Hydroxyl Group Tolerated Polymerization of N-Substituted Glycine N-Thiocarboxyanhydride Mediated by Aminoalcohols: A Simple Way to α-Hydroxyl-ω-aminotelechelic Polypeptoids
2017
Tao, Xinfeng | Zheng, Botuo | Bai, Tianwen | Zhu, Baoku | Ling, Jun
N-Carboxyanhydride (NCA) polymerization cannot tolerate nucleophilic groups that have the ability of initiation, e.g., hydroxyl group. In contrast, N-thiocarboxyanhydride (NTA) is a much more stable monomer to tolerate them. In this contribution, we investigate aminoalcohols including 2-amino-1-ethanol (AE), 3-amino-1-propanol (AP), 4-aminomethylbenzyl alcohol (AMB), 6-amino-1-hexanol (AH), and 12-amino-1-dodecanol (AD) as initiators for ring-opening polymerization of N-substituted glycine N-thiocarboxyanhydride (NNTA) to prepare α-hydroxyl-ω-aminotelechelic water-soluble polypeptoids. Hydroxyl groups of AE, AP, and AMB are activated by hydrogen bonding with amino groups, which results in a mixture of α,ω-diaminotelechelic and α-hydroxyl-ω-aminotelechelic polypeptoids confirmed by ¹H NMR, MALDI-ToF, and SEC measurements. Pure α-hydroxyl-ω-aminotelechelic polypeptoids are synthesized for the first time initiated by AH and AD with controlled molecular weights (1.3–12.4 kg/mol) and low polydispersity indices (<1.30). Hydroxyl groups in AH and AD remain inactive to generate hydrogen bonding due to the long distance from amino groups. Water-soluble polypeptoids with special functional end groups are attractive alternatives of PEG for their nontoxicity and biocompatibility having great potential in biomedical applications.
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