Ethylene Copolymerization with Limonene and β-Pinene: New Bio-Based Polyolefins Prepared by Coordination Polymerization

Abstract

Synthesis of new semicrystalline polymers by copolymerization of ethylene with R-(+)-limonene (Lim) and β-pinene (Pin) has been demonstrated by using phenoxide-modified half-titanocene catalysts, Cp’TiCl2(O-2,6- i Pr2-4-RC6H2) (Cp’ = cyclopentadienyl; R = H and SiEt3), in the presence of a methylaluminoxane (MAO) cocatalyst. High-molecular-weight poly­(ethylene-co-Lim)­s (M n = 4.09–16.4 × 104) were prepared by using the (1,2,4-Me3C5H2)­TiCl2(O-2,6- i Pr2C6H3)–MAO catalyst system. Synthesis of high-molecular-weight poly­(ethylene-co-Pin)­s (M n = 2.10–22.4 × 104) was attained by using Cp*TiCl2(O-2,6- i Pr2-4-R-C6H2) (R = H and SiEt3)–MAO catalyst systems. The comonomer (Lim and Pin) incorporation was affected by the cyclopentadienyl fragment (Cp’) employed. The catalytic activity was affected by the Al/Ti molar ratio and polymerization temperature (at 50 °C), which did not affect both comonomer (Lim and Pin) incorporation and the M n values significantly. On the basis of microstructural analysis by using 13C nuclear magnetic resonance spectra, these comonomers (Lim and Pin) were incorporated as an isolated unit (due to low comonomer contents, up to 3.6 mol %), and the poly­(ethylene-co-Lim)­s possessed resonances ascribed to the 1,2-Lim insertion unit and subsequent cyclization (favored 2′,1′-insertion); the degree of 1,2-insertion/cyclization (expressed as the S value) was affected by the Cp’ employed.

Ethylene/Myrcene Copolymers as New Bio-Based Elastomers Prepared by Coordination Polymerization Using Titanium Catalysts

“…Table summarizes the results for ethylene copolymerizations with myrcene (My) using various half-titanocene ( 1 – 4 , Chart )–MAO catalyst systems. The phenoxide- or ketimide-modified half-titanocenes shown in Chart , Cp′TiCl 2 (O-2,6- i Pr 2 -4-RC 6 H 2 ) [R = H, Cp′ = Cp* ( 1 ), t BuC 5 H 4 ( 3 ); R = SiEt 3 , Cp′ = Cp* ( 2 )] and CpTiCl 2 (N = C t Bu 2 ) ( 4 ), have been chosen in this study − because these catalysts demonstrated efficient comonomer incorporations in the ethylene copolymerizations with sterically encumbered olefins, ,− cyclic olefins, − and aromatic vinyl monomers. , An AlMe 3 -free MAO white solid, which was prepared from the commercially available MAO sample [8.9 wt % (Al) toluene solution, see the Experimental Section] by removing toluene and AlMe 3 in vacuo , ,− ,− was used as the cocatalyst. The results by the ordinary linked-amide half-titanocene, [Me 2 Si­(C 5 Me 4 )­(N t Bu)]­TiCl 2 ( 5 ), , and the metallocene catalyst, Cp 2 ZrCl 2 ( 6 ), conducted under the same conditions are also placed for comparison.…”

“…Moreover, resonances at 53 ppm (quaternary carbon confirmed by dept) and 46.5–49.5 ppm (tertiary carbon confirmed by dept) were observed. These resonances were apparently different from those considered by 1,2-, 2,1-, or 1,4-My insertion. , It also seems likely that resonances observed at 22–23 ppm (secondary carbon) could be ascribed to those corresponding to methylene carbon in a cyclopentane inserted unit observed in ethylene/cyclopentene copolymers with exclusive 1,2-cyclopentene insertion. − We thus further explored the microstructural analysis of poly­(ethylene- co -My)­s and the polymer after hydrogenation by RhCl­(PPh 3 ) 3 (see the Experimental Section), including the dept analysis (Figure ). No significant differences in the M n , Đ ( M w / M n ) values and their thermal properties ( T m , T g ) in the resultant polymers (runs 17, 20, Table ) were observed before/after the hydrogenation (see the Experimental Section).…”

“…AlMe 3 -Free MAO white solids (d-MAO) were prepared by removing toluene and AlMe 3 from the commercially available methylaluminoxane (MAO) [TMAO-S, 9.5 wt % (Al) toluene solution, Tosoh Finechem Co.] in vacuo in the dry box (at ca. 50 °C for removing toluene and AlMe 3 , and then heated at >100 °C for 1 h for completion). ,− ,− Cp*TiCl 2 (O-2,6- i Pr 2 C 6 H 3 ) ( 1 ), Cp*TiCl 2 (O-2,6- i Pr 2 -4-SiEt 3 -C 6 H 2 ) ( 2 ), t BuC 5 H 4 TiCl 2 (O-2,6- i Pr 2 C 6 H 3 ) ( 3 ), CpTiCl 2 (N = C t Bu 2 ) ( 4 ), and [Me 2 Si­(C 5 Me 4 )­(N t Bu)]­TiCl 2 ( 5 ) , were prepared according to the reported procedure. Cp 2 ZrCl 2 ( 6 ) (Kanto Kagaku Co. Ltd.) was used as received.…”

“…We herein present that the synthesis of the random E/My copolymers has been attained by the phenoxide-modified half-titanocene catalysts, Cp*TiCl 2 (O-2,6- i Pr 2 -4-RC 6 H 2 ) [R = H ( 1 ), SiEt 3 ( 2 )], which has been known as efficient catalysts − for ethylene copolymerization with aromatic vinyl monomers , as well as sterically encumbered olefins, − in the presence of the methylaluminoxane (MAO) cocatalyst. It has also been demonstrated that the resultant poly­(E- co -My)­s possessed a unique microstructure containing a cyclopentane unit, presumably formed by cyclization after 2,1- or 1,4-My incorporation (through π-allyl intermediates assumed as dormant) and subsequent ethylene insertion (Scheme ).…”

Bioderived 4D Printable Terpene Photopolymers from Limonene and β-Myrcene

“…A number of interesting green material sourcing trends have gathered recent interest, including terpenes, neoligans, amino acids, sugars/carbohydrates, cellulose, silk, and others. − Of great interest to us is the terpene limonene, which has been examined for 3D printing directly of the monomer using thiol–ene reactions, modified through thiol–ene chemistry before incorporation into thermoplastic polymers displaying performance/engineering plastic behaviors, and has even been selectively oxidized prior to synthesis of degradable polyesters and polycarbonates. − However, polymerization of limonene without modification has been characterized by low yields and oligomeric products. − A second terpene of interest is β-myrcene, which possesses a linear structure containing three alkenes and has been utilized as a comonomer with petrochemicals such as styrene as well as with itaconic acid, farnesene, or ocimene. − Modification of myrcene commonly focuses on functionalizing with reactive groups such as acrylates or similar derivatives to increase reactivity and better control over the resultant molecular weights. − However, a key characteristic of the β-myrcene-containing polymers is the low elastic modulus and high strain at break, with block copolymers particularly demonstrating this behavior …”