A NEW FLUORINATED POLYURETHANE - POLYMERIZATION, CHARACTERIZATION, AND MECHANICAL-PROPERTIES

A fluorinated polyurethane based on the ethylene-fluoroalkyl-ethylene diol 3-(trifluoromethyl)3, 4,4,5,5,6,6,7,7,8,8-undecafluoro-1,10-decanediol, HO(CH2)2(CF2)4(CF2CFCF3)(CH2)2OH (including 5% 4-trifluoromethyl isomer), and 1,6-hexamethylene diisocyanate, OCN(CH2)6NCO, was prepared. The kinetics of polymerization was studied using Fourier transform infrared spectroscopy. The resulting polyurethane was characterized by viscometry, differential scanning calorimetry (DSC), and gel permeation chromatography. Correlations among the glass transition temperature, intrinsic viscosity, and molecular weight were established. Interestingly, multiple exotherms appeared in the DSC data, the areas and positions of which were time-dependent. The appearance of ordered domains in the solid state correlated with the decreased ratio of the "free" to "bound" C=O stretching frequencies in the infrared spectra. The effect of this apparent crystallization on mechanical properties was evaluated via stress-strain and dynamic mechanical testing.