Hu Zhen, Xu Richard, Cranston Emily D, Pelton Robert H
Department of Chemical Engineering, McMaster University , 1280 Main Street West, Hamilton, Ontario L8S 4L7, Canada.
Biomacromolecules. 2016 Dec 12;17(12):4095-4099. doi: 10.1021/acs.biomac.6b01641. Epub 2016 Nov 30.
The addition of cellulose nanocrystals (CNC) greatly enhanced the properties of methylcellulose (MC) stabilized aqueous foams. CNC addition decreased air bubble size, initial foam densities and drainage rates. Mixtures of 2 wt % CNC + 0.5 wt % MC gave the lowest density foams. This composition sits near the onset of nematic phase formation and also near the overlap concentration of methylcellulose. More than 94% of the added CNC particles remained in the foam phase, not leaving with the draining water. We propose that the nanoscale CNC particles bind to the larger MC coils both in solution and with MC at the air/water interface, forming weak gels that stabilize air bubbles. Wet CNC-MC foams were sufficiently robust to withstand high temperature (70 °C for 6 h) polymerization of water-soluble monomers giving macroporous CNC composite hydrogels based on acrylamide (AM), 2-hydroxyethyl methacrylate (HEMA), or polyethylene glycol diacrylate (PEGDA). At high temperatures, the MC was present as a fibrillar gel phase reinforced by CNC particles, explaining the very high foam stability. Finally, our CNC-MC foams are based on commercially available forms of CNC and MC, already approved for many applications. This is a "shovel-ready" technology.
添加纤维素纳米晶体（CNC）极大地增强了甲基纤维素（MC）稳定的水性泡沫的性能。添加CNC可减小气泡尺寸、降低初始泡沫密度和排水速率。2 wt% CNC + 0.5 wt% MC的混合物产生了密度最低的泡沫。该组成接近向列相形成的起始点，也接近甲基纤维素的重叠浓度。超过94%的添加CNC颗粒保留在泡沫相中，不会随排水流失。我们认为，纳米级CNC颗粒在溶液中以及在气/水界面处与较大的MC线圈结合，形成稳定气泡的弱凝胶。湿的CNC-MC泡沫足够坚固，能够承受水溶性单体在高温（70°C，6小时）下的聚合反应，从而得到基于丙烯酰胺（AM）、甲基丙烯酸2-羟乙酯（HEMA）或聚乙二醇二丙烯酸酯（PEGDA）的大孔CNC复合水凝胶。在高温下，MC以由CNC颗粒增强的纤维状凝胶相存在，这解释了极高的泡沫稳定性。最后，我们的CNC-MC泡沫基于市售的CNC和MC形式，已被批准用于许多应用。这是一项“准备就绪”的技术。
