To help identifying the latter, the partial methanolysis products were then analyzed by MALDI-TOF (Figure ). Keeping in mind that the response of each polymer to ionization is not known, absolute quantification of the different series in the analyzed sample is not possible. The spectrum at t = 0 min shows the presence of two series of peaks named A and B, corresponding respectively to the cyclic polymer and the presence of 4-cumylphenol end group (linear polymer), as described before. The profile of the spectrum at 2 min is similar to the initial time, with the main difference being the appearance of a series of peaks, with a measured mass of residual units of 212 g•mol -1 -C series. After 5 minutes of reaction, this profile evolves with the almost complete disappearance of the B series peaks and the appearance of three new series of peaks, named D, E and F, with measured residual unit masses of 32 and 90 and 228 g•mol -1 respectively. From 15 min the almost complete disappearance of the A series can be observed, with the C, D and E series representing now the majority of the peaks detected. The spectrum profile of the samples taken at 30 min is rather similar to that at 15 min. Finally, for the 120 min sample, the disappearance of peaks above 2000 m/z is clearly observed. This confirms the results obtained by SEC i.e. the presence in the sample of only small-sized oligomers. In this case, the degree of polymerization is calculated to be less than 7. In order to identify these end peak series with their corresponding end groups, it must be noted that methanolysis is carried out by the action of methanolate in the form of a double transesterification at the carbonate level. This can lead first to the formation of a hydroxyl end group and methyl carbonate followed by formation of a second hydroxyl endgroup. The molar masses of these expected structures are as follows: 212.1 g•mol -1 for PBPAC with end groups that are composed of a 4-cumylphenol unit and a hydroxyl group (corresponding to series C here); 228.1 g•mol -1 for PBPAC with two hydroxyl end groups (corresponding to series D here); 32.0 g•mol -1 for a polymer with hydroxyl and methyl carbonate end groups (series E); and 90.0 g•mol -1 for PBPAC with two methyl carbonate end groups (series F). The corresponding product structures are shown in Table . The correspondence between the masses of the measured and theoretical end groups clearly demonstrates MALDI-TOF efficiency for oligomers' structure determination, and more especially end groups. When plotting peak area for each peak series as a function of time now (Figure , sum of the area of all the peaks in a given series divided by the sum of the areas of all the series at a given time), it is possible to estimate the degradation rate evolution, and it also allows to identify which type of depolymerization has occurred. At 2 min, the SEC chromatogram (Figure ) shows that Mn has decreased from 32 000 g•mol -1 to 22 000 g•mol -1 while at the same time Figure shows that series A and B make up the majority in the sample. We can therefore conclude that the cleaved polymer chains make up only a small part of the mixture (10 %). The concordance of this information with the significant decrease in Mn leads us to believe once again that this is very likely a case of an endo degradation. Additionally, at this point we can also observe a decrease in the relative intensity of the series B (linear polymer) compared to series A (cyclic polymer). The direct consequence of this is an increase in the relative intensity of the series A from 0 to 2 min, as A and B make up the majority of the composition. This therefore seems to indicate a preferential depolymerization of the linear polymer over the cyclic polymer. This preference seems to be confirmed by the almost total disappearance of the series B peaks after 5 minutes, whereas series A only disappears after 15 min. This is further confirmed by the rapid appearance of the peaks of series C at 2 min without the appearance of series E. Indeed, when trans-esterifying polymers of series B, we end up with series C population, on the side where the hydroxyl group is released. It must be noted that the other population formed, with a 4-cumylphenol chain end and a methyl carbonate, with a theoretical residual unit mass of 270.1 g•mol -1 , was not observed under our conditions, even though we cannot yet explain why. Conversely, when the cyclic polymer (series A) is trans-esterified, we obtain series E as the first intermediate, with a hydroxyl group and a methyl carbonate at the chain ends. More generally, the combined appearance of the series D, E and F and the gradual disappearance of the cyclic polymer confirms the overall depolymerization of the polymer. In addition, the presence in equivalent proportions of the series D, E and F at the end of the reaction confirms the complexity of the mixture previously analyzed by SEC, and validates the impossibility of using SEC to identify the diversity of polymers present in the sample unlike MALDI-TOF mass spectrometry. Moreover, the appearance of signals attributed to the reaction intermediates as early as 2 min, accompanied by a decrease in the signals corresponding to the raw polymer, suggests that the detection limit for confirming depolymerization by MALDI-TOF under these conditions can be estimated at 0.5 % degradation, by correlation with SEC results. Therefore, despite the fact that it is not directly quantitative, MALDI-TOF is clearly a key analytical method for studying the depolymerization of PBPAC, and more generally of many polymers, in order to identify decomposition intermediates, especially as its use is now adaptable to high throughput, as we recently demonstrated for another application. Figure : Stacking of MALDI-TOF spectra of partial methanolysis of PBPAC, detailed view of 1400 m/z to 2200 m/z, samples taken at t = 0, 2, 5, 15, 30 and 120 min. Peaks corresponding to polymers from the same series are identified with the letters A, B, C, D, E and F, the corresponding structure are shown in table . To further analyze the degradation, and add another analytical technique to the comparison, samples issued from the partial PBPAC methanolysis were analyzed by FT-IR (Figure ). Here, depolymerization is first manifested by the appearance of the peak corresponding to the hydroxyl group between 3600 and 3200 cm -1 after 15 min. In parallel, the intensity of the peak at 1776 cm -1 , corresponding to the carbonyl bond of the carbonate moiety, gradually decreases, revealing a doubling of the peak at higher degradation percentage after 30 min. The appearance of a peak at 1612 cm -1 and peak doubling at 1235 cm -1 can also be observed. Finally, the intensity of the peak at 1194 cm -1 , which can be assigned to the C-O bond of the carbonate moiety, also decreases. Interestingly, the appearance of doubling in certain peaks could be the result of intermolecular hydrogen bonding between the polymer chain and the BPA released, and more specifically between the oxygen from the carbonyl of the carbonate and the hydroxyl group of BPA, resulting in a blue shifting of the peak. Nonetheless, these observations clearly generally confirm that the decrease in molecular weight observed in SEC is effectively the result of the carbonate bond cleavage in favor of the appearance of a hydroxyl group. In addition, in agreement with the SEC and MALDI-TOF results, depolymerization is found to be incomplete after 120 min, as evidenced by the remaining presence of the carbonyl carbonate bonds. Even more interestingly, the detailed analysis of these spectra revealed the possibility to develop a quantitative approach to PBPAC methanolysis based on FT-IR. It is largely inspired from the study by Ferreira et al. which performs the quantification of the BPA units in a copolymer PBT/PBPAC using this analytical method. In our case, we focus on quantifying the BPA end groups formed during depolymerization, which relies on the area ratio between two carefully selected peaks belonging only to BPA and to the PBPAC. For the polymer, the peak at 1777 cm -1 corresponding to C=O carbonate stretching was chosen for its high resolution and no overlap with other peaks. For BPA quantification, two choices are possible: the first is to the hydroxyl group that can be detected between 3600 and 3200 cm -1 , while the second is the peak corresponding to the stretching of BPA C=C bonds between 1646 cm -1 and 1583 cm -1 . While the first remains the indicator most used in the literature to confirm PBPAC degradation, it should be pointed out that in real-life situations, depending on the type of catalysis being studied, this choice could prove problematic, particularly in cases where, for example in biological samples, other hydroxylated products are present in the mixture (sugars, glycerols, etc.), which is often the case. In such cases, it may be worth considering the use of the C=C stretching peak. That's why we've tested both here, to effectively compare the sensitivity and error that can be obtained with each. To determine the equation for the correlation function linking the ratios of the two selected peaks in each case, we carried out a calibration curve mixing BPA and PBPAC in increasing proportions, from 5/95 to 90/10 molar ratios (i.e. 0.053 to 9 BPA equivalent to PBPAC polymeric unit). The results are presented in Figure , Table , figure . For the peak area ratio between the O-H from BPA and C=O from PBPAC, we can first clearly observe a linear correlation starting from the 20/80 ratio (i.e. 0.25 eq, figure ). In the case of the area ratio between the C=C from BPA and C=O from PBPAC, the response is also linear but starting at a lower 5/95 ratio (i.e. 0.053 eq), showing how the choice of the peak to be considered can drastically influence the range of application of the method. To discriminate further between the two ratios, the relative errors (RE %) of the area ratios were measured (Table ), and it clearly appears that the values are smaller in the case of the C=C and C=O peak area ratio, with errors between 2 and 8 % compared to 7 and 13 % for the ratio of the O-H and C=O bonds. Additionally, relative error measured in the case of the 90/10 ratio (BPA/PBPAC) being 20.5 and 16.0 % for the two peak couples, this point was excluded from the calibration curve. Finally, the molar ratio LODs for the two peak couples were calculated, with as a result a minimum ratio of 25/75 (0.35 eq) for the O-H and C=O bonds and 10/90 (0.11 eq) for the C=C and C=O bonds, which once again shows the superiority of the latter in our conditions. It should also be pointed out that under our current conditions, this corresponds to a detection limit for depolymerization confirmation of 10 %. To conclude, this study shows that it is possible to effectively quantify the proportion of BPA in a BPA/PBPAC mixture through the ratio of characteristic peak areas of the polymer and monomer, at least up to 4 BPA molar equivalent to PBPAC. In addition, this also confirms that the O-H bond from BPA may not be the most ideal one to consider for quantitative monitoring of PBPAC degradation, as its sensitivity is lower than that of other characteristic peaks of the monomer such as C=C. This may be due to the fact that it is a poorly resolved peak, strongly influenced by the presence of other hydroxylated molecules, starting with water, despite being located in a region of the spectrum that contains no other peaks. Table : Calibration data obtained from the ratio of the areas of the two selected peaks for BPA and PBPAC as a function of the ratio of the molar concentration of BPA to PBPAC.