Comparison of three elements (In, Sn, and Sb) in the same period as catalysts in the ring-opening polymerization of l-lactide: from amorphous to semicrystalline polyesters.

The ring-opening polymerization (ROP) of l-lactide (l-LA) is the main method for synthesizing poly(l-lactide) (PLLA), in which choosing the catalyst is one of the most important parameters. In this work, we focused on the systematic study of catalysts based on p-block elements from period 5, such as indium(iii), tin(ii), tin(iv) and antimony(iii) acetates, which displayed contrasting performances influenced by the oxidation state of the metal center. Analysis of the obtained oligomers by different techniques, including nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), polarized optical microscopy (POM) and matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF), revealed the selectivity of each catalyst toward the ROP of l-LA. Tin(ii) acetate showed the best performance, making it the best catalyst of this series for synthesizing PLLA. Indium(iii) and tin(ii) acetates induced an amorphous and semicrystalline polyester, respectively. The kinetic study evidenced the excellent performance of tin(ii) acetate in the ROP of l-LA. This catalyst reached high conversions in a quarter of the total reaction time, positioning it as the most catalytically active of the selected p-block acetate catalysts. Finally, the coordination-insertion mechanism by the catalyst in the initiation step was corroborated through the development of a mechanistic study applying the density functional theory (DFT).

Synthesis and characterization of macrodiols and non-segmented poly(ester-urethanes) (PEUs) derived from α,ω-hydroxy telechelic poly(ε-caprolactone) (HOPCLOH): effect of initiator, degree of polymerization, and diisocyanate.

Nine different macrodiols derived from α,ω-hydroxy telechelic poly(ε-caprolactone) (HOPCLOH) were prepared by ring-opening polymerization of ε-caprolactone (CL) using three linear aliphatic diols (HO-(CH2) n -OH, where n = 4, 8, and 12) as initiators and catalyzed by ammonium decamolybdate (NH4)8[Mo10O34]. The crystallization temperature (T c) and crystallinity (x i) were relatively high for HOPCLOH species with a long aliphatic chain [-(CH2)12-] in the oligoester. Also, HOPCLOH was the precursor of twenty-seven different poly(ester-urethanes) (PEUs) with various degrees of polymerization (DP) of HOPCLOH and three types of diisocyanates such as 1,6-hexamethylene diisocyanate (HDI), methylene diphenyl diisocyanate (MDI), and 4,4'-methylenebis (cyclohexyl isocyanate) (HMDI). HOPCLOH exhibited the melting temperature (T m) and crystallinity (x i) with a proportional dependency to the degree of polymerization (DP). PEUs showed significant thermal and mechanical properties, which had a direct correlation in terms of the type of DP and diisocyanate. PEUs derived from HDI versus MDI or HMDI exhibited an apparent effect where aliphatic diisocyanate (HDI) induced a significant x i with respect to aromatic and cyclic diisocyanate (MDI or HMDI). The profile of PEUs films according to mechanical properties is mainly a plastic behavior. The chemical nature and properties of HOPCLOH and PEUs were characterized by NMR, FT-IR, GPC, MALDI-TOF, DSC, and mechanical properties.

Difluoroboron Complexes Based on Benzimidazole-Phenolates as Blue Emitters.

Novel four-coordinated boron complexes (1-5) were synthesized via a reaction between BF3·CH3OH and benzimidazole-phenolate ligands (L1-L5), which are N,O-donors. These complexes exhibit intense blue emission in the solution and solid states accompanied by notable fluorescence quantum yields (ΦF). The study of the structure-property relation, through theoretical and experimental approaches, revealed a distinctive trend where compounds incorporating electron-donating substituents (methyl and ethoxy groups) in the phenolate moiety manifest shifts in emission wavelengths across the blue spectrum, concomitant with an increase in ΦF. Furthermore, the incorporation of an aromatic ring into the benzimidazole moiety considerably intensifies the rate of radiative relaxation from excited states. Notably, in the solid phase, either as a crystalline powder or loaded into polymer films, these modified complexes maintain or even surpass ΦF values observed in molecular solutions, ranging from 0.18 to 0.57, depending on the substitution. This characteristic makes these compounds attractive for applications in optoelectronics. All of the compounds were characterized using 1H, 13C, 11B, and 19F NMR, elemental analysis, and the molecular structures were corroborated through single-crystal X-ray diffraction analysis. Computational calculations via time-dependent density functional theory further elucidate the tunability of optical bandgaps through group substitution on ligands, aligning well with experimental observations.

Integrating a Community Advisory Board Into a Pragmatic Trial of Mindfulness for Chronic Low Back Pain.

Background: To improve the implementation of clinical trial interventions, there is a need to facilitate communication between key stakeholders and research teams. Community Advisory Boards (CAB) bring together a range of stakeholders not historically included in the research process to inform and work collaboratively with research teams. Objective: To describe our procedures and processes for (1) integration of a CAB into a pragmatic clinical trial of a telehealth-delivered group mindfulness program for persons with chronic low back pain (cLBP) within primary care, and (2) for the rapid uptake and implementation of CAB recommendations. Methods: The CAB we convened includes persons with cLBP who have undergone the mindfulness intervention, health care system leadership, advocacy groups, and mindfulness experts. The CAB members underwent a two hour initial training that introduced the research process and the CAB's role as research partners. The CAB met monthly for 1 hour. We used the Lighting Report method to summarize meetings and share feedback with the research team. Results: The recommendations of the CAB during the first year they met were divided into recruitment, informed consent, and survey recommendations. The study website also was overhauled based on recommendations, including a more engaging first page with rotating images of nature and testimonials. The language on the website was edited to be more concise and participant-friendly. The CAB recommended talking points to discuss with participants during screening or informed consent about the benefits of participating in research. Conclusion: We established a CAB that represented diverse perspectives, organizations, and experience with cLBP and mindfulness. The differing perspectives of the CAB resulted in recommendations that the research team itself would not have decided on their own. The Lightning Reports were also an effective way to efficiently communicate the CAB recommendations to the research team.

Sustainable xanthophylls-containing poly(ε-caprolactone)s: synthesis, characterization, and use in green lubricants.

Three xanthophylls [(3R,3'R,6'R)-lutein (1), (3R,3'S)-zeaxanthin (2), and (3R,3'S)-astaxanthin (3)] were used for the first time as initiators in the ring-opening polymerization (ROP) of ε-caprolactone (CL) catalyzed by tin(ii) 2-ethylhexanoate [Sn(Oct)2] for the synthesis of novel sustainable xanthophyll-containing poly(ε-caprolactone)s (xanthophylls-PCL). The obtained polyesters were characterized by 1H and 13C NMR, FT-IR, DSC, SEC, and MALDI-TOF MS, and their use as additives in green lubricants was evaluated using a sliding friction test under boundary conditions. Xanthophylls-PCL were obtained with good conversions and with molecular weights determined by SEC to be between 2500 and 10 500 Da. The thermal properties of xanthophyll-polyesters showed a crystalline domain, detected by DSC. Lastly, the green lubricant activity of these polymers was evaluated and the results showed that xanthophylls-PCL could be employed as additives for biodegradable lubricant applications since they have better tribological behavior than current additives, which demonstrates their potential as future commercial materials with interesting eco-friendly properties for diverse applications.

On the Tribological and Oxidation Study of Xanthophylls as Natural Additives in Castor Oil for Green Lubrication.

The present study focuses on an introductory analysis of the use of three xanthophylls as additives for green lubricant applications. For this purpose, the additives were characterized by FTIR and 1H-NMR techniques, and the bio-lubricants were described by their physical properties. The effect of the natural compounds on the friction and wear properties of bio-lubricants were evaluated by sliding friction tests under boundary conditions, as confirmed by an analysis of the lubricating film thickness. The antioxidant capacity was analyzed by FTIR spectroscopy. It was observed better wear protection in castor oil with xanthophylls than without these additives. The wear rate was reduced up to 50% compared with neat oil. Lesser beneficial effects were appreciated in friction coefficient since it was increased 25%. The best contribution was observed with astaxanthin as an additive. In addition, a significant improvement in the oxidation of castor oil, complemented with this additive, was exhibited by FTIR analysis. It was found that xanthophylls could be employed as additives for totally biodegradable lubricant applications since they have better tribological and antioxidant behavior than current additives.

The design and methods of the OPTIMUM study: A multisite pragmatic randomized clinical trial of a telehealth group mindfulness program for persons with chronic low back pain.

Mindfulness-based stress reduction (MBSR) is an evidence-based non-pharmacological approach for chronic low back pain (cLBP), yet it is not readily available or reimbursable within primary care clinics. Primary care providers (PCPs) who wish to avoid prescribing opioids and other medications typically have few options for their cLBP patients. We present the protocol of a pragmatic clinical trial entitled OPTIMUM (Optimizing Pain Treatment In Medical settings Using Mindfulness). OPTIMUM is offered online via telehealth and includes medical group visits (MGV) with a PCP and a mindfulness meditation intervention modeled on MBSR for persons with cLBP. In diverse health-care settings in the US, such as a safety net hospital, federally qualified health centers, and a large academic health system, 450 patients will be assigned randomly to the MGV + MBSR or to usual PCP care alone. Participants will complete self-report surveys at baseline, following the 8-week program, and at 6- and 12-month follow-up. Health care utilization data will be obtained through electronic health records and via brief monthly surveys completed by participants. The primary outcome measure is the PEG (Pain, enjoyment, and general activity) at the 6-month follow-up. Additionally, we will assess psychological function, healthcare resource use, and opioid prescriptions. This trial, which is part of the NIH HEAL Initiative, has the potential to enhance primary care treatment of cLBP by combining PCP visits with a non-pharmacological treatment modeled on MBSR. Because it is offered online and integrated into primary care, it is expected to be scalable and accessible to underserved patients. Clinical Trials.gov: NCT04129450.

Bismuth subsalicylate, a low-toxicity catalyst for the ring-opening polymerization (ROP) of l-lactide (l-LA) with aliphatic diol initiators: synthesis, characterization, and mechanism of initiation.

The ring-opening polymerization (ROP) of l-lactide (l-LA) was induced by the catalytic action of bismuth subsalicylate (BiSS) using linear aliphatic diols [HO(CH2) n OH, where n = 2, 3, 4, 5, 6, and 8] as initiators and chain transfer agents. The theoretical and experimental degree of polymerization (DP) in all samples of α,ω-hydroxy telechelic poly(l-lactide) (HOPLLAOH) had a good agreement in all samples, an effect attributed to the interaction of BiSS with HO(CH2) n OH inducing a transfer reaction. HOPLLAOH was synthesized and characterized by a range of analytical techniques, confirming the insertion of methylene groups from the initiator into the main chain of the polyester. The glass-transition temperature (T g) of HOPLLAOH was found to be proportional to the number of methylene groups present in the diol. Various parameters regarding the ROP of l-LA were studied, such as temperature, time of reaction, amount of catalyst, and the nature of the diols. A kinetic study of the reaction allowed the determination of the rate constants (k) and activation energy (E a). A mechanism of initiation is proposed based on a computational study using density functional theory (DFT), evidencing the role of the alkyl diol as an initiator, producing an alkoxide (Bi-OROH). This species then acts as a nucleophile, attacking the carbonyl group, inducing its insertion, and ultimately completing the ring-opening of l-LA.

A Simple and Efficient Method for the Partial Synthesis of Pure (3R,3'S)-Astaxanthin from (3R,3'R,6'R)-Lutein and Lutein Esters via (3R,3'S)-Zeaxanthin and Theoretical Study of Their Formation Mechanisms.

Carotenoids are natural compounds that have important roles in promoting and maintaining human health. Synthetic astaxanthin is a highly requested product by the aquaculture industry, but natural astaxanthin is not. Various strategies have been developed to synthesize this carotenoid. Nonetheless, these approaches have not only provided limited global yields, but its main commercial source also carries several health risks for humans. In this contribution, the one-pot base-catalyzed reaction of (3R,3'R,6'R)-lutein (1) esters has resulted in a successful isomerization process to easily obtain up to 95% meso-zeaxanthin (2), which in turn is oxidized to (3R,3'S)-astaxanthin (3) with a global yield of 68%. The same oxidation performed with UV irradiation (365 nm) for 5 min provided the highest global yield (76%). These chemical transformations have also been achieved with a significant reduction of the health risks associated with its potential human consumption. Furthermore, this is the first time only one of the configurational isomers has been obtained semisynthetically. The poorly understood formation mechanisms of these two compounds were also investigated using Density-Functional Theory (DFT) calculations. These theoretical studies revealed that the isomerization involves a base-catalyzed deprotonation at C-6', followed by C-4' protonation, while the oxidation occurs via free radical mechanisms.

Chiral polymers of intrinsic microporosity: selective membrane permeation of enantiomers.

Following its resolution by diastereomeric complexation, 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane (TTSBI) was used to synthesize a chiral ladder polymer, (+)-PIM-CN. (+)-PIM-COOH was also synthesized by the acid hydrolysis of (+)-PIM-CN. Following characterization, both (+)-PIM-CN and (+)-PIM-COOH were solvent cast directly into semipermeable membranes and evaluated for their ability to enable the selective permeation of a range of racemates, including mandelic acid (Man), Fmoc-phenylalanine, 1,1'-bi-2-naphthol (binol), and TTSBI. High ee values were observed for a number of analytes, and both materials exhibited high permeation rates. A selective diffusion-permeation mechanism was consistent with the results obtained with these materials. Their high permeability, processability, and ease of chemical modification offer considerable potential for liquid-phase membrane separations and related separation applications.