The Topology of Polymer Brushes Determines Their Nanoscale Hydration.

Time-of-flight neutron reflectometry (ToF-NR) performed under different relative humidity conditions demonstrates that polymer brushes constituted by hydrophilic, cyclic macromolecules exhibit a more compact conformation with lower roughness as compared to linear brush analogues, due to the absence of dangling chain ends extending at the polymer-vapor interface. In addition, cyclic brushes feature a larger swelling ratio and an increased solvent uptake with respect to their linear counterparts as a consequence of the increased interchain steric repulsions. It is proposed that differences in swelling ratios between linear and cyclic brushes come from differences in osmotic pressure experienced by each brush topology. These differences stem from entropic constraints. The findings suggest that to correlate the equilibrium swelling ratios at different relative humidity for different topologies a new form of the Flory-like expression for equilibrium thicknesses of grafted brushes is needed.

Combining Click Sulfur(VI)-Fluoride Exchange with Photoiniferters: A Facile, Fast, and Efficient Strategy for Postpolymerization Modification.

"Click" type reactions represent the currently most prevalent postpolymerization strategy for the preparation of functional polymeric materials. Herein, a novel photoiniferter agent 4-(fluorosulfonyl)benzyl diethylcarbamodithioate (FSB-DECT) containing both dithiocarbamates and sulfonyl fluoride moieties is developed to act as both photoinitiator and click sulfur(VI)-fluoride exchange (SuFEx) agent. The photopolymerization behavior of FSB-DECT is demonstrated via standard photoiniferter-mediated polymerization for various types of monomer including N-isopropylacrylamide (NIPAAm), glycidyl methacrylate, and vinyl acetate (VAc). Gel permeation chromatography data show that the polymerization is relatively well controlled, with polydispersity indices of the product homopolymers in the range of 1.3-1.6. 1 H and 19 F NMR spectra and "reinitiated" photopolymerization indicate that the sulfonyl fluoride and diethyldithiocarbamyl groups remain at the respective ends of the homopolymer chains. Furthermore, using the sulfonyl fluoride end-functionalized poly(N-isopropylacrylamide) as a model polymer, the utility of the SuFEx reaction for efficient postpolymerization functionalization is demonstrated.

Toxicological effects of micro/nano-plastics on mouse/rat models: a systematic review and meta-analysis.

Micro/nano-plastics (MNPs) are considered a heterogeneous class of environmental contaminants that cause multiple toxic effects on biological species. As the commonly used mammalian models to study the effects of MNPs with regard to their toxic effects, the mouse and rat models are making a great contribution to the disciplines of environmental toxicology and medical health. However, the toxic effects of MNPs have not been systematically summarized. Therefore, a systematic review and a meta-analysis of the toxic effects of MNPs on mouse/rat models were conducted. A total of seven main categories were established in this systematic review, and 24 subcategories were further divided according to the specific physiological significance of the endpoint or the classification of the physiological system, which covered all the selected pieces of literature. A total of 1,762 biological endpoints were found, and 52.78% of them were significantly affected. This fact indicates that there are relative factors, including the size, polymer type, concentration, and exposure time of MNPs and different sexes of mouse/rat models that could significantly affect the biological endpoints. These biological endpoints can be classified into various factors, such as the dose-response relationships between MNP concentration and physiological categories of the nervous system, growth, reproduction, digestive tract histopathology, and inflammatory cytokine level, among others. MNPs negatively affected the blood glucose metabolism, lipid metabolism, and reproductive function in mice. The reproductive function in male mice is more sensitive to the toxic effects of MNPs. These findings also provide insights into and directions for exploring the evidence and mechanisms of the toxic effects of MNPs on human health. It is clear that more research is required on the pathological mechanisms at the molecular level and the long-term effects of tissue accumulation.

Protein-resistant properties of poly(N-vinylpyrrolidone)-modified gold surfaces: The advantage of bottle-brushes over linear brushes.

Poly(N-vinylpyrrolidone) (PVP)-modified surfaces have been shown to possess excellent protein resistance and good biocompatibility. However, PVP-modified surfaces with different molecular architectures have not been prepared, and their protein-resistant properties have not been studied. Herein, gold surfaces modified with linear PVP brush and PVP bottle-brush architectures were prepared by photoinitiated surface grafting polymerization. Ellipsometry, X-ray photoelectron spectroscopy (XPS), water contact angle, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) were utilized to characterize the prepared surfaces. The protein-resistant properties were investigated by a quartz crystal microbalance with dissipation (QCM-D) with bovine serum albumin (BSA), fibrinogen (Fg) and lysozyme (Lyz). Compared with the ungrafted QCM-D chips, the PVP bottle-brush-grafted chips (9.3 nm thickness) showed superior protein resistance over linear PVP brush-grafted chips (9.9 nm thickness). Furthermore, the PVP bottle-brushes reduced the levels of BSA, Fg and Lyz adsorption by 97%, 85% and 69%, respectively. Moreover, to demonstrate potential applications as functional biosensors and in the biomedical field, PVP bottle-brushes containing glycopolymer-grafted gold surfaces were fabricated. Laser scanning confocal microscopy (LSCM) demonstrated that these glycopolymer surfaces showed excellent protein resistance and specific ConA binding ability. Overall, we speculate that the data presented here can provide useful information for the development of excellent antifouling materials and functional biosensors.