Biopolymer-based slow-release fertilizers (SRFs) have attracted increasing interest because of their environmental benefits. Herein, a hydrophobic thermoplastic lignin with favorable film formation properties was synthesized through simple crosslinking followed by esterification reactions. The chemical structure, glass transition temperature, and hydrophobicity were determined using Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and contact angle studies. The newly synthesized esterified crosslinked sodium lignosulfonate (ECSL) enables the encapsulation of urea via a solvent-free coating method to prepare SRFs because of its appropriate glass transition temperature (Tg) and excellent film formation properties. The ECSL-based SRF released only 86.9% of the encapsulated urea within 44 d, which is superior to most lignin-based SRFs in previous studies. The release rate can also be tuned by adjusting the ECSL ratio. The synthesis of hydrophobic lignin biocomposites with suitable Tgs for film formation resolves the bottleneck of using these types of non-thermoplastic polymers (e.g., lignin) for SRFs. This study not only maximizes the value of biowaste lignin but also offers a non-paradigm approach toward low-cost SRFs for sustainable agriculture.

基于生物聚合物的缓释肥料 (SRF) 因其环境效益而引起越来越多的兴趣。在此，通过简单的交联和酯化反应合成了具有良好成膜性能的疏水性热塑性木质素。化学结构、玻璃化转变温度和疏水性使用傅里叶变换红外光谱测定，¹H 核磁共振波谱、差示扫描量热法和接触角研究。新合成的酯化交联木质素磺酸钠 (ECSL) 具有合适的玻璃化转变温度 (Tg) 和优异的成膜性能，因此能够通过无溶剂涂层法封装尿素以制备 SRF。基于 ECSL 的 SRF 在 44 d 内仅释放 86.9% 的封装尿素，这优于先前研究中大多数基于木质素的 SRF。还可以通过调整 ECSL 比率来调整释放速率。具有适合成膜的 Tg 的疏水性木质素生物复合材料的合成解决了将这些类型的非热塑性聚合物（例如木质素）用于 SRF 的瓶颈。