*Article* **Short-Branched Fluorinated Polyurethane Coating Exhibiting Good Comprehensive Performance and Potential UV Degradation in Leather Waterproofing Modification**

**Shouhua Su, Juan Wang, Chao Li, Jinfeng Yuan, Zhicheng Pan and Mingwang Pan \***

Hebei Key Laboratory of Functional Polymers, School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130, China; shouhuasu@163.com (S.S.); juanwang117@163.com (J.W.); chaoli1129@163.com (C.L.); yuanjf@hebut.edu.cn (J.Y.); panz@hebut.edu.cn (Z.P.) **\*** Correspondence: mwpan@126.com

**Abstract:** In the current leather market, waterproof leather occupies a large proportion, where waterproofness has become one of the important standards for leather selection. However, the most advanced fluorine-containing waterproofing agents on the market always have long chains of over eight carbons (C8), whose use has been restricted due to their bioaccumulation and recalcitrance in natural environment. Consequently, creating waterproof materials characterized by their environmentally friendly qualities and high performance is of great significance. Herein, we report a novel strategy for preparation of the fluorinated polyurethanes containing short branched fluorocarbon chains, and apply it in leather waterproofing. Because the fluorine-containing chain segments are enriched on the coating surface, the waterproof agent coating shows good hydrophobicity, low water absorption, high wear resistance and potential photodegradation of performances. Additionally, the water and oil proof performances of the coating are comparable to that of the marketed C8 waterproofing agent. Its solvent-resistant and antifouling performances are also outstanding. Therefore, the coating can meet the property requirements for daily use and has broad application prospects.

**Keywords:** short branched fluorocarbon chain; fluorinated polyurethane (FPU); waterproof coating; leather surface modification
