## 5 Analysis of Template-Monomer Functional Interactions
### UV-Vis Spectroscopy  
The UV-Vis spectroscopy analytical method aims to determine the strength of the intermolecular interaction between the template and the functional monomer. The strength and affinity of the template-monomer will affect the selectivity and affinity of the polymer. Therefore, it is crucial to determine the suitable functional monomer which will interact strongly with the template to form a stable complex [52]. The interaction of template and monomer can be investigated using UV titration with nothing changes in absorbance [103]. The titration method using UV-Vis spectroscopy can evaluate the template-monomer association constant (Ka) so that the intramolecular interaction between template and functional monomer can be determined during the prepolymerization process and also the specificity and selectivity of the polymer [104; 105]. The Ka is calculated using the Benesi-Hildebrand equation [103] as follows:  
\[\frac{1}{\Delta\mathrm{Y}}=\frac{1}{\mathrm{Y}\Delta\mathrm{H}\mathrm{GKa}[ \mathrm{G}]}+\frac{1}{\mathrm{Y}\Delta\mathrm{H}\mathrm{G}} \tag{2}\]  
where \(\Delta\)Y is the change in absorbance, \(\mathrm{Y}\Delta\mathrm{H}\mathrm{G}\) is the change in absorbance at the end of the titration, and [G] is the concentration of the monomer added [106]. [PERSON] et al. [103] used UV titration to determine the interaction between atenol (template) and itaconic acid (functional monomer). Based on the calculation results, the association constant was 542.67 M\({}^{-1}\) in methanol solvent. [103]. In another study, [PERSON] et al. [107] used UV spectroscopy to determine the value of the association constant between atenol template and Itaconic acid as a functional monomer in a mixture of methanol: acetonitrile (1:1) resulted in a constant association value of 6.277 \(\times\) 10\({}^{2}\) M\({}^{-1}\). The interaction between atenol and itaconic acid is a hydrogen bond from the amine groups, and the carboxylic group of atenol and itaconic acid as the Ka value was increased in a more polar aprotic solvent [103; 105]. [PERSON] et al. [108] used UV Vis spectroscopy to see the interaction between itaconic acid monomer and diazepam as a template. The value of Ka obtained using the Benesi-Hildebrand formula was 381.9 M\({}^{-1}\) \(\pm\) 0.4. As stated by [PERSON] and [PERSON] [109], a weak interaction has a Ka value less than 25 M\({}^{-1}\), and a strong interaction has a Ka value more than 100 M\({}^{-1}\). So the interaction between itaconic acid and diazepam includes a strong interaction [108]. [PERSON] et al. [52] also used UV-Vis spectroscopy to see the strength of the interaction between template luteolin and three functional monomers, namely acrylamide (AM), 4-vinyl pyridine (4-VP), and 1-aryl piperazine (1-ALPP) with different concentrations. Interaction strength was detected from significant changes of absorbance on maximum wavelength. 1-ALPP was found to cause reducing absorbance on maximum wavelength due to the \(\pi\)-\(\pi\) transition of luteolin when added in higher concentration. Meanwhile, no changes were found on AM and slight changes on 4-VP [52]. Based on the literature search, UV-Vis spectroscopy is usually used to see the strength of the interaction (from Ka value) or binding experiment. In [PERSON]'s research in 2019 [110], a critical study was conducted to evaluate the adsorption performance of MIP and NIP for gossypol (an acidic organic compound) made with 2-(Dimethylamineino)ethyl methacrylate (DMAEMA) monomer using UV spectroscopy at 373 nm by comparing absorbance values before and after absorption. More significant differences in the value represented higher binding. The gossypol molecule has a pKa value of 6.5 [110; 111] and six phenolic hydroxyl functional groups -OH in its structure; it can form an acid-base ionic pair interaction with the basic amino group -NH\({}_{2}\) of DMAEMA monomer. Theoretically, functional monomers containing basic groups can interact strongly with phenolic acid hydroxyl groups through acid-base interactions [112].