# Role of Functional Monomers upon the Properties of Bisphenol A Molecularly Imprinted Silica Films
## 3 Results and Discussion
### Structure of BPA-MIP and NIP Films  
FTIR spectroscopy was used to characterize the films and specifically to prove the presence of BPA molecules upon the organosilica matrix. In Figure 2a,b, FTIR spectra of imprinted sol-gel films BPA-MIPMPTES and BPA-MIPDAMOT and non-imprinted homologues NIPMPTES and NIPDAMOT, respectively, were compared with the spectrum of BPA template molecule. FTIR analysis of BPA-MIP and NIP films presented some similarities and showed the main characteristic polymeric bands.  
The stretching vibrations characteristic to the organic functionalities of the two monomers, \(\
u\)-CH2 and \(\
u\)-CH-, recorded in the 2950-2920 cm\({}^{-1}\) and 650-680 cm\({}^{-1}\) region were observed in the spectra of all films. Distinctive bands of the organosilica backbone network (i.e., Si-O-Si, Si-OH and Si-O stretching vibrations) were identified in all the spectra of films in the 1250-850 cm\({}^{-1}\) spectral range (bands overlapping in the spectra of  
Figure 1: Steps undertaken for the preparation of the BPA-MIPs films.  
Figure 2: FTIR spectra (KBr pellets) of (**a**) BPA-MIPMPTES and corresponding NIPMPTES and (**b**) BPA-MIP-DAMOT and its control NIPDAMOT sol-gel films, compared to the spectrum of BPA.  
BPA-MIPs and NIPs). For MPTES-based films (Figure 2a), the band at 2552 cm\({}^{-1}\) revealed the presence of mercapto group (-SH) in the organosilica matrix. In addition to mercapto band, other characteristic bands in the BPA-MIPMPTES spectrum were distinguished as follows: the bands of the methoxy groups, asymmetric \(\
u_{\text{asym}}\) (Si-OCH\({}_{3}\)) and symmetric \(\
u_{\text{sym}}\) (Si-OCH\({}_{3}\)) stretching vibrations at 2924 and 2864 cm\({}^{-1}\). In Figure 2b, spectra of films with DAMO-T, some of the characteristic bands of N-H bonds form DAMO-T were spotted at 3381 cm\({}^{-1}\) (\(\
u_{\text{N-H}}\)) and the bending vibrations at 1652 cm\({}^{-1}\) (\(\delta_{\text{N-H}}\)). The results indicate that the organosilica functional monomers were quantitatively incorporated into the hybrid crosslinked networks by alcohol/aldol polycondensation of DAMO-T or MPTES.  
In the spectrum of BPA (Figure 2a,b), we can distinguish the characteristic band of the aromatic ring \(\
u_{\text{C = C}}\) (Ar-C=C) recorded at 1603 cm\({}^{-1}\) and bands recorded at 1508, 1437, and 1360 cm\({}^{-1}\) assigned to the C-H bending. The stretching vibrations from 3319 cm\({}^{-1}\) (very intense band) and 2970/3030 cm\({}^{-1}\) were assigned to the \(\
u_{\text{OH}}\) (Ar-OH) and \(\
u_{\text{CH3}}\)- (C-CH\({}_{3}\)) bonds, respectively. The band recorded at 1223 cm\({}^{-1}\) is due to C-O stretching. Figure 2a also revealed the characteristic bands of BPA in the spectrum of BPA-MIPMPTES film, meaning the aromatic rings vibration at 1601 cm\({}^{-1}\), the bands for C-H bending at 1510 cm\({}^{-1}\), 1437, and 1354 cm\({}^{-1}\) and the stretching of C-O bonds given by the spiked intensity of the band at 1234 cm\({}^{-1}\), indicating that BPA molecules were successfully imprinted in the matrix [37; 38]. For BPA-MIPQAMOT, Figure 2b, these bands overlap with those of DAMO-T. Yet, a hint to BPA imprinting was given by the significant shifting of bands from 1652 and 1565 cm\({}^{-1}\) (in the spectrum of NIP) to 1665 and 1593 cm\({}^{-1}\) (in the spectrum of BPA-MIPQAMOT) and the presence of a band assigned to C-H bending at 1441 cm\({}^{-1}\).  
The bands at 3335 cm\({}^{-1}\) (sharp band) and 3032 cm\({}^{-1}\) in BPA-MIPMPTES and 3272 cm\({}^{-1}\) (wide band) in BPA-MIPQAMOT spectra were attributed to the stretching and bending mode of O-H groups from BPA implied in the monomer-template interactions through hydrogen bonding. When comparing the spectra of the two imprinted films, it is important to point out that a more visible imprinting effect was highlighted for BPA-MIPMPTES (as compared to BPA-MIPQAMOT).