Radiation-Induced Cationic Polymerization of Limonene Oxide, α-Pinene Oxide, and β-Pinene Oxide

Abstract

After suitable drying, the subject monomers in the form of neat liquids undergo radiation-induced poly merization with no apparent side reactions and high conversions to precipitatable polymers of low molec ular weight. A high frequency of chain (proton) transfer to monomer is indicated by the fact that the kinetic chain lengths are estimated to be several hundred times larger than the range of DP n values (12-4). Structural characterization of the limonene oxide polymer by 1 H and 13 C NMR spectroscopy provides conclusive evidence that the polymerization proceeds by the opening of the epoxide ring to yield a 1,2 -trans polyether. Similar NMR studies on the polymers formed from the α-pinene and ß-pinene oxides show that the opening of the epoxide ring for these monomers is generally accompanied by the concomitant ring opening of the cyclobutane ring structure to yield a gem-dimethyl group in the main chain.The radiation-induced cationic polymerization of vinyl and unsatu rated monomers in the liquid state has been studied for over 25 years, and the essential features of this type of polymerization appear to be well established (1,2)· In contrast to cationic polymer ization by catalysts where the propagating species is usually described as a solvated ion pair, the distinctive characteristic of cationic polymerization induced by high energy radiation is that propagation occurs by free ions with very large rate constants, the range of kp values for observable polymerization being from 10 M"" 1 s" 1 to 10 8 M" 1 s" 1 . Since the concentration of free ions is typically about 10" 10 M for dose rates obtainable from kilocurie Co gamma-radiation sources, the rates of polymerization are very sensi tive to traces of impurities, including water (3), that can function as efficient terminating agents. Consequently, much attention has been paid to the development of stringent experimental techniques for the rigorous drying of monomers (1H>), since otherwise this type of polymerization may go unrecognized.

Catalytic Approaches to Monomers for Polymers Based on Renewables

“…The mono-epoxidation leads to limonene oxide ( E4 ), while the oxidation of both double bonds gives limonene dioxide ( E4a ). The limonene derivatives E4 and E4a can be used as monomers in the polymer industry. , A huge amount of catalytic systems have been developed for the epoxidation of A4 to E4 or E4a , mostly with H 2 O 2 , which include heterogeneous catalysts based on Co, Mn, Ru, Mo, Re, Fe, polyoxometalates, and Ti-substituted zeolites (Scheme ). …”

“…The limonene derivatives E4 and E4a can be used as monomers in the polymer industry. 358,359 A huge amount of catalytic systems have been developed for the epoxidation of A4 to E4 or E4a, mostly with H 2 O 2 , which include heterogeneous catalysts based on Co, Mn, Ru, Mo, Re, Fe, polyoxometalates, and Ti-substituted zeolites (Scheme 52). 360 In 2009, Ding and co-workers reported the conversion of A4 with H 2 O 2 in the presence of a tungsten-based polyoxometalate catalyst, giving epoxide E4 in 98% yield.…”

Terpene-Based Renewable Monomers and Polymers via Thiol–Ene Additions

“…Likewise, limonene has been radically copolymerized by Sharma and Srivastava with styrene, methyl methacrylate, acrylonitrile, N -vinylpyrrolidone, and other comonomers . Regarding the polymerization of terpene derivatives, Aikins and Williams reported the radiation-induced cationic polymerization of limonene oxide, α-pinene oxide, and β-pinene oxide, which led to low molecular weight polyethers with high monomer conversions . More recently, Coates and co-workers reported the syntheses of alternating polycarbonate copolymers of ( R )-limonene oxide and carbon dioxide using β-diiminate zinc complexes .…”

Bringingd-limonene to the scene of bio-based thermoset coatings via free-radical thiol–ene chemistry: macromonomer synthesis, UV-curing and thermo-mechanical characterization

“…[37][38][39][40][41][42][43][44][45] In a previous study, Aikins and Williams (1981) reported on the radiation-induced cationic polymerization of neat LO at room-temperature by ring-opening of the epoxide moiety yielding a low molecular weight 1,2-trans polyether (7.6 < DP < 18.7) accompanied by very high monomer conversions into polymer (at least 80%). 46 Duchateau and co-workers (2013) synthesized partially bio-based alternating polyesters by catalytic ring-opening copolymerization of LO and phthalic anhydride via a series of metal t-Bu-salophen complexes combined with different cocatalysts and various mono-/di-/tri-functional chain-transfer agents (CTA)s. Chromium-chloride based catalysts provided the best results without any major drop in catalytic activity. Inclusion of (CTA)s enabled molecular weight reduction of the copolymers while retaining low polydispersities.…”