A critical challenge in the application of functional cellulose fibrils is to perform efficient surface modification without disrupting the original properties. Three-component Passerini reaction (Passerini 3-CR) is regarded as an effective functionalization approach which can be carried out under mild and fast reaction condition. In this study, we investigated the application of Passerini 3-CR for the synthesis of thermoresponsive cellulose fibrils by covalently tethering poly(N-isopropylacrylamide) in aqueous condition at ambient temperature. The three components, a TEMPO-oxidized cellulose nanofiber bearing carboxylic acid moieties (TOCN-COOH), a functionalized polymer with aldehyde group (pNIPAm-COH) and a cyclohexyl isocyanide, were reacted in one pot resulting in 36% of grafting efficiency within 30 min. The chemical coupling was evidenced by improved aqueous dispersibility, which was further confirmed by FT-IR, TGA, UV–vis, and turbidity study. It was observed that the grafting efficiency is strongly dependent on the chain length of the polymer. Furthermore, AFM and X-ray diffraction measurements affirmed the suitability of the proposed method for chemical modification of cellulose nanofibers without significantly compromising the original morphology and structural integrity.

中文翻译：

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通过三组分帕塞里尼反应将温度响应性 pNIPAm 共价束缚在 TEMPO 氧化纤维素纳米纤丝上

应用功能性纤维素原纤维的一个关键挑战是在不破坏原始特性的情况下进行有效的表面改性。三组分帕塞里尼反应（Passerini 3-CR）被认为是一种有效的官能化途径，可在温和、快速的反应条件下进行。在这项研究中，我们研究了 Passerini 3-CR 在通过共价束缚聚 ( N-异丙基丙烯酰胺）在环境温度下的水性条件下。这三种组分，一种带有羧酸部分的 TEMPO 氧化纤维素纳米纤维 (TOCN-COOH)、一种带有醛基的功能化聚合物 (pNIPAm-COH) 和一种环己基异氰化物，在一个锅中反应，在 30 分钟内产生 36% 的接枝效率分钟。改进的水分散性证明了化学耦合，FT-IR、TGA、UV-vis 和浊度研究进一步证实了这一点。据观察，接枝效率强烈依赖于聚合物的链长。此外，AFM 和 X 射线衍射测量证实了所提出的纤维素纳米纤维化学改性方法的适用性，而不会显着损害原始形态和结构完整性。