Polymerization of Myrcene in Both Conventional and Renewable Solvents: Postpolymerization Modification via Regioselective Photoinduced Thiol–Ene Chemistry for Use as Carbon Renewable Dispersants

Abstract

Polymeric dispersants are useful materials used in many different industries and often derived from oil-based chemicals, for example, in automotive fluids so as to prevent particulates from precipitation and causing potential damage. These are very often polyisobutene derivatives, and there is a growing need to replace these using chemicals using renewable resources such as the use of naturally occurring myrcene. Polymyrcene (PMy), with an ordered microstructure, has been successfully synthesized via both anionic and radical polymerization in different solvents and subsequently subjected to functionalization via photoinduced thiol−ene click reactions with a number of thiols, methyl thioglycolate, 3-mercaptopropionic acid, 3-mercapto-1-hexanol, 2mercaptoethanol, and 1-thioglycerol, using 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator under UV irradiation (λ = 365 nm) at ambient temperature. The polarity of the solvent has an important impact on the microstructure of the produced polymyrcene and, in particular, 1,2-unit (∼4%), 3,4-unit (∼41%), and 1,4-unit (∼51%) PMy were obtained via anionic polymerization in a polar solvent (THF) at ambient temperature, while 3,4-unit (∼6%) and 1,4-unit (∼94%, including cis and trans) PMy were obtained with cyclohexane as the solvent. Subsequently, photochemical thiol−ene reactions were carried out on the resulting PMy with different isomers exhibiting different reactivities of the double bonds. This strategy allows for the introduction of functional/polar groups (−COOH, −OH) into hydrophobic PMy in a controlled process. Hydrogenation of PMy and derivatized PMy was carried out to investigate any effects on the stabilities of the products which are desirable for many applications.

Anionic synthesis and end-functionalization of polymyrcene in a flow microreactor system

“…This results in a significant variation of the V/V percentage of hexanes in the reaction medium (hexanes/THF): 14% (batch) and 29% (flow) with obvious consequences on the reactivity and selectivity. 42…”

“…This results in a significant variation of the V/V percentage of hexanes in the reaction medium (hexanes/THF): 14% (batch) and 29% (flow) with obvious consequences on the reactivity and selectivity. 42 The influence of the residence time t R was further evaluated at both of these temperatures from t R = 19 to 600 s by modifying the flow rates in a fixed length reactor (L = 0.5 m; entries 1-6, Table 3). As expected, the molar mass increased according to t R as well as to the temperature.…”

Quo Vadis Carbanionic Polymerization?

“…Recently, many other research groups have shown tremendous interest in the anionic polymerization of terpenes and the postpolymerization reactions of these polymers (hydrogenation, epoxidation, etc. ). − Furthermore, major contributions on the synthesis and study of terpene-based linear and branched macromolecular architectures have been reported by Frey’s group. ,− They have synthesized via anionic polymerization, several combinations of linear and complex macromolecular architectures of terpene-based copolymers (linear copolymers with PS, graft copolymers, polymerization of functionalized terpenes, etc.) (Figure ).…”

Anionic Polymerization of the Terpene-Based Diene β-Ocimene: Complex Mechanism Due to Stereoisomer Reactivities

“…Similar to myrcene and farnesene structures, the presence of an additional double bond can offer a benefit over the vastly used nonfunctionalized isoprene- and butadiene-based materials. , Functionalization via several routes like thiol–ene “click” chemistry, epoxidation, hydrosilylation, etc. can be carried out on either the monomers or introduced via postpolymerization modifications to synthesize functional polymers. ,,− …”