Synthesis of Bottlebrush Polymers by Z-/E-Specific Living Ring-Opening Metathesis Polymerization, Exhibiting Different Thermal Properties.

Synthesis of bottlebrush polymers (BBPs) and block copolymers by Z-/E-specific living ring-opening metathesis polymerization (ROMP) of N-substituted-norbornene-2,3-dicarboximides containing long alkyl chains (n-octadecyl, n-tetradecyl, etc.) has been attained by the vanadium(V)-alkylidene catalysts V(CHSiMe3)(ArN)[OC(CF3)3](PMe3)2 [Ar = 2,6-Cl2C6H3 (1), C6F5 (2)] and V(CHSiMe3)(2,6-F2C6H3N)(OC6Cl5)(PMe3)2 (3). The ROMPs using 1 afforded the BBPs with exclusive Z selectivity (98 to >99% cis) even at high temperature (up to 80 °C) in the presence of PMe3, whereas the ROMPs using 3 gave the BBPs with high E selectivity (90% trans). These ROMPs proceeded in a living manner (even at 80 °C using 1), affording various (amphiphilic) block copolymers while maintaining high E/Z selectivity. The resultant Z- and E-selective BBPs especially prepared from N-(n-octadecyl)norbornene-2,3-dicarboximide possessed different melting temperatures due to different degrees of interpolymer alkyl side chain interaction (side chain crystallization).

Time-dependent DFT study of the K-edge spectra of vanadium and titanium complexes: effects of chloride ligands on pre-edge features.

X-ray absorption near edge structures (XANES) of vanadium and titanium complexes were investigated with time-dependent density functional theory (TDDFT). In particular, observed characteristic K-edge features in the presence of chloride ligands were assigned. Although TDDFT includes a large systematic error attributed to the 1s core energy levels of transition metals, pre-edge spectral shapes could be reproduced by a simple energy shift in the calculated excitation energies. The doublet peak in the pre-edge region was assigned to dipole-allowed transitions from 1s to 3d + 4p hybridized orbitals, while a characteristic shoulder peak in the chloride complex was assigned to excitations of chloride 4p orbitals. A similar but weak absorption band was computed for the methyl complex as excitation to C-H σ* orbitals. However, because these excitations were highly dependent on the direction of the C-H bonds, the shoulder peak was not experimentally observed because of methyl free rotation. Hence, the intensity of the shoulder peak was proportional to the number of chloride ligands unless other ligands contribute to this energy region and, therefore, could be used to detect the presence or absence of chloride ligands in unknown compounds, such as reaction intermediates.

The Effect of SiMe3 and SiEt3 Para Substituents for High Activity and Introduction of a Hydroxy Group in Ethylene Copolymerization Catalyzed by Phenoxide-Modified Half-Titanocenes.

Remarkable effects of SiMe3 and SiEt3 para-substituents in the phenoxide-modified half-titanocenes, Cp*TiCl2 (O-2,6-i Pr2 -4-R-C6 H2 ) [R=SiMe3 (6), SiEt3 (7)], toward the catalytic activities in ethylene copolymerizations with 2-methyl-1-pentene, 1-decene, 1-dodecene and with 9-decen-1-ol (DC-OH) have been demonstrated. The activities by 6, 7 at 50 °C showed higher than those conducted at 25 °C in all cases in the presence of MAO cocatalyst. Efficient synthesis of high-molecular-weight (HMW) ethylene copolymers incorporating DC-OH (or 5-hexen-1-ol, HX-OH) has been attained in the copolymerization by 7, which showed better DC-OH (HX-OH) incorporation at 50 °C to afford the HMW copolymers, poly(ethylene-co-DC-OH)s, with high activities (activity 1.21-3.81×105  kg-polymer mol-1 -Ti h, Mn =6.55-10.0×104 , DC-OH 2.3-3.6 mol %).

Synthesis of Ultrahigh Molecular Weight Polymers with Low PDIs by Polymerizations of 1-Decene, 1-Dodecene, and 1-Tetradecene by Cp*TiMe2(O-2,6-iPr2C6H3)⁻Borate Catalyst.

Polymerizations of 1-decene (DC), 1-dodecene (DD), and 1-tetradecene (TD) by Cp*TiMe2(O-2,6-iPr2C6H3) (1)-[Ph3C][B(C6F5)4] (borate) catalyst have been explored in the presence of Al cocatalyst. The polymerizations of DC and DD, in n-hexane containing a mixture of AliBu3 and Al(n-C8H17)3, proceeded with high catalytic activities in a quasi-living manner, affording high molecular weight polymers (activity 4120-5860 kg-poly(DC)/mol-Ti·h, Mn for poly(DC) = 7.04-7.82 × 105, after 20 min at -30 °C). The PDI (Mw/Mn) values in the resultant polymers decreased upon increasing the ratio of Al(n-C8H17)3/AliBu3 with decreasing the activities at -30 °C. The PDI values also became low when these polymerizations were conducted at low temperatures (-40 or -50 °C); high molecular weight poly(DD) with low PDI (Mn = 5.26 × 105, Mw/Mn = 1.16) was obtained at -50 °C. The TD polymerization using 1-borate-AliBu3 catalyst (conducted in n-hexane at -30 °C) afforded ultrahigh molecular weight poly(TD) (Mn = 1.02 × 106, Mw/Mn = 1.38), and the PDI values also decreased with increasing the Al(n-C8H17)3/AliBu3 ratio.

Synthesis of Mono-, Di-, and Trinuclear Rhodium Diphosphine Complexes Containing Light-Harvesting Fluorene Backbones.

Syntheses and structural determination of rhodium complexes ligated by diphosphines containing light-harvesting fluorene backbones are presented. In these rhodium complexes, the rhodium center is surrounded by a light-absorbing diphosphine unit. The presence of Rh-Rh bonding interactions is suggested by density functional theory studies.

Vanadium NMR Chemical Shifts of (Imido)vanadium(V) Dichloride Complexes with Imidazolin-2-iminato and Imidazolidin-2-iminato Ligands: Cooperation with Quantum-Chemical Calculations and Multiple Linear Regression Analyses.

The NMR chemical shifts of vanadium (51V) in (imido)vanadium(V) dichloride complexes with imidazolin-2-iminato and imidazolidin-2-iminato ligands were calculated by the density functional theory (DFT) method with GIAO. The calculated 51V NMR chemical shifts were analyzed by the multiple linear regression (MLR) analysis (MLRA) method with a series of calculated molecular properties. Some of calculated NMR chemical shifts were incorrect using the optimized molecular geometries of the X-ray structures. After the global minimum geometries of all of the molecules were determined, the trend of the observed chemical shifts was well reproduced by the present DFT method. The MLRA method was performed to investigate the correlation between the 51V NMR chemical shift and the natural charge, band energy gap, and Wiberg bond index of the V═N bond. The 51V NMR chemical shifts obtained with the present MLR model were well reproduced with a correlation coefficient of 0.97.

Synthesis of Poly(arylene vinylene)s with Different End Groups by Combining Acyclic Diene Metathesis Polymerization with Wittig-type Couplings.

A series of end-functionalized poly(9,9'-di-n-octylfluorene vinylene)s (EF-PFVs) with different end groups were obtained by 1) synthesizing EF-PFV with vinyl end groups by acyclic diene metathesis (ADMET) polymerization with a molybdenum catalyst and termination with an aldehyde and 2) subsequent olefin metathesis of the vinyl group with the molybdenum catalyst followed by Wittig-type coupling with another aldehyde. The exclusive formation of EF-PFVs containing a vinyl end group by the ADMET polymerization was confirmed by grafting PEG, and by the synthesis of amphiphilic triblock copolymers by combining atom transfer radical polymerization from the PFV chain end with PEG grafting through a click reaction. Various EF-PFVs with different end groups, such as C6 F5 , pyridyl, ferrocenyl, and terthiophene, have thus been prepared. Their fluorescence spectra (e.g., intensities, emission wavelengths) were influenced by the end groups and the length of the conjugation.

Ring-Opening Metathesis Polymerization of Cyclic Olefins by (Arylimido)vanadium(V)-Alkylidenes: Highly Active, Thermally Robust Cis Specific Polymerization.

Ring-opening metathesis polymerization (ROMP) of various cyclic olefins especially using three (arylimido)vanadium(V)-alkylidene catalysts, V(CHSiMe3)(N-2,6-Cl2C6H3) (OC6F5) (PMe3)2 (3), V(CHSiMe3) (NR)[OC(CF3)3](PMe3)2 [R = Ph (6), 2,6-Cl2C6H3 (7)] have been explored. Complex 3 exhibited the highest catalytic activity (ex. TOF = 603 000 h(-1), 168 s(-1)) for ROMP of norbornene (NBE) among a series of (imido)vanadium(V)-alkylidenes, and the cis-specific living ROMPs of NBE proceeded with remarkable activities (TOF = 125 000-157 000 h(-1) at 25 °C) by the fluorinated alkoxo analogues (6, 7). The activities by 6, 7 increased at high temperature (50 and 80 °C) and/or upon addition of PMe3 without decrease in the cis selectivity (98%). The ROMPs in the presence of 1-hexene by 3, 7 proceeded without significant decrease in the activities, and the Mn values could be controlled by degree of chain transfer (cross metathesis). These dichlorophenylimido analogues (3, 7) were effective for ROMPs of various norbornene derivatives; ROMP of cyclooctene took place by 3, and the activity increased at high temperature (50, 80 °C).

(Arylimido)vanadium(V)-alkylidene complexes containing fluorinated aryloxo and alkoxo ligands for fast living ring-opening metathesis polymerization (ROMP) and highly cis-specific ROMP.

(Arylimido)vanadium(V)-alkylidene complexes, V(CHSiMe3)(N-2,6-X2C6H3)(OC6F5)(PMe3)2 [X = Me (2), Cl (4)], exhibited remarkable catalytic activities for ring-opening metathesis polymerization (ROMP) of norbornene, and the ROMP by 2 proceeded in a living manner, affording ultrahigh molecular weight polymers. Cis-specific ROMP was achieved with the alkoxo analogues, V(CHSiMe3)(N-2,6-X2C6H3)[OC(CH3)(CF3)2]-(PMe3)2 [X = Me (5), Cl (6)]. Both the activity and the selectivity increased upon addition of PMe3, even at 50 °C.

Synthesis of Well-Defined Oligo(2,5-dialkoxy-1,4-phenylene vinylene)s with Chiral End Groups: Unique Helical Aggregations Induced by the Chiral Chain Ends.

Oligo(2,5-dialkoxy-1,4-phenylenevinylene)s containing three different chiral alkoxy substituents on the phenyl end groups with structurally regular (all trans) controlled repeat units have been prepared; these compounds showed highly enhanced aggregation-induced circular dichroism (AICD; formation of supramolecular polymers), and an inversion of the CD signal was observed even with the same end groups under certain conditions.

Synthesis and structural analysis of (imido)vanadium(V) dichloride complexes containing imidazolin-2-iminato- and imidazolidin-2-iminato ligands, and their use as catalyst precursors for ethylene (co)polymerization.

A series of (imido)vanadium(V) dichloride complexes containing 1,3-imidazolin-2-iminato or 1,3-imidazolidin-2-iminato ligands of the type, V(NR')Cl2(L) [R' = 2,6-Me2C6H3, L = 1,3-R2(CHN)2C═N (1a-c,e) or 1,3-R2(CH2N)2C═N (2a-d), R = (t)Bu (a), 2,6-Me2C6H3 (b), 2,6-(i)Pr2C6H3 (c), C6H5 (d), 2,6-(Ph2CH)2-4-MeC6H2 (e); L = 1,3-(2,6-(i)Pr2C6H3)2(CHN)2C═N, R' = 1-adamantyl (Ad, 3c), C6H5 (4c); L = 1,3-(2,6-(i)Pr2C6H3)2(CH2N)2C═N, R' = Ad (5c)], were prepared and characterized. The molecular structures of 1a, 2a,c,d, 3c, 4c, and 5c were determined by X-ray crystallography. All complexes showed high catalytic activity for ethylene polymerization especially in the presence of Et2AlCl cocatalyst; the 2,6-R2C6H3 analogues (R = Me, (i)Pr; 1b,c, 2b,c) exhibited higher catalytic activities than the (t)Bu analogues (1a, 2a), which display rather unique (small) V-N-C(imido) bond angles in the solid state. A good correlation between the activity and the (51)V NMR chemical shift was found for the (arylimido)vanadium precatalysts (1a-c,e, 2a-d, and 4c). These complexes showed high catalytic activity for the copolymerization of ethylene with norbornene (NBE), affording ultrahigh molecular weight copolymers with uniform molecular weight distributions. The activities were affected by the imido ligand as well as by the substituents in the anionic ligand, and the 2,6-(i)Pr2C6H3 analogues (especially 2c and 4c) showed the higher activities. The complexes 2c and 4c also showed high activities with efficient comonomer incorporation for the ethylene copolymerization with 5-ethylidene-2-norbornene (ENB) in the presence of Et2AlCl; both the comonomer incorporation and the molecular weight in the resulting polymers were affected by the comonomer employed (NBE vs ENB).

Synthesis of Polyesters Containing Long Aliphatic Methylene Units by ADMET Polymerization and Synthesis of ABA-Triblock Copolymers by One-Pot End Modification and Subsequent Living Ring-Opening Polymerization.

The synthesis of high-molecular-weight (Mn up to 62,000 g/mol) polyesters has been achieved by acyclic diene metathesis (ADMET) polymerization of α,ω-dienes prepared from biobased bis(undec-10-enoate) and diols [ethylene glycol (M1), propylene glycol (M2), 1,9-nonanediol (M3), 1,4-benzenedimethanol (M4), and hydroquinone (M5)] using ruthenium-carbene catalysts. Replacement of the solvent during the ADMET polymerization was effective for obtainment of the high-molecular-weight polymers (expressed as P1-P5). The melting temperatures (Tm) in the resultant polyesters were dependent upon the diol (middle) segment employed, and the polymer prepared from M5 exceeded 100 °C (a Tm value of 122.5 °C). The polymerization of M3 and M4 in the presence of 1,4-cis-diacetoxy-2-butene (DAB, as the chain transfer agent) afforded the telechelic polyesters [P3(OAc)2 and P4(OAc)2, respectively] containing acetoxy end groups exclusively. The resultant polymers containing hydroxy group termini [P3(OH)2 and P4(OH)2], prepared by the selective deprotection of the acetoxy end groups, were treated with AlEt3 followed by addition of ε-caprolactone to afford the ABA-type triblock copolymers exclusively, through a living ring-opening polymerization. The depolymerization (hydrolysis) under basic conditions (NaOH aqueous solution) of P3 was explored.

Amorphous Elastomeric Ultra-High Molar Mass Polypropylene in High Yield by Half-Titanocene Catalysts.

Propylene polymerizations with different ketimide-modified half-titanocene catalysts, Cp'TiCl2(N=CtBu2) [Cp' = C5H5 (1), C5Me5 (2), Me3SiC5H4 (3)], with MAO as a cocatalyst, were investigated. The obtained polymers were studied in detail by determining their microstructure, molar masses, thermal, and mechanical properties. The Cp*-ketimide, (C5Me5)TiCl2(N=CtBu2) (2), exhibited higher catalytic activities than Cp'TiCl2(N=CtBu2) (1,3), yielding higher molar mass polymers, Mw up to 1400 Kg/mol. All the synthesized polypropylenes (PP) are atactic and highly regioregular, with predominant rrrr pentads, especially PP prepared with catalyst 1. Differential scanning calorimetry (DSC) established that the polymers are fully amorphous aPP, and no melting endotherm events are detected. Glass transition temperatures were detected between -2 and 2 °C. These polypropylenes have been established to be high-performance thermoplastic elastomers endowed with remarkably high ductility, and a tensile strain at break higher than 2000%.

Synthesis of Network Biobased Aliphatic Polyesters Exhibiting Better Tensile Properties than the Linear Polymers by ADMET Polymerization in the Presence of Glycerol Tris(undec-10-enoate).

Development of biobased aliphatic polyesters with better mechanical (tensile) properties in film has attracted considerable attention. This report presents the synthesis of soluble network biobased aliphatic polyesters by acyclic diene metathesis (ADMET) polymerization of bis(undec-10-enyl)isosorbide diester [M1, dianhydro-D-glucityl bis(undec-10-enoate)] in the presence of a tri-arm crosslinker [CL, glycerol tris(undec-10-enoate)] using a ruthenium-carbene catalyst, and subsequent olefin hydrogenation using RhCl(PPh3)3. The resultant polymers, after hydrogenation (expressed as HCP1) and prepared in the presence of 1.0 mol% CL, showed better tensile properties than the linear polymer (HP1) with similar molecular weight [tensile strength (elongation at break): 20.8 MPa (282%) in HP1 vs. 35.4 MPa (572%) in HCP1]. It turned out that the polymer films prepared by the addition of CL during the polymerization (expressed as a 2-step approach) showed better tensile properties. The resultant polymer film also shows better tensile properties than the conventional polyolefins such as linear high density polyethylene, polypropylene, and low density polyethylene.

Synthesis and structural analysis of (imido)vanadium(V) complexes containing chelate (anilido)methyl-imine ligands: ligand effect in ethylene dimerization.

A series of (imido)vanadium dichlorido complexes containing chelate anionic donor ligands of the type, VCl2(L)(NR) [R = 1-adamantyl (Ad), L = 2-(2,6-Me2C6H3)NCH2(C9H6N) (2), 8-(2,6-Me2C6H3)NCH2(C9H6N) (3); L = 2-(2,6-R'2C6H3)NCH2(C5H4N), R = 2-MeC6H4, R' = Me (4a), (i)Pr (4b); L = 2-(2,6-Me2C6H3)NCH2(C5H4N), R = 4-MeC6H4 (5), 3,5-Me2C6H3 (6)], have been prepared and identified. The reactions with ethylene by 2,3 in the presence of methylaluminoxane (MAO) afforded a mixture of high molecular weight polyethylene and oligomers. Reactions with ethylene by VCl2[2-(2,6-R'2C6H3)NCH2(C5H4N)](NAd) (1a,b), 4-6 afforded 1-butene with high selectivities (>92%), and the activities by 4a,b are at the same level as those in 1a,b. The activities by 5,6 were lower than 4a,b and were at the same level of that by VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)](NPh). These results thus suggest that both the chelate anionic donor and the imido ligands play a role for both the activity and the selectivity.

Chemical Upcycling of PET into a Morpholine Amide as a Versatile Synthetic Building Block.

A catalytic chemical upcycling methodology for polyesters has been developed. Commodity polyesters, such as polyethylene terephthalate (PET), are depolymerized with morpholine by using a Cp*TiCl3 catalyst under ambient pressure without any additives, which provides morpholine amides exclusively. The method can also apply to other polyesters, polybutylene terephthalate (PBT), polyethylene adipate (PEA), polybutylene adipate (PBA), and polybutylene succinate (PBS), as well as an actual PET waste of a 50 g postconsumer beverage bottle. The product, morpholine amide, is a versatile building block in organic chemistry, and the synthetic utility has thus been demonstrated by further transformations, such as hydrolysis, selective reductive conversions, and Grignard reaction.

Synthesis of High-Molecular-Weight Biobased Aliphatic Polyesters by Acyclic Diene Metathesis Polymerization in Ionic Liquids.

Acyclic diene metathesis (ADMET) polymerization of an α,ω-diene monomer of bis(undec-10-enoate) with isosorbide (M1) using a RuCl2(IMesH2)(CH-2-O i Pr-C6H4) (HG2, IMesH2 = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) catalyst and conducted at 50 °C (in vacuo) in ionic liquids (ILs) afforded higher-molecular-weight polymers (P1, M n = 32 200-39 200) than those reported previously (M n = 5600-14700). 1-n-Butyl-3-methyl imidazolium hexafluorophosphate ([Bmim]PF6) and 1-n-hexyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)imide ([Hmim]TFSI) were suitable as effective solvents among a series of imidazolium salts and the pyridinium salts. The polymerization of α,ω-diene monomers of bis(undec-10-enoate) with isomannide (M2), 1,4-cyclohexanedimethanol (M3), and 1,4-butanediol (M4) in [Bmim]PF6 and [Hmim]TFSI also afforded the higher-molecular-weight polymers. The M n values in the resultant polymers did not decrease even under the scale-up conditions (300 mg to 1.0 g scale, M1, M2, and M4) in the polymerizations in [Hmim]TFSI; the subsequent reaction of P1 with ethylene (0.8 MPa, 50 °C, and 5 h) gave oligomers (proceeded via depolymerization). Tandem hydrogenation of the resultant unsaturated polymers (P1) in a [Bmim]PF6-toluene biphasic system upon the addition of Al2O3 (1.0 MPa H2 at 50 °C) gave the corresponding saturated polymers (HP1), which waswere isolated by a phase separation in the toluene layer. The [Bmim]PF6 layer containing the ruthenium catalyst could be recycled without a decrease in the activity/selectivity of the olefin hydrogenation at least eight times.

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

Synthesis of high molecular weight polyesters prepared by acyclic diene metathesis (ADMET) polymerization of bis(undec-10-enoate) with isosorbide (M1), isomannide (M2), and 1,3-propanediol (M3) and the subsequent hydrogenation have been achieved by using a molybdenum-alkylidene catalyst. The resultant polymers (P1) prepared by the ADMET polymerization of M1 (in toluene at 25 °C) possessed high Mn values (Mn = 44400-49400 g/mol), and no significant differences in the Mn values and the PDI (Mw/Mn) values were observed in the samples after the hydrogenation. Both the tensile strength and the elongation at break in the hydrogenated polymers from M1 (HP1) increased upon increasing the molar mass, and the sample with an Mn value of 48200 exhibited better tensile properties (tensile strength of 39.7 MPa, elongation at break of 436%) than conventional polyethylene, polypropylene, as well as polyester containing C18 alkyl chains. The tensile properties were affected by the diol segment employed, whereas HP2 showed a similar property to HP1.

Synthesis of oligo(thiophene)-coated star-shaped ROMP polymers: unique emission properties by the precise integration of functionality.

A facile synthesis of oligo(thiophene)-modified (coated) "soluble" star (ball)-shaped polymers has been achieved via sequential living ring-opening metathesis polymerization (ROMP) of norbornene and a cross-linking reagent using Mo(CHCMe(2)Ph)(N-2,6-(i)Pr(2)C(6)H(3))(O(t)Bu)(2) as the initiator and oligo(thiophene) carboxaldehydes for termination. The resultant star-shaped ROMP polymers containing ter- and tetrathiophene moieties exhibit unique emission properties due to an integration of the ROMP polymers (arranged functionalities): the blue emission was tuned to the white emission upon addition of 2-[2-[(E)-4-(dimethylamino)styryl]-6-methyl-4H-pyran-4-ylidene]malononitrile.

High Conversion of CaO-Catalyzed Transesterification of Vegetable Oils with Ethanol.

Fatty acid ethyl esters (FAEEs) derived from vegetable oils and ethanol are promising bio-based chemicals for various applications such as biofuel, monomers for polyesters, and fine chemicals. However, the limited conversion and yield are obtained in the conventional methods due to low boiling point of ethanol that thus requires conducting the reaction at low temperature. This work demonstrates high yield of FAEEs from soybean, rice bran and palm oil with ethanol by performing the transesterification at high temperatures of 150-200°C by using CaO catalyst in a high pressure reactor. The results demonstrate the complete reaction for all vegetable oils with low ethanol to oil molar ratio of 6:1 and 1 wt.% CaO catalyst. Higher reaction temperature results in faster reaction while keeping high conversion of ≥ 99.0%. The unsaturated components in FAEE products are consistent with their original fatty acid chain. Moreover, the high conversion can be achieved even in the reaction conducted with low ethanol to oil molar ratio of 4.5:1 and 0.5 wt.% CaO catalyst at 180 °C in the palm oil transesterification. The catalyst can be reused for at least 3 times with the conversion higher than 94.0%. In addition, the activation energy (Ea), enthalpy of activation (ΔH‡), entropy of activation (ΔS‡) and Gibbs free energy of activation (ΔG‡) are also obtained.