Copolymerizations of limonene

Figure 1.12 Copolymerization of limonene oxide and C02 in the presence of P-diiminate-zinc acetate complex.

The radical copolymerization of limonene with MMA [61, 62], AN [63], St [64] and N-vinylpirrolidone [65] gave alternating copolymers because both reactivity ratios were close to zero. Figure 2.17 shows the mechanism proposed for this process in the case of MMA. 

Figure 2.17 Proposed mechanism for the radical copolymerization of limonene and MMA.

Sharma S., Srivastava A.K., Free radical copolymerization of limonene with butyl methacrylate Synthesis and characterization, Lndian J. Chem. Technol, 12(1), 2005, 62-67. 

MaslinskasoUch J., Kupka T., Kluczka M., SoUch A., Optically-active polymers. 2. Copolymerization of limonene with maleic-anhydride, MactomoZ. Chem. Phys., 195(5), 1994, 1843-1850. 

Several reports describe the radical copolymerization of limonene with vinyl monomers, i.e., maleic anhydride, acrylonitrile, MMA, styrene, vinyl acetate, and A-vinyl pyrrolidone. The coordination copolymerization of limonene oxide and carbon dioxide has also been reported, see below. 

The radical copolymerization of /-limonene and maleic anhydride has been performed in THF solution at 40°C using AIBN as the initiator and a reaction... 

Scheme 5 Copolymerization of limonene oxide and CO2 using P-diiminate zinc acetate complexes [76] (reprinted with permission from American Chemical Society)...

K. Satoh, M. Matsuda, K. Nagai, M. Kamigaito, AAB-sequence living radical chain copolymerization of naturally occurring limonene with maleimide an end-to-end sequence-regulated copolymer, J. Am. Chem. Soc. 132 (2010) 10003-10005. 

Figure 3.4 [A] AAB sequence-controlled radical copolymerization of d-limonene (Ml) with phenylmaleimide (M2). [B] MALDI-TOF-MS...

Butadiene and myrcene have been copolymerized by either batch or continuous processes using finely divided alkali metal (Na or K) as catalyst and ether (preferably diethyl ether or 1,4-dioxane) as solvent at 25-95°C. Conversions of 90% or higher were obtained within 6-24 h. Other terpenes, like a-terpinene, dipentene (racemic limonene), or p-pinene, react little or not at all with 1,3-butadiene, while the copolymerization of alloocimene with 1,3-butadiene gives a low conversion of partially gelled copolymer [37]. 

Limonene can also be copolymerized with acrylonitrile (in DMF at 70°C, initiator AIBN) [69], MMA (xylene, 80°C, BPO) [70], styrene (xylene, 80°C, AIBN) [71], A(-vinylpyrrolidone (dioxane, 80°C, AIBN) [72], and (V-vinyl acetate (dioxane, 65°C, AIBN) [73], always producing alternating copolymers. Radical addition of limonene occurs via the exocyclic isopropenyl group (in contrast to the cationic system, see above). Also, a terpolymer of limonene, MMA, and styrene has been prepared by free-radical copolymerization (xylene, 80°C, BPO) [74]. Poly (limonene-co-MMA) can be converted into a LC polymer (cf. Scheme 2) [75]. 

The alternating copolymerization of cis/fraws-limonene oxide and carbon dioxide can be achieved with p-diiminate zinc acetate complexes (Scheme 5). The balance between high catalyst activity and selectivity is optimal with catalyst complex 8 (see Scheme 5, right) at 25°C. Catalysts exhibits high selectivity for the trans diasteriomer (% trans in the copolymer is >98%). The biodegradable polycarbonates have MWs in the range of 4.0-10.8 kg/mol, which can be controlled by the [epoxide]/[Zn] ratio, CO2 pressure, and reaction time. They also have narrow... 

The other class of acrylic compatible tackifiers includes those based on ter-penes. Terpenes are monomers obtained by wood extraction or directly from pine tree sap. To make the polyterpene tackifiers, the monomers have to be polymerized under cationic conditions, typically with Lewis acid catalysis. To adjust properties such as solubility parameter and softening point, other materials such as styrene, phenol, limonene (derived from citrus peels), and others may be copolymerized with the terpenes. 

The free radical polymerization of pinenes and limonene is of little interest, because of the modest yields and DPs obtained with their homopolymerizations. However, their copolymerization with a variety of conventional monomers has been shown to produce some interesting materials, particularly in the case of controlled reversible addition fragmentation chain-transfer (RAFT) systems involving P-pinene and acrylic comonomers [5]. 

Only a few studies have been devoted to the Ziegler-Natta polymerization of terpene monomCTs. a- and P-pinene, limonene and camphene were investigated by various authors and the corresponding homopolymers were shown to be structurally analogous to those obtained by cationic mechanisms [89, 90]. More recently, this type of catalysis was successfully applied to copolymerization systems involving a-pinene and MMA or St [56]. 

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