Dual-responsive pegylated polypeptoids with tunable cloud point temperatures.

A series of pegylated polypeptoids have been readily synthesized by a strategy combining ring-opening polymerization (ROP) and thiol-yne photoaddition. The polypeptoids simultaneously incorporated branched oligo(ethylene glycol) (OEG) units and thioether bonds in the side-chains. All the polypeptoids are readily soluble in aqueous solution and show reversible thermo-responsive properties. The cloud points (CPs) were demonstrated to be readily tunable in the range of ~25°C-60°C by varying the chemical composition, OEG chain length and the degree of polymerization. Attractively, the chemical compositions of the side chains are readily tunable via adjusting the molar ratios of a mixture of thiol terminated OEG molecules, which avoid synthesizing new monomers or copolymerization of different monomers. Further, the oxidation/reduction of thioether groups shows significant influence on the CPs, providing a second stimulus to tune the phase transition behaviors. Considering the biocompatibility and degradability, the dual-responsive polypeptoids are potential candidates for various biomedical or biotechnological applications.

Charge-Determined LCST/UCST Behavior in Ionic Polypeptoids.

Stimuli-responsive polymers have received increasing interest for a variety of applications. Here, we report a series of unique charge-determined thermoresponsive polypeptoids synthesized by a combination of ring-opening polymerization and click chemistry. The LCST-type and UCST-type behavior is mainly dominated by the charge state on the side chain. Further, the phase transition temperature highly depends on the degree of polymerization, the side-chain architecture, the pH value, and so on. The obtained polypeptoid solutions exhibit good stability against temperature and salt concentration. To our knowledge, this report presents the first charge-determined LCST/UCST-type polymer from identical homopolymer backbone that displays a wide range of tunable cloudy points in aqueous media. We propose the hydrogen-bonding interaction plays a critical part on the solution behavior. These features make polypeptoids ideal candidates for highly designable stimuli-responsive polymeric materials.