## 2 Applications in Chemistry
### Ring-Opening Polymerization  
The class of five- and six-membered cyclic alkylene carbonates is large and varied, offering a wide range of monomeric systems for ring-opening polymerization (ROP), leading to new polymers [112; 113; 114]. [PERSON] and co-workers [115] reported the synthesis of a \(\alpha\)-(cyclic carbonate), \(\omega\)-Hydroxyl/Ifaconic acid asymmetric telechelic poly(\(\varepsilon\)-caprolactone), by ROP followed by modification of the cyclic carbonates with 2-phenylethylamine (Scheme 46). Firstly, compound **86** was prepared with 96% yield by reacting GC **1a** as a functional bio-based initiator with \(\varepsilon\)-caprolactone **27** in the presence of tin 2-ethyllexanoate (110 \({}^{\circ}\)C, argon flow). The authors reported that the ROP technique allows control of the molecular weights, as well as a linear correlation of the molecular weight vs. monomer conversion. The reactivity of compound **86** was demonstrated through the modification with 2-phenylethylamine to give hydroxylurethane **87** using a non-isocyanate route. **Scheme 46. Synthesis of compound 86 and subsequent modification to give hydroxylurethane 87 using a non-isocyanate route. **  
In 2016, [PERSON] and co-workers developed an anionic ring-opening copolymerization technique for cyclic carbonate **1c** and _tert_-butyl glycidyl ether **2c**, followed by the removal of the protective group (Scheme 47) [116]. The hydroxy-functionalized PEG derivatives were submitted to sequential transcarbonylation, transalkylation, and fragmentation, aiming to replace carbonate groups with ether linkages. Poly(ethylene oxide-co-_tert_-butyl glycidyl ether)hydroxyl telechelic copolymer **88a** was synthetized via the reaction between **1c** and **2c** under mono-mode microwave irradiation, using CsOH as an initiator. After 15 h at 180 \({}^{\circ}\)C, **1c** was totally consumed, and the product **88a**, with molecular weight valuesof 750-1700 g.mol\({}^{-1}\), was obtained. Further, poly(ethylene oxide-co-glycidyl ether) **88b** was obtained after the removal of the _tert_-butyl protective group, generating hydrophilic reactive hydroxyl sites in the copolymer. The synthesis of a new polyether by cationic and anionic ROP of a cyclic carbonate-containing epoxide **1m** under different conditions was achieved by [PERSON] and co-workers [115] to improve the hydraulic barrier properties of Na-smectite liners to saline leachates (Scheme 48). By using a strong non-nucleophilic base, it was possible to perform concomitant ring-opening of both the epoxide and the cyclic carbonate, providing the respective poly[oxy(ethane-1,2-diyl)] **89** with 87% yield. In cationic conditions, poly[-oxy(ethane-1-[(methyloxy)methyl]oxirane]-1,2-diyl)] **90** was obtained with 52% yield by selective ring-opening of the cyclic carbonate functionality. In contrast, the treatment under nitrogen of the monomer with boron trifluoride resulted in ring-opening of the epoxide to give the poly(oxy[-ethane-1-[(4-methoxyphenylyl)-1,3-dioxolan-2-one]-1,2-diyl]) **91** with 63% yield. Thereafter, nanocomposites of sodium smectite were formed from those polymers via clay polymerization in situ and solution intercalation methods. The resulting nanocomposite **91** was shown to be more resistant to leaching in 3M NaCl than its respective cyclic carbonate **1m**. In 2017, [PERSON] and co-workers [117] described the degradation of poly(ethylene terephthalalate) by ethylene carbonate (EC) in the presence of potassium hydroxide, a low-cost catalyst. Degradation of PET at 130 \({}^{\circ}\)C produced short-chain oligomers with approximately 33% of carbonate units inserted in their structure, resulting from the ring-opening of EC with partial decarboxylation. Furthermore, the reaction of bis(2-hydroxyethyl) terephthalate (BHET) with EC in the absence of KOH produced difunctional oligomers with hydroxyl terminal groups, bearing aromatic rings esterified with polyether short chains. Generally, such oligomers could be applied as macroglycols for the preparation of thermoplastic polyurethane.