An organoclay nanocomposite polymer coating was used to improve the mechanical & gas barrier properties of thin plastic substrates. Often used as the material for food packaging, polyolefins (BOPP, LDPE, & HDPE) and polylactic acid (PLA) have only moderate water vapor transmission rate (WVTR) and high oxygen transmission rate (OTR), leading to widespread food spoilage. In a facile, scalable dip coating process, a coating layer consisting of a polyvinyl alcohol (PVA) matrix and highly-oriented montmorillonite (MMT) nanosheet fillers exhibits exceptional mechanical properties, barrier properties, and visible light transmittance. Chemical crosslinking can also be used to induce even lower vapor permeability. Due to the incredible performance, ease of application, and versatility for chemical modification, this coating technology is highly applicable to the field of food packaging technology.