Coating materials based on biodegradable and natural polymers exhibit considerable promise for applications in the paint industry, but these polymers are rarely used as primary ingredients for paint formulations. Lignin is a natural polymer that is able to adhere onto many oxide surfaces because of its phenolic/catecholic groups, but its film forming ability has been a major challenge. Herein, we report the synthesis and characterization of a lignin copolymer with aliphatic polyester oligomers that display excellent film forming capabilities and adhesion toward stainless-steel substrates. The strategy to synthesize the target copolymer is based on tuning the degree of polymerization (DP) of ε-caprolactone (CL) onto the lignin-OH groups via ring opening polymerization and the grafting-from method. This allows copolymers with polyester oligomers below a DP of 25 to be prepared in gram quantities and characterized by size exclusion chromatography and nuclear magnetic resonance spectroscopy. Physicochemical analysis of the copolymers provides evidence that the aliphatic polyester oligomers were mostly reacted on the aliphatic lignin alcohol, leaving the phenolic alcohol unmodified, which favors adhesion properties. Films prepared using copolymers with the DP of CL below 5 have strong adhesion to metals and considerable potential to act as a binder in metal primers/base coatings. We anticipate that this approach will provide important value addition for lignin in coating applications.

中文翻译：

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调整木质素-己内酯共聚物以涂覆金属表面

基于可生物降解的天然聚合物的涂料在涂料工业中具有广阔的应用前景，但是这些聚合物很少用作涂料配方的主要成分。木质素是一种天然聚合物，由于其酚/邻苯二酚基团能够粘附在许多氧化物表面上，但其成膜能力一直是主要挑战。本文中，我们报道了木质素共聚物与脂族聚酯低聚物的合成和表征，脂族聚酯低聚物显示出出色的成膜能力和对不锈钢基材的附着力。合成目标共聚物的策略是基于通过开环聚合和接枝方法将ε-己内酯（CL）的聚合度（DP）调整到木质素-OH基上。这允许以克数量制备具有低于DP的25的聚酯低聚物的共聚物，并通过尺寸排阻色谱法和核磁共振波谱法表征。共聚物的理化分析提供了证据，表明脂族聚酯低聚物大多与脂族木质素醇反应，而酚醇未改性，这有利于粘合性能。使用CL的DP小于5的共聚物制备的膜具有对金属的强粘合力，并且在金属底漆/基础涂料中具有作为粘合剂的相当大的潜力。我们预计这种方法将为涂料应用中的木质素提供重要的附加值。共聚物的理化分析提供了证据，表明脂族聚酯低聚物大多与脂族木质素醇反应，而酚醇未改性，这有利于粘合性能。使用CL的DP小于5的共聚物制备的膜具有对金属的强粘合力，并且在金属底漆/基础涂料中具有作为粘合剂的相当大的潜力。我们预计这种方法将为涂料应用中的木质素提供重要的附加值。共聚物的理化分析提供了证据，表明脂族聚酯低聚物大多与脂族木质素醇反应，而酚醇未改性，这有利于粘合性能。使用CL的DP值低于5的共聚物制备的薄膜对金属具有很强的附着力，并且在金属底漆/基础涂料中具有作为粘合剂的巨大潜力。我们预计这种方法将为涂料应用中的木质素提供重要的附加值。使用CL的DP小于5的共聚物制备的膜具有对金属的强粘合力，并且在金属底漆/基础涂料中具有作为粘合剂的相当大的潜力。我们预计这种方法将为涂料应用中的木质素提供重要的附加值。使用CL的DP小于5的共聚物制备的膜具有对金属的强粘合力，并且在金属底漆/基础涂料中具有作为粘合剂的相当大的潜力。我们预计这种方法将为涂料应用中的木质素提供重要的附加值。