Cl Units Research Articles

Improved thermal, mechanical, and dielectric properties of thermotropic liquid crystalline poly(ester amide)s containing lactam-derived segmental units

We prepared two different series of thermotropic liquid crystalline poly(ester amide)s (TPEAs) via bulk polycondensation reactions of 4-hydroxybenzoic acid (HBA, 75.0 mol %) and 6-hydroxy-2-naphthoic acid (HNA, 25.0–17.5 mol %) with ε-caprolactam (CL, 0.0–7.5 mol %) or γ-butyrolactam (BL, 0.0–7.5 mol %). Our investigation aimed to explore the impact of lactam-derived aliphatic amide units’ length and content on the liquid crystalline feature, microstructure, thermal transition, thermal stability, mechanical/relaxational/rheological behavior, and dielectric characteristics of TPEAs. The molecular structure and fibrillar formation of TPEAs containing aliphatic amide units were confirmed through FT-IR and SEM analysis. With increasing CL or BL-derived units from 1.0 mol % to 5.0 mol %, we observed an increase in crystallinity, glass transition temperature, melting temperature, complex melt viscosity, and storage modulus of TPEAs, attributed to the enhanced intermolecular hydrogen bonding interactions. However, at 7.5 mol % CL or BL-derived unit content, these properties decreased due to increased chain irregularity as well as lowered crystallinity. Notably, the dielectric constants (3.31–3.04 at 2 MHz) of TPEAs decreased with the increase of lactam-derived aliphatic amide units owing to the restricted chain mobility by intermolecular hydrogen bonding interactions. We believe that the TPEAs synthesized in this study hold significant potential for applications in technical plastics, superfibers, and printed circuit board materials.

Evaluating the global cortical Centiloid value for predicting functional decline

AbstractBackgroundPrevious results on amyloid‐PET imaging for predicting functional decline are conflicting. Given that the Centiloid approach (CL) may serve for inclusion in anti‐amyloid trials, we investigated the extent to which CL may predict functional decline in the AMYPAD‐Prognostic and Natural History Study (PNHS), including 1094 participants.MethodWe analyzed, cross‐sectionally and longitudinally, the associations between CL and global and sum‐of‐boxes (SOB) Clinical Dementia Rating (CDR), and Instrumental Activity of Daily Living (IADL) scores. Mean follow‐up duration ranged from 2.7‐3.0 years (±1.1‐1.6) depending on the functional score. Longitudinal CDR‐SOB and IADL changes were modeled using linear mixed‐effects models with random intercepts and slopes, covarying age and sex, stratified by CDR global score. Analyses included comparisons between three CL groups (Aβ‐: CL<12; grey‐zone: CL = 12‐50; Aβ+: CL>50) and correlation between the baseline CL and the time for progression on the CDR global score.ResultThe baseline CL was significantly higher in CDR = 0 (Mdn = 6.6) than in CDR = 0.5 participants (Mdn = 17.2; p<.001). Baseline CDR‐SOB was significantly higher in Aβ+ (M = 0.48) than in Aβ‐ (M = 0.12) and grey‐zone participants (M = 0.13, p‐values <.001). Baseline IADL was (marginally) significantly lower in Aβ+ (Mdn = 81.3) than in Aβ‐ (Mdn = 82.8, p = .02) and grey‐zone participants (Mdn = 83.5, p = .08, Table 1). Baseline CL significantly predicted subsequent changes in CDR‐SOB and IADL, both in CDR = 0 and CDR = 0.5 participants, but only in the CL>50 groups (βCL12‐50 = 0.03, p = .32,βCL>50 = 0.14, p<.001 for CDR‐SOB in CDR = 0 participants;βCL12‐50 = 0.19, p = .31,βCL>50 = 1.04, p = .01 for CDR‐SOB in CDR = 0.5 participants;βCL12‐50 = ‐0.002, p = .99, βCL>50 = ‐1.00, p = .08 for IADL in CDR = 0 participants; Fig.1). The participants who progressed from global CDR = 0 to CDR = 0.5 (N = 90) had a higher baseline CL (Mdn = 15.16) than stable participants (Mdn = 5.95, p = .002). However, the baseline CL was not associated with a shorter time of clinical progression (rs= ‐.02, p = .8; Fig.2).ConclusionCross‐sectionally, amyloid burden expressed in CL units was associated with functional outcomes. A baseline CL>50 predicted subsequent functional decline in CDR‐SOB and IADL scores in clinically normal and mildly clinically impaired participants. At lower CL values, no functional decline was observed during a three‐year follow‐up. Clinically normal individuals with increasing global CDR scores had higher baseline CL values, but these values were not associated with faster clinical progression.

CSF Biomarkers and [18F]flutemetamol PET‐Derived Centiloids in Patients with SCD or MCI

AbstractBackgroundCSF biomarkers are well characterised as surrogate markers for amyloid deposition and neurofibrillary tau tangles reflecting pathological features of Alzheimer’s disease. Amyloid PET images provide a visual and quantitative assessment of brain amyloid burden. In diagnostic workup these biomarkers are considered interchangeable, however their relationship is not fully understood.MethodCentiloid (CL) values for 387 [18F]flutemetamol images from the Swedish BioFINDER I study were derived following the methods of Klunk et.al. (Alzheimer’s & Dementia, 2015). Subjects, comprising Controls, SCD and MCI (Table 1), were ranked by Centiloid values (lowest to highest) and the average for each consecutive group of 30 subjects calculated. Corresponding CSF biomarker values (Aß42/40 and pTau181) were plotted for each group.ResultSubjects in groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) Aß 42/40 ratio of 0.144 (±0.033, range 0.051 to 0.236, n = 240) with no statistically significant differences between groups (Fig. 1A). A statistically significant fall in CSF Aß42/40 ratio between the 29.0 CL and 47.3 CL groups (from 0.134 (+0.041, 0.066 to 0.236) to 0.088(+0.031, 0.045 to 0.183), p<0.0001) was observed. The average CSF Aß42/40 ratio value for all subjects ranging from 66.3 Cl to129.8 CL was 0.072 (±0.017, 0.030 to 0.127, n = 117) with no statistically significant difference in CSF levels across these CL bands. Subjects in the groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) pTau181 value of 48.9 pg/mL (±15.9, 22 to 138) with no statistically significant difference between groups (Fig. 1B). A statistically significant (p<0.05) increase between 29.0 CL (47.3±19.3, 24 to 116 pg/mL) and 47.3 CL groups (67.8±29.4, 24 to 175 pg/mL) was observed. For all Subjects from 66.3 CL to129.8 CL mean pTau181 levels were 79.6 (±30.3, 32 to 209 pg/mL) with no statistically significant difference across these CL bands.ConclusionComparison of [18F]flutemetamol image quantitation and CSF biomarkers indicates CSF Aß42/40 and pTau181 starts to show amyloid positivity at approximately 30‐40 CL units. Recent comparisons between visual rating and Centiloids from PET imaging indicate visual positivity from approximately 20 CL units indicating sensitivity of amyloid PET imaging for the detection of early amyloid deposition.

CSF Biomarkers and [18F]flutemetamol PET‐Derived Centiloids in Patients with SCD or MCI

AbstractBackgroundCSF biomarkers are well characterised as surrogate markers for amyloid deposition and neurofibrillary tau tangles reflecting pathological features of Alzheimer’s disease. Amyloid PET images provide a visual and quantitative assessment of brain amyloid burden. In diagnostic workup these biomarkers are considered interchangeable, however their relationship is not fully understood.MethodsCentiloid (CL) values for 387 [18F]flutemetamol images from the Swedish BioFINDER I study were derived following the methods of Klunk et.al. (Alzheimer’s & Dementia, 2015). Subjects, comprising Controls, SCD and MCI (Table 1), were ranked by Centiloid values (lowest to highest) and the average for each consecutive group of 30 subjects calculated. Corresponding CSF biomarker values (Aβ42/40 and pTau181) were plotted for each group.ResultsSubjects in groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) Aβ 42/40 ratio of 0.144 (±0.033, range 0.051 to 0.236, n = 240) with no statistically significant differences between groups (Fig. 1A). A statistically significant fall in CSF Aβ42/40 ratio between the 29.0 CL and 47.3 CL groups (from 0.134 (±0.041, 0.066 to 0.236) to 0.088(±0.031, 0.045 to 0.183), p<0.0001) was observed. The average CSF Aβ42/40 ratio value for all subjects ranging from 66.3 Cl to129.8 CL was 0.072 (±0.017, 0.030 to 0.127, n = 117) with no statistically significant difference in CSF levels across these CL bands.Subjects in the groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) pTau181 value of 48.9 pg/mL (±15.9, 22 to 138) with no statistically significant difference between groups (Fig. 1B). A statistically significant (p<0.05) increase between 29.0 CL (47.3±19.3, 24 to 116 pg/mL) and 47.3 CL groups (67.8±29.4, 24 to 175 pg/mL) was observed. For all Subjects from 66.3 CL to129.8 CL mean pTau181 levels were 79.6 (±30.3, 32 to 209 pg/mL) with no statistically significant difference across these CL bands.ConclusionsComparison of [18F]flutemetamol image quantitation and CSF biomarkers indicates CSF Aβ42/40 and pTau181 starts to show amyloid positivity at approximately 30‐40 CL units. Recent comparisons between visual rating and Centiloids from PET imaging indicate visual positivity from approximately 20 CL units indicating sensitivity of amyloid PET imaging for the detection of early amyloid deposition.

Copolymerization of polyethylene terephthalate and polycaprolactone using catalytic transesterification

A random copolymer between polyethylene terephthalate (PET) and polycaprolactone (PCL) is formed using catalytic transesterification in the melt. The copolymer, poly[(ET)2-co-(CL)2], has a backbone structure similar to that of polybutylene adipate terephthalate (PBAT) and could replace it at a lower cost, while simultaneously managing waste PET. Theoretically, a biodegradable copolymer is achieved when only two consecutive ET blocks remain. This degree of transesterification requires an active catalyst, capable of selective transesterification while limiting undesired chain scission. 1H NMR spectroscopy revealed that titanium alkoxide catalysts were the most effective for rapid transesterification, leading to di-blocks of both ET and CL units. It was found that the random copolymer could only be produced by catalysts containing both highly acidic metal ions and highly basic, small linear ligands. These observations led to the proposal that catalytic transesterification is likely to occur via an insertion-coordination mechanism. Increasing catalyst loading from 0.35 to 1.1 parts per hundred when using Ti(OBu)4 significantly accelerates transesterification, but a plateau is reached at about 0.85. Pleasingly, a reaction time of 2 min was sufficient for the reaction to be complete, suggesting reactive extrusion could be feasible. DSC thermograms of Ti(OEt)4 and Ti(OBu)4 catalysed blends have no observable recrystallization and melting peaks along with a sharp glass transition temperature suggesting the copolymer was highly amorphous with no unreacted homopolymers. Gel permeation chromatography of THF soluble blends revealed that a high extent of transesterification led to a decrease in chain length such that the Mn was reduced from about 68000 (PCL) to 13000–20000 (copolymer), suggesting that there is a need to use a minimum amount of catalyst to avoid excessive chain scission. The results demonstrate a proof-of-concept that transesterification of PET with PCL is possible to a high extent and that the reaction proceeds via an insertion-coordination mechanism. The results will inspire future research towards repurposing waste PET on extrusion scales and the creation of other biodegradable polyester materials using waste polymers.

All-natural environmentally degradable poly (butylene terephthalate-co-caprolactone): A theoretical and experimental study of its degradation properties and mechanisms

The design and production of materials with excellent mechanical properties and biodegradability face significant challenges. Poly (butylene terephthalate-co-caprolactone) copolyesters (PBTCL) is obtained by modifying the engineering plastic polybutylene terephthalate (PBT) with a simple one-pot process using readily biodegradable ε-caprolactone (ε-CL). The material has mechanical properties comparable to those of commercial biodegradable copolyester PBAT. Besides, this copolyester exhibited remarkable degradability in natural environments such as soil and ocean, for example, PBTCL1.91 lost >40 % of its weight after 6 months of immersion in the Bohai Sea. The effect and diversity of specific microorganisms acting on degradation in the ocean were analyzed by 16 s rDNA gene sequencing. Theoretical calculations such as Fukui function and DFT, and experimental studies on water-soluble intermediates and residual matrixes produced after degradation, confirmed that the insertion CL units not only act as active sites themselves susceptible to hydrolysis reactions, but also promote the reactivity of ester bonds between aromatic segments. This work provides insight for the development of novel materials with high performance and environmental degradability.

Comonomer Inclusion in Single Crystals of Isodimorphic Random Copolymers of Butylene Succinate and ε-Caprolactone

Random copolymers exhibit diverse crystallization behavior depending on whether comonomers are excluded or included in the crystalline phase. To understand the crystallization behavior of crystallizable isodimorphic random copolymer, in this work, we selected poly[(butylene succinate)-ran-(ε-caprolactone)], BSxCLy, copolyesters and studied their single crystal structure and morphology. The single crystals of PBS homopolymer and BS-rich copolymers were prepared by the self-seeding method in o-dichlorobenzene. The prepared single crystals were characterized by atomic force microscopy (AFM) and transmission electron microscopy. The suitable seeding temperature and the dissolution temperature of the copolymers decreased with the comonomer content. The morphological features, including size, shape, layer number, and thickness, of the single crystals depend on the seeding temperature, crystallization temperature, and, most interestingly, the composition. The size of the single crystals increased with the seeding temperature, while the aspect ratio increased with the crystallization temperature. Higher CL content in the copolymers contributed to multilayered crystals and curved edges. These characteristics were explained by the difference in growth rate and the number of dislocations, both of which are expected to be influenced by the comonomers. As revealed by AFM, the thickness of the single crystals increased with CL contents, which is the opposite of what has been reported for copolymers with high degree of comonomer exclusion. Electron diffraction of the single crystals showed smaller lattice expansion as compared to melt crystallized samples, indicating a lower degree of comonomer inclusion of CL units.

Self-Assembled Encapsulation of CuX2- (X = Br, Cl) in a Gold Phosphine Box-like Cavity with Metallophilic Au-Cu Interactions.

Synthetic routes to the crystallization of two new box-like complexes, [Au6(Triphos)4(CuBr2)](OTf)5·(CH2Cl2)3·(CH3OH)3·(H2O)4 (1) and [Au6(Triphos)4 (CuCl2)](PF6)5·(CH2Cl2)4 (2) (triphos = bis(2-diphenylphosphinoethyl)phenylphosphine), have been developed. The two centrosymmetric cationic complexes have been structurally characterized through single-crystal X-ray diffraction and shown to contain a CuX2- (X = Br or Cl) unit suspended between two Au(I) centers without the involvement of bridging ligands. These colorless crystals display green luminescence (λem = 527 nm) for (1) and teal luminescence (λem = 464 nm) for (2). Computational results document the metallophilic interactions that are involved in positioning the Cu(I) center between the two Au(I) ions and in the luminescence.

A tetracobalt(II) cluster with a two vertex truncated dicubane topology endogenously supported by carboxylate-based (2-pyridyl)methylamine ligands: magneto-structural and DFT studies.

A reaction between CoCl2 and L3-(CO2-)2 (2 : 1 stoichiometry) in CH3OH affords a discrete complex [CoII4-{L3-(CO2-)2}2(μ3-OCH3)2(CH3OH)2(H2O)2Cl2] (1) [L3-(CO2-)2 = 3-[N-{2-(pyridin-2-yl)methyl}amino]-bis(propionate)]. The structure of 1 reveals two terminal mononuclear CoII{L3-(CO2-)2}Cl units connected by a dimeric CoII2(μ3-OCH3)2(CH3OH)2(H2O) unit present in the centre through two methoxo (μ3-OCH3)- and two carboxylate (μ-1,1-OCO-) bridges affording a tetranuclear coordination cluster of Co(II) with a defective dicubane topology. In 1, Co1 (terminal) has distorted octahedral CoIIN2O3Cl and the central Co2 has CoIIO6 coordination. Such coordination arrangements afford the observed topology. Variable-temperature magnetic studies reveal anti-ferromagnetic coupling in 1. Three magnetic exchange interactions (one anti-ferromagnetic and two ferromagnetic: J1 = +3.3 cm-1 (Co⋯Co 3.176 Å; μ-1,1-OCO- and μ3-OCH3 bridges), J2 = -2.5 cm-1 (Co⋯Co 3.228 Å; μ-1-OCO- and μ3-OCH3 bridges) and J3 = +10.6 cm-1 (Co⋯Co 3.084 Å; two μ3-OCH3 bridges)) have been identified, with the inclusion of the orbital reduction parameter (α = Aκ = 1.38), spin-orbit coupling (λ = -158 cm-1) and axial distortion (energy gap Δ = -975 cm-1 between singlet and doublet levels), rationalized by density functional theory (DFT) calculations.

Revisiting the structure of copolymer via anionic hybrid copolymerization of methyl methacrylate and ε-caprolactone

Anionic hybrid copolymerization of vinyl and cyclic monomers provides a powerful strategy to synthesize heteropolymers. Yet, there are some open questions regarding its mechanism and the structure of the resulted polymer. We reported that the copolymer (Poly(MMA- co -CL)) of methyl methacrylate (MMA) and ε-caprolactone (CL) via such copolymerization was random. However, a recent study proposed that the copolymer might be simple graft one with poly(methyl methacrylate) (PMMA) as the main chain and poly(ε-caprolactone) (PCL) as the graft chain. In this study, we synthesized a model graft copolymer (PMMA- g -PCL) by using a combination of reversible complexation-mediated polymerization and ring-opening polymerization, and made comparison with Poly(MMA- co -CL) in their properties and hydrolysis. Differential scanning calorimeter (DSC) measurements show that the graft copolymer PMMA- g -PCL possesses two glass transitions and a melt peak. In contrast, Poly(MMA- co -CL) exhibits only one glass transition without a melt peak because it is amorphous, clearly indicating that it is random. Proton nuclear magnetic resonance ( 1 H NMR) measurements reveal that the hydrolysis of PMMA- g -PCL yields only PMMA oligomers. However, the hydrolyzed products of Poly(MMA- co -CL) consist of MMA and CL units. The facts further indicate that the copolymer Poly(MMA- co -CL) is random. Considering that the transesterification reactions are unavoidable in the anionic hybrid copolymerization, the copolymer should consist of random main chain and random branches. • The present study demonstrates that anionic hybrid copolymerization of MMA and CL generally yields random copolymer but not graft copolymer. • Transesterification is not the essential step in the anionic hybrid copolymerization, but it can cause branching of the copolymer. • The hybrid copolymer of MMA and CL consists random main chain and random branches.

Anionic Hybrid Copolymerization of Cyclic and Vinyl Monomers without Transesterification

AbstractAnionic hybrid copolymerization (AHcP) of cyclic and vinyl monomers provides a powerful strategy to synthesize biodegradable heteropolymers. However, transesterification between comonomeric units often happens making the mechanism complex. Here, AHcP of N,N‐dimethylacrylamide (DMA) with ε‐caprolactone (CL) is investigated at 25 °C, where DMA does not have ester group so that no transesterification between DMA and CL units happens. Nuclear magnetic resonance (NMR) and matrix‐assisted laser desorption/ionization time of flight mass spectrometry measurements reveal that DMA and CL units are randomly distributed in the resulted polymer. Differential scanning calorimetry measurements show that the copolymer has only one glass transition temperature (Tg). Thermogravimetric analysis demonstrates the copolymer has a single‐stage decomposition from 255 to 425 °C, which is between those of the corresponding homopolymers. Thes facts further indicate that the copolymer is random. This study clearly demonstrates that AHcP takes place regardless of transesterification though it may have some effects.

Bio‐based and hydrolytically degradable hydroxyurethane acrylates as photocurable thermosets

AbstractThis study focuses on the synthesis of bio‐based and hydrolytically degradable photocurable thermosets made from hydroxyurethane acrylates (HUA). The hydroxyurethanes (HUs) are prepared from the reaction between ethylene carbonate and a bio‐based diamine, Priamine 1074. Subsequently, the HU initiates the ring opening polymerization of ε‐caprolactone (CL), resulting in telechelic groups of 5 CL units at both ends of the HU. The resulting HU‐CL5 is finally acrylated to prepare the degradable HUA (HU‐CL5‐A) with transformations confirmed following each step via proton nuclear magnetic resonance (1H‐NMR) and Fourier‐transform infrared (FTIR) spectroscopies. HU‐CL5‐A is photocured with 4‐acryloylmorpholine (ACMO) as a photosensitive reactive diluent. The photocurable thermosets exhibit slight water swelling (swelling index of 46%), as Priamine 1074 and ACMO are hydrophobic and hydrophilic, respectively, leading to the slow and partial degradation of the films in water at 85°C for 14 days. The cleavage of the CL units from the film networks is proven via 1H‐NMR and FTIR, which demonstrates the main objective of this study in synthesizing photocurable and degradable HUA resins.

Upgrading of the recording system of complex loading testing machine

The effectiveness of experimental studies of the mechanical properties of materials and the reliability of the results obtained are determined by the technical level of testing machines. The stress-strain state of the object is monitored using recording sensors. The reading accuracy for the existing CL unit is 8%. However, this accuracy appeared insufficient when studying the developed plastic deformations. The problem of insufficient accuracy is partially related to the outdated recording system of the experimental setup, both when taking the results of the experiments and when managing the experiment. Getting of the reliable data upon complex loading is necessary to identify the reserves of the bearing capacity of structural elements in conditions of multi-parameter loading. All the experiments on a CL testing machine were carried out at room temperature. An additional amplifier of the electric signal of the strain gauge sensor was introduced to improve the accuracy of the readings of the recording system. The results of modernizing the recording system of the CL testing machine intended for static isothermal tests of tubular specimens are presented. The testing machine provides testing of the samples under axial tensile force and torque.

Assessment of integration of methane-reduced ceria chemical looping CO2/H2O splitting cycle to an oxy-fired power plant

In this paper, we investigated the effect of reaction kinetics and moving bed reactors for chemical looping (CO2/H2O) splitting unit (CL) that produces syngas and fed back to the power plant to gain the efficiency loss due to carbon capture. The reduction reactor (RED) produces methane is partially oxidized to make syngas and reducing the non-stoichiometric ceria which is transported to oxidation reactor (OXI) where the flue gases (CO2 and H2O) split to produce syngas. We developed the kinetics for methane reduced ceria and CO2/H2O splitting in a tubular reactor for an operating temperature range of (900–1100 °C) for different methane concentration which yielded to Avrami-Erofeev (AE3) model fits well for both redox reaction with different reaction constants. A moving bed reactors system is developed representing RED and OXI reactors of CL unit with kinetics hooked to the model in Aspen Plus with FORTRAN code. The effect of thermodynamics and the kinetics of redox reaction was investigated in the proposed integrated plant. The CL unit efficiency obtained is 42.8% for kinetic-based CL unit compares to 64% for thermodynamic based CL unit. However, the maximum available efficiency of the proposed layout lowered as 50.9% for kinetic-based CL unit plant compare to than 61.5% for thermodynamic based CL unit. However, the proposed plant shows an improvement in the energy efficiency penalty from 11.3% to 3.8% after CCS.

Correction to: Tobramycin Clearance Is Best Described by Renal Function Estimates in Obese and Nonobese Individuals: Results of a Prospective Rich Sampling Pharmacokinetic Study

There was a mistake in the units of CL and Q, and in the parentheses of the formula for CL in the final model in Table 2. The corrected Table appears below.

3D printing of implantable elastic PLCL copolymer scaffolds.

Poly(l-lactic acid) (PLLA) scaffolds have been used in regenerative medicine, however, they commonly suffer from low flexibility, restricting their application in the repair and reconstruction of soft tissues. In this study, poly(l-lactide-co-ε-caprolactone) (PLCL) copolymers were examined to modulate the elasticity of PLLA with the random presence of CL units in PLLA. Thermodynamic analysis revealed that the introduction of PCL could significantly decrease the melting point and glass transition temperature of PLLA, benefiting the extrusion and printing of PLCL. Diverse scaffolds with designed architectures including porous cubes with or without large holes, cambered plates with holes and round tubes could be easily constructed by 3D printing. In the process of elastic deformation, the maximum elastic stress of the copolymer scaffold was obviously increased from 19.6 to 31.5 MPa when the relative content of PCL was increased to 70%, while the elongation at break was evidently increased from 388% to about 1974%. The Young's modulus of PLCL was also significantly decreased (P < 0.05) in comparison with that of PLLA. PLCL scaffolds have good platelet and endotheliocyte adhesion ability and no obvious hemolysis was observed. In vivo subcutaneous implantation of PLCL scaffolds demonstrated superior biocompatibility. Collectively, this work highlights that copolymerization of PCL segments into PLLA is an effective approach to tune the 3D printability and the stiffness and elasticity of PLLA scaffolds. PLCL scaffolds hold great promise for the regeneration of soft tissues including but not limited to cartilage, myocardium, muscle, tendon and nervous tissues.

Generation of a zinc and rhodium containing metallomacrocycle by rearrangement of a six-coordinate precursor complex.

Two pentadentate N3,P2 ligands coordinate zinc(ii) by their N3 pocket. Four free phosphine donors allow the coordination of four AuCl moieties leading to a pentanuclear ZnAu4 complex. In contrast, the attempt to use the phosphines for chelating coordination of two Rh(CO)Cl units results in a well-organized rearrangement that ends up with the formation of a metallomacrocycle in high yields.

Double-Hydrophilic Block Copolymers Based on Functional Poly(ε-caprolactone)s for pH-Dependent Controlled Drug Delivery.

The use of double-hydrophilic block copolymers (DHBCs) in biomedical applications is limited by their lack of degradability. This additional functionality has been obtained in the past through multistep chemical strategies associated with low yields. In this work, a series of DHBCs composed of a bioeliminable poly(ethylene glycol) (PEG) block and hydrolyzable functional poly(ε-caprolactone) (PCL) blocks bearing carboxylic (PEG-b-PCL(COOH)), amino (PEG-b-PCL(NH2)), or hydroxyl side groups (PEG-b-PCL(OH)) is synthesized in only three steps. DHBCs with 50% substitution degree with respect to the CL units are obtained for all functional groups. The pH-dependent self-assembly behavior of the DHBCs is studied showing critical micelle concentration (CMC) variations by a factor of 2 upon pH changes and micellar mean diameter variations of 20-30%. The potential of these partly degradable DHBCs as drug-loaded polyion complex micelles is further exemplified with the PEG-b-PCL(COOH) series that is associated with the positively charged anticancer drug doxorubicin (DOX). Encapsulation efficiencies, drug loadings, pH-controlled release, and cytotoxicity of the DOX-loaded micelles toward cancer cells are demonstrated. This set of data confirms the interest of the proposed straightforward chemical strategy to generate fully bioeliminable and partly degradable DHBCs with potential as pH-responsive drug-delivery systems.

The peculiar case of conformations in coordination compounds of group V pentahalides with N-heterocyclic carbene and synthesis of their imidazolium salts

Reaction of niobium or tantalum pentafluoride (MF5; M=Nb, Ta) with N-heterocyclic carbene 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (LDipp) yields neutral [(LDipp)MF5] (M=Nb (1), Ta (2)) complex. Special attention in their characterization was given to the structural analysis and to the comparison of structural features to the equivalent chloride complexes. Particularly interesting is conformation of the MX5 (M=Nb, Ta; X=F, Cl) unit in relation to the bonded LDipp ligand. In presented compounds (1, 2) the MF5 group is in a staggered position, which concurs with DFT calculations of structurally optimized [(LDipp)NbF5]. In contrast, eclipsed orientation is preferred in equivalent chloride complexes, according to both experiment and DFT calculations. The preference between staggered and eclipsed conformations is attributed to an interplay between attractive C–H⋯X interactions and steric repulsion between equatorial halogen atoms and “wingtips” of the ligand. To help distinguish products detected by NMR spectroscopy, ionic [(LDipp)H][MF6] (M=Nb (3), Ta (4)) compounds were prepared in the reaction between MF5 and “naked” fluoride reagent [(LDipp)H][F]. Disorder in the anionic part of the [(LDipp)H][MF6] prevented unambiguous determination in the crystal structure. Therefore, additional crystallization systems were used and crystal structures of [(LDipp)H][MF6]·2MeCN (M=Nb (3a), Ta (4a)) and [(LDipp)H][MF6]·DCM (M=Nb (3b), Ta (4b)) solvates were obtained in which no disorder was observed.

Double bridged μ2-Halide Cu (II) complexes for the electrocatalytic reduction of CO2

Two dicopper (II) complexes of general formula [CuLX2]2 {L = 2, 5-diphenyl-3, 4(2-pyridyl) cyclopenta-2, 4-dien-1-one, X = Cl (1) or Br (2)} have been synthesized and characterized by elemental analysis, IR, UV–Vis spectroscopic methods. The crystal structures of both complexes have been determined by single-crystal X-ray diffraction; 1 and 2 have binuclear structures and Cu (II) centres in both complexes adopt a distorted square pyramidal geometry. Two [CuLX] (X = Cl or Br) units in both complexes are linked via μ-X coordination bridge modes with the Cu–Cu distances of 3.534 and 3.716 Å for 1 and 2 respectively. The electrochemical behaviour of the free L ligand and the corresponding Cu (II) complexes was studied in acetonitrile. The cyclic voltammetry of the complexes 1 and 2 show three ligand based reduction processes and two metal-centred reductions that are assigned to copper (II) to copper (I) and copper (I) to copper (0). The electrocatalytic activity for the reduction of CO2 of the two complexes was investigated; both complexes are active for the CO2 reduction and result in the formation of CO.