Nontrivial ultraslow dynamics under electric-field in nematics of bent-shaped molecules.

For over decades, nematic liquid crystals have been recognized as highly fluidic materials that respond to electric field on the millisecond scale. In contrast to traditional nematics with fast responsivity, we herein report nontrivial ultraslow electric-driven dynamics in bent-shaped nematic materials. Varying the alkyl chain spacers of bent-shaped cyanobiphenyl dimers (COOm and OCOm) shows a 'transition' in the dynamics behavior between the bent-dimeric and bent-core materials. Interestingly, with short alkyl chain spacers, COO2 exhibits unexpected ultra-slow dynamic pathways, i.e., "quasi-static" electrohydrodynamic convection. A significant observation is that the on/off-electro-switching time of COO2 is 10 000 times higher than that of typical nematic materials, which is the largest value reported ever in the kilo-second range. In addition, the threshold voltage for inducing the reorientation of the nematic director for COO2 is higher than 5 V, which is uncommon in traditional N materials. These properties are distinct from those of traditional nematic materials and discussed in terms of dielectric constants and electrohydrodynamic convection.

Correction: Synthesis and stereocomplex formation of enantiomeric alternating copolymers with two types of chiral centers, poly(lactic acid-alt-2-hydroxybutanoic acid)s.

[This corrects the article DOI: 10.1039/D0RA08351H.].

Thioether-Linked Liquid Crystal Trimers: Odd-Even Effects of Spacers and the Influence of Thioether Bonds on Phase Behavior.

We report the synthesis, phase-transition behavior, and mesophase structures of the first homologous series of thioether-linked liquid crystal (LC) trimers, 4,4'-bis[ω-(4-cyanobiphenyl-4'-ylthio)alkoxy]biphenyls (CBSnOBOnSCB with a wide range of spacer carbon numbers, n = 3-11). All CBSnOBOnSCB homologs exhibited LC phases. Interestingly, even-n and odd-n homologs showed monotropic layered smectic A (SmA) and pseudo-layered twist-bend nematic (NTB) phases, respectively, below a nematic (N) phase. This alternate formation, which depends on spacer chain parity, is attributed to different average molecular shapes, which are associated with the relative orientations of the biphenyl moieties: linear and bent shapes for even-n and odd-n homologs, respectively. In addition, X-ray diffraction analysis indicated a strong cybotactic N phase tendency, with a triply intercalated structure. The phase-transition behavior and LC phase structures of thioether-linked CBSnOBOnSCB were compared with those of the all-ether-linked classic LC trimers CBOnOBOnOCB. Overall, thioether linkages endowed CBSnOBOnSCB with a monotropic LC tendency and lowered phase-transition temperatures, compared to those of CBOnOBOnOCB, for the same n. This is attributed to enhanced flexibility and bending (less molecular anisotropy) of the molecules, caused by the greater bond flexibility and smaller inner bond angles of the C-S-C bonds, compared to those of the C-O-C bonds.

Complete Genome Sequence of Gelria sp. Strain Kuro-4, a Thermophilic Anaerobe Isolated from a Thermophilic Anaerobic Digestion Reactor Treating Poly(L-Lactic Acid).

Strain Kuro-4 was isolated as a novel member of the genus Gelria from a thermophilic anaerobic digestion reactor treating poly(l-lactic acid). Here, we report a 2,880,462-bp complete circular genome sequence of Kuro-4, with a G+C content of 61.9%. The chromosome harbors 2,831 protein-coding genes and 62 RNA-coding genes.

Viscoelastic properties of a thioether-based heliconical twist-bend nematogen.

The twist-bend nematic (NTB) phase is one of the new types of nematics found recently, which possesses local nematic order with a heliconical orientational modulation at the nanoscale. Herein, we quantitatively determined, for the first time, the temperature-dependent elastic and viscosity properties in both the nematic (N) and NTB phases using a thioether-linked cyanobiphenyl dimer CBS7SCB exhibiting a broad temperature range of the NTB phase which is stable down to room temperature. In the N phase, the fundamental elastic moduli: splay and bend elastic moduli (K11 and K33, respectively) are found to be in the order of 10-12 N, and the effective rotational viscosity (γ1) is determined to be in the range of 5-200 mPa s. Meanwhile, the NTB phase is found to exhibit a compressive elastic modulus B in the order of several tens of kilopascals, the effective K11 in the order of 10-10-10-8 N, and a considerably large γ1 value of ∼68.7 Pa s right below the N-NTB phase transition. The present study provides insights into the comprehensive viscoelastic properties based on comparison of the obtained experimental data with not only the existing theoretical prediction but also the preceding experimental works.

Ether- and Thioether-Linked Naphthalene-Based Liquid-Crystal Dimers: Influence of Chalcogen Linkage and Mesogenic-Arm Symmetry on the Incidence and Stability of the Twist-Bend Nematic Phase.

The twist-bend nematic (NTB ) phase with a heliconical nanostructure of the local director generating symmetry breaking by achiral bent-shaped molecules is a hot topic of current liquid-crystal science. As opposed to the most common methylene-linked dimers, this study demonstrates chalcogen ether- and/or thioether-linked 6-(4-cyanophenyl)-2-naphthyl-based liquid-crystal dimers with symmetric and asymmetric π-conjugated mesogenic-arm structures that exhibit the NTB phase. Although the symmetric bis(ether)-linked dimer exhibits only the conventional nematic (N) phase, the asymmetric bis(ether)-linked dimer can form the NTB phase. All thioether-linked dimers form the NTB phase, wherein the dimers with asymmetric arms vitrify in the NTB phase on cooling to room temperature. The phase transitions are discussed in terms of the chalcogen linkage combination, mesogenic-arm symmetry, and spacer length. It is revealed that thioether-linked dimers based on asymmetric π-conjugated mesogenic arms with terminal cyano groups are highly beneficial for the realization of materials that form a wide range of NTB phases and glassy NTB states at room temperature.

Synthesis and stereocomplex formation of enantiomeric alternating copolymers with two types of chiral centers, poly(lactic acid-alt-2-hydroxybutanoic acid)s.

Stereocomplex (SC) formation was reported for the first time for enantiomeric alternating copolymers consisting of repeating units with two types of chiral centers, poly(lactic acid-alt-2-hydroxybutanoic acid)s [P(LA-alt-2HB)s]. l,l-Configured poly(l-lactic acid-alt-l-2-hydroxybutanoic acid) [P(LLA-alt-l-2HB)] and d,d-configured poly(d-lactic acid-alt-d-2-hydroxybutanoic acid) [P(DLA-alt-d-2HB)] were amorphous. Blends of P(LLA-alt-l-2HB) and P(DLA-alt-d-2HB) were crystallizable and showed typical SC-type wide-angle X-ray diffraction profiles similar to those reported for stereocomplexed blends of poly(l-lactic acid) and poly(d-lactic acid) homopolymers and of poly(l-2-hydroxybutanoic acid) and poly(d-2-hydroxybutanoic acid) homopolymers, and of l,l-configured poly(l-lactic acid-co-l-2-hydroxybutanoic acid) [P(LLA-co-l-2HB)] and d,d-configured poly(d-lactic acid-co-d-2-hydroxybutanoic acid) [P(DLA-co-d-2HB)] random copolymers. The melting temperature values and melting enthalpy values at 100% crystallinity for stereocomplexed solvent-evaporated and precipitated P(LLA-alt-l-2HB)/P(DLA-alt-d-2HB) blends were correspondingly 187.5 and 187.9 °C, and 98.1 and 91.8 J g-1. Enantiomeric polymer blending of P(LLA-alt-l-2HB) and P(DLA-alt-d-2HB) can confer crystallizability by stereocomplexation and the biodegradable materials with a wide variety of physical properties and biodegradability are highly expected to be prepared by synthesis of alternating copolymers of various combinations of two types of chiral α-substituted 2-hydroxyalkanoic acid monomers and their SC crystallization.

Nitrate removal performance and diversity of active denitrifying bacteria in denitrification reactors using poly(L-lactic acid) with enhanced chemical hydrolyzability.

Poly(L-lactic acid) (PLLA) can be used as an external electron donor in denitrification reactors to treat drinking water, aquaculture water, and industrial wastewater with an imbalanced carbon/nitrogen ratio. However, for PLLA to function in these applications, its chemical hydrolyzability requires improvement. Although the adjustment of the crystallinity (Xc) is effective in improving the hydrolyzability of PLLA, the condition for the Xc of PLLA, in which a sufficient amount of lactic acid is released for denitrification, must be clarified. Therefore, this study investigated the effective Xc range and optimal PLLA content as an electron donor for continuous nitrate removal in denitrification reactors. This study also explored the abundance, succession, and diversity of active denitrifying bacteria in denitrification reactors. The nitrate removal activity of activated sludge using the highly crystalline PLLA (Xc = 39.4%) was 1.8 mg NO3- -N g MLSS-1 h-1, which is 2.4 times higher than that using the nearly amorphous PLLA (Xc = 0.9%). During the 57 days of operation, the denitrification reactor with 3% (w/v) highly crystalline PLLA continued to completely remove nitrate, with a maximum nitrate removal activity of 22.8 mg NO3- -N g MLSS-1 h-1. The 16S rRNA amplicon sequencing and clone library analyses are using transcripts of two nitrite reductase genes, encoding cytochrome cd1 nitrite reductase, and copper-containing nitrite reductase revealed that bacteria belonging to the families Comamonadaceae, Rhodocyclaceae, and Alcaligenaceae were active denitrifying bacteria in the denitrification reactor using PLLA.

Prokaryotic Community Structures in a Thermophilic Anaerobic Digestion Reactor Converting Poly(l-Lactic Acid) for a Long Period Revealed by 16S rRNA Gene Amplicon Sequencing.

Little information on poly(l-lactic acid) (PLLA) treatment-associated microbiota in thermophilic anaerobic digestion reactors is available. Here, we provide 16S rRNA gene sequence data on microbiota in a thermophilic anaerobic digestion reactor converting PLLA to methane for 336 days. Data comprising 99,566 total high-quality reads were tabulated at the taxonomic class level.

Draft Genome Sequence of Thermodesulfovibrio sp. Strain Kuro-1, a Thermophilic, Lactate-Degrading Anaerobe Isolated from a Thermophilic Anaerobic Digestion Reactor.

Thermodesulfovibrio sp. strain Kuro-1, newly isolated from a thermophilic anaerobic digestion reactor, is a thermophilic anaerobe that can utilize l-lactic acid in fermentation, sulfate respiration, and cocultivation with hydrogenotrophic methanogens. Here, we report its draft genome sequence, consisting of a 1.93-Mb sequence with a G+C content of 34.0%.

A versatile strategy for the synthesis and mechanical property manipulation of networked biodegradable polymeric materials composed of well-defined alternating hard and soft domains.

The present paper proposes a versatile strategy for the synthesis and mechanical property manipulation of networked biodegradable polymeric materials composed of well-defined alternating soft and hard domains. As an example of the strategy, we selected biodegradable poly(l-lactide) (PLLA) and poly(ε-caprolactone) (PCL) as the hard and soft components, respectively, and synthesized networked biodegradable polymeric materials composed of well-defined alternating PLLA and PCL domains with different l-lactide (LLA) unit contents via crosslinking of well-defined four-armed diblock copolymers of PLLA and PCL (4-C-L). The strategy reported here, which is also applicable to non-biodegradable polymeric materials, successfully facilitated the synthesis of the networked biodegradable materials composed of alternating hard and soft domains and their mechanical properties of the synthesized materials were largely manipulated by the LLA unit contents of the precursor four-armed diblock 4-C-L copolymers. Moreover, the crystallization behavior and thermal properties of 4-C-L copolymers before and after crosslinking were investigated and discussed.

Improvement of methanogenic activity of anaerobic digestion using poly(l-lactic acid) with enhanced chemical hydrolyzability based on physicochemical parameters.

Because packing bags and disposable items of poly (l-lactic acid) (PLLA) waste are discharged together with other organic waste including garbage, anaerobic co-digestion of PLLA and other organic waste is required. However, because of low hydrolyzability of PLLA products, the chemical hydrolyzability must be improved for PLLA treatment during anaerobic digestion. This study aimed to assess weight-average molecular weight (Mw) and crystallinity (Xc), to determine the chemical hydrolyzability of PLLA, for PLLA treatment during anaerobic digestion. Moreover, the possibility of anaerobic co-digestion of the PLLA after improvement of chemical hydrolyzability and other organic waste was also discussed. Detectable methanogenic activity of the mesophilic and thermophilic anaerobic sludges of PLLA occurred in the Mw range of 6,800 to 16,500, and 6,800 and 38,000, respectively. The methanogenic activity of mesophilic and thermophilic anaerobic sludge was higher with PLLA with a high crystallinity (Xc = 39.9-46.1%) than with nearly amorphous PLLA (Xc = 0.3-3.5%). The maximum methanogenic activity of anaerobic sludge using PLLA with an Xc of approximately 40-45% and with a Mw of 10,300 and 16,500 for mesophilic and thermophilic anaerobic sludge were 0.013 gCOD·gVS-1·d-1 and 0.13 gCOD·gVS-1·d-1, respectively. A survey on the possibility of anaerobic co-digestion of PLLA after improvement in chemical hydrolyzability based on Mw and Xc and organic wastes revealed that thermophilic conditions at 55 °C are more advantageous than mesophilic conditions at 37 °C.

Draft Genome Sequence of Moorella sp. Strain Hama-1, a Novel Acetogenic Bacterium Isolated from a Thermophilic Digestion Reactor.

Moorella sp. strain Hama-1 was isolated from a thermophilic anaerobic digestion reactor treating poly(l-lactic acid). The strain is a thermophilic acetogen capable of lactate oxidation under anaerobic conditions. Here, we report the draft genome sequence of strain Hama-1, comprising 3.27 Mb in 48 contigs, with a G+C content of 56.6%.

Corrigendum: Configurational Molecular Glue: One Optically Active Polymer Attracts Two Oppositely Configured Optically Active Polymers.

This corrects the article DOI: 10.1038/srep45170.

Stereocomplex Crystallization of Star-Shaped Four-Armed Stereo Diblock Poly(lactide) from the Melt: Effects of Incorporated Linear One-Armed Poly(l-lactide) or Poly(d-lactide).

Star-shaped four-armed stereo diblock poly(lactide) (4-LD) and linear one-armed PLLA or PDLA (1-L or 1-D) having a molecular weight similar to that of 4-LD [higher molecular weight 1-L(H) or 1-D(H)] and that of one block of 4-LD [lower molecular weight 1-L(L) or 1-D(L)] were synthesized, and the effects of incorporated 1-L or 1-D on the isothermal and nonisothermal crystallization of 4-LD blends from the melt were investigated. Solely stereocomplex crystallites were formed in unblended 4-LD and 4-LD blends incorporated with 1-L or 1-D during isothermal and nonisothermal crystallization. Incorporated 1-L or 1-D increased normalized stereocomplex crystallinity and accelerated cold nonisothermal crystallization and isothermal crystallization. The accelerating effect became higher with decreasing the molecular weight of 1-L or 1-D. The crystalline growth mechanism was not altered by the incorporation of 1-L and 1-D, whereas the crystalline growth geometry changed from line to sphere or circle, depending on the type of sample and Tc. The difference in crystallization half time and cold crystallization temperature between 4-LD/1-L(H) and 4-LD/1-D(H) blends or 4-LD/1-L(L) and 4-LD/1-D(L) blends was explained by the difference in radial growth rate and spherulite density, which was further discussed considering the non-interpenetrating and interpenetrating models.

Stereocomplex Crystallization of Linear Two-Armed Stereo Diblock Copolymers: Effects of Chain Directional Change, Coinitiator Moiety, and Terminal Groups.

Two-armed poly(l-lactide) (PLLA)-b-poly(d-lactide) (PDLA) (2-LD) copolymers with a wide-range of molecular weight were synthesized and the effect of coinitiator moiety, which functions as impurity and causes chain directional change in the middle of molecules (Effect A), and/or the additional effect of types of terminal groups (Effect B) on crystallization behavior of 2-LD copolymers were studied, in comparison with that reported for one-armed PLLA-b-PDLA (1-LD) copolymers. Formation of only stereocomplex (SC) crystallites in 2-LD and 1-LD copolymers indicates that neighboring PLLA and PDLA blocks facilitated SC crystallization and neither Effect A nor B affected the crystalline species. Effect A and/or B (both hydroxyl terminal groups) disturbed cold SC crystallization of 2-LD copolymers compared to that of 1-LD copolymers. Crystalline growth morphologies of 2-LD and 1-LD copolymers during cold SC crystallization were spherical and solid sheaf, respectively, exhibiting that crystalline growth morphology was influenced by Effects A and/or B. The melting temperature or crystalline thickness of SC crystallites were determined by number-average molecular weight per one block and not affected by Effect A or B. Maximum radial growth rates of spherulites of 2-LD copolymers compared to those of 1-LD copolymers were largely decreased by Effect A and/or B (both hydroxyl terminal groups).

Configurational Molecular Glue: One Optically Active Polymer Attracts Two Oppositely Configured Optically Active Polymers.

D-configured poly(D-lactic acid) (D-PLA) and poly(D-2-hydroxy-3-methylbutanoic acid) (D-P2H3MB) crystallized separately into their homo-crystallites when crystallized by precipitation or solvent evaporation, whereas incorporation of L-configured poly(L-2-hydroxybutanoic acid) (L-P2HB) in D-configured D-PLA and D-P2H3MB induced co-crystallization or ternary stereocomplex formation between D-configured D-PLA and D-P2H3MB and L-configured L-P2HB. However, incorporation of D-configured poly(D-2-hydroxybutanoic acid) (D-P2HB) in D-configured D-PLA and D-P2H3MB did not cause co-crystallization between D-configured D-PLA and D-P2H3MB and D-configured D-P2HB but separate crystallization of each polymer occurred. These findings strongly suggest that an optically active polymer (L-configured or D-configured polymer) like unsubstituted or substituted optically active poly(lactic acid)s can act as "a configurational or helical molecular glue" for two oppositely configured optically active polymers (two D-configured polymers or two L-configured polymers) to allow their co-crystallization. The increased degree of freedom in polymer combination is expected to assist to pave the way for designing polymeric composites having a wide variety of physical properties, biodegradation rate and behavior in the case of biodegradable polymers.

Homo- and Stereocomplex Crystallization of Star-Shaped Four-Armed Stereo Diblock Copolymers of Crystalline and Amorphous Poly(lactide)s: Effects of Incorporation and Position of Amorphous Blocks.

Star-shaped four-armed stereo diblock copolymers with an amorphous poly(dl-lactide) (PDLLA) core and a crystalline poly(l-lactide) (PLLA) or poly(d-lactide) (PDLA) shell (4-DL-L and 4-DL-D) and with a crystalline PLLA or PDLA core and amorphous PDLLA shell (4-L-DL and 4-D-DL) copolymers were synthesized. The effects of incorporation and position of amorphous PDLLA blocks on homo- and stereocomplex (SC) crystallization behavior of unblended copolymers and their blends (4-DL-L/4-DL-D and 4-L-DL/4-D-DL) were investigated during isothermal crystallization from the melt and DSC heating. The incorporated amorphous PDLLA blocks disturbed the SC crystallization and orientation of SC lamellae in the copolymer blends as well as homocrystallization and orientation of homocrystalline lamellae in the unblended copolymers compared to those reported for four-armed PLLA/four-armed PDLA homopolymer blends or four-armed PLLA homopolymers, irrespective of the position of amorphous PDLLA blocks. The disturbance effect was stronger for the amorphous PDLLA shell than for the amorphous PDLLA core. The crystallizability was higher for SC crystallites in the copolymer blends than for homocrystallites in the unblended copolymers, irrespective of the position of amorphous PDLLA blocks. SC crystallization in the copolymer blends disclaimed the positional effects of crystalline PLLA and PDLA blocks and amorphous PDLLA blocks on spherulite growth rate and crystallinity.

Poly(lactic acid) stereocomplexes: A decade of progress.

Upon blending enantiomeric poly(l-lactide) [i.e., poly(l-lactic acid) (PLLA)] and poly(d-lactide) (PDLA) [i.e., poly(d-lactic acid) (PDLA)] or synthesis of stereo block poly(lactide) [i.e., poly(lactic acid) (PLA)], a stereocomplex (SC) is formed. PLA SC has a higher melting temperature (or heat resistance), mechanical performance, and hydrolysis-resistance compared to those of neat PLLA and PDLA. Because of such effects, PLA SC has been extensively studied in terms of biomedical and pharmaceutical applications as well as commodity, industrial, and environmental applications. Stereocomplexation stabilizes and strengthens PLA-based hydrogel or nanoparticles for biomedical applications. Stereocomplexation increases the barrier property of PLA-based materials and thereby prolongs drug release from PLA based materials. In addition, PLA SC is attracting significant attention because it can act as a nucleating agent for the widely used biobased polymer PLLA and thereby the heat resistance of PLLA-based materials can be enhanced. Interestingly, a wide variety of SCs other than PLA SC are found to have been formed in the enantiomeric substituted PLA blends and stereo block substituted PLA polymers. In the present review article, a decade of progress in investigation of PLA SCs is summarized.