With the increased prevalence of antibiotic-resistant infections, there is an urgent need for innovative antimicrobial treatments. One such area being actively explored is the use of self-assembling cationic polymers. This relatively new class of materials was inspired by biologically pervasive cationic host defense peptides. The antimicrobial action of both the synthetic polymers and naturally occurring peptides is believed to be complemented by their three-dimensional structure. In an effort to evaluate shape effects on antimicrobial materials, triblock polymers were polymerized from an assembly directing terephthalamide-bisurea core. Simple changes to this core, such as the addition of a methylene spacer, served to direct self-assembly into distinct morphologies-spheres and rods. Computational modeling also demonstrated how subtle core changes could directly alter urea stacking motifs manifesting in unique multidirectional hydrogen-bond networks despite the vast majority of material consisting of poly(lactide) (interior block) and cationic polycarbonates (exterior block). Upon testing the spherical and rod-like morphologies for antimicrobial properties, it was found that both possessed broad-spectrum activity (Gram-negative and Gram-positive bacteria as well as fungi) with minimal hemolysis, although only the rod-like assemblies were effective against Candida albicans.
Side-chain
polymers have the potential to be excellent dopant-free
hole-transporting materials (HTMs) for perovskite solar cells (PSCs)
because of their unique characteristics, such as tunable energy levels,
high charge mobility, good solubility, and excellent film-forming
ability. However, there has been less research focusing on side-chain
polymers for PSCs. Here, two side-chain polystyrenes with triphenylamine
substituents on carbazole moieties were designed and characterized.
The properties of the side-chain polymers were tuned finely, including
the photophysical and electrochemical properties and charge mobilities,
by changing the positions of triphenylamine substituents on carbazole.
Owing to the higher mobility and charge extraction ability, the polymer P2 with the triphenylamine substituent on the 3,6-positions
of the carbazole unit showed higher performance with power conversion
efficiency (PCE) of 18.45%, which was much higher than the PCE (16.78%)
of P1 with 2,7-positions substituted. These results clearly
demonstrated that side-chain polymers can act as promising HTMs for
PSC applications and the performance of side-chain polymers could
be optimized by carefully tuning the structure of the monomer, which
provides a new strategy to design new kinds of side-chain polymers
and obtain high-performance dopant-free HTMs.
Heterogeneous
single-metal-site catalysts (HSMSCs) have attracted
considerable interest, but most studies have focused on the metal
atoms in the active site while ignoring the key role of ligands. The
unique coordination environment of a single-site catalyst is crucial
for realizing its potential. Constructing this kind of catalyst via a feasible and practical fabrication method is challenging.
Herein, a single-site Pd catalyst with iodide ligands supported on
activated carbon (Pd1/AC) was successfully fabricated by
atomic dispersion of large Pd nanoparticles (NPs). Intermediate I•
radicals were detected during the atomic dispersion process of Pd
NPs by in situ imaging photoelectron photoion coincidence
spectroscopy (in situ iPEPICO) with vacuum ultraviolet
synchrotron radiation. The molecular structure of single-site Pd was
established as [Pd(CO)I4(OAC)]2– through combined characterization. Alkyne dialkoxycarbonylation
with high selectivity toward 1,4-dicarboxylic acid esters (>94%)
and
high acetylene conversion (>99%) was achieved. A sulfonic promoter
on the Pd1/AC catalyst for alkyne dialkoxycarbonylation
was avoided because of the iodide ligand. Good durability and a broad
substrate scope were successfully achieved.
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