# Lastingly Colored Polylactide Synthesized by Dye-Initiated Polymerization
## 2 Materials and Methods  
The synthesis of complexes and polymerization reactions, which required an inert atmosphere of N\({}_{2}\), was performed by using a glove-box (MBraun) or standard Schlenk apparatus and vacuum line techniques.  
Solvents for synthesis were purified by standard methods: MeOH (HPLC, VWR) distilled over Mg, dichloromethane (99.8% VWR), and _n_-hexane (HPLC, VWR) was dried and purified using the Solvent Purification Systems (Inert, PureSolv EN 1-7 Base), C6D6 was distilled over CaH2. _L_-LA ((3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione) (98%; Aldrich) was recrystallized from toluene and sublimized prior to its use. Chemicals that were obtained from commercial sources were used without further purification: 2,4-di-_tert_-butylphenol (99%, Sigma-Aldrich, St. Louis, MO, USA), _cis-2_,6-dimethylpiperidine (97%, Sigma-Aldrich), formaldehyde (37% solution in H2O, Sigma-Aldrich), diethylzinc solution (1.0 M in heptane, Sigma-Aldrich), di-_n_-butyl-magnesium solution (1.0 M in heptane, Sigma-Aldrich), Disperse Red 1 (2-[4-(Nitrophenylazo)-N-ethylphenylamino]ethanol, dye content 95%, Sigma-Aldrich), Disperse Red 13 (2-[4-(2-Chloro-4-nitrophenylazo)-N-ethylphenylamino]ethanol, dye content 95%, Sigma-Aldrich).  
The NMR spectra were recorded at 298 K using a Bruker Avance 500 MHz spectrometer. Chemical shifts are reported in ppm and referenced to the residual protons in the deuterated solvent (C6D6, 1H: 7.16 ppm, 13C: 128.06 ppm) [41]. HRMS spectra were recorded using Bruker MicOTOF-Q spectrometers with an Electrospray ionization technique(ESI) and time-of-flight mass analyzer. Microanalyses were conducted with an Elementar CHNS Vario EL III analyzer. The number-average molar mass (\(M_{n}\)) and the molar mass distribution index (\(\mathrm{D_{M}}\)) of the samples were determined by gel-permeation chromatography (GPC). The system was composed of a Viscotek GPCmax unit (pumping and degassing of solvent, sample injection with autosampler), a 305 TDA detection unit (consisting of column, a UV measuring cell, RI detector, hybrid Right-Angle Light Scattering/ Low-Angle Light Scattering (RALS/LALS) detectors, and a viscometer), and a PDA UV detector (190-500 nm). The system was equipped with a Jordi Labs DVB column (mixed bed, 5 um), which worked with dichloromethane at 30 \({}^{\circ}\)C, with a flow rate of 1 cm\({}^{3}\)/min. The polymer populations (including repeating units and end groups) were characterized by a MALDI-ToF system. The spectrometer used was Bruker ultrafineXtreme, measurements were carried out in linear mode, with a DCTB (2-[(2E)-3-(4-tert-Butylphenyl)-2-methylprop-2-enylidene)malononitrile) matrix and potassium as an ion source.  
X-ray diffraction data for a suitable crystal of each sample were collected using an Xcalibur CCD Ruby with a \(\omega\) scan technique. The data collection and processing utilized the CrysAlis suite of programs [42]. The space groups were determined based on systematic absences and intensity statistics. Lorentz polarization corrections were applied. The structures were solved using intrinsic phasing SHELXT-2014/5 and refined by full-matrix least-squares on F2. All calculations were performed using the SHELX suite of programs [43]. All non-hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atom positions were calculated with geometry and were not allowed to vary. Thermal ellipsoid plots were prepared with 50% of probability displacements for non-hydrogen atoms by using the Mercury 3.9 program [44]. All of the data have been deposited with the Cambridge Crystallographic Data Centre CCDC-1982025 for (L\({}^{\mathrm{dmp}}\))2 Zn and -1982026 for (L\({}^{\mathrm{dmp}}\))2 Mg. Copies of the data can be obtained free of charge by application to CCDC, 12 Union Road, Cambridge CB21 EZ, UK or e-mail: [EMAIL_ADDRESS].  
Syntheses details are presented in Appendix A.