SB compounds were synthesized from (para, ortho, meta)-phenylenediamine as a cross-linking agent through vanillin. The chemical structure of the formed SB complexes is confirmed by FT-IR spectroscopy. Among the three complexes, para-phenylenediamine (p-SB), possessing a stable resonance structure with the lowest steric repulsion, was obtained in the highest yield of 87%. Hence, the present work focused on reducing the brittle behavior and improving the antimicrobial activity of PLA by reacting it with p-SB. FT-IR investigation revealed the existence of an intermolecular hydrogen bonding between PLA and SB, which led to an increased toughness in the PLA-p-SB complex. This is further confirmed through SEM analysis. The tensile and contact angle measurements determined an improvement in mechanical properties and hydrophobic nature of the PLA-p-SB film. DSC results demonstrated an increase in flexibility, which indicated a 10 °C reduction in glass transition temperature (T g) of PLA-p-SB films. The antimicrobial activity of the PLA-p-SB films had a maximum of 15 mm zone of inhibition, which was found to be more effective than the neat PLA film. PLA-p-SB coating on Kraft paper showed improved mechanical and barrier properties than neat PLA coatings and could be tried as a possible replacement for conventional synthetic packaging materials. Graphic abstract

中文翻译：

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用于包装应用的席夫碱 (SB) 改性聚乳酸​​ (PLA) 抗菌薄膜的设计和开发。

SB化合物由（对，邻，间）-苯二胺作为交联剂通过香草醛合成。所形成的 SB 配合物的化学结构通过 FT-IR 光谱得到证实。在这三种配合物中，对苯二胺（p-SB）具有稳定的共振结构，空间排斥力最低，产率最高，为87%。因此，目前的工作重点是通过与 p-SB 反应来降低 PLA 的脆性行为和提高其抗菌活性。FT-IR 研究表明 PLA 和 SB 之间存在分子间氢键，这导致 PLA-p-SB 复合物的韧性增加。通过 SEM 分析进一步证实了这一点。拉伸和接触角测量确定了 PLA-p-SB 薄膜的机械性能和疏水性的改进。DSC 结果表明柔韧性增加，这表明 PLA-p-SB 薄膜的玻璃化转变温度 (T g) 降低了 10 °C。PLA-p-SB 薄膜的抗菌活性最大为 15 mm，比纯 PLA 薄膜更有效。牛皮纸上的 PLA-p-SB 涂层显示出比纯 PLA 涂层更好的机械和阻隔性能，可以尝试作为传统合成包装材料的替代品。图形摘要 PLA-p-SB 薄膜的抗菌活性最大为 15 mm，比纯 PLA 薄膜更有效。牛皮纸上的 PLA-p-SB 涂层显示出比纯 PLA 涂层更好的机械和阻隔性能，可以尝试作为传统合成包装材料的替代品。图形摘要 PLA-p-SB 薄膜的抗菌活性最大为 15 mm，比纯 PLA 薄膜更有效。牛皮纸上的 PLA-p-SB 涂层显示出比纯 PLA 涂层更好的机械和阻隔性能，可以尝试作为传统合成包装材料的替代品。图形摘要