PEG-amine-initiated polymerization of sarcosine N-thiocarboxyanhydrides toward novel double-hydrophilic PEG-b-polysarcosine diblock copolymers

Abstract

Amino acid N-thiocarboxyanhydride (NTA), the thioanalog of N-carboxyanhydride (NCA), is much more stable than NCA against moisture and heat. The convenient monomer synthesis without rigorous anhydrous requirements makes the ring-opening polymerization of NTA a competitive alternative to prepare polypeptoid-containing materials with potential of large-scale production. Polysarcosines (PSars) with high yields (>90%) and low polydispersities (<1.2) are synthesized from sarcosine N-thiocarboxyanhydride (Sar-NTA) at 60 °C initiated by primary amines including poly(ethylene glycol) amine (PEG-NH2 ). The lengths of PSar segments are controlled by various feed ratios of Sar-NTA to initiator. PEG-b-PSar products, a class of novel double-hydrophilic diblock copolymers, are effective in stabilizing oil-in-water emulsions at nano- and microscale, which demonstrates promising encapsulation applications in food, cosmetics, and drug delivery. Due to the different solubility of PEG and PSar blocks, PEG-b-PSar copolymers form micelles in organic solvents with the capability to incorporate metal cations including Cu(2+) and Ni(2+) .

Keywords: encapsulation of metal cations; polyether-polypeptoide; ring-opening polymerization; sarcosine N-thiocarboxyanhydrides; surfactants.