Biobased Polymers via Radical Homopolymerization and Copolymerization of a Series of Terpenoid-Derived Conjugated Dienes with exo-Methylene and 6-Membered Ring

Abstract

A series of exo-methylene 6-membered ring conjugated dienes, which are directly or indirectly obtained from terpenoids, such as β-phellandrene, carvone, piperitone, and verbenone, were radically polymerized. Although their radical homopolymerizations were very slow, radical copolymerizations proceeded well with various common vinyl monomers, such as methyl acrylate (MA), acrylonitrile (AN), methyl methacrylate (MMA), and styrene (St), resulting in copolymers with comparable incorporation ratios of bio-based cyclic conjugated monomer units ranging from 40 to 60 mol% at a 1:1 feed ratio. The monomer reactivity ratios when using AN as a comonomer were close to 0, whereas those with St were approximately 0.5 to 1, indicating that these diene monomers can be considered electron-rich monomers. Reversible addition fragmentation chain-transfer (RAFT) copolymerizations with MA, AN, MMA, and St were all successful when using S-cumyl-S’-butyl trithiocarbonate (CBTC) as the RAFT agent resulting in copolymers with controlled molecular weights. The copolymers obtained with AN, MMA, or St showed glass transition temperatures (Tg) similar to those of common vinyl polymers (Tg ~ 100 °C), indicating that biobased cyclic structures were successfully incorporated into commodity polymers without losing good thermal properties.

Terpenoid-derived conjugated dienes with exo-methylene and a 6-membered ring: high cationic reactivity, regioselective living cationic polymerization, and random and block copolymerization with vinyl ethers

“…The cationic homopolymerization of (-)-VnD proceeded quantitatively with all Lewis acids, including EtAlCl 2 , TiCl 4 , BF 3 •OEt 2 , and SnCl 4 , in a 1:1 mixture of toluene and CH 2 Cl 2 at -78 °C and resulted in homopolymers with relatively high molecular weights (M n > 25000), unlike its radical homopolymerization, which yielded only low molecular weight oligomers (M n < 1000). 41 In addition, the cationic polymerizations were almost instantaneous except for BF 3 •OEt 2 , indicating that the reactivity of (-)-VnD is extremely high despite the absence of electron-donating heteroatoms such as the oxygen in VEs. The poly((-)-VnD) obtained from all Lewis acid catalysts showed similar 1 H NMR spectra (Fig.…”

“…Verbenone (enantiomeric pure (-)-form) and piperitone (mixture of enantiomers, predominantly (R)-(-)-form) were converted into exo-methylene-conjugated dienes, (-)-VnD (purity: >99%, [] D = -43.5°) and PtD (purity: 95%, [] D = +15.7°), respectively, by the Wittig reaction as reported previously. 41,42 Racemic (±)-HCvD ([] D = -1.9°) was prepared by mixing equimolar amounts of (+)-and (-)-HCvD, which were synthesized via selective hydrogenation of the pendant olefins in (+)-and (-)-carvone, respectively, followed by the Wittig reaction as reported. 28 These biobased compounds are all exomethylene-conjugated dienes with a 6-membered cyclohexenyl ring, whereas the position of the methyl group as the substituent reaction is different or 4-position (VnD and PtD) to the exo-methylene carbon in the conjugated diene).…”

“…The polymers resulting from the cationic polymerization of PtD and (±)-HCvD had higher molecular weights (M n ~ 78000 and 360000, respectively) than those obtained by radical homopolymerizations. 41 In addition, these M n values are likely underestimated, as they correspond only to the soluble fractions of the polymers in CHCl 3 and tetrahydrofuran (THF) (Fig. S1).…”

“…We recently reported the synthesis of verbenone-and piperitone-derived conjugated dienes with exo-methylene and 6-membered rings, i.e., VnD and PtD, respectively, and radical homo-and copolymerizations, although their radical homopolymerizabilities were very low. 41 Matsumoto and Yamamoto previously reported radical copolymerization of these dienes with maleimide derivatives, 42 but there have been no studies on their cationic polymerizations or properties of homopolymers. Herein, we investigated the cationic polymerizations of a series of biobased conjugated dienes with exo-methylene and 6membered rings to clarify the reactivity of the monomers as well as the properties of the polymers originating from unique biobased structures.…”

RAFT Polymerization of 2‐(tert‐Butoxycarbonyloxy)Ethyl Methacrylate and Transformation to Functional Polymers via Deprotection and the Subsequent Polymer Reactions

“…[ 33–37 ] The polymer structure control for methyl methacrylate (MMA) and other many kinds of conjugated monomers were performed using trithiocarbonate compounds as the RAFT agent. [ 38–43 ] In many cases, however, it has been reported that the precise control of the living radical polymerization is interfered by polar and functional groups included in the methacrylate monomers, such as HEMA. [ 44–50 ] In this study, therefore, we synthesized PBHEMA with well‐controlled molecular weight, molecular weight distribution, and chain end groups as well as the block copolymers containing PBHEMA and the other polymethacrylate segments using the RAFT polymerization process using 4‐cyano‐4‐((dodecylsulfanylthiocarbonyl)sulfanyl)pentanoic acid (CDTPA) as the RAFT agent ( Figure ).…”