A Priori Prediction of Mass Spectrometric Product Patterns of Photoinitiated Polymerizations

We introduce a method for the a priori prediction of mass spectra of complex poly­(methyl methacrylate)­s initiated by photoinitiators featuring multiple cleavage points. The method is based on permutation mathematics using multinomial coefficients to predict the probability of each poly­(methyl methacrylate) species’ isotopic pattern contribution to the overall mass spectrum. The method assumes a statistical behavior for the cleavage of the photoinitiator. The excellent agreement of the predicted mass spectrum based on multinomial coefficients with the experimental mass spectrum confirms a multipoint cleavage mechanism of the assessed photoinitiators. We exemplify our method for the prediction of mass spectra of poly­(methyl methacrylate)­s initiated by four tetraacylgermane derivates and one bisacylgermane, recorded after visible light pulsed-laser polymerization by high resolution Orbitrap electrospray ionization mass spectrometry (ESI-MS). The excellent agreement of our approach with experimental data suggests that a wide array of polymer mass spectra of polymers initiated by initiators capable of multiple cleavage events can be quantitatively predicted.