# Role of Functional Monomers upon the Properties of Bisphenol A Molecularly Imprinted Silica Films
## 3 Results and Discussion  
### Preparation of the BPA-MIP Films  
This work was aimed at obtaining BPA-MIP films having two different organosilane functional monomers i.e., DAMO-T and MPTES. It is worth to mention that sol-gel hybrid films have attracted attention due to their efficient immobilization on various substrates, their enhanced stability and, in this case, easy access to the recognition cavities thus created. In this respect, the MPTES organosilane monomer was chosen for its adhesive properties and the ability to interact with the template, whereas DAMO-T monomer was expected to create stronger interactions with the template due to its diamino functionalities. For the later formulation, the adhesive properties to the substrate were compensated by addition of TEOS. Furthermore, the preparation method of films via sol-gel was very simple, quick, and did not require expensive chemicals or instrumentation.  
The synthesis recipes for the precursor solutions used to obtain BPA-MIP and NIP films are given in Table 1. Previously reported results showed that aromatic templates are difficult to extract from MIP films with over 4-5 \(\upmu\)m thickness and thinner films under 100 nm detach from the glass slide after multiple washing procedures [21]. Therefore, the monomer(s)/solvent/catalyst ratios were similar to the ones reported previously.  
The schematic representation for BPA imprinting in sol-gel films and deposition on glass substrates is given in Figure 1. An alkaline solution (1 N NaOH) was used to clean the surface of the glass substrates before film casting. The cleaning per glass slide was carried out in triplicate by immersing it in 10 mL of alkaline solution for 30 min. Finally, it was dried in a vacuum oven at 60 \({}^{\circ}\)C for 2 h. Herein, monolayers of polymeric films were prepared by spraying the obtained precursor solutions directly on cleaned glass substrates. In the first step, following the MI principle, a polymerizable complex between the organosilane precursors DAMO-T or MPTES and BPA molecules is formed in ethanol and, further on, a partial hydrolysis of this assembly takes place in basic medium (NH\({}_{4}\)OH, H\({}_{2}\)O) [22]. The second step consists of sols formation [34]. Non-hydrolyzed and partially hydrolyzed DAMO-T/MPTES-BPA molecules undergo a polycondensation reaction to form cross-linked and homogeneous tridimensional networks in the third step [14; 36]. After  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Notation** & **DAMO-T** & **MPTES** & **TEOS** & **BPA** \\  & **(mmoles)** & **(mmoles)** & **(mmoles)** & **(mmoles)** \\ \hline BPA-MIP\({}_{\text{MPTES}}\) & 0 & 0.364 & 0 & 0.0364 \\ NIP\({}_{\text{MPTES}}\) & 0 & 0.364 & 0 & 0 \\ BPA-MIP\({}_{\text{DAMOT}}\) & 0.364 & 0 & 0.0058 & 0.0364 \\ NIP\({}_{\text{DAMOT}}\) & 0.364 & 0 & 0.0058 & 0 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The synthesis recipes for control NIP and BPA-MIP films.  
a suitable maturation/curing protocol [28], the hybrid MIP films were washed several times and BPA was properly extracted with the formation of specific imprints.