Ionically Triggered Cleavage of Poly(ethylene glycol) End Capped with Calcium Alginate Oligomers

Triggered degradation activated by external stimuli in natural environments is desirable for water-soluble polymers (WSPs), such as poly(ethylene glycol) (PEG), as they often accumulate in natural environments and are difficult to capture or recycle. To incorporate this function, coordination polymers are attractive due to their reversible linkages. We report the synthesis of PEG end-capped with alginate oligosaccharides (AOS), which, when linked with divalent calcium ions (PEG-AOS-Ca), exhibited higher viscosity (3.8 × 10^-3 Pa·s) compared to the original polymer (PEG-AOS, 1.9 × 10^-3 Pa·s), demonstrating their utility as a viscosity modifier. In addition, PEG-AOS-Ca degraded back to the original PEG-AOS through ion exchange by monovalent sodium ions, mimicking the conditions in the natural environment. This new degradable WSP with competitive viscosity to high molar mass PEG solutions during its use period exhibits triggered degradation behavior in high sodium environments and informs the design of future degradable WSPs.