Copolymerization of Ethylene with Functionalized 1,1-Disubstituted Olefins Using a Fluorenylamido-Ligated Titanium Catalyst.

Considering the sustainability of material development, coordination polymerization catalysts effective for 1,1-disubstituted olefins are receiving a great deal of attention because they can introduce a variety of plant-derived comonomers, such as ß-pinene and limonene, into polyolefins. However, due to their sterically encumbered property, incorporating these monomers is difficult. Herein, we succeeded in the copolymerization of ethylene with various hydroxy- or siloxy-substituted vinylidenes using a fluorenylamido-ligated titanium catalyst-MMAO system. This is the first example of ethylene/polar 1,1-disubstituted olefins' copolymerization using an early transition metal catalyst system. The polymerization proceeded at room temperature without pressurizing ethylene, and high-molecular-weight, functionalized polyethylene was obtained. The obtained copolymer showed a reduced water contact angle compared with that of the ethylene/isobutene copolymer, demonstrating the increment in hydrophilicity by hydroxy groups.

Synthesis, Properties, and Biodegradability of Novel Sequence-Controlled Copolyesters Composed of Glycolic Acid, Dicarboxylic Acids, and C3 or C4 Diols.

We have previously reported that sequence-controlled copolyesters such as poly((ethylene diglycolate) terephthalate) (poly(GEGT)) showed higher melting temperatures than those of the corresponding random copolymers and high biodegradability in seawater. In this study, to elucidate the effect of the diol component on their properties, a series of new sequence-controlled copolyesters composed of glycolic acid, 1,4-butanediol or 1,3-propanediol, and dicarboxylic acid units was studied. 1,4-Butylene diglycolate (GBG) and 1,3-trimethylene diglycolate (GPG) were prepared by the reactions of 1,4-dibromobutane or 1,3-dibromopropane with potassium glycolate, respectively. Polycondensation of GBG or GPG with various dicarboxylic acid chlorides produced a series of copolyesters. Terephthalic acid, 2,5-furandicarboxylic acid, and adipic acid were used as the dicarboxylic acid units. Among the copolyesters bearing terephthalate or 2,5-furandicarboxylate units, the melting temperatures (Tm) of the copolyesters containing 1,4-butanediol or 1,2-ethanediol units were substantially higher than those of the copolyester containing the 1,3-propanediol unit. Poly((1,4-butylene diglycolate) 2,5-furandicarboxylate) (poly(GBGF)) showed a Tm at 90 °C, while the corresponding random copolymer was reported to be amorphous. The glass-transition temperatures of the copolyesters decreased as the carbon number of the diol component increased. Poly(GBGF) was found to show higher biodegradability in seawater than that of poly(butylene 2,5-furandicarboxylate) (PBF). On the other hand, the hydrolysis of poly(GBGF) was suppressed in comparison with that of poly(glycolic acid). Thus, these sequence-controlled copolyesters have both improved biodegradability compared to PBF and lower hydrolyzability than PGA.

Synthesis of Chain-End Functional Polydienes Using Diene Comonomer Bearing Boronic Acid Masked with Diaminonaphthalene.

Diene comonomers bearing boronic acid masked with 1,8-diaminonaphthalene (dan) were applied to copolymerization with isoprene or butadiene using neodymium borohydride complex as a catalyst. The comonomers were tolerant to excess modified methylaluminoxane (MMAO) and thus were applicable to the polymerization system using MMAO. On the other hand, the corresponding pinacol borate was highly reactive toward MMAO, and no incorporation into the obtained polymer was observed. A 13C NMR microstructural analysis of the hydrogenated copolymer revealed that all of the comonomers were located at the chain end. Further functionalization using the boron moiety at the polymer chain end was also investigated.

Synthesis, Properties, and Biodegradability of Thermoplastic Elastomers Made from 2-Methyl-1,3-propanediol, Glutaric Acid and Lactide.

An innovative type of biodegradable thermoplastic elastomers with improved mechanical properties from very common and potentially renewable sources, poly(L-lactide)-b-poly(2-methyl-1,3-propylene glutarate)-b-poly(L-lactide) (PLA-b-PMPG-b-PLA)s, has been developed for the first time. PLA-b-PMPG-b-PLAs were synthesized by polycondensation of 2-methyl-1,3-propanediol and glutaric acid and successive ring-opening polymerization of L-lactide, where PMPG is an amorphous central block with low glass transition temperature and PLA is hard semicrystalline terminal blocks. The copolymers showed glass transition temperature at lower than -40 °C and melting temperature at 130-152 °C. The tensile tests of these copolymers were also performed to evaluate their mechanical properties. The degradation of the copolymers and PMPG by enzymes proteinase K and lipase PS were investigated. Microbial biodegradation in seawater was also performed at 27 °C. The triblock copolymers and PMPG homopolymer were found to show 9-15% biodegradation within 28 days, representing their relatively high biodegradability in seawater. The macromolecular structure of the triblock copolymers of PLA and PMPG can be controlled to tune their mechanical and biodegradation properties, demonstrating their potential use in various applications.

Synthesis, Properties, and Biodegradation of Sequential Poly(Ester Amide)s Containing γ-Aminobutyric Acid.

Poly(ester amide)s are attracting attention because they potentially have excellent thermal and mechanical properties as well as biodegradability. In this study, we synthesized a series of novel poly(ester amide)s by introducing γ-aminobutyric acid (GABA) regularly into polyesters, and investigated their properties and biodegradabilities. GABA is the monomer unit of biodegradable polyamide 4 (PA4). The new poly(ester amide)s were synthesized from the reaction of ammonium tosylate derivatives of alkylene bis(γ-aminobutylate) and p-nitrophenyl esters of dicarboxylic acids. All the obtained polymers showed relatively high melting temperatures (Tm). Their thermal decomposition temperatures were improved in comparison with that of PA4 and higher enough than their Tm. The poly(ester amide)s exhibited higher biodegradability in seawater than the corresponding homopolyesters. Their biodegradabilities in activated sludge were also studied.

Crystal structure of di-µ-tri-hydro-(penta-fluoro-phenyl)-borato-tetra-kis-(tetra-hydro-furan)-disodium.

The title compound, [Na(µ-C6F5BH3)(C4H8O)2]2, represents a dimeric structure of sodium and organoborohydride, located about a centre of inversion. The Na⋯B distances of 2.7845 (19) and 2.7494 (18) Šwere apparently longer than the Li⋯B distances (2.403-2.537 Å) of the lithium organotri-hydro-borates in the previous reports. Moreover, an inter-action between the sodium atom and one fluorine atom on the 2-position of the benzene ring is observed [Na-F = 2.6373 (12) Å]. In the crystal, the dimeric mol-ecules are stacked along the b-axis via a π-π inter-action between the benzene rings.

Impregnation of poly(L-lactide-ran-δ-valerolactone) with essential bark oil using supercritical carbon dioxide.

This work studied the incorporation of essential bark oil from Thujopsis dolabrata var. hondae, which is known to repel various insects, in poly(L-lactide-ran-δ-valerolactone) [poly(L-LA-ran-VL)] using supercritical carbon dioxide (scCO2). The poly(L-LA-ran-VL) was synthesized by first purifying the monomers by azeotropic distillation with benzene, followed by polymerization with Sn(oct)2 using the same equipment, representing an efficient one-pot process. The copolymerization of L-LA with VL using this technique at a feed ratio of 90/10 mol/mol gave poly(L-LA-ran-VL) (91/9) with a molecular weight of 6.48 × 104 g/mol and a high yield of 74.9%. Products with molecular weights over 5.0 × 104 g/mol were obtained at L-LA feed proportions of 70 to 90%. Impregnation trials were conducted between 40 and 120 °C at 14 MPa for 3 h. The oil content of a 73/27 specimen was found to increase significantly during processing at 100 or 120 °C. During enzymatic degradation with proteinase K, the 91/9 specimen showed the fastest degradation rate. Although the 71/29 sample was slowly hydrolyzed in a phosphate buffer at pH 7.0, the release of oil vapor from this material was slightly higher than that from the 91/9 specimen, and the vapor release rate continuously increased throughout the hydrolysis process.

Copolymerization of Norbornene and Styrene with Anilinonaphthoquinone-Ligated Nickel Complexes.

Poly(norbornene-co-styrene)s were synthesized by the use of anilinonaphthoquinone-ligated nickel complexes [Ni(C10H5O2NAr)(Ph)(PPh3): 1a, Ar = C6H3-2,6-iPr; 1b, Ar = C6H2-2,4,6-Me; 1c, Ar = C6H5] activated with modified methylaluminoxane (MMAO) or B(C6F5)3 in toluene. The effects of the cocatalysts were more significant than those of the nickel complexes, and MMAO gave higher activity than B(C6F5)3. The structural characterizations of the products indicated the formation of statistical norbornene copolymers. An increase of the styrene ratio in feed led to an increase in the incorporated styrene (S) content of the resulting copolymer. The molecular weight of the copolymer decreased with increasing the S ratio in feed at 70 °C. The copolymerization activity, using MMAO as a cocatalyst, decreased with lowering of the temperature from 70 to 0 °C, accompanied by an increase in the molecular weight of the copolymer. The S incorporation up to 59% with Mn of 78,000 was achieved by the 1b-B(C6F5)3 catalytic system. The glass transition temperatures of the norbornene (N)/S copolymers determined by differential scanning calorimetry, decreased from 329 to 128 °C according to the S content.

Stereospecific polymerization of conjugated dienes using neodymium alkylborohydride complexes.

Two neodymium alkylborohydride complexes that differ with respect to the number of hydrides on the boron center were synthesized and characterized. The µ2-ligated complex exhibits Nd-B bond lengths that are approximately 10% longer than those in previously reported µ3-ligated borohydride complexes. For the µ3-alkylborohydride complex, the Nd-H-B stretching bands observed by IR spectroscopy suggested stronger borohydride coordination than that of [BH4]-, which is probably due to the electron donation of the alkyl groups. These newly prepared complexes successfully promoted trans-1,4 specific polymerization of conjugate dienes upon activation by Bu2Mg, whereas activation of these complexes by Bu2Mg/MMAO gave cis-1,4 regular polymer. The trans-1,4 defect of the polyisoprene obtained from the Nd µ2-alkylborohydride complex/Bu2Mg/MMAO system (<2%) was much lower than that obtained from previously reported µ3-BH4-ligated neodymium complex (11%). Moreover, µ2-alkylborohydride complex was a good initiator for the polymerization of MMA, probably because of its anionic nature.

Optically Transparent Functional Polyolefin Elastomer with Excellent Mechanical and Thermal Properties.

Synthesis of a variety of optically transparent polyolefin elastomers consisting of hard segment of polynorbornene and several kinds of soft segments such as atactic polypropylene, poly(ethylene-co-propylene), and poly(ethylene-co-1-hexene) was achieved. The block copolymers exhibited excellent toughness and thermal property with efficient elastic recovery. Most importantly, the introduction of hydroxyl group into polynorbornene segment not only modulated surface property of block copolymers, but also improved their mechanical properties.

Synthesis and Biodegradation of Poly(l-lactide-co-ß-propiolactone).

Although the copolymerizations of l-lactide (LA) with seven- or six-membered ring lactones have been extensively studied, the copolymerizations of LA with four-membered ring lactones have scarcely been reported. In this work, we studied the copolymerization of LA with ß-propiolactone (PL) and the properties of the obtained copolymers. The copolymerization of LA with PL was carried out using trifluoromethanesulfonic acid as a catalyst and methanol as an initiator to produce poly(LA-co-PL) with Mn of ~50,000 and PL-content of 6-67 mol %. The Tg values of the copolymers were rapidly lowered with increasing PL-contents. The Tm and ΔHm of the copolymers gradually decreased with increasing PL-contents, indicating their decreased crystallinity. Biodegradation test of the copolymers in compost demonstrated their improved biodegradability in comparison with the homopolymer of LA.

Quasi-Living Polymerization of Propene with an Isotactic-Specific Zirconocene Catalyst.

Propene polymerization with isotactic (iso)-specific C2-symmetric rac-Me2Si(2-Me-Benz(e)-Ind)2ZrCl2 (1) and rac-Me2Si(2-Me-4-Ph-1-Ind)2ZrCl2 (2) were conducted under various conditions for achieving iso-specific living polymerization of propene. When Complex 1 was activated with trialkylaluminum-free modified methylaluminoxane (dMMAO) at -40 °C, the number-average molecular weight (Mn) linearly increased against the polymerization time to reach Mn = 704,000 within 15 min of polymerization, although the molecular weight distributions was broad (Mw/Mn < 3). Thus, it was found that quasi-living polymerization of propene proceeded in the 1-dMMAO system. The living nature of iso-polypropene was confirmed by the block copolymerization, where the Mn value increased from 221,000 to 382,000 after the addition of 1-octene to yield the block copolymer with a melting point of 150 °C.

Synthesis of Hydroxy-Functionalized Cyclic Olefin Copolymer and Its Block Copolymers with Semicrystalline Polyolefin Segments.

Synthesis of hydroxy-functionalized cyclic olefin copolymer (COC) is achieved with remarkably high activity (up to 5.96 × 107 g-polymer mol-Ti-1 h-1 ) and controlled hydroxy group in a wide range (≈17.1 mol%) by using ansa-dimethylsilylene (fluorenyl)(amido)titanium complex. The catalyst also promotes living/controlled copolymerization to afford novel diblock copolymers consisting of hydroxy-functionalized COC and semicrystalline polyolefin sequence such as polyethylene and syndiotactic polypropylene, where the glass transition temperature of the norbornene/10-undecen-1-ol segment and each block length are controlled by comonomer composition and copolymerization time, respectively.

Substituent Effects of Adamantyl Group on Amido Ligand in Syndiospecific Polymerization of Propylene with Ansa-Dimethylsilylene(Fluorenyl)(Amido) Zirconium Complex.

A series of new fluorenylamido-ligated zirconium complexes bearing an electron-donating adamantyl group on the amido ligand were synthesized and characterized by elemental analysis, ¹H NMR, and single crystal X-ray analysis. The coordination mode of the fluorenyl ligand to the zirconium metal was η³ manner, and all the complexes were Cs-symmetric in solution. The complexes showed moderate activity (1.0 × 105 g-polymer mol-Zr-1·h-1), even at a low Al/Zr ratio of 50. The increase of propylene pressure improved the activity by one order of magnitude (up to 1.0 × 106 g-polymer mol-Ti-1·h-1). All catalyst systems gave syndiotactic polypropylene, where the complex containing the 3,6-di-t-butyl fluorenyl ligand was more effective for the enhancement of the syndiospecificity. The increase of propylene pressure also improved the syndiospecificity with the syndiotactic pentad of 0.96 and the melting point of 159 °C.

Living Polymerization of Propylene with ansa-Dimethylsilylene(fluorenyl)(cumylamido) Titanium Complexes.

A series of ansa-silylene(fluorenyl)(amido) titanium complexes (1a⁻1c, 2a, and 2b) bearing various substituents on the amido and fluorenyl ligands are synthesized and characterized by elemental analysis, ¹H NMR, and single crystal X-ray analysis. The coordination mode of the fluorenyl ligand to the titanium metal is η³ manner in each complex. The propylene polymerization is conducted with these complexes at 0 and 25 °C in a semi batch-type method, respectively. The catalytic activity of 1a⁻1c bearing cumyl-amido ligand is much higher than that of 2a and 2b bearing naphthyl group in amido ligand. High molecular weight polypropylenes are obtained with narrow molecular weight distribution, suggesting a living nature of these catalytic systems at 0 °C. The polymers produced are statistically atactic, regardless of the structure of the complex and the polymerization temperature.

Precision Chain-Walking Polymerization of trans-4-Octene Catalyzed by α-Diimine Nickel(II) Catalysts Bearing ortho-sec-Phenethyl Groups.

α-Diimine nickel complexes bearing bulky ortho-sec-phenethyl groups (bis{[N,N'-(4-methyl-2,6-di-sec-phenethylphenyl)imino]-1,2-dimethylethane}dibromonickel (1), bis{[N,N'-(4,6-dimethyl-2-sec-phenethylphenyl)imino]-1,2-dimethylethane}dibromonickel (2), bis{[N,N'-(4-methyl-2-sec-phenethylphenyl)imino]-1,2-dimethylethane}dibromonickel (3)) and {bis[N,N'-(2,4,6-trimethylphenyl)imino]-1,2-dimethylethane}dibromidonickel (4) are used as a precatalyst for the polymerization of trans-4-octene upon activation with modified methylaluminoxane. These catalysts conduct chain-walking polymerization of trans-4-octene to give polymers possessing propyl and butyl branches with high molecular weight and narrow molecular weight distribution. The branching structure depends on the nickel complex as well as the polymerization temperature, and the ratio of propyl branch was increased with increasing the bulkiness of the ligand and decreasing the polymerization temperature. Consequently, the most bulky 1 among the complexes used is found to polymerize trans-4-octene with high 1,5-regioselectivity at -20 °C to give poly(1-propylpentan-1,5-diyl).

Facile Synthesis of Novel Polyethylene-Based A-B-C Block Copolymers Containing Poly(methyl methacrylate) Using a Living Polymerization System.

Ethylene-propylene-methyl methacrylate (MMA) and ethylene-hexene-MMA A-B-C block copolymers with high molecular weight (>100,000) are synthesized using fluorenylamide-ligated titanium complex activated by modified methylaluminoxane and 2,6-di-tert-butyl-4-methylphenol for the first time. After diblock copolymerization of olefin is conducted completely, MMA is added and activated by aluminum Lewis acid to promote anionic polymerization. The length of polyolefin and poly (methyl methacrylate) (PMMA) is controllable precisely by the change of the additive amount of olefin and polymerization time, respectively. A soft amorphous polypropylene or polyhexene segment is located between two hard segments of semicrystalline polyethylene and glassy PMMA blocks.

Synthesis of Highly Branched Polyolefins Using Phenyl Substituted α-Diimine Ni(II) Catalysts.

A series of α-diimine Ni(II) complexes containing bulky phenyl groups, [ArN = C(Naphth)C = NAr]NiBr2 (Naphth: 1,8-naphthdiyl, Ar = 2,6-Me2-4-PhC6H2 (C1); Ar = 2,4-Me2-6-PhC6H2 (C2); Ar = 2-Me-4,6-Ph2C6H2 (C3); Ar = 4-Me-2,6-Ph2C6H2 (C4); Ar = 4-Me-2-PhC6H3 (C5); Ar = 2,4,6-Ph3C6H2 (C6)), were synthesized and characterized. Upon activation with either diethylaluminum chloride (Et2AlCl) or modified methylaluminoxane (MMAO), all Ni(II) complexes showed high activities in ethylene polymerization and produced highly branched amorphous polyethylene (up to 145 branches/1000 carbons). Interestingly, the sec-butyl branches were observed in polyethylene depending on polymerization temperature. Polymerization of 1-alkene (1-hexene, 1-octene, 1-decene and 1-hexadecene) with C1-MMAO at room temperature resulted in branched polyolefins with narrow Mw/Mn values (ca. 1.2), which suggested a living polymerization. The polymerization results indicated the possibility of precise microstructure control, depending on the polymerization temperature and types of monomers.

Highly Active Syndiospecific Living Polymerization of Higher 1-Alkene with ansa-Fluorenylamidodimethyltitanium Complex.

1-Hexene polymerization was conducted by [t-BuNSiMe(2) (3,6-t-Bu(2) Flu)]TiMe(2) (1) using trialkylaluminum-free modified methylaluminoxane (dMMAO) as a cocatalyst in toluene. The system produced living syndiotactic poly(1-hexene) with high turnover frequency of propagation (TOF, 98 s(-1) ) at 0 °C. The propagation rate was increased linearly against the 1-hexene concentration, which indicates that the first-order dependence of the propagation rate on monomer concentration. Polymerizations of 1-octene, 1-decene and 1-dodecene were also conducted for investigating the effect of chain length of 1-alkene on propagation rate by means of the livingness of this system. The propagation rate decreased according to the chain length until 1-decene but almost unchanged in longer 1-alkene: TOF, 1-octene (62 s(-1) )>1-decene (32 s(-1) ) ≈ 1-dodecene (31 s(-1) ).

Analysis of the bacterial community found in clay wall material used in the construction of traditional Japanese buildings.

Clay wall (also called mud wall in English and tsuchikabe in Japanese) material is used in traditional Japanese buildings. Clay wall material is manufactured by fermenting a mixture of clay, sand, and rice straw. A culture-independent study based on 16s rRNA sequences revealed that Clostridiales of Firmicutes, alpha-, gamma- and delta-proteobacteria of Proteobacteria, and Acidobacterium of Acidobacteria exist in the clay wall material. Of these, we focused on Clostridium and Geobacter and their possible roles in the degradation of the cellulose component of the straw and the reduction of ferric iron in the clay during fermentation.