Time series Fourier transform infrared spectroscopy for characterization of water vapor sorption in hydrophilic and hydrophobic polymeric films.

• Time series FTIR spectroscopy was used to study water vapor sorption in different polymeric films. • PVOH sorbed many water vapor molecules, leading to swelling and dissolving of polymer crystallites. • The amount of water sorbed was higher in PLLA and PVC than in PE or PTFE due to hydrophilic groups. • Band shift of difference spectra indicated stronger hydrogen-bonding network in the PTFE matrix. This work investigates the nature of the molecular interactions between water vapor and polymers using time series Fourier transform infrared (FTIR) spectroscopy. A detailed analysis of the frequency shifts and relative peak intensities led to the conclusion that polyvinyl alcohol (PVOH) sorbed a large quantity of water vapor molecules, resulting in swelling and dissolving of polymer crystallites. Difference spectra were calculated to investigate spectral changes occurring upon sorption by dividing the spectra of polymers during the sorption time series by the spectrum of the dry sample and subsequently subtracting the water vapor spectrum. Based on the absorbance area of the OH stretching vibration region (4000–3000 c m - 1 ) in difference spectra, the amount of water sorbed was significantly higher in poly-L-lactic acid (PLLA) and polyvinyl chloride (PVC) than in polyethylene (PE) and polytetrafluoroethylene (PTFE), increasing with the hydrophilicity of the surface. The OH stretching band of difference spectra shifted from 3499 c m - 1 for PVC, to 3416 c m - 1 for PE and finally to 3387 c m - 1 for PTFE, indicating a more strengthened hydrogen-bonding network in the PTFE matrix upon water vapor sorption. [ABSTRACT FROM AUTHOR]