# Role of Functional Monomers upon the Properties of Bisphenol A Molecularly Imprinted Silica Films
## 1 Introduction  
Bisphenol A (BPA) [2,2-bis (4-hydroxyphenyl)propane], an endocrine disruptor chemical (EDC), is known as the most widely used and toxic additive in the production of plastic together with polycarbonates, epoxy and polyester resins, and others (flame retardants, polyacrylate, polysulfone resins, polyetherimide). Many studies revealed that BPA beaches out from plastic products used for food packaging such as: plastic (baby) bottles, industrial supplies, dental sealant, medical devices, or sport equipment [1, 2, 3, 4]. Despite the ongoing COVID-19 pandemic that has affected the sales of paints and coatings in 2020, the global volume consumption of BPA is growing dynamically and is estimated to reach more than ten million metric tons by 2022 [5]. In 2019, the European Commission decided to form a research cluster namely EURION to find novel testing and screening methods to identify EDC [6]. BPA is easily released into the atmosphere and the natural environment through direct discharge, landfill leachate, is and frequently found in food and water sources [7, 8]. Long-term exposure to BPA alters endocrine function, causing many diseases as diabetes, obesity, cardiovascular diseases, chronic respiratory, thyroid and immune systems diseases, and even cancer [9, 10, 11]. Exposure to BPA occurs mostly via the oral route (approximately 90%) meaning dietary contamination and non-dietary sources such as sea water and cosmetics [12]. So far, several analytical methods have been established andextensively used to measure BPA, from which gas chromatography-mass spectrometry (GC-MS), immunoassay detection, liquid chromatography-mass spectrometry (LC-MS), and spectrophotometric and optical sensors are frequently used [13]. Yet, most of these methods are expensive, with time-consuming manipulation steps, complicated instrumentation, highly skilled operators, and a large amount of chemicals. Notwithstanding the many available techniques, there is an urgent need to establish a simple, rapid, and low-cost method for monitoring BPA. Ever since molecular recognition systems with artificial receptors have emerged, the attention of the research community for designing effective separation systems and chemical/sensors has increased significantly. Such molecular recognition systems, named molecularly imprinted polymers (MIPs) are prepared using the molecular imprinting (MI) technique. This is a versatile and inexpensive method to synthesize artificial polymers that mimic the behavior of natural receptors binding sites. The procedure usually involves the polymerization and crosslinking of functional monomers in the presence of a template molecule (that interacts with the polymer network via hydrogen, covalent, or ionic bonding interactions. After the removal of the template molecule, specific binding cavities toward the target molecules are left in the resulting polymers. Thus, the complementary molecular information of the template is transposed into the polymer, endowing the final material with specificity for this analyte but also with selectivity vs. other structural-resemblant analytes. Furthermore, the resulted MIPs are robust, exhibiting reusability, long-term stability and low production cost [14; 15]. Using this MI technique and the various polymerization procedures, MIPs in different shapes and sizes were developed, e.g., pearls [16], particles [17; 18], membranes [19; 20; 21], thin films [22; 23], nanospheres/nanofibers [24; 25], or electrochemical sensing receptors [13; 17; 26]. Nevertheless, depending on the polymerization procedure (for instance bulk polymerization [27]), MIPs can still present some inherent drawbacks, such as heterogeneous distribution of binding sites, low binding capacity, and poor site accessibility, which is why a great deal of attention should be focused on finding the proper procedure for delivering performant MIPs adequate for the targeted application.