Department of Chemical and Biomolecular Engineering, Lafayette College , Easton, Pennsylvania 18042, United States.
Langmuir. 2014 Feb 25;30(7):1748-57. doi: 10.1021/la403963c. Epub 2014 Feb 11.
Functionalized nanoparticles can assist in stabilizing fluid-fluid interfaces; however, developing and applying the appropriate surface modification presents a challenge because successful application of these nanomaterials for biotechnological, food processing, and environmental applications requires their long-term stability in elevated ionic strength media. This work studies stimulus responsive polymeric materials based on random copolymers of di(ethylene glycol) methyl ether methacrylate (x = MeO2MA) and oligo(ethylene glycol) methyl ether methacrylate (y= OEGMA) which, when grafted to gold nanoparticles, show significant, tunable, colloidal stability. The nanoparticles Au@(MeO2MAx-co-OEGMAy) display tunable, reversible aggregation that is highly dependent on the (x:y) ratio and ionic strength. Effects of these parameters on the initial rate constant of aggregation (k11) are studied by time-resolved dynamic light scattering (TR-DLS) experiments. At the same nanoparticle concentration, a strong sensitivity to salt concentration is observed. Over less than 300 mM increase in NaCl concentration, we observed a two-order of magnitude increase in aggregation rate constants, 4.2 × 10(-20) < k11 < 1.8 × 10(-18) m(3)s(-1). Additionally, for the same gold nanoparticles, a higher fraction of OEGMA requires a higher salt concentration to induce aggregation. A linear relationship between the critical NaCl coagulation concentration (CCC) and the copolymer composition is observed. Analysis of the experimental data with an extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) theory that includes hydration and osmotic forces is used to explain the stability of these systems. We find the hydration pressure, 2.4 < P(h,0) < 7.2 MPa, scales linearly both with the osmotic pressure and the OEGMA monomer concentration (5 < y < 20%). Specific knowledge of P(h,0)(y, C(NaCl)) enables design of both aggregation kinetics and stability as a function of the copolymer ratio and external stimuli.
功能化纳米粒子可以帮助稳定液-液界面；然而，开发和应用适当的表面改性是一个挑战，因为这些纳米材料在生物技术、食品加工和环境应用中的成功应用需要它们在高离子强度介质中的长期稳定性。这项工作研究了基于二（乙二醇）甲基醚甲基丙烯酸酯（x = MeO2MA）和聚（乙二醇）甲基醚甲基丙烯酸酯（y = OEGMA）的无规共聚物的刺激响应聚合物材料，当接枝到金纳米粒子上时，显示出显著的、可调的胶体稳定性。金纳米粒子 Au@（MeO2MAx-co-OEGMAy）显示出可调的、可逆的聚集，这高度依赖于（x:y）比和离子强度。通过时间分辨动态光散射（TR-DLS）实验研究了这些参数对聚集初始速率常数（k11）的影响。在相同的纳米粒子浓度下，观察到对盐浓度的强烈敏感性。在 NaCl 浓度增加不到 300mM 的情况下，我们观察到聚集速率常数增加了两个数量级，4.2×10(-20) < k11 < 1.8×10(-18) m(3)s(-1)。此外，对于相同的金纳米粒子，OEGMA 的比例越高，需要更高的盐浓度来诱导聚集。观察到临界 NaCl 凝聚浓度（CCC）与共聚物组成之间存在线性关系。使用包括水合和渗透压的扩展德贾古林-兰德维厄-奥弗贝克（xDLVO）理论对实验数据进行分析，以解释这些系统的稳定性。我们发现水合压力 2.4 < P(h,0) < 7.2 MPa，与渗透压和 OEGMA 单体浓度（5 < y < 20%）呈线性关系。对 P(h,0)(y, C(NaCl))的具体了解，使得能够根据共聚物比例和外部刺激设计聚集动力学和稳定性。
