Engineered polylactic acid (PLA) nanoparticles synthesized from oligo(lactic acid) macromonomers have been studied over the last decades for controlled drug delivery. These macromonomers are typically produced via ring-opening polymerization (ROP) of the cyclic dimer lactide, initiated by 2-hydroxyethyl methacrylate (HEMA). This reaction route, despite leading to well-defined macromonomers, relies on the production of lactide from lactic acid, which burdens the ROP overall cost for more than 30%. In this work, we report the synthesis of PLA-based macromonomers by direct polycondensation of lactic acid in the presence of HEMA as a valuable alternative to ROP. In particular, we compare the two processes side by side, focusing on the production of three HEMA-LAn macromonomers, with n = 2, 4, and 6. Detailed kinetic models are developed for both reaction systems, and the corresponding parameters are estimated by fitting the experimental data. Through these models, the reaction kinetics as well as the time evolution of the entire chain length distributions of the products from polycondensation and ROP could be reliably predicted. This way, we demonstrated that polycondensation is a valuable alternative to ROP only for macromonomers with an average chain length of up to 4 and that ROP remains the main route to longer chains, when a strict control over the chain length distribution is required. 相似文献
A more sustainable and efficient protocol for the photocatalytic α-amino arylation promoted by fac-Ir(ppy)3 was developed. Three noteworthy results were achieved: i) the replacement of toxic medium DMA with the greener solvents NBP and NHP, and the concurrent improvement of the process efficiency by lowering both the amine and the base amount; ii) the development of a recycling protocol for both the sustainable solvent NHP and the commercially available costly photocatalyst fac-Ir(ppy)3, achieving environmental and economic benefits. This approach to the photocatalyst recovery avoids very demanding catalyst structural modifications; iii) the protocol in green solvents proved to be scalable up to 10 mmol of limiting reagent, maintaining excellent performance also lowering the photocatalyst loading down to 0.05 mol%. This is the first example of photocatalytic α-arylation of amines promoted by such a low amount of catalyst. Lastly, the versatility of this approach was demonstrated by extending the use of the green solvent NBP to another photoredox process.
Low-bandgap nonfullerene acceptors (NFAs) offer a unique potential for photovoltaic (PV) applications, such as transparent PV and agrivoltaics. Evaluating each new PV system to achieve the optimum thickness, microstructure, and device performance is, however, a complex multiparametric challenge with large time and resource requirements. Herein, the PV potential of low-bandgap donor and NFA materials by combining high-throughput screening and statistical methods is evaluated. The use of thickness gradients (20–600 nm) facilitates the fabrication of more than 2000 doctor-bladed devices from 24 different low-bandgap blend combinations. The corresponding power conversion efficiencies varies significantly, from 0.06% to 10.45% across materials and thicknesses. The self-consistency of the large dataset allows to perform a parameter sensitivity study as well as parameter correlation analysis. These reveal that the choice of materials and energy alignment-related features (i.e., electron affinity offset, ionization energy offset, bandgap, and energy loss) has the largest influence on final device performance, while processing conditions appear less important for the final efficiencies. Our study demonstrates that high-throughput experimentation is a perfect match for correlation analyses in order to gain a statistically meaningful understanding of these systems, potentially accelerating the discovery of new materials. 相似文献
Calculation of the scattering pattern from aggregates of spheres through the T-matrix approach yields high-precision results but at a high-computational cost, especially when the aggregate concerned is large or is composed of large-size spheres. With reference to a specific but representative aggregate, we discuss how and to what extent the computational effort can be reduced but still preserve the qualitative features of the signature of the aggregate concerned. 相似文献
