Potassium methoxide

Poly(D,L-lactic acid; Mw=20.2 kDa, Mn=12.4 kDa) was purchased from Lactel. PEG-b-Polylactic acid di-block polymer (Mw PEG=5 kDa, Mw PLA=10 kDa) was purchased from Polysciences, Inc. (Warrington, PA, USA). Anhydrous N,N-dimethylformamide, dichloromethane, N,N′-diisopropylcarbodiimide, 4-(dimethylamino)pyridine, glycidol, potassium methoxide (25% in methanol), poly(vinyl alcohol) (Avg Mw=30–70 kDa), paraformaldehyde, Tween 80 and 1,1,1-tris(hydroxymethyl)propane were obtained from Sigma-Aldrich (St Louis, MO, USA). Diethyl ether, ethyl acetate, methanol, acetonitrile and dimethylsulfoxide (DMSO) were obtained from J.T. Baker (Avantor Performance Materials, Central Valley, PA, USA). 0.5–1 kDa dialysis device (10 ml volume size) were purchased from VWR International (Bridgeport, NJ, USA).

PLA (Mn = 11–12 kDa) was obtained from Lactel Absorbable Polymers. 1,1,1‐tris(hydroxymethyl)propane, potassium methoxide, 4‐dimethylaminopyridine (DMAP), N,Nʹ‐diisopropylcarbodiimide (DIC), dimethylformamide (DMF), diethyl ether (ether), and PO, and poly(l‐lysine) (PLL) were obtained from Sigma‐Aldrich. Glycidol, octinoxate, ethyl acetate (EtOAc), dimethyl sulfoxide (DMSO), dichloromethane (DCM), acetonitrile (ACN), acetone, methanol, deionized water, trifluoroacetic acid (TFA), phosphate‐buffered saline (PBS), DiIC₁₈(5) solid (DiD), and dihydrorhodamine 123 (DHR123) were purchased from Thermo Fisher Scientific. Eusolex‐9020 and ‐OCR were obtained from EMD Millipore. Sunscreen purity was confirmed by gas chromatography mass spectrometry and high‐performance liquid chromatography (HPLC) analysis against secondary standards from Aldrich. VITRO‐SKIN^® was obtained from IMS, Inc., and HelioPlates HD6 polymethylmethacrylate (PMMA) plates from Labsphere. Aldehyde quantification assay (ab138882) was purchased from Abcam. Polymers HPG and PLA‐HPG were prepared using literature methods.41