Pavlovic Marko, Adok-Sipiczki Monika, Nardin Corinne, Pearson Samuel, Bourgeat-Lami Elodie, Prevot Vanessa, Szilagyi Istvan
Department of Inorganic and Analytical Chemistry, University of Geneva , 30 Quai Ernest-Ansermet, CH-1205 Geneva, Switzerland.
Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Matériaux, Université de Pau et des Pays de l'Adour, 2 Avenue du Président Angot, F-64000 Pau, France.
Langmuir. 2015 Nov 24;31(46):12609-17. doi: 10.1021/acs.langmuir.5b03372. Epub 2015 Nov 12.
The colloidal behavior of layered double hydroxide nanoparticles containing Mg(2+) and Al(3+) ions as intralayer cations and nitrates as counterions (MgAl-NO3-LDH) was studied in the presence of a short statistical copolymer of acrylic acid (AA) and butyl acrylate (BA) terminated with 4-cyano-4-thiothiopropylsulfanyl pentanoic acid (CTPPA) (P(AA7.5-stat-BA7.5)-CTPPA) synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization. Surface charge properties and aggregation of the particles were investigated by electrophoresis and dynamic light scattering (DLS), respectively. The negatively charged P(AA7.5-stat-BA7.5)-CTPPA adsorbed strongly on the oppositely charged particles, leading to charge neutralization at the isoelectric point (IEP) and charge reversal at higher copolymer concentrations. The dispersions were unstable, i.e., fast aggregation of the MgAl-NO3-LDH occurred near the IEP while high stability was achieved at higher P(AA7.5-stat-BA7.5)-CTPPA concentrations. Atomic force (AFM) and transmission electron (TEM) microscopy imaging revealed that the platelets preferentially adopted a face-to-face orientation in the aggregates. While the stability of the bare particles was very sensitive to ionic strength, the P(AA7.5-stat-BA7.5)-CTPPA copolymer-coated particles were extremely stable even at high salt levels. Accordingly, the limited colloidal stability of bare MgAl-NO3-LDH dispersions was significantly improved by adding an appropriate amount of P(AA7.5-stat-BA7.5)-CTPPA to the suspension.
研究了层状双氢氧化物纳米颗粒（MgAl-NO3-LDH）的胶体行为，其层内阳离子为Mg(2+)和Al(3+)离子，抗衡离子为硝酸根离子。研究是在一种由可逆加成-断裂链转移（RAFT）聚合合成的、以4-氰基-4-硫代硫丙基硫烷基戊酸（CTPPA）封端的丙烯酸（AA）和丙烯酸丁酯（BA）的短统计共聚物（P(AA7.5-stat-BA7.5)-CTPPA）存在的情况下进行的。分别通过电泳和动态光散射（DLS）研究了颗粒的表面电荷性质和聚集情况。带负电荷的P(AA7.5-stat-BA7.5)-CTPPA强烈吸附在带相反电荷的颗粒上，导致在等电点（IEP）处电荷中和，在较高共聚物浓度下电荷反转。分散体不稳定，即MgAl-NO3-LDH在IEP附近快速聚集，而在较高的P(AA7.5-stat-BA7.5)-CTPPA浓度下实现了高稳定性。原子力显微镜（AFM）和透射电子显微镜（TEM）成像显示，在聚集体中血小板优先采取面对面的取向。虽然裸颗粒的稳定性对离子强度非常敏感，但P(AA7.5-stat-BA7.5)-CTPPA共聚物包覆的颗粒即使在高盐水平下也极其稳定。因此，通过向悬浮液中加入适量的P(AA7.5-stat-BA7.5)-CTPPA，显著提高了裸MgAl-NO3-LDH分散体有限的胶体稳定性。
