Lin Fangbo, Cousin Fabrice, Putaux Jean-Luc, Jean Bruno
Université Grenoble Alpes, CNRS, CERMAV, 38000 Grenoble, France.
Laboratoire Léon Brillouin, Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA) Saclay, F-91191 Gif-sur-Yvette, France.
ACS Macro Lett. 2019 Apr 16;8(4):345-351. doi: 10.1021/acsmacrolett.8b01005. Epub 2019 Mar 11.
We present here the grafting of thermoresponsive polyetheramines at the reducing ends of cellulose nanocrystals (CNCs) using a two-step protocol involving an end carboxylation followed by a peptide coupling with the primary amine moiety of the polyetheramine. In aqueous suspensions these end-modified CNCs became associated by their derivatized tips when the temperature was raised past a lower critical solution temperature (LCST), above which these polyetheramines are known to collapse and become hydrophobic. The CNC association was reversible when the temperature was lowered and the phenomenon of association/disassociation was totally reproducible in repeated temperature cycles as followed by dynamic light scattering (DLS). Small-angle neutron scattering (SANS) data revealed the presence of grafted chains with an extended conformation and showed the assembly of modified CNCs into swollen aggregates in suspension at > LCST. Transmission electron microscopy (TEM) images confirmed that the once dispersed derivatized CNCs at low temperature became associated through their reducing ends above the LCST. At such temperatures, these modified CNCs attached themselves in a remarkable fashion, forming the arms of regular four-, five-, or six-branched stars.
我们在此展示了通过两步法在纤维素纳米晶体（CNC）的还原端接枝热响应性聚醚胺，该两步法包括末端羧化，然后与聚醚胺的伯胺部分进行肽偶联。在水性悬浮液中，当温度升高超过较低临界溶液温度（LCST）时，这些末端改性的CNC通过其衍生化的末端相互缔合，已知在此温度以上这些聚醚胺会塌陷并变得疏水。当温度降低时，CNC的缔合是可逆的，并且通过动态光散射（DLS）跟踪，缔合/解离现象在重复的温度循环中完全可重现。小角中子散射（SANS）数据揭示了存在具有伸展构象的接枝链，并表明改性的CNC在> LCST时在悬浮液中组装成肿胀的聚集体。透射电子显微镜（TEM）图像证实，曾经在低温下分散的衍生化CNC在LCST以上通过其还原端相互缔合。在这样的温度下，这些改性的CNC以一种显著的方式相互连接，形成规则的四分支、五分支或六分支星形的臂。
