Steric effects on the rheology of nanocomposite gels of organoclay in dicarboxyl-terminated polybutadiene

作者：Li Fei; Lania Katie; Wang Xiaoliang; Xue Gi; Winter H Henning^*

来源：Soft Matter, 2010, 6(11): 2442-2448.

DOI：10.1039/b921774f

Nanocomposite gels were formed by mixing organically modified clay into a linear, end-functionalized polymer (dicarboxyl-terminated polybutadiene). Two differently sized but otherwise similar counterions were chosen for preparing the organoclay. Hydrogen bonding between polymer and clay causes the polymer/clay interface to grow by splitting the clay aggregates into smaller clay particles, then swelling these particles, exfoliating the clay sheets, and eventually assuming a stable dispersion in the polymer matrix. The clay with the larger counterion exfoliates faster, but does not form the stronger network (lower modulus, lower yield stress), and it needs more clay to reach its gel point (percolation threshold phi(c)). These seemingly contradictory observations (fast exfoliation but weak gel and later gel point) are attributed to steric effects of the larger macro-counterion. Parameters of the study are clay concentration phi and distance from the gel point. The low frequency linear viscoelastic behavior was analyzed using a percolation model (near phi(c)) and a power law in concentration (far above phi(c)). The use of two different organoclays allows comparison of the observed phenomena. The extent of agreement between experimental data and known models was used to theorize that the particle-polymer interactions are the controlling factor in the increasing solid-like behavior with increasing clay content.

• 出版日期2010
• 单位南京大学