Charged polystyrene nanoparticles: role of ionic comonomers structures.
Charged polystyrene nanoparticles: role of ionic comonomers structures.
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DOI：
10.1016/j.jcis.2011.06.005
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发表时间：
2011-09
影响因子：
9.9
通讯作者：
D. Arunbabu;T. Jana
中科院分区：
文献类型：
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作者：
D. Arunbabu;T. Jana
以丙烯酸（AAc）、甲基丙烯酸（MAA）、甲基丙烯酸羟乙酯（HEMA）和苯乙烯磺酸钠（NaSS）4种不同结构的离子型共聚单体为单体，进行了苯乙烯的乳液共聚合，研究了单体结构对共聚动力学、粒子尺寸、形貌、电荷密度和自组装的影响。共聚动力学被认为是高度依赖于离子共聚单体的结构，这种依赖性的性质改变从均匀胶束成核制度。在所有情况下观察到随着表面活性剂浓度（S）的增加，颗粒尺寸（D）减小;然而，并非所有情况下D与S的指数都相似。在均质成核区，指数的顺序为AAc（0.446）>MAA（0.396）>NaSS（0.252）>HEMA（0.241），而在胶束成核区，指数的顺序几乎相反，为NaSS（0.406）>HEMA（0.228）>AAc（0.206）>MAA（0.172）。疏水/亲水特性和空间因素被认为是与离子共聚单体结构的D与S指数的变化的驱动力。由离子共聚单体贡献的粒子表面上的电荷的存在触发了粒子在沉降和衍射可见光时的自组装，从而遵守布拉格定律。
Emulsion copolymerizations of styrene were carried out with four structurally different ionic comonomers namely acrylic acid (AAc), methacrylic acid (MAA), 2-hydroxyethyl methacrylate (HEMA), and sodium styrene sulfonate (NaSS) to study the effect of monomer structure on the copolymerization kinetics and size, morphology, charge density, and the self-assembly of the particles. The copolymerization kinetics was found to be highly dependent upon the ionic comonomer structure, and the nature of this dependence altered from homogeneous to micellar nucleation regime. The decrease in particle size (D) with increasing surfactant concentration (S) was observed in all the cases; however, the exponents of D vs. S were not similar for all the cases. In the homogeneous nucleation regime, exponents followed the order as AAc (0.446)>MAA (0.396)>NaSS (0.252)>HEMA (0.241), whereas the order was almost reversed in the micellar nucleation regime as NaSS (0.406)>HEMA (0.228)>AAc (0.206)>MAA (0.172). The hydrophobic/hydrophilic character and the steric factors were found to be the driving force for the variation in D vs. S exponents with ionic comonomer structure. The presence of charges on the particle surface contributed by the ionic comonomers triggered the self-assembly of the particles upon sedimentation and diffracted visible light obeying Bragg’s law.