix-assisted laser desorption/ ionization time-of-flight (MALDI-TOF) and nuclear magnetic resonance spectroscopy (H-1 NMR) were used to analyze the PTHF macroinitiator, while clear evidence for the formation of well-defined block copolymer structures was obtained by 1H NMR, gel permeation chromatography (GPC), and infrared spectroscopy (FT-IR). The amorphous PtBA block in PTHF-b-PtBA resulted in a decrease of the crystallinity and the melting point of PTHF, as shown by differential scanning calorimetry (DSC). Self-assembly of PTHF-b-PAA copolymers in water into aggregates and micelles when exposed to specific pH values was confirmed by dynamic light scattering, infrared, and NMR spectroscopies.