摘要
采用原子力显微镜 ,分别对无机交联体系聚丙烯酰胺 Cr3+ 和有机交联体系聚丙烯酰胺 酚醛胶态分散凝胶的微观结构进行了显微图像分析 .发现无论是在有机还是无机交联体系中 ,也无论聚丙烯酰胺和交联剂浓度如何变化 ,在微米尺度上最终形成的都是具有自相似性的树枝状分形图像 ,在更小尺度上则发现单个小树杈分形体都是由纳米级的颗粒紧密堆积而成 .在所研究的胶态分散凝胶体系中 ,树枝状分形结构的形成及其具体的形态取决于聚丙烯酰胺的浓度 ,而交联剂的有无及其多少只对树枝状凝胶分形的几何形态产生一定影响 .实验结果还表明纳米级 (≤ 10 0nm)的胶体颗粒构成的分形结构的凝胶其弹性模量G′比微米级的高出一个数量级 .且粒子尺度越小 。
Many scholars have made contributions on the formulae of the colloidal dispersion gel (CDG) and the factors affecting on the gelation performance. However, few reports were concentrated on studying the microstructure of the CDG. Polyacrylamide (HPAM)/Chromium acetate and HPAM/phenolic aldehyde colloidal dispersion gel, which come respectively from different cross-linking systems, inorganic and organic, were studied by the microscopic image analysis with the atomic force microscope(AFM). All of the CDG is founded to present eventually a self-assembly branch-like fractal structure under the scanning range of micrometer magnitude, and the fractal of a single twig was formed by compact stock of nanometer particles on a smaller scale regardless of the concentration variation of HPAM and the cross-linking reagent in either inorganic cross-linking system or organic cross-linking system. It is revealed that formation and morphology of the branch-like fractal structure depend on the concentration of HPAM, and the presence and concentration of cross-linking reagent only affect the topography of branch-like gel fractal. Moreover, the experimental results demonstrate that the elastic modulus of the gel with the fractal structure formed by the nanometer colloid particles is higher one order of magnitude than that by micrometer ones, and that the smaller the particle diameter is, the higher the gel kinetic stability is.
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2002年第5期592-597,共6页
Acta Polymerica Sinica
基金
国家自然科学基金 (基金号 4963 2 0 70 )
国土资源部"九五"重点学科生长点项目资助
