Polymers limonene

Synonyms Cyclohexene Dipentene polymer Limonene polymer Po limonene... 

Humidity does not affect the permeabihty, diffusion coefficient, or solubihty coefficient of flavor/aroma compounds in vinyhdene chloride copolymer films. Studies based on /n j -2-hexenal and D-limonene from 0 to 100% rh showed no difference in these transport properties (97,98). The permeabihties and diffusion coefficients of /n j -2-hexenal in two barrier polymers are compared in Table 12. Humidity does not affect the vinyhdene chloride copolymer. In contrast, transport in an EVOH film is strongly plasticized by humidity. 

D-Limonenediozonide Polymer (Diozonid des d-Limonens in Ger). (C j 0Hl 6 06 )x, white, solid, mp 60—65°, explds on heating to about 85°. Sol in w, ale, eth, benz v sol in chlf, ethyl acetate and AcOH. Prepd by ozonization of d-limonene, C10H16, dissolved in chlf or CC14 Note Llmonenediozonide was first described by H. Neresheimer, Dissertation, Kiel (1907)... 

Terpene resins are most commonly used in adhesive production, where they confer very strong tackifying properties. The terpene resins improve the resistance of adhesives to oxidative degradation. These resins are normally produced from p-pinene and are light yellow in colour. Polymers of dipentene and limonene are also available as resins. 

Hydrocarbon resins comprise a range of low-molecular-weight products (M < 3000) used as adhesives, hot-melt coatings, tackifying agents, inks, and additives in rubber. These include products based on monomers derived from petroleum as well as plant sources. The petroleum-derived products include polymers produced from various alkenes, isoprene, piperylene, styrene, a-methylstyrene, vinyltuolene, and dicyclopentadiene. The plant-derived products include polyterpenes obtained by the polymerization of dipentene, limonene,... 

Terpenes are polymers of the 5-carbon compound isoprene (Figure 1.12) and, as such, generally display properties similar to those of hydrocarbons. Terpenoids are substituted terpenes (i.e. contain additional chemical groups, such as an alcohol, phenols, aldehydes, ketones, etc.). Only a few such substances could be regarded as true drugs. Terpenes, such as limonene, menthol and camphor, form components of various essential oils with pseudo-pharmaceutical uses. A number of these molecules, however, exhibit anti-tumour activity, of which taxol is by far the most important. 

Limonene -polymer permeation [BARRIER POLYMERS] (Vol 3) - [CINNAMIC ACID, CINNAMALDEHYDE AND C INN AMYL ALCOHOL] (Vol 6) - [METALLICCOATINGS - SURVEY] (Vol 16) -in tagetes oil [OILS, ESSENTIAL] (Vol 17)... 

As already noted by Verkuijlen and Boelhouwer in 1974 [29], the SM of highly unsaturated fatty esters produces, among other compounds, considerable amounts of 1,4-cyclohexadiene (1,4-CHD). This fact has been exploited by Mathers et al. for the production of 1,3-cyclohexadiene (1,3-CHD) via metathesis and isomerization reactions of plant oils [141]. For instance, 1,4-CHD was obtained by treatment of soybean oil with C4 and was subsequently isomerized with RuHCl(CO)(PPh3)3. Then, the produced 1,3-CHD was polymerized with nickel(II)acetylacetonate/ methaluminoxane. Interestingly, the polymerizations could be carried out in bulk and using hydrogenated D-limonene as renewable solvent. The polymers thus obtained presented / m around 300°C. 

In the limonene oxidation reaction, various immobilized systems have been tested as catalyst. The use of MTO supported on poly(vinylpyridine) polymers however turned out to be a poor system for the limonene oxidation since both the conversions and the selectivities were quite a bit lower than the optimal non-immobilized system [56]. These systems were also used in combination with ionic liquids, and here, a similar result as with the non-immobilized system was found, yielding mostly diepoxide, with the best-performing catalyst MTO/PVP-25% in [BMIM][BF4], giving 92% of diepoxide at full conversion [61]. 

Roberts and Day (172) postulate that solid polymer formation from a-pinene occurs via isomerization to limonene which then yields the polymer. However, the expected polylimonene does not explain the fact that considerably more than one double bond per monomer consumed disappears during polymerization. Thus it was postulated (172) that double bonds in different molecules mutually react and consume each other by crosslinking. Apparently, the expected (analogous to poly-/S-pinene) polymer does not form from a-pinene. 

Rearrangement of limonene with a cationic exchange resin, rather than with soluble acids,218 substantially reduces polymer formation. Limonene is hydrated using chloroacetic acids to furnish (-t-)-a-terpineol selectively in high yield, depending upon the conditions.219... 

Renewable feedstocks can also be used as the raw materials for the synthesis of green, biodegradable polymers. A pertinent example is polylactate, derived from lactic acid which is produced by fermentation (see earlier). Another recent example is the production of polycarbonates by reaction of C02 with (R)-limonene oxide in the presence of a zinc catalyst (Fig. 8.47) [221]. 

Figure 5.11 Polymers prepared in D-limonene poly(cyclopentene) (PCP), isotactic polypropylene (PP) and poly(methylphenylsilane) (PMPS).

D-Limonene and ot-pinene have been used as renewable solvents and chain transfer agents in metallocene-methylaluminoxane (MAO) catalysed polymerization of ot-olefins. Chain transfer from the catalyst to the solvent reduces the achieved in limonene compared with toluene and also reduces the overall catalyst activity. This was confirmed, as in the ROMP studies, by performing identical reactions in hydrogenated limonene. However, an increase in stereospecificity was seen when D-limonene was used as the solvent. This is measured as the mole fraction of [mmmm] pentads seen in NMR spectra of the polymer. 100% isotactic polypropylene would give a value of 1.0. On performing the same propylene polymerization reactions in toluene and then in limonene, the mole fraction of [mmmm] pentads increased from 0.86 to 0.94, indicating that using a chiral solvent influences the outcome of stereospecific polymerizations. Unfortunately, when a-pinene was used, some poly(a-pinene) was found to form and this contaminates the main polymer product. 

In summary, D-limonene has been exploited with interesting results in polymer chemistry however, it remains to be seen whether its chirality can be used to induce similar effects in small molecule syntheses. Many of the benchmark reactions e.g. Diels-Alder, Michael addition) used in the alternative solvent field are reactions of olefinic substrates and therefore could not be performed successfully in a terpene solvent. 

A rather different type of macromolecule is generated from the polymerization of certain terpenes such as limonene and a-pinene. The polymers generated from these compounds retain a double bond in the structure of the molecule, and it can be argued that they have a mixed saturated and unsaturated carbon chain backbone as shown below ... 

Small molecule epoxides, and some epoxy oligomers also are used as reactive diluents, mixing them with other polymers for crosslinking purposes. An example of epoxide used as curing additive is poly(limonene dioxide) or poly[1-methyl-4-(2-methyloxiranyl)-7-oxabicyclo[4.1.0]heptane], CAS 29616-43-1. This compound can form ether bonds upon heating or by photoinduction in the presence of aryl substituted sulfonium salts. Poly(dicyclopentadiene dioxide), CAS 29987-76-6, has similar properties. The idealized structure of the two monomers with the intact epoxy groups are shown below ... 

Besides pyridine-containing polystyrene and pol)q5ropylene resins, polybenzimidazole has been employed as support for nickel(II) acetylacetonate [94]. The nickel-loaded polymer was shown to be an efficient catalyst for the epoxidation of (S)-(—)-limonene, a-pinene, and 1-octene using isobutyraldehyde/02 as coreac-tant/oxidant. However, significant metal leaching from the support associated with a loss of activity upon recycling was reported. It was shown that the reaction is heterogeneously catalyzed, and leached metal species did not contribute to the catal)d ic activity. 

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