The 2D platelet confinement effect on the membrane hole structure probed by electrochemical impedance spectroscopy

In this paper, ethyl cellulose (EC)/montmorillonite (MMT) composite membranes were prepared. As a potential candidate for drug delivery, the hole structures during acid treatment were characterized by XRD, SEM and electrochemical impedance spectroscopy (EIS). SEM pictures showed the formation of micrometer-size holes after adding MMT in the EC matrix. A new time constant appeared in the impedance spectrum of the composite membrane, implying structure variation by MMT. These rigid platelets would confine the relaxation of EC chain segments around MMT in the phase inversion process. During the acid treatment, EIS results indicated these micrometer-size holes would tend to shrink while the small holes in the EC matrix enlarged. The shrinkage of the micrometer-size holes could be attributed to the chain disentanglement due to the acid treatment. The above results suggest that it is easier to distinguish the hole variation by EIS, which is beneficial for analyzing the mechanism of the drug-releasing process. [Display omitted] •The 2D platelet confinement effect induces the formation of micrometer-size holes in ethyl cellulose (EC) membrane.•During the acid treatment, the micro-size holes in EC/MMT composite membrane tend to shrink.•The hole variation in the membrane can be effectively distinguished by electrochemical impedance spectroscopy.