Anionic Hybrid Copolymerization of Sulfur with Acrylate: Strategy for Synthesis of High-Performance Sulfur-Based Polymers.

Copolymerization of elemental sulfur (S8) with vinyl monomers to develop new polymer materials is significant. Here, for the first time, we report the anionic hybrid copolymerization of S8 with acrylate at 25 °C, yielding a copolymer with short polysulfide segments; i.e., each of them consists of only one to four sulfur atoms. The formation of a longer polysulfide segment would be ceaselessly disrupted by carbon anions through the chain-transfer reaction. The copolymer of S8 with diacrylate was cross-linked and exhibited excellent mechanical properties, with an ultimate tensile strength as high as 10.7 MPa and a breaking strain of 22%. Furthermore, the introduction of tertiary amide groups to the copolymer enabled it not only to be reprocessed via press molding at room temperature but also to exhibit self-healing properties without external intervention. This study provides a facile strategy to synthesize high-performance sulfur-based copolymers under mild conditions.

Noncovalent Postmodification Guided Reversible Compartmentalization of Polymeric Micelles.

Compartmentalized micelles (CMs) are promising tailor-made soft matters that mimic natural designed structures and functions. Despite the structure of complex CMs, manipulating CM structures accessibly and reversibly remains elusive. Here, we report the fabrication of CMs via a generally valid noncovalent postmodification process. Starting from precursor micelles (PMs) based on one diblock copolymer, aromatic modification leads to the compartmentalization of PMs into well-defined spherical CMs. Control over compartment number, size and distribution in CMs, and segment distribution in their linear hierarchical assemblies is attained by simply tuning the postmodification degree and solvent composition. We also demonstrate the reversible transformation between PM and CMs during several heating-cooling cycles, which endows the micelles with potential in reversible functional transitions in situ close to nature's capability. Moreover, both hierarchically assembled or ill-structured micelles can rearrange into homogeneous CMs after one heating-cooling cycle, featuring the postmodification guided compartmentalization strategy with unprecedented micelle reproducibility.

Remarkable untangled dynamics behavior of multicyclic branched polystyrenes.

A typical multicyclic branched-topology polystyrene (c-BPS) with high molecular weight (30 K ≤ Mw MALLS ≤ 300 K g mol-1) and narrow dispersity (1.2 ≤ D ≤ 1.3) was efficiently synthesized by combining atom transfer radical polymerization (ATRP) and atom transfer radical coupling (ATRC) techniques. The topological constraints imposed by the presence of cyclic units and branch points had a marked influence on the entanglement behaviors of the polymer chains in solution. Therefore, c-BPS possesses the lowest loss modulus (G'') and viscosity (η), the highest diffusion coefficient (D0), the largest mesh size (ξ) and the fastest terminal relaxation (TR), compared with branched and linear precursors.

Highly Efficient Amide Michael Addition and Its Use in the Preparation of Tunable Multicolor Photoluminescent Polymers.

The amide bond is one of the most pivotal functional groups in chemistry and biology. It is also the key component of proteins and widely present in synthetic materials. The majority of studies have focused on the formation of the amide group, but its postmodification has scarcely been investigated. Herein, we successfully develop the Michael additions of amide to acrylate, acrylamide, or propiolate in the presence of phosphazene base at room temperature. This amide Michael addition is much more efficient when the secondary amide instead of the primary amide is used under the same conditions. This reaction was applied to postfunctionalize poly(methyl acrylate-co-acrylamide), P(MA-co-Am), and it is shown that the amide groups of P(MA-co-Am) could be completely modified by N,N-dimethylacrylamide (DMA). Interestingly, the resulting copolymer exhibited tailorable fluorescence with emission wavelength ranging from 380 to 613 nm, which is a desired property for luminescent materials. Moreover, the emissions of the copolymer increased with increasing concentration in solution for all excitation wavelengths from 320 to 580 nm. Therefore, this work not only develops an efficient t-BuP4-catalyzed amide Michael addition but also offers a facile method for tunable multicolor photoluminescent polymers, which is expected to find a wide range of applications in many fields, such as in anticounterfeiting technology.

Highly Branched Copolymers with Degradable Bridges for Antifouling Coatings.

The antifouling properties of traditional self-polishing marine antifouling coatings are mainly achieved based on their hydrolysis-sensitive side groups or the degradable polymer main chains. Here, we prepared a highly branched copolymer for self-polishing antifouling coatings, in which the primary polymer chains are bridged by degradable fragments (poly-ε-caprolactone, PCL). Owing to the partial or complete degradation of PCL fragments, the remaining coating on the surface can be broken down and eroded by seawater. Finally, the polymeric surface is self-polished and self-renewed. The designed highly branched copolymers were successfully prepared by reversible complexation mediated polymerization (RCMP), and their primary main chains had an Mn of approximately 3410 g·mol-1. The hydrolytic degradation results showed that the degradation of the copolymer was controlled, and the degradation rate increased with increasing contents of degradable fragments. The algae settlement assay tests indicated that the copolymer itself has some antibiofouling ability. Moreover, the copolymer can serve as a controlled release matrix for antifoulant 4,5-dichloro-2-octylisothiazolone (DCOIT), and the release rate increases with the contents of degradable fragments. The marine field tests confirmed that these copolymer-based coatings exhibited excellent antibiofouling ability for more than 3 months. The current copolymer is derived from commonly used monomers and an easily conducted polymerization method. Hence, we believe this method may offer innovative insights into marine antifouling applications.

The Effectiveness and Safety of Corticosteroids Therapy in Adult Critical Ill Patients With Septic Shock: A Meta-Analysis of Randomized Controlled Trials.

OBJECTIVE: To investigate the effectiveness and safety of corticosteroids therapy in adult critical ill patients with septic shock. METHODS: The PUBMED, EMBASE, Web of Science, Cochrane Library databases were systematically searched from the inception dates to March 24, 2018. To identify randomized controlled trials that evaluating the role of corticosteroids therapy in adult critical ill patients with septic shock. The primary outcome was 28-day mortality. The second outcomes included 90-day mortality, intensive care unit (ICU) mortality, in-hospital mortality, length of stay in ICU, length of stay in hospital, reversal of shock, and superinfection. RESULTS: A total of 18 randomized controlled trials involving 8,128 adult critical ill patients with septic shock fulfilled the inclusion criteria. The outcomes of this meta-analysis showed that corticosteroids therapy did not significantly reduce the 28-day mortality [RR = 0.94; 95% CI, 0.84-1.05; Z = 1.07 (P = 0.285)]. However, corticosteroids therapy was associated with a significantly shorter length of stay in ICU [WMD = -1.55; 95% CI, -2.19 to -0.91; Z = 4.74 (P = 0.000)]. 90-day mortality, ICU mortality, in-hospital mortality, length of stay in hospital, reversal of shock, and superinfection had no significant difference between the corticosteroids therapy and placebo therapy (P > 0.05). Similar results were obtained in subgroups of trials stratified according to the dose of corticosteroids (high dose or low does). CONCLUSIONS: Based on the results of this meta-analysis, corticosteroids therapy was associated with a significantly shorter length of stay in ICU among adult critical ill patients with septic shock. The mortality was similar between the corticosteroids therapy and placebo.

A bioreducible supramolecular nanoparticle gene delivery system based on cyclodextrin-conjugated polyaspartamide and adamantyl-terminated polyethylenimine.

This article describes a novel reduction degradable supramolecular nanoparticle gene delivery system via host-guest interaction based on cyclodextrin-conjugated polyaspartamide with disulfide linkage (Pasp-SS-CD) and adamantyl-terminated polyethylenimine (Ad4-PEI). The reduction responsiveness of Pasp-SS-CD and the Pasp-SS-CD/Ad4-PEI/pDNA supramolecular nanoparticles (SNPs) in the presence of dl-dithiothreitol (DTT) was confirmed by SEC-MALLS and DLS analysis, respectively. Compared with the Ad4-PEI/pDNA polyplexes, the bioreducible supramolecular polycation/pDNA polyplexes exhibited smaller particle size, slightly higher zeta potential, lower cytotoxicity and hemolysis ratio, improved cellular internalization and higher gene transfection efficiency. It was found that introducing Pasp-SS-CD to assemble Ad4-PEI could substantially enhance the tolerance of protein adsorption and maintain the gene transfer capacity of polycationic carriers, which might be beneficial for in vivo use. In addition, the cellular uptake pathway of the supramolecular polycation/pDNA polyplexes was investigated using different uptake inhibitors. The present study demonstrates that the proper assembly of cyclodextrin-conjugated polyaspartamide and adamantyl-terminated polyethylenimine is an effective strategy for the production of a new gene delivery system.

A light and reduction dual sensitive supramolecular self-assembly gene delivery system based on poly(cyclodextrin) and disulfide-containing azobenzene-terminated branched polycations.

Novel reduction degradable and photosensitive disulfide-containing azobenzene-terminated branched poly(2-(dimethylamino)ethyl methacrylate)s (Az-ss-BPDMs) and supramolecular host-guest self-assembly systems with poly(cyclodextrin) (PCD) were prepared and evaluated as non-viral gene delivery vectors. The reduction and light dual sensitive properties of the supramolecular polycations PCD/Az-ss-BPDMs and their polyplexes PCD/Az-ss-BPDMs/DNA were confirmed by UV-Vis, SEC, DLS and zeta potential analyses, respectively. It was shown that the inclusion of PCD, introduction of disulfide bonds into branched polycations, increase of the branching degree of the branched Az-ss-BPDMs and use of UV irradiation could enhance the gene transfection efficiency and cellular internalization of the supramolecular disulfide-containing azobenzene-terminated branched polycationic polyplexes (PCD/Az-ss-BPDM/DNA). Importantly, the transfection efficiency of the light and reduction dual-sensitive supramolecular PCD/Az-ss-BPDM/DNA polyplexes achieved almost 10 times higher value than that of 25 kDa PEI control; whereas the cytotoxicity of the supramolecular polyplexes was lower than that of PEI control. Thus this light and reduction dual responsive supramolecular host-guest system containing azobenzene-terminated branched cationic polymers with disulfide bonds and PCD is a promising gene vector.

Supramolecular host-guest polycationic gene delivery system based on poly(cyclodextrin) and azobenzene-terminated polycations.

This article describes the supramolecular host-guest polycationic gene delivery system based on poly(ß-cyclodextrin) (PCD) and azobenzene-terminated polycations. The azobenzene-terminated linear (Az-LPDM) and branched (Az-BPDM) cationic polymers were synthesized by atom transfer radical polymerization (ATRP) of 2-dimethylamino ethyl methacrylate (DMAEMA). The formation and photosensitive behavior of the supramolecular polycations of azobenzene-terminated polycations Az-LPDM and Az-BPDM with PCD were confirmed by UV-vis and NMR analysis. The supramolecular PCD/Az-BPDM/DNA and PCD/Az-LPDM/DNA polyplexes showed smaller size and were less positive than those of their corresponding polyplexes without PCD. Moreover, the UV irradiation may promote release of DNA from the photosensitive supramolecular polyplexes due to dissociation of supramoelcular polyplexes. In vitro experiments revealed that the photosensitive supramolecular polycationic polyplexes (PCD/Az-LPDM/DNA and PCD/Az-BPDM/DNA) exhibited enhancement of cellular uptake, higher transfection efficiency, and lower cytoxicity compared to the azobenzene-terminated polycation/DNA polyplexes in the absence of PCD. Branched polycationic polyplexes showed higher transfection efficiency than its linear polycationic polyplexes. Furthermore, after UV irradiation, the transfection efficiency of photosensitive supramolecular polyplexes was improved resulting from more DNAs delivered and released inside of the cell nuclei. Thus this photoresponsive supramolecular host-guest system containing azobenzene-terminated branched cationic polymers and PCD is a promising gene vector.