Combination of atom transfer radical polymerization and click chemistry toward cellulose-rosin derived UV-absorbent copolymers

UV absorption coating is an important function material, which can protect the substrates from photoaging. In this work, a class of sustainable UV-absorbent copolymers derived from ethyl cellulose (EC), fatty acid and rosin were prepared by a combination of atom transfer radical polymerization (ATRP) and click chemistry. To fulfill this strategy, the pendant azides were first attached onto the backbone of EC. Then, ATRP was applied to fabricate well-defined poly(lauryl methacrylate) (PLMA) bearing terminal alkynes. Finally, click chemistry between the pendant azides in EC and the alkynes in PLMA as well as in rosin esters (DAPE), was performed to achieve the cellulose-rosin graft copolymers (EC-(g-DAPE)-g-PLMA) with UV absorption property. The chemical structure of cellulose-rosin graft copolymers was confirmed by FTIR, 1H NMR and GPC. Thermodynamic performance analysis indicated that these EC-rosin graft copolymers showed better thermal stability than EC. Due to the synergistic hydrophobic interaction of rosin and the hydrophobic lauryl groups in PLMA, these graft copolymers showed excellent hydrophobic property, and the static contact angles were all above 90°. In addition, all the EC-rosin graft copolymers showed outstanding and stable UV absorption capability, and maintained excellent UV absorption capability after continuous UV-irradiation for 1 h or being heated to 100 °C for 0.5 h, which had potential application in UV absorption materials.