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A sustainable CO2 polymerization using surface activated zinc glutarate catalysts produces industrially useful polymers with good catalytic activity.

Synthetic biodegradable polyesters tend to undergo slow biodegradation under ambient natural conditions and, hence, have been rejected or even banned recently in ecofriendly applications. Here, we demonstrate the preparation of polyesters exhibiting enhanced biodegradability, which were generated through a combination of old controversial macromolecules and aggregate theories. H

The reactor fouling is a notorious obstacle in managing continuous synthetic processes of polyketones. The fouling raises synthetic costs and reduces the bulk density of polymers. Thus, efficient seed materials are required for antifouling performance. Hollow microporous organic polymers (HMOPs) were prepared using ZIF-8 nanoparticles as templating materials. Sulfonic groups were incorporated into HMOP via a post synthetic approach. The resultant HMOP–SO3H (20–90 μg/mL in methanol) showed successful catalyst activation and antifouling performance in polyketone synthesis.

We synthesized a series of Me2Si-bridged ansa-zirconocene complexes coordinated by thiophene-fused cyclopentadienyl and fluorenyl ligands (Me2Si(2-R1-3-R2-4,5-Me2C7S)(2,7-R32C13H6))ZrMe2 (R1 = Me or H, R2 = H or Me, R3 = H, tBu, or Cl) for the subsequent preparation of supported catalysts. We determined that the fluorenyl ligand adopts an η3-binding mode in 9 (R1 = Me, R2 = H, R3 = H) by X-ray crystallography. Further, we synthesized a derivative 15 by substituting the fluorenyl ligand in 9 with a 2-methyl-4-(4-tert-butylphenyl)indenyl ligand, derivatives 20 and 23 by substituting the Me2Si bridge in 12 (R1 = Me, R2 = H, R3 = tBu) and 15 with a tBuO(CH2)6(Me)Si bridge, and the dinuclear congener 26 by connecting two complexes with a –(Me)Si(CH2)6Si(Me)– spacer. The silica-supported catalysts prepared using 12, 20, and 26 demonstrated up to two times higher productivity in ethylene/1-hexene copolymerization than that prepared with conventional (THI)ZrCl2 (21–26 vs. 12 kg-PE/g-(supported catalyst)), producing polymers with comparable molecular weight (Mw, 330–370 vs. 300 kDa), at a higher 1-hexene content (1.3 vs. 1.0 mol%) but a lower bulk density of polymer particles (0.35 vs. 0.42 g/mL).

Numerous efforts have been made to achieve “on-purpose” 1-octene production since Sasol discovered a Cr-based selective ethylene tetramerization catalyst in the early 2000s. By preparing a series of bis(phosphine) ligands iPrN(PAr2)2 where the Ar contains a bulky –SiR3 substituent (Ar = −C6H4-p-Si(nBu)3 (1), −C6H4-p-Si(1-hexyl)3 (2), −C6H4-p-Si(1-octyl)3 (3), −C6H4-p-Si(2-ethylhexyl)3 (4), −C6H4-p-Si(3,7-dimethyloctyl)3 (5)), we obtained an extremely active catalyst that meets the criteria for commercial utilization. The Cr complexes [iPrN(PAr2)2−CrCl2]+[B(C6F5)4]–, obtained by reacting ligands 1–5 with [(CH3CN)4CrCl2]+[B(C6F5)4]–, showed high activity exceeding 6000 kg/g-Cr/h, when combined with the inexpensive iBu3Al, thus avoiding the use of expensive modified methylaluminoxane (MMAO). The bulky –SiR3 substituents played a key role in the success of catalysis by blocking the formation of inactive species (Cr complexes coordinated by two iPrN(PAr2)2 ligands, that is, [(iPrN(PAr2)2)2−CrCl2]+[B(C6F5)4]–). Among the complexes prepared, [3−CrCl2]+[B(C6F5)4]– exhibited the highest activity (11,100 kg/g-Cr/h, 100 kg/g-catalyst) with high 1-octene selectivity (75 wt%) and, moreover, mitigated the generation of undesired &gt, C10 fractions (10.7 wt%). A 10-g-scale synthesis of 3 was developed, as well as a facile and low-cost synthetic method for [(CH3CN)4CrCl2]+[B(C6F5)4]–.

Synthesis of long-chain branched polymers has been a crucial concern in the polyolefin industry. In this study, a method to produce long-chain branches (LCBs) in coordinative chain transfer copolym...

Homogeneous olefin polymerization catalysts are activated in situ with a co-catalyst ([PhN(Me)2-H]+[B(C6F5)4]− or [Ph3C]+[B(C6F5)4]−) in bulk polymerization media. These co-catalysts are insoluble in hydrocarbon solvents, requiring excess co-catalyst (&gt, 3 eq.). Feeding the activated species as a solution in an aliphatic hydrocarbon solvent may be advantageous over the in situ activation method. In this study, highly pure and soluble ammonium tetrakis(pentafluorophenyl)borates ([Me(C18H37)2N-H]+[B(C6F5)4]− and [(C18H37)2NH2]+[B(C6F5)4]−) containing neither water nor Cl− salt impurities were prepared easily via the acid–base reaction of [PhN(Me)2-H]+[B(C6F5)4]− and the corresponding amine. Using the prepared ammonium salts, the activation reactions of commercial-process-relevant metallocene (rac-[ethylenebis(tetrahydroindenyl)]Zr(Me)2 (1-ZrMe2), [Ph2C(Cp)(3,6-tBu2Flu)]Hf(Me)2 (3-HfMe2), [Ph2C(Cp)(2,7-tBu2Flu)]Hf(Me)2 (4-HfMe2)) and half-metallocene complexes ([(η5-Me4C5)Si(Me)2(κ-NtBu)]Ti(Me)2 (5-TiMe2), [(η5-Me4C5)(C9H9(κ-N))]Ti(Me)2 (6-TiMe2), and [(η5-Me3C7H1S)(C10H11(κ-N))]Ti(Me)2 (7-TiMe2)) were monitored in C6D12 with 1H NMR spectroscopy. Stable [L-M(Me)(NMe(C18H37)2)]+[B(C6F5)4]− species were cleanly generated from 1-ZrMe2, 3-HfMe2, and 4-HfMe2, while the species types generated from 5-TiMe2, 6-TiMe2, and 7-TiMe2 were unstable for subsequent transformation to other species (presumably, [L-Ti(CH2N(C18H37)2)]+[B(C6F5)4]−-type species). [L-TiCl(N(H)(C18H37)2)]+[B(C6F5)4]−-type species were also prepared from 5-TiCl(Me) and 6-TiCl(Me), which were newly prepared in this study. The prepared [L-M(Me)(NMe(C18H37)2)]+[B(C6F5)4]−-, [L-Ti(CH2N(C18H37)2)]+[B(C6F5)4]−-, and [L-TiCl(N(H)(C18H37)2)]+[B(C6F5)4]−-type species, which are soluble and stable in aliphatic hydrocarbon solvents, were highly active in ethylene/1-octene copolymerization performed in aliphatic hydrocarbon solvents.

CrCl3(thf)3 is a common starting material in the synthesis of organometallic and coordination compounds of Cr. Deposited as an irregular solid with no possibility of recrystallization, it is not a purity guaranteed chemical, causing problems in some cases. In this work, we disclose a well-defined form of the THF adduct of CrCl3 ([CrCl2(μ-Cl)(thf)2]2), a crystalline solid, that enables structure determination by X-ray crystallography. The EA data and XRD pattern of the bulk agreed with the revealed structure. Moreover, its preparation procedure is facile: evacuation of CrCl3·6H2O at 100 °C, treatment with 6 equivalents of Me3SiCl in a minimal amount of THF, and crystallization from CH2Cl2. The ethylene tetramerization catalyst [iPrN{P(C6H4-p-Si(nBu)3)2}2CrCl2]+[B(C6F5)4]– prepared using well-defined [CrCl2(μ-Cl)(thf)2]2 as a starting material exhibited a reliably high activity (6600 kg/g-Cr/h, 1-octene selectivity at 40 °C, 75%), while that of the one prepared using the impure CrCl3(thf)3 was inconsistent and relatively low (~3000 kg/g-Cr/h). By using well-defined [CrCl2(μ-Cl)(thf)2]2 as a Cr source, single crystals of [(CH3CN)4CrCl2]+[B(C6F5)4]– and [{Et(Cl)Al(N(iPr)2)2}Cr(μ-Cl)]2 were obtained, allowing structure determination by X-ray crystallography, which had been unsuccessful when the previously known CrCl3(thf)3 was used as the Cr source.

Propylene oxide (PO) binding and ring-opening reaction with the bifunctional CO2/epoxide copolymerization catalyst, based on the Co(III)-salcy complex including two quaternary ammonium salts with n-butyl substituents (N+-chains) were investigated by Density Functional Theory (DFT) calculations and compared with the model systems without the N+-chains. The importance of the different possible stereoisomers and the stereoselectivity of these processes for (S)- and (R)-enantiomers of PO were considered. To explore the conformational space for the real catalyst, a complex approach, developed previously was applied. The calculations for the model systems directly demonstrate that PO-ring opening proceeds preferentially in trans catalysts’ configuration and no participation of cis-β isomers is viable, nucleophilic attack at the methylene-carbon atom is preferred over that at methine-carbon atom. For the real bifunctional catalyst, with the (S,S)-configuration of cyclohexane, the results indicate a preference of (R)-PO ring-opening over (S)-PO ring-opening (ca. 6 : 5). Concerning stereoisomers resulting from the orientation of N+-chains in the real catalyst, different groups of structures participate in the ring-opening reaction for (R)-PO, and different for (S)-PO. The high population of nonreactive complexes of (R)-PO may be the key factor responsible for decreasing the activity of the analyzed catalyst in the epoxide ring-opening reaction.

Chemically synthesized retinyl palmitate has been widely used in the cosmetic and biotechnology industry. In this study, we aimed to demonstrate the microbial production of retinyl palmitate and the benefits of microbial retinyl palmitate in skin physiology. A heterologous retinyl palmitate biosynthesis pathway was reconstructed in metabolically engineered Escherichia coli using synthetic expression modules from Pantoea agglomerans, Salinibacter ruber, and Homo sapiens. High production of retinyl palmitate (69.96 &plusmn, 2.64 mg/L) was obtained using a fed-batch fermentation process. Moreover, application of purified microbial retinyl palmitate to human foreskin HS68 fibroblasts led to increased cellular retinoic acid-binding protein 2 (CRABP2) mRNA level [1.7-fold (p = 0.001) at 100 &mu, g/mL], acceleration of cell proliferation, and enhancement of procollagen synthesis [111% (p &lt, 0.05) at 100 &mu, g/mL], strongly indicating an anti-ageing-related effect of this substance. These results would pave the way for large-scale production of retinyl palmitate in microbial systems and represent the first evidence for the application of microbial retinyl palmitate as a cosmeceutical.

The demand for poly(&alpha, olefin)s (PAOs), which are high-performance group IV lubricant base oils, is increasingly high. PAOs are generally produced via the cationic oligomerization of 1-decene, wherein skeleton rearrangement inevitably occurs in the products. Hence, a transition-metal-based catalytic process that avoids rearrangement would be a valuable alternative for cationic oligomerization. In particular, transition-metal-catalyzed selective trimerization of &alpha, olefins has the potential for success. In this study, (N,N&prime, N&Prime, tridodecyltriazacyclohexane)CrCl3 complex was reacted with MAO-silica (MAO, methylaluminoxane) for the preparation of a supported catalyst, which exhibited superior performance in selective &alpha, olefin trimerization compared to that of the corresponding homogeneous catalyst, enabling the preparation of &alpha, olefin trimers at ~200 g scale. Following hydrogenation, the prepared 1-decene trimer (C30H62) exhibited better lubricant properties than those of commercial-grade PAO-4 (kinematic viscosity at 40 &deg, C, 15.1 vs. 17.4 cSt, kinematic viscosity at 100 &deg, C, 3.9 vs. 3.9 cSt, viscosity index, 161 vs. 123). Moreover, it was shown that 1-octene/1-dodecene mixed co-trimers (i.e., a mixture of C24H50, C28H58, C32H66, and C36H74), generated by the selective supported Cr catalyst, exhibited outstanding lubricant properties analogous to those observed for the 1-decene trimer (C30H62).

In this work, we prepared fluorescently labeled poly(&epsilon, caprolactone-ran-lactic acid) (PCLA-F) as a biomaterial to fabricate three-dimensional (3D) scaffolds via salt leaching and 3D printing. The salt-leached PCLA-F scaffold was fabricated using NaCl and methylene chloride, and it had an irregular, interconnected 3D structure. The printed PCLA-F scaffold was fabricated using a fused deposition modeling printer, and it had a layered, orthogonally oriented 3D structure. The printed scaffold fabrication method was clearly more efficient than the salt leaching method in terms of productivity and repeatability. In the in vivo fluorescence imaging of mice and gel permeation chromatography of scaffolds removed from rats, the salt-leached PCLA scaffolds showed slightly faster degradation than the printed PCLA scaffolds. In the inflammation reaction, the printed PCLA scaffolds induced a slightly stronger inflammation reaction due to the slower biodegradation. Collectively, we can conclude that in vivo biodegradability and inflammation of scaffolds were affected by the scaffold fabrication method.

The preference of open chain of growing macromolecule vs. possible cyclic form was examined for the bifunctional cobalt(III)-salen catalyst for the copolymerization of CO2 with epoxides. A variety of possible isomers was considered (resulting from trans/cis-β salen arrangement, different mutual orientation of quaternary ammonium-chains, and possible binding modes). To explore the conformational space, a combined approach was applied, utilizing semiempirical (PM7) MD and the DFT calculations. The preference of the open and cyclic macromolecules attached to the metal center was compared with the corresponding results for isolated model macromolecules, and the systems built of the macromolecule interacting with the tetra-butyl ammonium cation. Result shows that the cyclic structures are strongly preferred for isolated ions, with relatively low cyclization barriers. In the field of positive point charge, the open structures are strongly preferred. For the ions interacting with tetrabutyl ammonium cation, the cyclic structures are preferred, due to delocalization of the positive charge in the cation. For the complexes involving model and “real” Co(III)-salen catalysts, the open structures are strongly preferred. The possible cyclization by dissociation of alkoxide and its transfer to the neighborhood of quaternary ammonium cation is characterized by high activation barriers. Further, the transfer of alkoxide from the metal center to the cation is less likely than the transfer of carbonate, since the metal-alkoxide bond-energy energy is much stronger than energy of metal-carbonate bonding, as shown by ETS-NOCV results. The conclusions are in qualitative agreement with experimental data showing high selectivity towards copolymer formation in the copolymerization processes catalyzed by bifunctional Co(III) salen-complexes.

The preference of open chain of growing macromolecule vs. possible cyclic form was examined for the bifunctional cobalt(III)-salen catalyst for the copolymerization of CO2 with epoxides. A variety of possible isomers was considered (resulting from trans/cis-β salen arrangement, different mutual orientation of quaternary ammonium-chains, and possible binding modes). To explore the conformational space, a combined approach was applied, utilizing semiempirical (PM7) MD and the DFT calculations. The preference of the open and cyclic macromolecules attached to the metal center was compared with the corresponding results for isolated model macromolecules, and the systems built of the macromolecule interacting with the tetra-butyl ammonium cation. Result shows that the cyclic structures are strongly preferred for isolated ions, with relatively low cyclization barriers. In the field of positive point charge, the open structures are strongly preferred. For the ions interacting with tetrabutyl ammonium cation, the cyclic structures are preferred, due to delocalization of the positive charge in the cation. For the complexes involving model and “real” Co(III)-salen catalysts, the open structures are strongly preferred. The possible cyclization by dissociation of alkoxide and its transfer to the neighborhood of quaternary ammonium cation is characterized by high activation barriers. Further, the transfer of alkoxide from the metal center to the cation is less likely than the transfer of carbonate, since the metal-alkoxide bond-energy energy is much stronger than energy of metal-carbonate bonding, as shown by ETS-NOCV results. The conclusions are in qualitative agreement with experimental data showing high selectivity towards copolymer formation in the copolymerization processes catalyzed by bifunctional Co(III) salen-complexes. Graphical abstract Electronic supplementary material The online version of this article (10.1007/s00894-020-04364-x) contains supplementary material, which is available to authorized users.

A practical and simple method for the preparation of ABA-type olefin triblock copolymers, e.g., PE-b-poly(ethylene-co-propylene)-b-PE, has been described. The performance of the so-called “coordinative chain transfer polymerization” (CCTP) by sequential feed of ethylene and ethylene/propylene mixed gas generated a Zn-bound diblock copolymer (i.e., (PE-b-poly(ethylene-co-propylene)yl)2Zn). Treatment of the Zn-bound diblock copolymer with lauroyl peroxide (CH3(CH2)10C(O)O-OC(O)(CH2)10CH3) led to a C(sp3)–C(sp3) coupling reaction between the two diblock chains bound on the zinc site and an ABA-type olefin triblock copolymer, PE-b-poly(ethylene-co-propylene)-b-PE, was formed. Upon the treatment with lauroyl peroxide, the number-average molecular weight increased by 1.5–1.7 times. The occurrence of the coupling reaction was verified using a model compound, (Oct)2Zn. The ABA-type triblock copolymer exhibited thermoplastic elastomeric properties and dramatically improved mechanical properties (twice the tensile ...

Model catalysts for CO2 /epoxide copolymerization based on Co(III) complexes were studied, with focus on the preference of their alternative isomers, cisβ vs. trans. The systems range from model structures without the co-catalyst, as derived from crystallographic data, to complex models with two (CH2 )4 N+ R3 co-catalyst chains (R = Me, Bu) grafted onto a Co(III)-salcy core. To explore the conformational space of the latter complexes, a computational protocol was developed, combining a systematic model-building approach with static and molecular dynamics calculations, and multilevel energy assessment (PM7 and DFT). Results demonstrate an influence of the co-catalyst on the relative stability of the isomers. The cisβ isomer is preferred for complexes without N+ -chains and the cisβ ↔ trans isomerization is feasible. Five-coordinate species and open-shell electronic configurations are energetically disfavored. The cisβ preference decreases with the introduction and enlargement of (CH2 )4 N+ R3 : both isomers can be populated for R = Me, while the trans isomer is visibly preferred for R = Bu. © 2018 Wiley Periodicals, Inc.

This study is the first to assess the applicability of biodegradable poly(1,4-butylene carbonate) (PBC) as a printing ink for fused deposition modeling (FDM). Here, PBC was successfully prepared via the bulk polycondensation of 1,4-butanediol and dimethyl carbonate. PBC was melted above 150°C in the heating chamber of an FDM printer, after which it flowed from the printing nozzle upon applying pressure and solidified at room temperature to create a three-dimensional (3D) scaffold structure. A 3D scaffold exactly matching the program design was obtained by controlling the temperature and pressure of the FDM printer. The compressive moduli of the printed PBC scaffold decreased as a function of implantation time. The printed PBC scaffold exhibited good in vitro biocompatibility, as well as in vivo neotissue formation and little host tissue response, which was proportional to the gradual biodegradation. Collectively, our findings demonstrated the feasibility of PBC as a suitable printing ink candidate for the creation of scaffolds via FDM printing.

Pd(II) nanosalts formed from [LnPd(OAc)2] (Ln = 1,3-bis(di-o-methoxyphenylphosphino)propane) and ammonium tethered carboxylic acids in MeOH were utilized for the synthesis of antifouling polyketones from CO and olefin; this is the first instance of the synthesis of antifouling polyketones in the absence of additional heterogeneous seeds. The polymerization of CO and olefin achieved with the in situ-generated Pd(II) nanosalts was studied, and the nanosalts were analyzed by dynamic light scattering (DLS) experiments.

Nanoseeds with silica@sulfonated microporous organic polymer (SiO2@S-MOP) structure were prepared by the formation of MOP layers on the surface of SiO2 spheres and the successive sulfonation of the MOPs. Using the SiO2@S-MOPs as seed materials, catalytic terpolymerization of CO, ethylene, and propylene was studied. The designed SiO2@S-MOP nanoseeds not only activated catalyst precursors but also controlled the catalytic formation of polyketones. While the homogeneous system showed a severe reactor fouling and a wide molecular weight distribution of terpolymer, the SiO2-190@S-MOP system resulted in the narrow molecular weight distribution of terpolymers without a reactor fouling. The size of nanoseeds was critical to obtaining the granular terpolymers. Moreover, the SiO2-190@S-MOP system showed a good activity of 17.2 kg of polymer/g of Pd, comparable to the homogeneous system with 19.6 kg of polymer/g of Pd. We believe that more various nanoseeded catalytic polymerizations can be developed using new nanos...

Synthesis of polyolefin (PO)-based block copolymers is of immense research interest. In this work, we report a strategy for the construction of polystyrene (PS)-block-PO-block-PS, a useful thermoplastic elastomer, directly from olefin and styrene monomers. Multinuclear zinc species Et[Zn(CH2)6]aZnEt were prepared through successive additions of BH3 and Et2Zn to 1,5-hexadiene. Poly(ethylene-co-propylene) chains were biaxially grown from the −(CH2)6– units in Et[Zn(CH2)6]aZnEt via “coordinative chain transfer polymerization (CCTP)” using the pyridylaminohafnium catalyst. PS chains were subsequently grown in one pot from the generated polymeryl–Zn sites by subsequent introduction of the anionic initiator Me3SiCH2Li·(pmdeta) (pmdeta, pentamethyldiethylenetriamine) and styrene monomers. The fraction of the extracted PS homopolymer grown from the Me3SiCH2 sites was low (homo-PS (g)/total PS (g), 15–22%). The gel permeation chromatography (GPC) curves shifted evidently after styrene polymerization, and change in...

Block copolymers of polyolefins (PO) and polystyrene (PS) are attractive materials that are not synthesized directly from the olefin and styrene monomers. A strategy for construction of PS-b-PO-b-PS triblock units directly from the olefin and styrene monomers is disclosed herein. PO chains (ethylene/1-octene or ethylene/1-pentene copolymers) were grown from dialkylzinc species bearing the α-methylstyrene moiety (i.e., [4-(isopropenyl)benzyl]2Zn) by ‘coordinative chain transfer polymerization (CCTP)’ using a typical ansa-metallocene catalyst, rac-[Me2Si(2-methylindenyl)2]ZrCl2 activated with modified-methylaluminoxane (MMAO). PS chains were subsequently grown from the Zn-alkyl sites and from the α-methylstyrene moieties of the resulting PO chains by switching to anionic polymerization. When nBuLi(tmeda)2 was fed into the system as an initiator in a quantity fulfilling the criterion [Li] > [Zn] + [Al in MMAO], nBuLi(tmeda)2 successfully attacked the α-methylstyrene moieties to initiate the anionic styrene polymerization at both ends of the PO chains generated in the CCTP process. However, in model studies, the attack of nBuLi(tmeda)2 on α-methylstyrene in the presence of (hexyl)2Zn consumed two molecules of α-methylstyrene per nBuLi to afford mainly R–CH2C(Ph)(Me)–CH2C(Ph)(Me)Li, where R is either an nbutyl or hexyl group originating from nBuLi or (hexyl)2Zn, respectively. This observation suggests that the block copolymer does not simply comprise the PS-b-PO-b-PS triblock, but instead comprises a multiblock containing PS-b-PO-b-PS units. The molecular weight of the polymer increased after performing anionic polymerization. Even though the phase separation of the PS and PO blocks observed in the TEM images is less regular in the multiblock copolymers, the elastomeric property of the multiblock copolymers observed in the hysteresis testing is better than that of the diblock analogue.

Pincer-type [Cnaphthyl, Npyridine, Namido]HfMe2 complex is a flagship among the post-metallocene catalysts. In this work, various pincer-type Hf-complexes were prepared for olefin polymerization. Pincer-type [Namido, Npyridine, Namido]HfMe2 complexes were prepared by reacting in situ generated HfMe4 with the corresponding ligand precursors, and the structure of a complex bearing 2,6-Et2C6H3Namido moieties was confirmed by X-ray crystallography. When the ligand precursors of [(CH3)R2Si-C5H3N-C(H)PhN(H)Ar (R = Me or Ph, Ar = 2,6-diisopropylphenyl) were treated with in situ generated HfMe4, pincer-type [Csilylmethyl, Npyridine, Namido]HfMe2 complexes were afforded by formation of Hf-CH2Si bond. Pincer-type [Cnaphthyl, Sthiophene, Namido]HfMe2 complex, where the pyridine moiety in the flagship catalyst was replaced with a thiophene unit, was not generated when the corresponding ligand precursor was treated with HfMe4. Instead, the [Sthiophene, Namido]HfMe3-type complex was obtained with no formation of the Hf-Cnaphthyl bond. A series of pincer-type [Cnaphthyl, Npyridine, Nalkylamido]HfMe2 complexes was prepared where the arylamido moiety in the flagship catalyst was replaced with alkylamido moieties (alkyl = iPr, cyclohexyl, tBu, adamantyl). Structures of the complexes bearing isopropylamido and adamantylamido moieties were confirmed by X-ray crystallography. Most of the complexes cleanly generated the desired ion-pair complexes when treated with an equivalent amount of [(C18H37)2N(H)Me]+[B(C6F5)4]&minus, which showed negligible activity in olefin polymerization. Some complexes bearing bulky substituents showed moderate activities, even though the desired ion-pair complexes were not cleanly afforded.

For application in commercial slurry and gas-phase processes, single-site homogeneous metallocene catalysts are typically immobilized on silica surfaces to control the size and morphology of the generated polymer particles. However, the main challenge limiting the commercialization of these catalysts is the enhancement of their productivity (measured in kg-PE/g-(supported catalyst)). Herein, we demonstrate that the productivity of supported catalysts can be enhanced by using dinuclear metallocene complexes instead of the conventional mononuclear analogs to prepare the supported catalysts. Thus, the productivity of the supported catalysts prepared by reacting methylaluminoxane (MAO)-treated silica (denoted as silica-MAO) with dinuclear ansa-metallocene complexes synthesized with silylene-bridged and thiophene-fused cyclopentadienyl ligands was almost twice that of the catalysts prepared with the mononuclear analogs. The enhanced productivity is because of the higher loading of the dinuclear complexes than that of the mononuclear analogs; the fed dinuclear complexes were entirely anchored on silica-MAO at 90–150 μmol-Zr/g-(silica-MAO) feed, whereas only a part of the fed mononuclear metallocene complexes was anchored on silica-MAO even at 90 μmol-Zr/g-(silica-MAO) feed. In addition, the supported catalysts prepared with the dinuclear complexes suppressed the formation of large polymer particles.

Hydrocarbon resins, which are defined as low molecular weight, amorphous, and thermoplastic polymers, are widely used as tackifiers for various types of adhesives, as processing aids in rubber compounds, and as modifiers for paint and ink products, and for use in plastics polymers such as isotactic polypropylene. Recently, the quantities of the hydrocarbon resin׳ raw materials which are the side products from naphtha cracking process have decreased because of light-feed cracking such as gas cracking, so new raw materials for hydrocarbon resin production are essential. To be satisfied with the previously mentioned factors, the substitution of hydrocarbon resin raw materials with renewable resources is a worthy consideration. Moreover, new hydrocarbon resin having high adhesion performance, low specific gravity, and good compatibility with various polymers has been requested in various adhesives. To meet those requests, in this study, propylene instead of side product from naphtha cracking as main raw material of hydrocarbon resin were partially used. The propylene serves as a new, sustainable raw material and was successfully grafted onto dicyclopentadiene. The reaction of the propylene with dicyclopentadiene was confirmed because, according to NMR and FT-IR analyses, a pendant methyl-propylene group exists in the structure of the propylene-grafted, hydrogenated dicyclopentadiene hydrocarbon resin. To establish an optimal production condition regarding the propylene-grafted, hydrogenated dicyclopentadiene hydrocarbon resin, numerous experiments were conducted according to the mole ratio of the raw materials and the polymerization temperature. The propylene-grafted, hydrogenated dicyclopentadiene hydrocarbon resin that was manufactured according to optimal conditions results in a lower specific gravity and a high molecular weight, whereby the advantages of the adhesion properties of an SIS-based pressure-sensitive-adhesive are exploited. When the propylene-grafted, hydrogenated dicyclopentadiene hydrocarbon resin was formulated with the SIS-based pressure-sensitive-adhesive, both the heat stability and the shear-adhesion strength are sound.

Two representative bulk polymers, polyolefin (PO) and polystyrene (PS), were molecularly connected to form PO-block-PS by sequentially performing coordination and anionic polymerizations in one pot. Ethylene/1-octene copolymerization was performed using a typical ansa-metallocene catalyst, rac-[Me2Si(2-methylindenyl)]2ZrCl2, in the presence of (benzyl)2zinc to grow PO-chains at the Zn site. Anionic styrene polymerization was subsequently performed using nBuLi·(tmeda) (tmeda, N,N,N′,N′-tetramethylethylenediamine) initiator to consecutively grow PS-chains at the Zn site. The composition and the molecular weight of the PO-blocks were controllable depending on the feed amounts of 1-octene and (benzyl)2zinc (1-octene fraction: ∼20, ∼40 wt %; PO-Mw, 77,000–174,000) and the PS-block size was also controlled (PS-Mn, ∼21,000) with the complete conversion of the styrene monomer. Formation of block copolymers was evident in the GPC curves, TEM images, and strain-stress curves. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3110–3118

Sulfonic acid groups were anchored on a silica surface through robust Si C bonds. The successive treatment of dehydroxylated silica with benzylmagnesium chloride and H 2 SO 4 resulted in the surface tethering of CH 2 C 6 H 4 SO 3 H groups at a high coverage rate (0.50-CH 2 C 6 H 4 SO 3 H/nm 2 ). The pore structure of the silica remained unchanged during this surface-modification process. Next, the CH 2 C 6 H 4 SO 3 H groups on the surface were successfully used for preparing a supported catalyst for CO/ethylene copolymerization; the ≡Si CH 2 C 6 H 4 SO 3 H groups on the surface were reacted with [1,3-bis(di(2-methoxyphenyl)phosphino)propane]Pd(OAc) 2 to generate dicationic palladium species, which were anchored on the silica surface through ionic interactions with the sulfonate anions generated on the surface. The supported catalyst prepared in this way exhibited a high activity (up to 43 kg/g-Pd or 0.61 kg/g-cat) with respect to CO/ethylene copolymerization. The morphology of the obtained polymer particles replicated that of the silica particles. Thus, a polymer powder that exhibited a high bulk density (0.30 g/mL) could be obtained while causing minimal reactor fouling.

Lithium bis(phosphino)aluminate (4, [Et2Al(PPh2)2]Li·(THF); 5, [Et2Al(PCy2)2]Li·(THF)2), lithium bis(amino)aluminate (6, [Et2Al(NC4H8)2]Li·(THF); 7, [Et2Al(NiPr2)2]Li; 8, [iBu2Al(NiPr2)2]Li), and potassium bis(phosphino)borate ligands (11, [(C6F5)2B(PPh2)2]K; 12, [(C6F5)2B(PCy2)2]K) were prepared. Reaction of 4–6 with CrCl3(THF)3 did not provide any discrete chromium complexes, but the reaction of 5–6 with CrCl2(THF) yielded zwitterion-type Cr(II) complexes (13, [Et2Al(PCy2)2]2Cr(II); 14, [Et2Al(NC4H8)2]2Cr(II)). Reaction of THF-free 7–8 with CrCl3(THF)3 resulted in the formation of Cl-bridged Cr(II) dimer complexes {[Et(Cl)Al(NiPr2)2]Cr(II)-μ2-Cl}2 (15) and {[iBu(Cl)Al(NiPr2)2]Cr(II)-μ2-Cl}2 (16). A similar Cl-bridged Cr(II) dimer complex {[(C6F5)2B(PCy2)2]Cr(II)-μ2-Cl}2 (17) was also obtained by reacting the borate ligand 12 with CrCl2(THF). The structures of 13–17 were elucidated by X-ray crystallography. None of the prepared zwitterion-type Cr(II) complexes 13–17 exhibited any activity after activation with MAO, supporting catalytic cycle involving Cr(I/III) oxidation states in ethylene oligomerization.

The pyridylamido hafnium complex (I) discovered at Dow is a flagship catalyst among postmetallocenes, which are used in the polyolefin industry for PO-chain growth from a chain transfer agent, dialkylzinc. In the present work, with the aim to block a possible deactivation process in prototype compound I, the corresponding derivatives were prepared. A series of pyridylamido Hf complexes were prepared by replacing the 2,6-diisopropylphenylamido part in I with various 2,6-R2C6H3N-moieties (R = cycloheptyl, cyclohexyl, cyclopentyl, 3-pentyl, ethyl, or Ph) or by replacing 2-iPrC6H4C(H)- in I with the simple PhC(H)-moiety. The isopropyl substituent in the 2-iPrC6H4C(H)-moiety influences not only the geometry of the structures (revealed by X-ray crystallography), but also catalytic performance. In the complexes bearing the 2-iPrC6H4C(H)-moiety, the chelation framework forms a plane, however, this framework is distorted in the complexes containing the PhC(H)-moiety. The ability to incorporate &alpha, olefin decreased upon replacing 2-iPrC6H4C(H)-with the PhC(H)-moiety. The complexes carrying the 2,6-di(cycloheptyl)phenylamido or 2,6-di(cyclohexyl)phenylamido moiety (replacing the 2,6-diisopropylphenylamido part in I) showed somewhat higher activity with greater longevity than did prototype catalyst I.

Polyolefins (POs) are the most abundant polymers. However, synthesis of PO-based block copolymers has only rarely been achieved. We aimed to synthesize various PO-based block copolymers by coordinative chain transfer polymerization (CCTP) followed by anionic polymerization in one-pot via conversion of the CCTP product (polyolefinyl)2Zn to polyolefinyl-Li. The addition of 2 equiv t-BuLi to (1-octyl)2Zn (a model compound of (polyolefinyl)2Zn) and selective removal or decomposition of (tBu)2Zn by evacuation or heating at 130 &deg, C afforded 1-octyl-Li. Attempts to convert (polyolefinyl)2Zn to polyolefinyl-Li were unsuccessful. However, polystyrene (PS) chains were efficiently grown from (polyolefinyl)2Zn, the addition of styrene monomers after treatment with t-BuLi and pentamethyldiethylenetriamine (PMDTA) in the presence of residual olefin monomers afforded PO-block-PSs. Organolithium species that might be generated in the pot of t-BuLi, PMDTA, and olefin monomers, i.e., [Me2NCH2CH2N(Me)CH2CH2N(Me)CH2Li, Me2NCH2CH2N(Me)Li&middot, (PMDTA), pentylallyl-Li&sdot, (PMDTA)], as well as PhLi&sdot, (PMDTA), were screened as initiators to grow PS chains from (1-hexyl)2Zn, as well as from (polyolefinyl)2Zn. Pentylallyl-Li&sdot, (PMDTA) was the best initiator. The Mn values increased substantially after the styrene polymerization with some generation of homo-PSs (27&ndash, 29%). The Mn values of the extracted homo-PS suggested that PS chains were grown mainly from polyolefinyl groups in [(polyolefinyl)2(pentylallyl)Zn]&minus, [Li&sdot, (PMDTA)]+ formed by pentylallyl-Li&sdot, (PMDTA) acting onto (polyolefinyl)2Zn.

We have designed and characterized an injectable, electrostatically bonded, in situ–forming hydrogel system consisting of a cationic polyelectrolyte [(methoxy)polyethylene glycol-b-(poly(e-caprolactone)-ran-poly(L-lactic acid)] (MP) copolymer derivatized with an amine group (MP-NH2) and anionic BMP2. To the best of our knowledge, there have been hardly any studies that have investigated electrostatically bonded, in situ–forming hydrogel systems consisting of MP-NH2 and BMP2, with respect to how they promote in vivo osteogenic differentiation of human turbinate mesenchymal stem cells (hTMSCs). Injectable formulations almost immediately formed an electrostatically loaded hydrogel depot containing BMP2, upon injection into mice. The hydrogel features and stability of BMP2 inside the hydrogel were significantly affected by the electrostatic attraction between BMP2 and MP-NH2. Additionally, the time BMP2 spent inside the hydrogel depot was prolonged in vivo, as evidenced by in vivo near-infrared fluorescence imaging. Biocompatibility was demonstrated by the fact that hTMSCs survived in vivo, even after 8 weeks and even though relatively few macrophages were in the hydrogel depot. The osteogenic capacity of the electrostatically loaded hydrogel implants containing BMP2 was higher than that of a hydrogel that was simply loaded with BMP2, as evidenced by Alizarin Red S, von Kossa, and hematoxylin and eosin staining as well as osteonectin, osteopontin, osteocalcin, and type 1α collagen mRNA expression. The results confirmed that our injectable, in situ–forming hydrogel system, electrostatically loaded with BMP2, can enhance in vivo osteogenic differentiation of hTMSCs.

Branched poly[1,4-butylene carbonate-co-terephthalate]s (PBCTs) have been synthesized by the addition of a small amount of glycerol propoxylate (1) or pentaerythritol (2) in the polycondensation of 1,4-butanediol, dimethyl carbonate, and dimethyl terephthalate. To avoid gel formation, the feed amount of 1 or 2 was carefully controlled at below 0.5 mol % for 1 and below 0.3 mol % for 2. When feed of 1 or 2 was used, a high-molecular weight melt state (Mw ∼180,000 g/mol) was reached in a total reaction time of 5.5 to 6.5 h with a yield higher than 90%. The generated PBCTs were a semicrystalline polymer (Tg ∼5 °C and Tm ∼120 °C) when the terephthalate content (F[TPA]) was 45 to 50 mol %. The crystallization rate increased with increasing F[TPA] and branch content (F[1 or 2]); PBCT composed of F[TPA] = 49 mol % and F[1] = 0.44 mol % was crystallized completely in a short time, ∼3 min, at a crystallization temperature of 50 °C. The branched PBCT exhibited more pronounced toughness in tensile test while providing the advantage of processibility at high shear rates due to the pronounced shear thinning in melt. It was also found that the branched PBCTs were biodegradable. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 914–923

Triblock copolymers of polystyrene (PS) and a polyolefin (PO), e.g., PS-block-poly(ethylene-co-1-butene)-block-PS (SEBS), are attractive materials for use as thermoplastic elastomers and are produced commercially by a two-step process that involves the costly hydrogenation of PS-block-polybutadiene-block-PS. We herein report a one-pot strategy for attaching PS chains to both ends of PO chains to construct PS-block-PO-block-PS directly from olefin and styrene monomers. Dialkylzinc compound containing styrene moieties ((CH₂=CHC₆H₄CH₂CH₂)₂Zn) was prepared, from which poly(ethylene-co-propylene) chains were grown via "coordinative chain transfer polymerization" using the pyridylaminohafnium catalyst to afford di-end functional PO chains functionalized with styrene and Zn moieties. Subsequently, PS chains were attached at both ends of the PO chains by introduction of styrene monomers in addition to the anionic initiator Me₃SiCH₂Li·(pmdeta) (pmdeta = pentamethyldiethylenetriamine). We found that the fraction of the extracted PS homopolymer was low (~20%) and that molecular weights were evidently increased after the styrene polymerization (ΔMn = 27⁻54 kDa). Transmission electron microscopy showed spherical and wormlike PS domains measuring several tens of nm segregated within the PO matrix. Optimal tensile properties were observed for the sample containing a propylene mole fraction of 0.25 and a styrene content of 33%. Finally, in the cyclic tensile test, the prepared copolymers exhibited thermoplastic elastomeric properties with no breakage up over 10 cycles, which is comparable to the behavior of commercial-grade SEBS.

To the best of our knowledge, no studies have yet examined the electrostatic interaction of polyelectrolytes with electrolyte drugs for the treatment of rheumatoid arthritis (RA). Here, an injectable, electrostatically interacting drug depot is described. We prepared methoxy polyethylene glycol- b-poly(e-caprolactone)-ran-poly( l -lactic acid) (MC) diblock copolymers with a carboxylic acid group (MC-C) at the pendant position. MC-C was polyelectrolytes that exhibited negative zeta potentials . Sulfasalazine [Sul(−)] and minocycline [Min(+)], electrolyte RA drugs, exhibited negative and positive zeta potentials, respectively. The electrolyte RA drugs were loaded into the polyelectrolyte MC-C solution to prepare injectable, electrostatically interacting depot formulations. The formulation with an attractive electrostatic interaction [Min(+)-MC-C] exhibited gradual release of Min(+) from the MC-C depot over an extended period and suppressed the growth of inflammatory RAW 264.7 cells without affecting synovial cells. Mature chondrocytes were observed after H&E and safranin O staining of the cartilage of Min(+)-MC-C intra-articularly injected RA-induced rats. In comparison with other formulations, Min(+)-MC-C induced the suppression of the expression of pro-inflammatory proteins TNF-α and IL-1β in the articular knee joint, which resulted in the amelioration of RA. In conclusion, an injectable, electrostatically interacting depot formulation administered through intra-articular injection successfully provided almost complete amelioration of RA.

Recently, several thermogelling materials have been developed for biomedical applications. In this study, we prepared methoxy polyethylene glycol (MPEG)-b-(poly(epsilon-caprolactone)-ran-poly(2-chloride-epsilon-caprolactone) (PCL-ran-PfCL)) (MP-Cl) diblock copolymers at room temperature via the ring-opening polymerization of caprolactone (CL) and 2-chloride-epsilon-caprolactone (fCL) monomers, using the terminal alcohol of MPEG as the initiator in the presence of HCl. MPEG-b-(poly(epsilon-caprolactone)-ran-poly(2-azide-epsilon-caprolactone) (PCL-ran-PCL-N-3)) (MP-N-3) was prepared by the reaction of MP-Cl with sodiumazide. MPEG-b-(poly(epsilon-caprolactone)-ran-poly(2-amine-epsilon-caprolactone) (PCL-ran-PCL-NH2)) (MP-NH2) was subsequently prepared by Staudinger reaction. MP-Cl and MP-N-3 showed negative zeta potentials, but MP-NH2 had a positive zeta potential. MP-Cl, MP-N-3, and MP-NH2 solutions formed opaque emulsions at room temperature. The solutions exhibited a solution-to-hydrogel phase transition as a function of the temperature and were affected by variation of the chloride, azide, and the amine pendant group, as well as the amount of pendant groups present in their structure. Additionally, the phase transition of MP-Cl, MP-N-3, and MP-NH2 copolymers was altered by pendant groups. The solution-to-hydrogel phase transition was adjusted by tailoring the crystallinity and hydrophobicity of the copolymers in aqueous solutions. Collectively, MP-Cl, MP-N-3, and MP-NH2 with various pendant-group contents in the PCL segment showed a solution-to-hydrogel phase transition that depended on both the type of pendant groups and their content.

Dimethyl carbonate (DMC) is an environmentally benign chemical currently produced using CO2. Using the conventional Dean–Stark apparatus, a method was developed for the effective and selective removal of the methanol generated in the transesterification of DMC with alcohol. Using this device, various diols (HO-A-OH; A = (CH2)4, (CH2)2O(CH2)2, CH2C6H10CH2, and CH2C6H4CH2) were converted to mixtures of the corresponding MeOC(O)[O-A-OC(O)]OMe and MeOC(O)[O-A-OC(O)]2OMe. Dialkyl carbonates such as dibutyl carbonate, dibenzyl carbonate, and diallyl carbonate were also efficiently prepared from the corresponding alcohols using this device. The compound prepared from 1,4-butanediol, MeOC(O)[O(CH2)4OC(O)]1.5OMe, was subjected to polycondensation with HO(CH2)4[O2CC6H4CO2(CH2)4]1.5OH or HO(CH2)4[O2CC6H4CO2(CH2)4]1.8OH, which directly was prepared from terephthalic acid and 1,4-butanediol. The polycondensation afforded high-molecular-weight poly(1,4-butylene carbonate-co-terephthalate)s (PBCTs) with Mw of 80–270 kDa and 0.40–0.46 terephthalate mole fractions. PBCTs are attractive materials with potential biodegradability and LDPE-like thermal properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44951.

The Me2Si-bridged ansa-Cp/amido half-metallocene, [Me2Si(η5-Me4C5)(NtBu)]TiCl2, termed a “constrained-geometry catalyst (CGC)”, is a representative homogeneous Ziegler catalyst. CGC derivatives with the [1,2]azasilinane framework, in which the amide alkyl substituent is joined by the Si-bridge, were prepared, and the catalytic performances of these species was studied. Me4C5HSi(Me)(CH2CH=CH2)-NH(C(R)(R’)CH=CH2) (R, R’ = H or methyl; Me4C5H = tetramethylcyclopentadienyl) was susceptible to ring closure metathesis (RCM) when treated with Schrock’s Mo-catalyst to afford -Si(Me4C5H)(Me)CH2CH=CHC(R)(R’)NH- containing a six-membered ring framework. Using the precursors and the products of RCM, various CGC derivatives, i.e., [-Si(η5-Me4C5)(Me)CH2CH=CHC(R)(H)N-]TiMe2 (13, R = H; 15, R = Me), [-Si(η5-Me4C5)(Me)CH2CH2CH2CH2N]TiMe2 (14), [(η5-Me4C5)Si(Me)(CH2CH=CH2)NCH2CH=CH2]TiMe2 (16), [(η5-Me4C5)Si (Me)(CH=CH2)NCH2CH=CH2]TiMe2 (17), and [(η5-Me4C5)Si(Me)(CH2CH3)NCH2CH2CH3]TiMe2 (18), were prepared. The catalytic activity of the newly prepared complexes was lower than that of CGC when activated with [Ph3C][B(C6F5)4]/iBu3Al. However, the catalytic activity of these species was improved by using tetrabutylaluminoxane ([iBu2Al]2O) instead of iBu3Al and the activity of 14/[Ph3C][B(C6F5)4]/[iBu2Al]2O was comparable to that of CGC/[Ph3C][B(C6F5)4]/iBu3Al (4.7 and 5.0 × 106 g/mol-Ti, respectively). Advantageously, the newly prepared complexes produced higher molecular weight poly(ethylene-co-1-octene)s than CGC.

This is the first report on the development of a covalently bone morphogenetic protein-2 (BMP2)-immobilized hydrogel that is suitable for osteogenic differentiation of human periodontal ligament stem cells (hPLSCs). O-propargyl-tyrosine (OpgY) was site-specifically incorporated into BMP2 to prepare BMP2-OpgY with an alkyne group. The engineered BMP2-OpgY exhibited osteogenic characteristics after in vitro osteogenic differentiation of hPLSCs, indicating the osteogenic ability of BMP2-OpgY. A methoxy polyethylene glycol-(polycaprolactone-(N3)) block copolymer (MC-N3) was prepared as an injectable in situ-forming hydrogel. BMP2 covalently immobilized on an MC hydrogel (MC-BMP2) was prepared quantitatively by a simple biorthogonal reaction between alkyne groups on BMP2-OpgY and azide groups on MC-N3 via a Cu(I)-catalyzed click reaction. The hPLSCs-loaded MC-BMP2 formed a hydrogel almost immediately upon injection into animals. In vivo osteogenic differentiation of hPLSCs in the MC-BMP2 formulation was confirmed by histological staining and gene expression analyses. Histological staining of hPLSC-loaded MC-BMP2 implants showed evidence of mineralized calcium deposits, whereas hPLSC-loaded MC-Cl or BMP2-OpgY mixed with MC-Cl, implants showed no mineral deposits. Additionally, MC-BMP2 induced higher levels of osteogenic gene expression in hPLSCs than in other groups. In conclusion, BMP2-OpgY covalently immobilized on MC-BMP2 induced osteogenic differentiation of hPLSCs as a noninvasive method for bone tissue engineering.