SYNTHESIS OF RENEWABLE DEGRADABLE ROSIN- SUBSTITUTED POLYESTERS BY A COMBINATION OF RING- OPENING POLYMERIZATION AND "CLICK CHEMISTRY"

Thus, the development of novel low-cost and scalable monomers and their polymers from renewable biomass is essential. On the other hand, the lack of available landfill space demands the synthesis of renewable and biodegradable polymers. As one of the major classes of petroleum chemicals, cycloaliphatic and aromatic compounds offer rigidity and chemical stability to polymers derived from them. However, such important polymeric materials are largely missing or ignored in the communities of renewable polymers. We have recently utilized gum rosin as a renewable resource for manufacturing of “green” plastics. 5 Gum rosin, whose major components are rosin acids, has characteristic hydrocarbon-based hydrophenanthrene rings, similar in rigidity and chemical stability to petroleum chemicals-based cycloaliphatic and aromatic compounds. 6 In the development of degradable polymers from renewable resources, we have combined renewable rosin acid moiety-containing segment and degradable caprolactone segment to develop a block copolymer through suitable functionalization and appropriate polymerization techniques. 7 However, this strategy is limited because the rosin-acid-containing segment is not degradable. Herein, we develop our rosin acid-containing polymers one major step forward, that is, to prepare rosin-acid substituted polycaprolactone. Such strategy would satisfy both renewability and full degradability since molecular rosin moiety is left after the degradation. To the best of our knowledge, this is the first report to prepare fully degradable rosin-acid-containing polymers. We integrated model rosin acids, hydrogenated gum rosin and raw gum rosin into the degradable polymers by a combination of ring-opening polymerization (ROP) and “click chemistry”. Experimental Materials. Dehydroabietic acid (DHAA, ~90%) and hydrogenated rosin were obtained from Wuzhou Chemicals, China and used as received. Gum rosin was purchased from Acros. Toluene and tetrahydrofuran (THF) were refluxed with sodium and distilled out just before use under nitrogen atmosphere. 2-Chlorocyclohexanone, m-chloroperoxybenzoic acid (mCPBA), oxalyl chloride, triethylamine, propargyl alcohol, Sn(II) 2-ethylhexanoate (Sn(Oct)2), dichloromethane (CH2Cl2), N, N-dimethylformamide (DMF), methanol, sodium azide, copper iodine and diazobicyclo[5.4.0undec-7-ene] (DBU) were used as received. α-Chloro-e-Caprolactone (αCleCL) and 2hydroxyethyl 2-bromoisobutyrate (HEBiB) was prepared according to the literature. 7