Despite the wide availability of cellulose, this polyhydroxylated polysaccharide has practically not been used in the synthesis of polyurethanes (PUs), a family of polymers with great versatility. Microcrystalline cellulose (MCC) was used as a polyol to synthesize PUs, mostly at room temperature, with no solvent or catalyst, and simultaneous film formation. Castor oil (CO) was used as an additional polyol and MCC dispersant in the reaction medium. 0–60% of MCC was used regarding the concentration of hydroxyl groups in CO. FTIR spectroscopy indicated that all of the isocyanate groups reacted. The films were extensively characterized; in short, they exhibit transparency, high crystallinity (~ 75%; scanning electron microscopy and polarized light microscopy suggest the formation of spherulite), intermediate hydrophobicity (contact angle > 85°). Considering the control film (100% CO as polyol) and the film prepared using 60% MCC, T_g ranged from sub-ambient (9 °C) to 78 °C, tensile strength from 0.2 to 14 MPa, Young's modulus from 2 to 474 MPa, and elongation from 21 to 13% (the film prepared using 45% MCC showed 102%). The results from ultraviolet–visible spectroscopy, thermogravimetry, and swelling tests are also shown. The properties of the films formed during the reaction performed at 100 °C (using 60% MCC) were discussed. Biocompatibility tests showed cell viability above 90% after 168 h, indicating non-cytotoxicity for the tested films. The wide range of results demonstrated the feasibility of using MCC as a polyol, indicating applications for the films generated as coatings, packaging, dressings, among others. As far as is known, the approach of this study is unprecedented.

Graphical abstract

中文翻译：

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纤维素作为多元醇用于合成生物基聚氨酯并同时成膜

尽管纤维素具有广泛的可用性，但这种多羟基化多糖实际上并未用于聚氨酯 (PU) 的合成，这是一个多功能的聚合物家族。微晶纤维素 (MCC) 用作多元醇来合成 PU，主要在室温下，没有溶剂或催化剂，同时成膜。蓖麻油 (CO) 用作反应介质中的附加多元醇和 MCC 分散剂。对于 CO 中羟基的浓度，使用了 0-60% 的 MCC。FTIR 光谱表明所有异氰酸酯基团都发生了反应。这些电影被广泛描述；简而言之，它们表现出透明性、高结晶度（~ 75%；扫描电子显微镜和偏光显微镜表明形成了球晶）、中等疏水性（接触角 > 85°）。_g范围从低于环境温度 (9 °C) 到 78 °C，拉伸强度从 0.2 到 14 MPa，杨氏模量从 2 到 474 MPa，伸长率从 21 到 13%（使用 45% MCC 制备的薄膜显示 102% ）。还显示了紫外-可见光谱、热重和溶胀测试的结果。讨论了在 100 °C（使用 60% MCC）下进行的反应过程中形成的薄膜的性质。生物相容性测试显示 168 小时后细胞活力超过 90%，表明测试薄膜无细胞毒性。广泛的结果证明了使用 MCC 作为多元醇的可行性，表明所产生的薄膜可用作涂料、包装、敷料等。据了解，这项研究的方法是前所未有的。

图形概要