The only change regards the dark blue spectrum referring to the UV/vis absorption profile on quartz. In the published Supporting Information, the spectrum is of a slightly compressed monolayer and was erroneously attributed to an uncompressed monolayer. The new corrected figure contains the right spectrum of an uncompressed monolayer. The difference between uncompressed and compressed monolayer is subtle. There is only a 1 nm red-shift in the peaks of the compressed one with respect to the uncompressed case. This is sensible because a slight red-shift is expected for more overlapping anthracenes. Other than that, the spectra are virtually superimposable. The new spectrum is additionally more resolved with better S/N ratio and better visible vibronic splitting of the anthracene species. The old spectrum was measured by depositing a monolayer on each face of the quartz wafer (two monolayers in total), whereas the new spectrum was measured by depositing a single monolayer; hence the intensity is roughly halved. Due to possible future publications which involve the characterization of these monolayers (compressed and uncompressed) by UV/vis absorption spectroscopy, we feel the need to report the correct spectrum, even if the change is subtle. Substituting the spectrum does not change in any way the conclusions, hypotheses, or the logical flow of the paper. In this case, the absorption spectrum on quartz was only measured in order to choose the proper irradiation wavelength for the polymerization reaction (405 nm). With the old and new spectra being superimposable, the irradiation wavelength remains the same.