Physiologically relevant, pH-responsive PEG-based block and statistical copolymers with N,N-diisopropylamine unitsThis article is dedicated to the memory of Prof. Gregory L. Baker (1954-2012)

• Main Authors: Lee, Annabelle, Lundberg, Pontus, Klinger, Daniel, Lee, Bongjae F, Hawker, Craig J, Lynd, Nathaniel A
• Format: Article
• Language: English
• ISSN: 1759-9954; 1759-9962
• DOI: 10.1039/c3py00747b

In order to impart pH-responsiveness within a physiologically-relevant context to PEG-based biomaterials, a new tertiary amine containing repeat unit, N , N -diisopropyl ethanolamine glycidyl ether (DEGE), was developed and incorporated into statistical and block copolymers with ethylene oxide (EO), and allyl glycidyl ether (AGE) via anionic ring-opening polymerization. The reactivity of this novel monomeric building block in copolymerizations with EO was investigated by spectroscopy with observed reactivity ratios of r DEGE = 1.28 ± 0.14 and r EO = 0.82 ± 0.10. It was further demonstrated that DEGE containing copolymers could serve as building blocks for the formation of new pH-responsive materials with a p K a of ca. 9, which allowed macroscopic hydrogels to be prepared from symmetric triblock copolymers PDEGE 5.3k - b -PEO 20k - b -PDEGE 5.3k . The triblock copolymers exhibited clear sol-to-gel transitions in a physiologically-relevant critical gelation range of pH 5.8-6.6 and pH-dependent viscoelastic properties. On the nanometer scale, the preparation of pH-responsive micro- or nanogels was demonstrated by crosslinking P(DEGE- co -AGE) copolymers in miniemulsion droplets stabilized by PEO- b -P(DEGE- co -AGE) diblock terpolymers. These nanoparticles exhibited a reversible pH-dependent swelling profile with a volume phase transition at physiological pH 6.5-7.5. In order to impart pH-responsiveness within physiologically relevant PEG-based biomaterials, a new tertiary amine-containing repeat unit was incorporated into statistical and block copolymers with ethylene oxide and allyl glycidyl ether via anionic ring-opening polymerization.