Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Langmuir. 2012 Sep 18;28(37):13181-8. doi: 10.1021/la302443f. Epub 2012 Sep 7.
The effects of polymers on the one-dimensional assembly of silica nanospheres (SNSs) in the liquid phase are systematically investigated using nonionic poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (abbreviated as PEO-PPO-PEO) triblock copolymers with varying hydrophilic-lipophilic balance (HLB) values. Scanning electron microscopy is employed for morphological observations of the polymer-mediated assemblies of SNSs on the basis of which the optimal pH for 1D assembly (pH(1D)) is determined. To clarify the polymers' effects on the 1D assembly of SNSs, the relationships between pH(1D) and polymers' HLB values, the numbers of hydrophilic EO and hydrophobic PO units, and the relative ratio of N(PO)/N(EO) are examined. Zeta potential measurements are conducted to investigate the electrostatic repulsion among the SNSs in the presence of block copolymers. It is found that the relative hydrophilicity of the block copolymers greatly affects the balance of interactions in the 1D assembly of SNSs. Block copolymers with large HLB values promote the 1D assembly of SNSs under near-neutral pH conditions, whereas the block copolymers with small HLB values promote 1D assembly under basic pH conditions. Therefore, the 1D assembly of SNSs is achieved over an extensive pH range (7.5-9.5) through the employment of block copolymers of different hydrophilic and hydrophobic block lengths.
系统研究了聚合物对二氧化硅纳米球（SNS）在液相中一维组装的影响，使用了不同亲水亲油平衡值（HLB）的非离子型聚（环氧乙烷）-b-聚（环氧丙烷）-b-聚（环氧乙烷）（简称 PEO-PPO-PEO）三嵌段共聚物。扫描电子显微镜用于基于聚合物介导的 SNS 组装的形态观察，根据该观察确定了一维组装的最佳 pH 值（pH(1D)）。为了阐明聚合物对 SNS 一维组装的影响，研究了 pH(1D)与聚合物 HLB 值、亲水性 EO 单元和疏水性 PO 单元的数量以及 N(PO)/N(EO)的相对比值之间的关系。进行了 Zeta 电位测量以研究在嵌段共聚物存在下 SNS 之间的静电排斥。发现嵌段共聚物的相对亲水性极大地影响了 SNS 一维组装中相互作用的平衡。HLB 值较大的嵌段共聚物在近中性 pH 条件下促进 SNS 的一维组装，而 HLB 值较小的嵌段共聚物在碱性 pH 条件下促进 SNS 的一维组装。因此，通过使用具有不同亲水和亲油链长的嵌段共聚物，可以在广泛的 pH 范围内（7.5-9.5）实现 SNS 的一维组装。
