*Article* **A New Approach Utilizing Aza-Michael Addition for Hydrolysis-Resistance Non-Ionic Waterborne Polyester**

**Hao Fu, Linbo Gong \* and Shuling Gong \***

College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China; haofu@whu.edu.cn **\*** Correspondence: gonglb@whu.edu.cn (L.G.); gongsl@whu.edu.cn (S.G.)

**Abstract:** This work first synthesized a series of linear polyesters by step-growth polycondensation, then an amino-terminated hydrophilic polyether was grafted to the polyester as side-chains through aza-Michael addition to prepare a self-dispersible, non-ionic waterborne comb-like polyester (NWCPE). In contrast to traditional functionalization methods that usually require harsh reaction conditions and complex catalysts, the aza-Michael addition proceeds efficiently at room temperature without a catalyst. In this facile and mild way, the NWCPE samples with number-average molecular weight (*M*n) of about 8000 g mol−<sup>1</sup> were obtained. All dispersions showed excellent storage stability, reflected by no delamination observed after 6 months of storage. The NWCPE dispersion displayed better hydrolysis resistance than an ionic waterborne polyester, as was indicated by a more slight change in pH value and *M*n after a period of storage. In addition, the film obtained after the NWCPE dispersion was cross-linked with the curing agent, it exhibited good water resistance, adhesion, and mechanical properties.

**Keywords:** aza-Michael addition; comb-like polymer; non-ionic waterborne polyester; hydrolysis resistance
