Long-range electrostatic effects from intramolecular Lewis acid binding influence the redox properties of cobalt-porphyrin complexes.

A CoII-porphyrin complex (1) with an appended aza-crown ether for Lewis acid (LA) binding was synthesized and characterized. NMR spectroscopy and electrochemistry show that cationic group I and II LAs (i.e., Li+, Na+, K+, Ca2+, Sr2+, and Ba2+) bind to the aza-crown ether group of 1. The binding constant for Li+ is comparable to that observed for a free aza-crown ether. LA binding causes an anodic shift in the CoII/CoI couple of between 10 and 40 mV and also impacts the CoIII/CoII couple. The magnitude of the anodic shift of the CoII/CoI couple varies linearly with the strength of the LA as determined by the pKa of the corresponding metal-aqua complex, with dications giving larger shifts than monocations. The extent of the anodic shift of the CoII/CoI couple also increases as the ionic strength of the solution decreases. This is consistent with electric field effects being responsible for the changes in the redox properties of 1 upon LA binding and provides a novel method to tune the reduction potential. Density functional theory calculations indicate that the bound LA is 5.6 to 6.8 Å away from the CoII ion, demonstrating that long-range electrostatic effects, which do not involve changes to the primary coordination sphere, are responsible for the variations in redox chemistry. Compound 1 was investigated as a CO2 reduction electrocatalyst and shows high activity but rapid decomposition.

Inhibition of silica scaling with functional polymers: Role of ionic strength, divalent ions, and temperature.

High concentrations of dissolved silica in saline industrial wastewaters and brines cause silica scale formation, significantly hampering the efficacy of diverse engineered systems. Applying functional polymers as scale inhibitors in process feedwater is a common strategy to mitigate silica scaling. However, feedwater characteristics often vary widely, depending on the specific processes, making the inhibition of silica scaling challenging and complex. In this study, we systematically investigate the role of ionic composition, specifically ionic strength and divalent ions, and solution temperature, in inhibiting silica scaling using molecularly designed amine/amide polymers. The inhibitor demonstrates effective stabilization of silicic acid, with inhibition efficiency of 74 and 55 % in the absence and presence of 20,000 ppm NaCl, respectively. However, further increasing the ionic strength of oversaturated silicic acid solutions significantly diminishes inhibition performance, rendering it ineffective at 180,000 ppm NaCl. Divalent inorganic cations exhibit a stronger impact on reducing inhibition efficiency compared to sodium ions. Molecular dynamics simulations reveal a competition mechanism between anionic silicic acid reactants (i.e., H3SiO4-) and chlorides for binding to ammonium groups within the polymeric inhibitor. Additionally, cations form clusters with H3SiO4- ions, hindering their stabilization with polymeric inhibitor. Notably, at elevated temperatures, the inhibitor achieves near-perfect inhibition for 500 ppm silicic acid solutions. This comprehensive assessment provides important insights into the effectiveness of silica scaling inhibitors under solution conditions relevant to real-world applications, addressing the challenges posed by varying solution parameters in diverse industrial processes.

Modifying the Backbone Chemistry of PEG-Based Bottlebrush Block Copolymers for the Formation of Long-Circulating Nanoparticles.

Nanoparticle physicochemical properties have received great attention in optimizing the performance of nanoparticles for biomedical applications. For example, surface functionalization with small molecules or linear hydrophilic polymers is commonly used to tune the interaction of nanoparticles with proteins and cells. However, it is challenging to control the location of functional groups within the shell for conventional nanoparticles. Nanoparticle surfaces composed of shape-persistent bottlebrush polymers allow hierarchical control over the nanoparticle shell but the effect of the bottlebrush backbone on biological interactions is still unknown. The synthesis is reported of novel heterobifunctional poly(ethylene glycol) (PEG)-norbornene macromonomers modified with various small molecules to form bottlebrush polymers with different backbone chemistries. It is demonstrated that micellar nanoparticles composed of poly(lactic acid) (PLA)-PEG bottlebrush block copolymer (BBCP) with neutral and cationic backbone modifications exhibit significantly reduced cellular uptake compared to conventional unmodified BBCPs. Furthermore, the nanoparticles display long blood circulation half-lives of ≈22 hours and enhanced tumor accumulation in mice. Overall, this work sheds light on the importance of the bottlebrush polymer backbone and provides a strategy to improve the performance of nanoparticles in biomedical applications.

Molecular Design of Functional Polymers for Silica Scale Inhibition.

Silica polymerization, which involves the condensation reaction of silicic acid, is a fundamental process with wide-ranging implications in biological systems, material synthesis, and scale formation. The formation of a silica-based scale poses significant technological challenges to energy-efficient operations in various industrial processes, including heat exchangers and water treatment membranes. Despite the common strategy of applying functional polymers for inhibiting silica polymerization, the underlying mechanisms of inhibition remain elusive. In this study, we synthesized a series of nitrogen-containing polymers as silica inhibitors and elucidated the role of their molecular structures in stabilizing silicic acids. Polymers with both charged amine and uncharged amide groups in their backbones exhibit superior inhibition performance, retaining up to 430 ppm of reactive silica intact for 8 h under neutral pH conditions. In contrast, monomers of these amine/amide-containing polymers as well as polymers containing only amine or amide functionalities present insignificant inhibition. Molecular dynamics simulations reveal strong binding between the deprotonated silicic acid and a polymer when the amine groups in the polymer are protonated. Notably, an extended chain conformation of the polymer is crucial to prevent proximity between the interacting monomeric silica species, thereby facilitating effective silica inhibition. Furthermore, the hydrophobic nature of alkyl segments in polymer chains disrupts the hydration shell around the polymer, resulting in enhanced binding with ionized silicic acid precursors compared to monomers. Our findings provide novel mechanistic insights into the stabilization of silicic acids with functional polymers, highlighting the molecular design principles of effective inhibitors for silica polymerization.

Hierarchically Structured Nanocomposites via Mixed-Graft Block Copolymer Templating: Achieving Controlled Nanostructure and Functionality.

Integrating inorganic and polymerized organic functionalities to create composite materials presents an efficient strategy for the discovery and fabrication of multifunctional materials. The characteristics of these composites go beyond a simple sum of individual component properties; they are profoundly influenced by the spatial arrangement of these components and the resulting homo-/hetero-interactions. In this work, we develop a facile and highly adaptable approach for crafting nanostructured polymer-inorganic composites, leveraging hierarchically assembling mixed-graft block copolymers (mGBCPs) as templates. These mGBCPs, composed of diverse polymeric side chains that are covalently tethered with a defined sequence to a linear backbone polymer, self-assemble into ordered hierarchical structures with independently tuned nano- and mesoscale lattice features. Through the coassembly of mGBCPs with diversely sized inorganic fillers such as metal ions (ca. 0.1 nm), metal oxide clusters (0.5-2 nm), and metallic nanoparticles (>2 nm), we create three-dimensional filler arrays with controlled interfiller separation and arrangement. Multiple types of inorganic fillers are simultaneously integrated into the mGBCP matrix by introducing orthogonal interactions between distinct fillers and mGBCP side chains. This results in nanocomposites where each type of filler is selectively segregated into specific nanodomains with matrix-defined orientations. The developed coassembly strategy offers a versatile and scalable pathway for hierarchically structured nanocomposites, unlocking new possibilities for advanced materials in the fields of optoelectronics, sensing, and catalysis.

High Level of Lipoprotein(a) as Predictor for Recurrent Heart Failure in Patients with Chronic Heart Failure: a Cohort Study / Nível Alto de Lipoproteína (a) como Preditor de Insuficiência Cardíaca Recorrente em Pacientes com Insuficiência Cardíaca Crônica: um Estudo de Coorte

Abstract Background: Elevated plasma levels of Lipoprotein(a) [Lp(a)] are recognized as a significant risk factor for atherosclerotic vascular disease. However, there are limited data regarding association between Lp(a) and recurrent heart failure (HF) in patients with chronic HF caused by coronary heart disease (CHD). Objective: Elevated levels of Lp(a) might have a prognostic impact on recurrent HF in patients with chronic HF caused by CHD. Methods: A total of 309 patients with chronic HF caused by CHD were consecutively enrolled in this study. The patients were divided into 2 groups according to whether Lp(a) levels were above or below the median level for the entire cohort (20.6 mg/dL): the high Lp(a) group (n = 155) and the low Lp(a) group (n = 154). A 2-sided p < 0.05 was statistically considered significant. Results: During the median follow-up period of 186 days, 31 cases out of a total of 309 patients (10.03%) could not be reached during follow-up. A Kaplan-Meier analysis demonstrated that patients with higher Lp(a) levels had a higher incidence of recurrent HF than those with lower Lp(a) levels (log-rank < 0.0001). A multivariate Cox regression analysis revealed that Lp(a) levels were independently correlated with the incidence of recurrent HF after adjustment of potential confounders (hazard ratio: 2.720, 95 % confidence interval: 1.730-4.277, p < 0.0001). Conclusions: In Chinese patients with chronic HF caused by CHD, elevated levels of Lp(a) are independently associated with recurrent HF.

Resumo Fundamento: Níveis plasmáticos elevados de lipoproteína (a) [Lp(a)] são reconhecidos como um fator de risco significativo para doença vascular aterosclerótica. No entanto, existem dados limitados sobre a associação entre a Lp(a) e insuficiência cardíaca (IC) recorrente em pacientes com IC crônica causada por doença arterial coronariana (DAC). Objetivo: Níveis elevados de Lp(a) podem ter um impacto prognóstico na IC recorrente em pacientes com IC crônica por DAC. Métodos: Um total de 309 pacientes com IC crônica causada por DAC foram consecutivamente incluídos neste estudo. Os pacientes foram divididos em 2 grupos de acordo com os níveis de Lp(a), acima ou abaixo do nível mediano de toda a coorte (20,6 mg/dL): o grupo Lp(a) alto (n = 155) e o grupo Lp ( a) baixo (n = 154). Um p < 0,05 bicaudal foi considerado estatisticamente significativo. Resultados: Durante a mediana do período de seguimento de 186 dias, 31 casos de um total de 309 pacientes (10,03%) não puderam ser contatados durante o acompanhamento. A análise de Kaplan-Meier demonstrou que pacientes com níveis mais elevados de Lp(a) apresentavam maior incidência de IC recorrente do que aqueles com níveis mais baixos de Lp(a) (log-rank < 0,0001). Uma análise de regressão multivariada de Cox revelou que os níveis de Lp(a) foram independentemente correlacionados com a incidência de IC recorrente após ajuste de potenciais fatores de confusão (hazard ratio 2,720, intervalo de confiança de 95%: 1,730-4,277, p < 0,0001). Conclusões: Em pacientes chineses com IC crônica causada por DAC, níveis elevados de Lp(a) estão associados de forma independente à IC recorrente.