Elizarova Iuliia S, Luckham Paul F
Department of Chemical Engineering and Chemical Technology, Imperial College London, Prince Consort Road, London SW7 2AZ, UK.
J Colloid Interface Sci. 2016 May 15;470:92-99. doi: 10.1016/j.jcis.2016.02.052. Epub 2016 Feb 23.
The layer-by-layer approach is a highly versatile method for the fabrication of multilayered polymeric films and capsules. It has been widely investigated in research for various polyelectrolyte pairs and core template particles. However, the fabrication of nano-sized capsules at the larger scale is difficult and time consuming, due to the necessity of washing and centrifugation steps before the deposition of each polyelectrolyte layer. This results not only in a very long fabrication time, but also in the partial loss of particles during those intermediate steps. In this study, we introduced a continuous approach for the fabrication of multilayer polyelectrolyte based nano-capsules using calcium phosphate core nanoparticles and a tubular flow type reactor with the potential for synthesizing tens of milligrams of capsules per hour. Adsorption of the polyelectrolyte layer occurred in the tubing where particles and polyelectrolyte solution of choice were mixed, creating a layer of polyelectrolyte on the particles. After this, these newly surfaced-modified particles passed into the next segment of tubing, where they were mixed with a second polyelectrolyte of opposite charge. This process can be continuously repeated until the desired number of layers is achieved. One potential problem with this method concerned the presence of any excess polyelectrolyte in the tubing, so careful control of the amount of polymer added was crucial. It was found that slightly under dosing the amount of added polyelectrolyte ensured that negligible unadsorbed polyelectrolyte remained in solution. The particles created at each deposition step were stable, as they all had a zeta potential of greater than ±25mV. Furthermore the zeta potential measurements showed that charge reversal occurred at each stage. Having achieved the necessary number of polyelectrolyte layers, the calcium phosphate cores were easily removed via dissolution in either hydrochloric or acetic acid.
层层组装法是一种用于制备多层聚合物薄膜和胶囊的高度通用的方法。它已在各种聚电解质对和核心模板颗粒的研究中得到广泛研究。然而，由于在沉积每一层聚电解质之前需要进行洗涤和离心步骤，大规模制备纳米级胶囊既困难又耗时。这不仅导致制备时间非常长，而且在这些中间步骤中会造成颗粒的部分损失。在本研究中，我们引入了一种连续方法，使用磷酸钙核心纳米颗粒和管式流动型反应器来制备基于多层聚电解质的纳米胶囊，该反应器每小时有合成数十毫克胶囊的潜力。聚电解质层的吸附发生在管道中，颗粒与所选的聚电解质溶液在管道中混合，从而在颗粒上形成一层聚电解质。此后，这些新表面改性的颗粒进入管道的下一段，在那里它们与带相反电荷的第二种聚电解质混合。这个过程可以连续重复，直到达到所需的层数。这种方法的一个潜在问题是管道中存在任何过量的聚电解质，因此仔细控制添加的聚合物量至关重要。结果发现，稍微少添加一些聚电解质可确保溶液中残留的未吸附聚电解质可忽略不计。在每个沉积步骤产生的颗粒都是稳定的，因为它们的zeta电位都大于±25mV。此外，zeta电位测量表明在每个阶段都发生了电荷反转。达到所需的聚电解质层数后，通过在盐酸或乙酸中溶解可轻松去除磷酸钙核心。
