Adolphe Merkle Institute, University of Fribourg , Chemin des Verdiers 4, 1700 Fribourg, Switzerland.
Virginia Polytechnic Institute and State University (Virginia Tech) , Macromolecules Innovation Institute (MII), Department of Materials Science and Engineering, 203 Holden Hall, 445 Old Turner Street, Blacksburg, Virginia 24061, United States.
Biomacromolecules. 2017 Feb 13;18(2):517-525. doi: 10.1021/acs.biomac.6b01639. Epub 2017 Jan 25.
Cellulose nanocrystals (CNCs) are mechanically rigid, toxicologically benign, fiber-like nanoparticles. They can easily be extracted from renewable biosources and have attracted significant interest as reinforcing fillers in polymers. We here report the modification of CNCs with the 2-ureido-4[1H]pyrimidinone (UPy) motif as an adaptive compatibilizer, which permits the dispersion of UPy-modified CNCs in nonpolar as well as polar media. In toluene, the UPy motifs appear to form intra-CNC dimers, so that the particles are somewhat hydrophobized and well-dispersible in this nonpolar solvent. By contrast, the UPy motifs dissociate in DMF and promote dispersibility through interactions with this polar solvent. We have exploited this adaptiveness and integrated UPy-modified CNCs into nonpolar and polar host polymers, which include different poly(ethylene)s, a polystyrene-block-polybutadiene-block-polystyrene elastomer and poly(ethylene oxide-co-epichlorohydrin). All nanocomposites display an increase of stiffness and strength in comparison to the neat polymer, and some compositions retain a high elongation at break, even at a filler content of 15% w/w.
纤维素纳米晶体（CNCs）是机械刚性的、无毒的纤维状纳米粒子。它们可以很容易地从可再生生物源中提取出来，并作为聚合物中的增强填料引起了人们的极大兴趣。在这里，我们报告了用 2-尿嘧啶-4[1H]嘧啶酮（UPy）基元对 CNC 进行改性，作为一种自适应增容剂，它允许 UPy 改性的 CNC 在非极性和极性介质中分散。在甲苯中，UPy 基元似乎形成了内-CNC 二聚体，因此颗粒在这种非极性溶剂中有些疏水性，分散性良好。相比之下，UPy 基元在 DMF 中解离，并通过与该极性溶剂的相互作用促进分散性。我们利用了这种适应性，将 UPy 改性的 CNC 整合到非极性和极性宿主聚合物中，包括不同的聚乙烯、聚苯乙烯嵌段-聚丁二烯嵌段-聚苯乙烯弹性体和聚（氧化乙烯-共-表氯醇）。与纯聚合物相比，所有纳米复合材料的刚性和强度都有所增加，一些组成物在填充剂含量为 15%w/w 时仍保持高断裂伸长率。
