In this article, Polymer/Clay Nanocomposite (PCNC) suspensions were prepared via a simple mixing approach of nanoclay and polymer latexes in aqueous solutions with ultrasonification. The XRD and DSC measurements indicated that, under certain conditions, the chemically modified nanoclay could be exfoliated in the composite although no rigorous delaminating process was applied. The effects of the variables, such as clay and polymer varieties, process conditions, clay contents, etc., on the nanoclay exfoliation, were correlated. It was found that the nanoclay properties and their interactions with the polymer matrix played a vital role in determining the PCNC’s barrier performances. The possible mechanism of exfoliation of the nanoclay was discussed.