A facile method for imparting hydrolytic degradability to poly(ethylene oxide) (PEO), compatible with current PEGylation strategies, is presented. By incorporating methylene ethylene oxide (MEO) units into the parent PEO backbone, complete degradation was defined by the molar incorporation of MEO, and the structure of the degradation byproducts was consistent with an acid-catalyzed vinyl-ether hydrolysis mechanism. The hydrolytic degradation of poly[(ethylene oxide)-co-(methylene ethylene oxide)] was pH-sensitive, with degradation at pH 5 being significantly faster than at pH 7.4 at 37 °C in PBS buffer while long-term stability could be obtained in either the solid-state or at pH 7.4 at 6 °C.

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 rDEGE = 1.28 ± 0.14 and rEO = 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 pKa of ca. 9, which allowed macroscopic hydrogels to be prepared from symmetric triblock copolymers PDEGE5.3k-b-PEO20k-b-PDEGE5.3k. 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.