Polymer Chemistry PAPER Cite this: Polym. Chem., 2015, 6, 2076 Received 28th December 2014, Accepted 7th January 2015 DOI: 10.1039/c4py01801j www.rsc.org/polymers A novel biodegradable polymeric surfactant synthesized from carbon dioxide, maleic anhydride and propylene epoxide† Yulei Liu, Kuirong Deng, Shuanjin Wang, Min Xiao,* Dongmei Han and Yuezhong Meng* Terpolymerizations of CO 2 , propylene epoxide (PO) and maleic anhydride (MA) using zinc adipate (ZnAA) as a catalyst were carried out in a toluene solution. A series of biodegradable terpolymers (PPCMAs) with different polyester and polycarbonate contents were synthesized. The molecular chain sequence struc- ture of these terpolymers was proved to be a gradient one based on 1 H NMR investigation combined with in situ infrared technology monitoring the reaction process. The sulfonation of biodegradable PPCMAs was carried out by the addition of sodium hydrogen sulphite into ethylenic double bonds of the unsatu- rated polyester unit. The surface activities and the aggregation of these sulfonated biodegradable terpoly- mers in aqueous solution were investigated by surface tension measurement and dynamic light scattering (DLS) technology. The results indicate that the sulfonated biodegradable terpolymer with comparable hydrophilic and hydrophobic segment contents tends to adsorb at the air/water interface and thus exhi- bits the best surface activities. The surface tension of the aqueous solution of the polymer with 56.8% hydrophilic segments reaches 47.5 mN m -1 at its critical micelle concentration (CMC). Introduction The synthesis of biodegradable polycarbonates from CO 2 and epoxides has been studied over 40 years since the pioneering work of Inoue and co-workers in 1969. 1 Numerous well- defined catalyst systems, typically based on zinc, 2 chromium, 3 cobalt, 4 aluminum 5 and bimetallic complexes, 6 have been developed for this copolymerization, which have resulted in greatly suppressing ether linkages, increasing polymer selecti- vity, controlling molecular-weight distributions and carbonate/ ether selectivity. 7 Despite the significant progress this field has made, the scope of epoxides used in the production of CO 2 copolymers is very narrow. Either thermal and mechanical pro- perties or the estimated production costs of the copolymers limit their widespread applications. Therefore, much effort has been devoted by researchers to synthesize more diverse CO 2 -based copolymers to improve material performances as well as enrich their categories in order to broaden the fields of application for these greener polymers. One approach is to syn- thesize terpolymers of CO 2 and two different epoxides, 8 or ter- polymers of CO 2 , one epoxide and another kind of monomer such as cyclic anhydrides, 9 lactides, 10 lactones, 11 etc., which was proved to be an effective way to tune the properties of CO 2 - based copolymers. Another approach is to design and syn- thesize a CO 2 -based copolymer containing active groups fol- lowed by post-modification to endow the polymer with improved properties or new functions. 12 Maleic anhydride (MA) is a well-known abundantly available monomer for synthesizing unsaturated polyesters. The terpoly- merization of CO 2 with an epoxide and MA was proved feasible by either Zn–Co(III) double metal cyanide complex catalyst 13 or zinc dicarboxylate, 14 and the corresponding random poly (ester-co-carbonate)s were prepared. Such a poly (ester-co-car- bonate) contains double bonds in its main chain, and the con- tents of the double bonds can be easily tuned by changing the feed ratios of monomers. The existence of the double bonds affords the opportunity for further modification to regulate the thermal and mechanical properties of the CO 2 -polymer or to endow it with new functions. In previous work, 15 we syn- thesized poly(propylene carbonate maleate) (PPCMA) with an ester content lower than 15% from CO 2 , propyleneoxide (PO) and MA using zinc dicarboxylate as a catalyst. These terpoly- mers can be easily cross-linked using dicumyl peroxide (DCP) as a cross-linking agent at elevated temperatures affording † Electronic supplementary information (ESI) available: 1 H NMR data. See DOI: 10.1039/c4py01801j The Key Laboratory of Low-carbon Chemistry & Energy Conservation of Guangdong Province/State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou 510275, PR China. E-mail: stsxm@mail.sysu.edu.cn, mengyzh@mail.sysu.edu.cn; Fax: +86 20 84114113; Tel: +86 20 84115506, +86 20 84114113 2076 | Polym. Chem. , 2015, 6, 2076–2083 This journal is © The Royal Society of Chemistry 2015