School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea.
Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea.
Langmuir. 2022 Aug 16;38(32):10010-10021. doi: 10.1021/acs.langmuir.2c01422. Epub 2022 Aug 7.
Oriental lacquer sap is attracting considerable attention as a renewable and eco-friendly natural resin with high durability, heat resistance, insulation, insect repellency, and antiseptic and antibacterial properties. However, to ensure excellent coating performance, it is necessary to improve the drying/curing process of lacquer sap with a time-consuming drying time at high humidity [relative humidity (RH), 70-90%] and ambient temperature (20-30 °C). Drawing on an understanding of the polymerization mechanism of urushiol, the main component of the lacquer sap consisted of a water-in-oil (W/O) emulsion, and this study presents an eco-friendly additive that mimics the structure-function of urushiol composed of a polar catechol head group and a nonpolar hydrocarbon tail. A photo-curable lacquer sap was thus developed by adding a tyrosine amino acid-based lipid agent (denoted as Y-ADDA), which allows faster and more effective drying/curing at lower humidity while maintaining the nature-derived properties of lacquer sap. Y-ADDA easily coassembles with urushiol in the W/O emulsion droplets, thereby significantly accelerating the formation of a polymer network along with urushiol during water evaporation leading to fast drying/curing under ultraviolet (UV) light irradiation at low humidity (∼50% RH). The UV-cured lacquer sap resins showed higher performance in terms of film processing and physicochemical properties compared with that of the lacquer containing only tyrosine amino acids without aliphatic tail conjugation, -(9-fluorenylmethoxycarbonyl)---butyl-l-tyrosine Fmoc-Tyr(Bu)-OH. Furthermore, the drying and curing times, film morphology, transmittance, hardness, and adhesion strength of the UV-cured lacquer were markedly superior compared to those of shellac, a general eco-friendly fast-drying primer. The study provides useful strategies and insights to promote the industrial application of lacquer sap resins by employing biocompatible nanoagents developed with an understanding of the curing mechanism of natural resins and from the viewpoint of green and sustainable chemistry perspective.
漆树液作为一种可再生且环保的天然树脂，具有高耐久性、耐热性、绝缘性、驱虫性和防腐抗菌性能，因此备受关注。然而，为了确保优异的涂层性能，需要改进漆树液的干燥/固化过程，而漆树液的干燥时间较长，且需要在高湿度[相对湿度（RH）为 70-90%]和环境温度（20-30°C）下进行。本研究基于对漆树液主要成分漆酚的聚合机制的理解，提出了一种环保型添加剂，该添加剂模拟了漆酚的结构-功能，由一个极性儿茶酚头部基团和一个非极性碳氢尾部基团组成。通过添加酪氨酸氨基酸基脂质剂（表示为 Y-ADDA），开发了一种光固化漆树液，可在较低湿度下实现更快、更有效的干燥/固化，同时保持漆树液的天然特性。Y-ADDA 容易与 W/O 乳液液滴中的漆酚共组装，从而在水蒸发过程中显著加速聚合物网络的形成，并伴随着漆酚的形成，从而在低湿度（约 50%RH）下通过紫外（UV）光照射实现快速干燥/固化。与仅含有酪氨酸氨基酸而没有脂肪族尾部连接的漆酚相比，UV 固化的漆树液树脂在薄膜加工和物理化学性能方面表现出更高的性能，-（9-芴甲氧羰基）---丁基-L-酪氨酸 Fmoc-Tyr（Bu）-OH。此外，与虫胶（一种通用的环保快干底漆）相比，UV 固化漆的干燥和固化时间、漆膜形貌、透光率、硬度和附着力明显更优。该研究从天然树脂固化机制的角度出发，从绿色可持续化学的角度出发，为利用对生物相容性的纳米试剂促进漆树液树脂的工业应用提供了有用的策略和见解。
