Synthesis of Ethylene/Isoprene Copolymers Containing Cyclopentane/Cyclohexane Units as Unique Elastomers by Half-Titanocene Catalysts

Abstract

Ethylene (E) copolymers with isoprene (IP) possessing higher glass-transition temperatures (T g values, −7.1 to 29.2 °C) than those prepared by the reported catalysts (T g below −18 °C) have been prepared in the copolymerization by using halftitanocene catalysts containing phenoxide ligand, Cp′TiCl 2 (O-2,6-i Pr 2 -4-R-C 6 H 2 ) [Cp′ = C 5 Me 5 (Cp*), R = H (1), SiEt 3 (2)]. Their microstructural analysis by NMR spectra revealed that the copolymers contained cyclopentane (major) and cyclohexane units, formed by cyclization after IP and subsequent ethylene insertions, in addition to 1,4-and 3,4-IP inserted units observed as major units in those prepared by reported catalysts. The 1,2,4-Me 3 C 5 H 2 analogue (R = H) showed better IP incorporation, but the resulting E/IP copolymers possessed rather low T g values compared to those prepared by 1,2 due to less cyclopentane unit in the microstructure. The T g value in the E/IP copolymer increased upon the increase of the IP content, and the degree was dependent upon the catalyst employed. Due to their unique microstructure, the resulting E/IP copolymers prepared by 1,2−MAO catalyst systems exhibit promising tensile and elastic properties. The tensile strength initially decreased with an increase in the IP content along with an increase of the elongation at break (up to 600%, IP 3.3−15.6 mol %) and then increased gradually with further increase in the IP contents (IP 18.1−21.5 mol %); the elongation at break then decreased with preserving the tensile strength along with the observation of the yield stress.

Synthesis of High Molecular Weight Biobased Aliphatic Polyesters Exhibiting Tensile Properties Beyond Polyethylene

“…The resultant polymers ( P1 – P2 ) were hydrogenated in the presence of RhCl(PPh 3 ) 3 in toluene (H 2 1.0 MPa, 50 °C) according to a reported procedure for hydrogenation of ethylene/conjugated diene copolymers, poly(ethylene- co -isoprene)s 39 and poly(ethylene- co -myrcene)s. 40 As summarized in Table S2 , no significant changes in the M n values and the M w / M n values were observed in all cases; the resultant polymers (expressed as HP1 and HP2 ) were identified by NMR spectra (selected NMR spectra, GPC traces are shown in the SI ).…”

Copolymerization of Olefins and Conjugated Dienes: A Promising Approach to Produce Recyclable Polyolefins

“…At high Al/Ti ratios (≥151), the catalytic species mainly led to cis -1,4 enriched polybutadiene with trace ethylene units (Table , entry 3). In contrast, ethylene and isoprene copolymerization catalyzed by half-titanocene catalysts containing phenoxide ligand, Cp*TiCl 2 (O-2,6- i Pr 2 -4-R-C 6 H 2 ) ( 32 : Cp* = C 5 Me 5 , R = H; 33 : Cp* = C 5 Me 5 , R = SiEt 3 ; 34 : Cp* = C 5 Me 3 , R = H), generated a copolymer containing cyclopentenyl units (major) and cyclohexane units (Table , entries 1–5) which were first observed in the E/BD copolymer afforded by neodymium metallocenes (Table , entry 1).…”

“…c Fraction of 1,4-cyclohexane units. C 5 Me 5 , R = SiEt 3 ; 34: Cp* = C 5 Me 3 , R = H), generated a copolymer containing cyclopentenyl units (major) and cyclohexane units (Table8, entries 1−5)113 which were first observed in the E/BD copolymer afforded by neodymium metallocenes (Table9, entry 1).The13 C NMR spectrum of E/BD copolymer afforded by neodymocene complexes {[Me 2 Si(C 13 H 8 ) 2 ]NdCl} (35) showed six intense unknown signals at 42.01, 33.96, 32.26, 30.59, 27.00, and 26.66 ppm…”