查看更多>>摘要：Siloxane bearing benzoxazines from renewable phenolics such as vanillin and coumarin were prepared and reacted with glycerol by silyl ether exchange reactions to yield processable, soft, and curable bio-hybrid gels. Moreover, these benzoxazine-based gels were cured below 200 C favored by the catalytic effect of hydroxyl groups present on glycerol moieties to yield bio-hybrid polybenzoxazines. All the synthesized intermediates, gels, and ultimate networks were characterized by H-1,C- 13 NMR, FTIR, and UV-Vis analyses. The curing behavior and thermal stabilities of the monomers, glycerol-based gels and related polybenzoxazines were investigated by differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). Moreover, the activation energies of polymerization of benzoxazine monomers were determined by DSC using the Kissinger and Ozawa methods.
查看更多>>摘要：An initiating system composed by ethylaluminum sesquichloride (Et3Al2Cl3)//2,6-dimethylpyridine (DMP) is established for fast living cationic polymerization of isobutylene. The polymerization can be accelerated at utmost to finish in only 4 s with extremely narrow molecular weight distribution in microflow system. Investigations on influence factors reveal that mixing intensity that dependent on Re affects the molecular weight distribution significantly. DMP has two-stage effect, corresponding to its interactions with protonic impurity and Lewis acid respectively. Polymerization rate can be facilely adjusted by changing the volume ratio of mixed solvent of n-hexane and CH2Cl2 from 8:2 to 7:3 with the assurance of livingness. This polymerization system can even operate at elevated temperature as high as -55 degrees C without the loss of livingness, which is of great beneficial to the commercialization of polyisobutylene-based functional polymer materials.
查看更多>>摘要：Enhancing tumor reactive oxygen species (ROS) is a promising strategy for improved cancer chemotherapy. However, the high level of glutathione (GSH) in hypoxic tumor cells can neutralize ROS, restricting the application of ROS boosted therapy. Herein, hypoxia-responsive polymer micelles (FAL@DOX) were constructed to amplify intra-tumor oxidative stress to enhance the chemotherapeutic efficacy of doxorubicin (DOX). The amphiphilic polymer consists of hydrophilic fucoidan (Fuc) linked by azobenzene with hydrophobic linolenic acid (LA), and can self-assemble into micelles to encapsulate DOX. Under hypoxia, FAL@DOX decreased intratumoral GSH by consuming nicotinamide adenine dinucleotide phosphate (NADPH), and caused accumulation of lethal ROS and lipid peroxides, resulting in mitochondrial damage and enhanced anti-tumor performance of DOX. FAL@DOX (IC50 1.685 mu g/mL) improved the effect of DOX (IC50 7.847 mu g/mL) on hypoxic tumor cells by nearly 4.6-fold. The current work provides a novel strategy for enhancing the antitumor efficacy via oxidative stress augmented chemotherapy.
Das, MithunBhattacharya, Asit BaranParathodika, Arshad RahmanNaskar, Kinsuk...
13页
查看更多>>摘要：The dynamic supramolecular crosslinking reactions like imine bond formation, disulfide metathesis reactions, Diels Alder reactions, metal-ligand interactions, H-bonding, and ionic interactions are broadly used for the self healing application of elastomers. Herein, we have developed a new self-healable and extremely stretchable elastomer based on robustness and dynamic metal-ligand coordination bonds between the API ligand and the Zn2+ metal ion moieties incorporated onto the XNBR rubber backbone. The FT-IR analysis confirmed the formation of amide linkage and metal-ligand coordination bonds into the XNBR rubber backbone. The healing performance and mechanical properties of various rubber compounds depend on the dosages of metal ions and the type of crosslinking systems. The metal-ligand crosslink compounds exhibit excellent healing performance over the sulfur crosslinking system. Differential scanning calorimetry, rubber process analyzer, crosslinking density, and morphology studies are indicated to characterize the metal-ligand interactions in the XNBR rubber matrix. The metal-ligand cross-linked XNBR rubber with 3 parts of Zn2+ metal ion demonstrates an excellent healing performance of 91.2%, with the tensile strength of 5.7 +/- 0.8 MPa at room temperature for 24 h is much higher than the covalently cross-linked elastomers. The metal-ligand coordination bonds are entirely dynamic and thermoreversible during the rebuilding process and obtain an excellent self-healing property than the sulfur curing system.
查看更多>>摘要：Injectable hydrogels possess strict requirements of network structure and biocompatibility for cell therapy. It is highly required to load and deliver cells with no damage during the injection operation and accelerate their proliferation after injection at the lesions. Herein, naturally derived chitosan (CS) and hyaluronic acid (HA) were chemically modified to synthesize methylacrylylated chitosan (CSMA) and aldehyde-containing hyaluronic acid (OHA). The imine cross-linkage can be rapidly constructed and reversibly broken between amino and aldehyde groups, endowing the resulting hydrogel with highly efficient mechanical adaptivity, including shearing-thinning and fast self-healing. Besides, the methacrylate groups of CSMA can be cross-linked by photoinitiation, making the dynamic hydrogel with adjustable elasticity and modulus to match the cell culture. The dynamic crosslinked hydrogel demonstrated good compatibility with a wide variety of body cells and bone marrow mesenchymal stem cells (BMSCs). Benefiting from the excellent mechanical adaptivity and cytocompatibility, BMSCs were in situ encapsulated in the dynamic hydrogel and then extruded through a clinically used syringe. Remarkably, the percentage of living cells still reached 87.6% after injection, with no significant cell damage compared with their original state before injection. Moreover, the osteogenic and chondrogenic differentiation abilities of stem cells were not affected by the extrusion injection due to the mechanically adaptive three-dimensional network of the dynamic hydrogel. Taken together, the proposed mechanically adaptive "all-sugar" hydrogels intensify the cellladen injectability and enhance the long-term viability of cell culture, which shows great potential in the field of cell therapy and tissue engineering.
查看更多>>摘要：Thermoresponsive bilayer hydrogels have gained attention due to their fast response time and excellent recovery. A side-by-side capillary-based microfluidic device has been used to produce thermoresponsive Janus fibers by photopolymerization of monomer streams. These fibers had one of their parts consisting in a thermoresponsive polymer obtained from oligo(ethylene glycol) acrylate, 2-ethoxyethyl acrylate, and poly(ethylene glycol) diacrylate, while the other one consisted in a non-thermoresponsive polymer. The fibers showed reversible coiling and uncoiling phenomena with two temperature transitions upon heating (and cooling). The unexpected dual thermoresponsiveness was investigated by screening a wide range of parameters including the nature of the photoinitiator and comonomers. The transition temperatures were tuned from 0 to 80 degrees C by varying the comonomer composition, but also the nature and concentration of the crosslinker used. The ability of these Janus fibers to act as thermally-triggered actuators was demonstrated by performing up to four heating-cooling cycles and attaching a small weight at one of the extremities of the fiber. These results pave the way to the development of easily tunable polymer-based fibrous thermoactuators.
查看更多>>摘要：In order to improve the poor degradability of polybutylene succinate (PBS) in marine environment, a series of copolyesters called poly(butylene succinate-co-epsilon-caprolactone)s (PBSCLs) were synthesized by one-pot melt polycondensation technique. Such copolyesters had excellent mechanical properties, with tensile strengths from 26.4 MPa to 47.6 MPa and elongation at break around 450%. In addition, the introduction of CL segment decreased the crystallinity and increased the hydrophilicity. Furthermore, four different degradation environments were settled to investigate the enzymatic hydrolysis, compost degradation, non-enzymatic hydrolysis, and natural seawater degradation performances of PBSCL copolyesters. The biodegradation and hydrolysis performances of the copolyesters were significantly different compared with PBS. Faster degradation of the copolyesters was detected not only in buffer solution with CALB and compost, but also in buffer solution and natural seawater. Besides, different degradation mechanisms, namely bulk erosion and surface erosion, coexisted during non-enzymatic hydrolysis and natural seawater degradation process. The higher CL content, the more the degradation mechanism of the copolyester was inclined to the latter.
Guerrero, FedericoDe la Flor, SilviaRamis, XavierSantos, Jose-Ignacio...
10页
查看更多>>摘要：Organic-inorganic hybrid materials combine the advantages of both phases: hardness and strength of inorganic phase and elasticity and toughness of the organic matrix. In the present study, we have prepared nanocomposites with a poly(thiourethane) polymeric matrix and silsesquioxane-type structures, with thiols as reactive groups (POSS-A or POSS-B, synthesized in different pressure conditions), looking for a covalent interaction between both phases, and good dispersion. Due to the click behavior of the reaction between the isocyanate and the thiol groups, highly homogeneous materials are obtained. Both monomers, catalyst (dibutyltin dilaurate, DBTDL), and the POSS precursor (3-mercaptopropyl trimethoxysilane, MPTMS), are commercially available, which present the advantage of being industrially scalable. The incorporation of POSS leads to an increase in glassy and rubbery storage moduli and the temperature of the maximum of tan delta curve. The vitrimeric behavior of the poly(thiourethanes) improved with the POSS incorporation, getting lower relaxation times. With a higher proportion of closed cages, POSS-B leads to the most significant improvements. All the materials prepared showed high transparency and the fracture of POSS modified materials indicates an improved toughness.
查看更多>>摘要：Elastomers that services under ultra-low temperature environments are of great strategic and technological importance. Among them, polysiloxanes are excellent precursors, however, the unfavorable crystallization greatly limits its ultra-low temperature application. Herein, we explore the synthesis, glass transition temperature (Tg), cross-linking behavior and long-time ultra-low temperature elasticity characterization of polydimethylsiloxane (PDMS) with flexible alkyl branches. The results demonstrated that the flexible alkyl branches play a dual role in PDMS, for it can not only unlock its ultra-low temperature elasticity by suppressing crystallization, but also provide more free radical attack sites to enhance the cross-linking activity. The resulting elastomer with a Tg lower than -120 degrees C exhibits excellent elasticity at such a low temperature down to -110 degrees C. Moreover, the facile and efficient one-step thiol-ene addition post-polymerization enables the large-scale preparation of this ultra-low temperature elastomer. The work demonstrated here reveals a general practical strategy to unlock PDMS ultra-low temperature performance, which is conducive to the development of cutting-edge scientific research.
Lee, Chang OhJo, Jin HuiRyu, Gun YoungJae, Hyunmo...
12页
查看更多>>摘要：Polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS)-ionic liquid (IL) block-graft copolymer was synthesized via a three-step process, including chloromethylation, quaternization, and anion exchange. The SEBS-IL block-graft copolymer exhibited good compatibility with the IL, affording defect-free SEBS-IL/IL membranes. The IL domain had a good affinity for specific gas molecules such as CO2 to allow selective gas solubility. In addition, the SEBS-IL/IL membranes exhibited a well-defined microphase-separated structure to achieve efficient transport pathways for the gas molecules. Consequently, a significant improvement in gas separation performance (permeability and selectivity) approaching the Robeson upper bound limit was achieved. In particular, the SEBS-IL/IL 50% membrane showed an H-2 permeability of 90.8 Barrer and CO2 permeability of 134 Barrer with CO2/N-2 selectivity of 26, CO2/CH4 selectivity of 10.6, H-2/N-2 selectivity of 17.6, and H-2/CH4 selectivity of 7.2. These gas permeation parameters were 2-3 times higher than those of pristine SEBS membrane. The presented SEBS-IL/IL membrane approach provides important insights to rationally design a microphase-separated polymer structure based on high compatibility with IL monomer for efficient gas separations.
NSTL
Elsevier