Novel RAFT Polymerization of Poly(ethyl oleate) (PEO) Based on Palm Oil: Effect of Reaction Parameters and Characterization

Green polymer feedstocks have received considerable attention in recent years, along with increasing concerns about petrochemical-based materials and the limited availability of fossil resources. As a prospective candidate, palm oil-derived monomers have been polymerized via RAFT polymerization to produce bio-based surfactants. The RAFT polymerization of poly(ethyl oleate) (PEO), an oil-soluble polymeric surfactant, has been investigated in the presence of 4-Cyano-(dodecylsulfanylthiocarbonyl)sulfanylpentanoic acid (CDP) as a chain transfer agent (CTA), and azobisisobutyronitrile (AIBN) as an initiator. The influence of several experimental parameters, such as monomer concentration [M], chain transfer agent to initiator molar ratio ([CTA]/[AIBN]), and monomer to chain transfer agent molar ratio ([M]/[CTA]), and temperature, has been studied concerning to number-average molecular weight values ( M _n ), weight-average molecular weight ( M _w ), and molecular weight distribution ( Ð ) during RAFT polymerization. This study investigates the influence of parameters reaction against molecular weight, molecular weight distribution, and surfactant characteristics, such as hydrophilic-lipophilic balance (HLB), critical micelle concentration (CMC), and interfacial tension (IFT). At the experimental parameters above resulted from molecular weight, molecular weight distribution ( Ð ), HLB value, CMC value, and IFT value of 1,473-1,896 \(\:g.{mol}^{-1}\) ( M _n ), 1,614-2,329 \(\:g.{mol}^{-1}\) ( M _w ), 1.112 ± 0.014–1.217 ± 0.005 ( Ð ), 1.24 ± 0.065–8.37 ± 0.087 (HLB), 0.187 ± 0.002–0.382 ± 0.020 \(\:mg.{mL}^{-1}\) (CMC), and 4.628 ± 0.179–10.744 ± 0.156 \(\:mN.{m}^{-1}\) (IFT), respectively. This novel approach also provides polymeric surfactant (e.i. PEO) from ethyl oleate monomer using RAFT polymerization. This study evidences the dominant parameters leading to an excellent control of molecular weight ( M _n , M _w ) and molecular weight distribution ( Ð ). Interestingly, the control over molecular weight and molecular weight distribution was achieved by increasing the molar ratio of monomer to chain transfer agent ([M]/[CTA]) from 50 to 300, which also improved the M _w values. However, an additional increase in this ratio to 200 led to narrow control, indicating the existence of an optimal [M]/[CTA] ratio. The chemical structure and functional groups of PEO polymerization were confirmed through FTIR, Raman spectroscopy, ¹ H-NMR, and ¹³ C-NMR. Furthermore, the initiation of polymeric surfactant properties on PEO, such as hydrophilic-lipophilic balance (HLB), interfacial tension (IFT), and critical micelle concentration (CMC) values, was determined by the acid number and saponification number, fluorescence, and spinning drop methods, respectively.