A difference in absorbance of the band at 1643 cm -1 , corresponding to stretching vibration of C=C, was observed. The carbon-carbon double bonds present in the macromonomer from the attached HEMA are converted into single carbon-carbon bonds during photopolymerization process. Thus, the higher absorbance of this band after photocuring in air indicates that oxygen inhibition had occurred. However, the gel fractions (see Table , in the SI) of all photocured elastomers were similar, approx. 93%-curing atmosphere did not affect gel fraction results.