Living cationic pinene

P-Pinene which is a main component of natural turpentine can be polymerized by living cationic isomerization polymerization [82] (Scheme 10) using TiCl3(OfPr) as a Lewis acid in conjunction with rc-Bu4NCl in CH2C12 at -40 °C. When initiator 31 was used, polymerization led to a poly(P-pinene) macromonomer with a methacrylate function at the a end and a chlorine atom at the co chain end [83]. Three macromonomers were prepared with DPn=8,15, and 25 respectively they had narrow MWD (Mw/Mn= 1.13-1.22) and the reported functionality was close to 1 (Fn=0.90-0.96). 

A macromonomer made of a block copolymer of p-MeS and P-pinene was also prepared by sequential living cationic polymerization of both monomers under the same experimental conditions. The first block had 12 p-MeS units and the second had 11 p-pinene units as evaluated by NMR spectroscopy. 

The synthesis of block, as well as random copolymers of 3-pinene with styrene and / -methylstyrene (pMeSt), was studied by living cationic polymerization, using both the styrene and vinyl ether adducts as initiators in the presence of Ti(OiPr)Cl3 in methylene chloride at —40°C [44,47]. For styrene (A) and 3-pinene (B), both AB and BA block copol3mers were obtained, as shown in Fig. 2.13, with Mn values of 4 000 and 3 600, respectively, and narrow Mw/Mn ratios (1.26 and 1.38, respectively). The efficiency of these block copolymerizations was attributed to the similar reactivity of the C—Cl bond derived from the two monomers [44]. 

The random living cationic polymerization of 3-pinene with styrene and pMeSt was also inspected [44]. With the 3-pinene/styrene mixtures, a faster consumption of the former monomer occurred, yielding tapered copolymers with Mn 5 000 and MWD of 1.4 at 100/65 per cent consumption of 3-pinene/styrene. In contrast, with the 3-pinene/j 7MeSt mixtures, both monomers were consumed at nearly the same rate, yielding statistical copolymers with Mn 5 000 and MWD of 1.5 at both monomer conversions higher than 90 per cent. 

Living cationic-radicai copolymerization of p-pinene with synthetic monomers... 

Lu J., Kamigaito M., Sawamoto M., Higashimura T., Deng Y.X., Living cationic isomerization polymerization of beta-pinene. 3. Synthesis of end-functionalized polymers and graft copolymers, J. Polym. Sci. A Polym. Chem., 35(8), 1997,1423-1430. 

Lu J., Liang H., Zhang R.F., Living cationic polymerization of beta-pinene with 1-phenylethyl chloride/TiCl4/Ti(OiPr)(4),... 

Li A.L., Liang H., Lu J., Synthesis of copolymers of beta-pinene by the combination of living cationic polymerization and /CPKP, Acta Polym. Sinica(l), 2006, 151-155. 

Turpentine, Monoterpenes, a-Pinene, p-Pinene, Cationic polymerization. Radical polymerization. Copolymerizations, Living polymerization, Mechanisms, Polymer properties... 

Figure 2.15 shows a different and more sophisticated approach to the combination of cationic and radical mechanisms, since in this case both processes bear a living character. Allylic brominated poly(pPIN) with Br/p-pinene unit ratios of 1.0 and 0.5 (Mn of 2 810 and 2 420, respectively and a similar MWD of 1.3) were obtained by treatment with A-bromosuccinimide/AIBN and then used as macroinitiators in conjunction with CuBr and 2,2 -bipyridine for the atom transfer radical polymerization (ATRP) of acrylic monomers [52, 53]. 

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