Thermal analysis goes with mass spectrometry to evaluate the molecular weight of a fluorinated plasma polymer
T. Fouquet, G. Mertz, M. Delmée, L. Fetzer, and C. Becker
Plasma Processes and Polymers, vol. 12, no. 9, pp. 980-990, 2015
A combination of thermal analysis (differential scanning calorimetry DSC) and mass spectrometry (MS) has been proposed to estimate the molecular weight (MW) of fluorinated plasma polymers, not reachable by MS only owing to their high dispersity. A noticeable crystalline index has been previously reported for these plasma polymers leading to a detectable melting peak in DSC, itself not sensitive to dispersity. Relying on the variation of the melting temperature as a function of MW, a set of standards of various MW have been synthesized by atom transfer radical polymerization (ATRP). MW (from MS) plotted as a function of melting temperatures (from DSC) provided a calibration curve further used to estimate the MW of plasma polymers based on their own melting temperature. The comparison of the DSC thermograms of plasma polymer and another reference made by free radical polymerization (FRP) finally offered an original insight into the contributions from insoluble and soluble parts, mimicked by a FRP (branched, low MW) and a ATRP (linear, high MW) polymer respectively.