Investigation of the interaction of CO₂ with poly (L‐lactide), poly(DL‐lactide) and poly(ε‐caprolactone) using FTIR spectroscopy

Abstract

Fourier transform infrared (FTIR) spectroscopy was used to reveal intermolecular interactions between carbon dioxide (CO 2 ) and the carbonyl groups of poly(L-lactide) (PLLA), poly(D,L-lactide) (PDLLA), and poly(e-caprolactone) (PCL). After exposing polymer films to high pressure CO 2 , the wave number of the absorption maxima of the polymer carbonyl groups shifted to higher values. Also, due to the interaction between CO 2 and the carbonyl groups of the polymers, a new broad peak in the bending mode region of CO 2 appeared. To distinguish between polymer-associated and nonassociated CO 2 , and to quantify these contributions, the bending mode peaks were deconvoluted. From these contributions, it was found that in the case of PCL more CO 2 is interacting with the polymer carbonyl groups than in the case of PDLLA and PLLA. Under our experimental conditions, 408C and pressures up to 8 MPa, a significant depression of the PCL melting temperature was observed.

On the unexpected non-monotonic profile of specific volume observed in PCL/CO2 solutions

“…As the peaks observed at 648 and 676 cm À1 can be assigned to CO 2 bending modes, which become Raman active by the interaction process, their presence in the Raman spectra of CO 2 -saturated PCL suggests that carbon dioxide is present in PCL in at least two 'populations', as also reported by Nawalade et al [10]: one 'polymer-associated', i.e. interacting with the PCL, and the other 'nonassociated'.…”

“…For this reason, spectroscopic techniques, such as Attenuated Total Reflectance (ATR), Fourier Transformed Infrared (FTIR) and Raman spectroscopy, are being widely used for the investigation of sorption behaviour of CO 2 (and of other low molecular weight penetrants) in polymers, as they provide useful information on both local gas concentration and on possible specific polymer/gas interactions. Actually, investigations based on the use of ATR and FTIR have revealed that CO 2 interacts with most polymers [9,10] as specific spectroscopic features of the solution (such as the observation of the splitting of the peak assigned to CO 2 bending mode) have been demonstrated to be the evidence of the interaction between the gas molecules and the polymer [8,9].…”

Experimental and modeling studies on the solubility of sub‐ and supercritical carbon dioxide (scCO2) in potato starch and derivatives

“…In addition, the CO 2 sorption in the starch matrix is relatively low compared with other semicrystalline polymers at the similar temperature and pressure range (Table 4). The differences in the CO 2 sorption of NPS compared with other materials may be due to differences in the physical properties (such as glass transition temperature ( T g ) and melting temperature ( T m )), morphological characteristics (such as the degree of crystallinity and swelling of the polymers) and also the occurrence of intermolecular interaction between CO 2 and the functional groups present in the polymers [18, 20, 26, 27, 32–37].…”

“…Furthermore, it can be concluded that the solubility of CO 2 in SA is higher than in NPS at all pressure values. The difference in the CO 2 solubility between NPS and SA may be related to a reduction in the crystallinity after the acetylation reaction ( vide supra ) [38, 39] and favorable intermolecular interaction between CO 2 and SA due to the presence of the carbonyl group (CO) in the SA matrix [32, 40, 41] (see later).…”

“…These observations indicate the presence of intermolecular interaction between CO 2 and the carbonyl group, which contributes to a positive effect on solubility of CO 2 in SA [20, 32].…”