Polymer Science and Engineering Group, Manchester Materials Science Centre, School of Materials, The University of Manchester, Grosvenor Street, Manchester M1 7HS, UK.
J Colloid Interface Sci. 2010 Feb 15;342(2):320-6. doi: 10.1016/j.jcis.2009.10.070. Epub 2009 Oct 30.
Synthetic heteroaggregate particle gels are a relatively unexplored area of colloidal science. In our previous work pH-triggered formation of heteroaggregate gels prepared from mixed pigment/polystyrene (PS) dispersions were investigated [Hui et al., J. Colloid Interface Sci. 324 (2008) 110]. The pigment was beta-copper phthalocyanine (beta-CuPc). In this study that work is extended by investigating the structure of the heteroaggregates formed at room temperature in greater detail and also studying the temperature-triggered gel breakdown that occurs upon moderate heating for the first time. In this work the heteroaggregate structures were studied using TEM, atomic force microscopy (AFM) and also SEM. AFM showed the mesoscale structure to consist of highly branched space-filling heteroaggregates. They are proposed to be the building blocks of the heteroaggregate gels. TEM data supported our previous suggestion that the pigment particles act as a crosslink centre within the heteroaggregate gels. SEM images showed evidence for softening and partial coalescence of the aggregates at elevated temperatures which helped to explain the temperature-triggered gel breakdown that occurred upon heating. The temperature-triggered gel breakdown was directly correlated with the glass transition temperature of the PS particles. A study of the maximum storage modulus, G', achieved just prior to gel breakdown, revealed a maximum at a volume fraction of pigment of 0.033. The data from the study are used to propose a conceptual model for the temperature-triggered breakdown of the pigment/PS heteroaggregate gels.
合成杂合粒子凝胶是胶体科学中一个相对未被探索的领域。在我们之前的工作中，研究了 pH 触发的由混合颜料/聚苯乙烯 (PS) 分散体制备的杂合粒子凝胶的形成[Hui 等人，J. Colloid Interface Sci. 324 (2008) 110]。颜料为β-铜酞菁（β-CuPc）。在这项研究中，通过更详细地研究在室温下形成的杂合粒子的结构，并首次研究适度加热时发生的温度触发凝胶破裂，扩展了这项工作。在这项工作中，使用 TEM、原子力显微镜 (AFM) 和 SEM 研究了杂合粒子的结构。AFM 显示出介观结构由高度分支的空间填充杂合粒子组成。它们被提议作为杂合粒子凝胶的构建块。TEM 数据支持了我们之前的假设，即颜料颗粒在杂合粒子凝胶中充当交联中心。SEM 图像显示了在升高的温度下，粒子的软化和部分聚结的证据，这有助于解释加热时发生的温度触发凝胶破裂。温度触发的凝胶破裂与 PS 粒子的玻璃化转变温度直接相关。对凝胶破裂前达到的最大储能模量 G'的研究表明，在颜料体积分数为 0.033 时达到最大值。该研究的数据用于提出颜料/PS 杂合粒子凝胶的温度触发破裂的概念模型。
