ACS polymers Au最新文献

DNA origami nanoparticles (DONs) hold great potential for interacting with biological systems, yet their applicability is limited by nuclease activity and challenging ionic conditions in biological environments. Among various stabilization strategies, oligolysine-PEG coatings have emerged as a preferred option due to their straightforward implementation and protective capacity. However, their static nature restricts compatibility with dynamic DON systems and may hinder the functional availability of preincorporated bioactive cues. Here, we introduce a strategy to confer responsiveness to these coatings by incorporating labile disulfide bridges at defined positions within the oligolysine segments. Upon exposure to the characteristic reductive conditions of the cellular cytoplasm, these linkers undergo cleavage, weakening the multivalent electrostatic interactions between the coatings and DONs. Through the synthesis and characterization of distinct oligolysine-PEG variants with varying degrees of peptide segmentation, we confirm their ability to protect DONs under physiological conditions while enabling efficient decomplexation in reductive environments, observing differences in DON functional recovery depending on the number and positioning of the linkers. This work provides a foundation for developing responsive oligolysine-PEG coatings, broadening the functional scope and biomedical applicability of stabilized DONs.

The aim of this study was to develop and characterize some freeze-dried wafers based on collagen and two mucoadhesive polymers, namely, hydroxypropyl methylcellulose (HPMC) and Carbomer 940 (CBM). The wafers were obtained by lyophilization of the corresponding hydrogels, which were evaluated by circular dichroism in order to investigate mucoadhesive polymers' influence on collagen's secondary structure. The obtained freeze-dried wafers were characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), contact angle measurements, and water uptake capacity. Furthermore, biocompatibility assessment was performed by evaluating the impact of freeze-dried wafer extracts on cell viability, morphology, and migration capacity. Circular dichroism showed more significant changes in the secondary structure of collagen associated with the addition of Carbomer 940. The FT-IR spectra displayed specific peaks for collagen and the two mucoadhesive polymers. SEM images illustrated a microporous structure for both collagen and Carbomer 940, while HPMC displayed a more sheet-like structure. The addition of HPMC increased the thermal stability of collagen, while Carbomer 940 had a negative impact on the samples' thermal stability. Contact angle measurements and water uptake capacity showed good hydrophilicity of the wafers. Except for CBM 100%, all samples supported the viability of human fibroblasts and did not have any inhibitory effect on cell migration capacity, demonstrating good biocompatibility, which is an essential attribute in developing drug delivery supports intended for mucosal applications.

Plasticizers are essential for improving the processability and flexibility of rubber compounds by reducing viscosity, aiding filler dispersion, and softening the rubber matrix. Traditionally, petroleum-based phthalate esters like dioctyl phthalate (DOP) and dibutyl phthalate (DBP) have been widely used for these purposes. However, these plasticizers pose significant challenges, including migration from the rubber over time, which can lower performance and raise environmental and health concerns. This study investigates the competing effects of plasticization and miscibility on the structure and dynamics of natural rubber (NR) and epoxidized natural rubber (ENR) when plasticized with glycerol trilevulinate (GT), a biobased plasticizer, and tris-(2-ethylhexyl) trimellitate (TOTM), a petroleum-derived plasticizer. Results show that GT accelerates vulcanization and reduces reversion risks, promoting faster curing and greater flexibility in the rubber network. In contrast, TOTM delays vulcanization and increases reversion, while forming a more rigid cross-linked network. Structurally, GT promotes longer sulfur bridges and strain-induced crystallization in NR, while TOTM favors the formation of shorter sulfur bonds and a more homogeneous network structure. In terms of miscibility, GT is fully miscible with ENR, improving segmental mobility, but shows partial miscibility in NR, restricting chain dynamics as evidenced by Broadband Dielectric Spectroscopy. These findings highlight GT as a potential sustainable alternative to petroleum-derived commercial plasticizers, offering promising advantages for high-performance, biobased rubber applications.

The exclusive introduction of end groups into biobased aliphatic polyesters containing vinyl chain ends, prepared by ADMET polymerization of nonconjugated diene monomers, has been achieved by adopting olefin metathesis with a molybdenum-alkylidene catalyst followed by treatment with various aldehydes, and their quantitative introductions were confirmed by grafting PEG with certified M _n values. The end-functionalized polyesters demonstrated unique emission and thermal properties through an interaction of the end groups; both melting and crystallization temperatures are affected by the end groups as well as the M _n values.

Since the seminal works on thermoreversible covalent networks followed by the discovery of vitrimers by L. Leibler and co-workers in 2011, numerous chemistries and strategies have flourished to design covalent adaptable networks (CANs) thus opening a novel research field. Using reversible covalent bonds that have been known for decades in molecular chemistry, CANs combine both the rheological characteristics of thermosets (chemically cross-linked networks, insoluble and infusible) and those of thermoplastics (entangled polymer chains able to be dissolved and to flow above their glass transition temperature). The aim of this tutorial review is to provide polymer chemists with guidelines to precisely and properly characterize CANs. Depending on the nature of the exchange mechanism (dissociative, associative, or a combination of both), on the kinetics of exchange, and on the cross-link density, characteristic relaxation times can vary from less than a second to a few hours. The time scale and distribution of relaxation times influence the rheological experiments and models that should be used. The present didactic review provides, from the rich recent literature, a guideline for adequate material characterizations and rheological measurements (and theoretical models applicable) that have been used to study CAN viscoelastic and thermomechanical properties.