Ionic liquids with reversible photo-induced conductivity regulation in aqueous solution.

Stimulus-responsive ionic liquids have gained significant attention for their applications in various areas. Herein, three kinds of azobenzimidazole ionic liquids with reversible photo-induced conductivity regulation were designed and synthesized. The change of electrical conductivity under UV/visible light irradiation in aqueous solution was studied, and the effect of chemical structure and concentration of ionic liquids containing azobenzene to the regulation of photoresponse conductivity were discussed. The results showed that exposing the ionic liquid aqueous solution to ultraviolet light significantly increased its conductivity. Ionic liquids with longer alkyl chains exhibited an even greater increase in conductivity, up to 75.5%. Then under the irradiation of visible light, the electrical conductivity of the solution returned to its initial value. Further exploration of the mechanism of the reversible photo-induced conductivity regulation of azobenzene ionic liquids aqueous solution indicated that this may attributed to the formation/dissociation of ionic liquids aggregates in aqueous solution induced by the isomerization of azobenzene under UV/visible light irradiation and resulted the reversible conductivity regulation. This work provides a way for the molecular designing and performance regulation of photo-responsive ionic liquid and were expected to be applied in devices with photoconductive switching and micro photocontrol properties.

Up/Down Tuning of Poly(ionic liquid)s in Aqueous Two-Phase Systems.

Thermally induced reversible up/down migration of poly(ionic liquid)s (PILs) in aqueous two-phase systems (ATPSs) was achieved for the first time in this study. Novel ATPSs were fabricated using azobenzene (Azo)- and benzyl (Bn)-modified PILs, and their upper and lower phases could be easily tuned using the grafting degree (GD) of the Azo and Bn groups. Bn-PIL with higher GDBn could go up into the upper phase and Azo-PIL come down to the lower phase when the temperature increased (>65 °C); this behavior was reversed at lower temperatures. Moreover, a reversible two-phase/single-phase transition was realized under UV irradiation. Experimental and simulation results revealed that the difference in the hydration capacity between Bn-PIL and Azo-PIL accounted for their unique phase-separation behavior. A versatile platform for fabricating ATPSs with tunable stimuli-responsive behavior can be realized based on our findings, which can broaden their applications in the fields of smart separation systems and functional material development.

Functional Porous Ionic Polymers as Efficient Heterogeneous Catalysts for the Chemical Fixation of CO2 under Mild Conditions.

The development of efficient and metal-free heterogeneous catalysts for the chemical fixation of CO2 into value-added products is still a challenge. Herein, we reported two kinds of polar group (-COOH, -OH)-functionalized porous ionic polymers (PIPs) that were constructed from the corresponding phosphonium salt monomers (v-PBC and v-PBH) using a solvothermal radical polymerization method. The resulting PIPs (POP-PBC and POP-PBH) can be used as efficient bifunctional heterogeneous catalysts in the cycloaddition reaction of CO2 with epoxides under relatively low temperature, ambient pressure, and metal-free conditions without any additives. It was found that the catalytic activities of the POP-PBC and POP-PBH were comparable with the homogeneous catalysts of Me-PBC and PBH and were higher than that of the POP-PPh3-COOH that was synthesized through a post-modification method, indicating the importance of the high concentration catalytic active sites in the heterogeneous catalysts. Reaction under low CO2 concentration conditions showed that the activity of the POP-PBC (with a conversion of 53.8% and a selectivity of 99.0%) was higher than that of the POP-PBH (with a conversion of 32.3% and a selectivity of 99.0%), verifying the promoting effect of the polar group (-COOH group) in the porous framework. The POP-PBC can also be recycled at least five times without a significant loss of catalytic activity, indicating the high stability and robustness of the PIPs-based heterogeneous catalysts.

Stable Porous Organic Polymers Used for Reversible Adsorption and Efficient Separation of Trace SO2.

The development of porous solid adsorbents for selective adsorption and separation of SO2 has attracted much attention recently. Herein, we design porous organic polymers (POPs) decorated with pyridine ligands as building units (POP-Py) through a radical polymerization of the 2,5-divinylpyridine (v-Py) monomer. Due to its high BET surface area, nanoporosity, and excellent stability, the prepared POP-Py can be used for reversible adsorption and efficient separation of SO2. The POP-Py possesses a SO2 capacity of 10.8 mmol g-1 at 298 K and 1.0 bar, which can be well retained after 6 recycles, showing an excellent reversible adsorption capacity. The POP-Py also shows superior separation performance for SO2 from a ternary SO2/CO2/N2 mixture (0.17/15/84.83v%), giving a breakthrough time and a saturated SO2 capacity at 178 min g-1 and 0.4 mmol g-1. The retention time was well maintained even under high moisture conditions, confirming its superior water resistance. Furthermore, when other vinyl-functionalized organic ligand monomers (bipyridine, pyrimidine, and pyrazine) were employed for radical polymerization, all of the resultant porous organic ligand polymers (POP-BPy, POP-PyI, and POP-PyA) exhibited superior performance for reversible adsorption and efficient separation of SO2. The combined features of reversible adsorption, efficient separation, and water resistance are important for the industrial applications of these materials as SO2 adsorbents.

Different functional groups modified porous organic polymers used for low concentration CO2 fixation.

Through a facile post-synthetic method, different kinds of polar group-functionalized ionic liquid porous organic polymers (POP-PA-COOH, POP-PA-OH, and POP-PA-NH2) were obtained. The materials can be used as efficient heterogeneous catalysts in the cycloaddition reaction of CO2 with epoxides under mild and co-catalyst-free conditions. It is demonstrated that POP-PA-NH2 possesses much higher catalytic activity than POP-PA-OH and POP-PA-COOH. Interestingly, this activity difference can further be amplified when the reaction is carried out under low CO2 concentration, and POP-PA-NH2 possesses a conversion of 84.7% with a selectivity of 99.0% in 96 h. It is noteworthy to mention that research focusing on the transformation of CO2 under low concentration using heterogeneous catalysts is rare and still a challenge. The excellent activities of POP-PA-NH2 under low CO2 concentration make this material a good candidate for CO2 elimination under mild conditions.

Nitrogen and sulfur-codoped porous carbon derived from a BSA/ionic liquid polymer complex: multifunctional electrode materials for water splitting and supercapacitors.

Bovine serum albumin (BSA) was complexed with a hydrophobic ionic liquid polymer (PIL) via electrostatic interaction to fabricate a carbon precursor. Then, a novel nitrogen (N) and sulfur (S) codoped micro-/mesoporous carbon (NSPC) was obtained via direct carbonization of the interpolyelectrolyte BSA@PIL complex. The newly developed NSPC materials exhibited excellent HER/OER electrocatalytic activity and stability, as well as outstanding capacitance performance. Remarkably, NSPC pyrolyzed at 1000 degrees (NSPC-1000) presented an overpotential as low as 172 mV vs. RHE (without iR correction) to achieve a current density of 10 mA cm-2 and a Tafel slope of 44.3 mV dec-1 in 0.5 M H2SO4 for HER, as well as a low overpotential of 460 mV vs. RHE in 0.1 M KOH for OER. Furthermore, NSPC-1000 offers a specific capacitance as high as 495 F g-1 at a current density of 0.1 A g-1. Such excellent performance of NSPC in electrocatalytic water splitting and supercapacitors originates from the synergistic effects of its N/S-codoping and micro-/mesoporous hierarchical architecture. Our facile protocol through combining biomacromolecules and synthetic polymers offers a new strategy in the development of effective, readily scalable and metal-free heteroatom-doped carbon materials for energy-related applications.

Reutilization of discarded biomass for preparing functional polymer materials.

Biomass is abundant and recyclable on the earth, which has been assigned numerous roles to human beings. However, over the past decades, accompanying with the rapid expansion of man-made materials, such as alloy, plastic, synthetic rubber and fiber, a great number of natural materials had been neglected and abandoned, such as straw, which cause a waste of resource and environmental pollution. In this review, based on introducing sources of discarded biomass, the main composition and polymer chains in discarded biomass materials, the traditional treatment and novel approach for reutilization of discarded biomass were summarized. The discarded biomass mainly come from plant wastes generated in the process of agriculture and forestry production and manufacturing processes, animal wastes generated in the process of animal husbandry and fishery production as well as the residual wastes produced in the process of food processing and rural living garbage. Compared with the traditional treatment including burning, landfill, feeding and fertilizer, the novel approach for reutilization of discarded biomass principally allotted to energy, ecology and polymer materials. The prepared functional materials covered in composite materials, biopolymer based adsorbent and flocculant, carrier materials, energy materials, smart polymer materials for medical and other intelligent polymer materials, which can effectively serve the environmental management and human life, such as wastewater treatment, catalyst, new energy, tissue engineering, drug controlled release, and coating. To sum up, the renewable and biodegradable discarded biomass resources play a vital role in the sustainable development of human society, as well as will be put more emphases in the future.

An autonomic self-healing organogel with a photo-mediated modulus.

A new method is described for fabricating autonomic, self-healing, deformable organogels. We combined imidazolium-based poly(ionic liquid) (PIL) and azobenzene-grafted poly(carboxylic acid) (PAA-Azo) in N,N-dimethyl formamide. Further, complexing PIL with unirradiated (trans) or irradiated (cis) PAA-Azo tuned the elastic modulus of the organogel.

Manipulating pH using near-infrared light assisted by upconverting nanoparticles.

Near-infrared light can be used to manipulate the pH of aqueous solutions by using upconverting nanoparticle-assisted photocleavage of a ruthenium complex photobase. Upconverting nanoparticles and the photobase were also introduced into a pH-responsive hydrogel, in which near-infrared irradiation induced swelling of the hydrogel.

Fabrication of dual-sensitive keratin-based polymer hydrogels and their controllable release behaviors.

Using feather keratin (FK) as a biocompatible and inexpensive biopolymer, a kind of dual-sensitive keratin-based polymer hydrogel (FK/PNiPA/PIAc-Gel) with interpenetrating network structure was prepared by two-step polymerization of N-isopropyl acrylamide (NiPA) and itaconic acid (IAc) in presence of crosslinker. After being characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy, its swelling behaviors and environmental sensitivity were investigated. The obtained biopolymer based hydrogel has good swelling and deswelling performance, and it is sensitive to pH value, temperature and salts of environment. Using anticancer drug, doxorubicin hydrochloride (Dox·HCl),  and Bovine serum albumin (BSA) as different drug molecules, its release behaviors in different environment were investigated. It was found that the release behaviors of FK/PNiPA/PIAc-Gel were controllable via adjusting pH value or temperature of environment. The cumulative release of the anticancer drug (Dox·HCl) reached 93.3% within 16 h, and the cumulative release rate of macromolecular drug (BSA) got to 75.9% in 24 h. In summary, the keratin-based biopolymer hydrogel with interpenetrating network structure, pH-sensitivity and temperature sensitivity are potentially applied to sustain drug carrier and humid medicinal material in the biomedical field or clinical nursing field.

Preparation of Thermo-Responsive Poly(ionic liquid)s-Based Nanogels via One-Step Cross-Linking Copolymerization.

In this study, thermo-responsive polymeric nanogels were facilely prepared via one-step cross-linking copolymerization of ethylene glycol dimethacrylate/divinylbenzene and ionic liquid (IL)-based monomers, 1,n-dialkyl-3,3'-bis-1-vinyl imidazolium bromides ([CnVIm]Br; n = 6, 8, 12) in selective solvents. The results revealed that stable and blue opalescent biimidazolium (BIm)-based nanogel solutions could be obtained without any precipitation when the copolymerizations were conducted in methanol. Most importantly, these novel nanogels were thermo-response, and could reversibly transform to precipitation in methanol with temperature changes. Turbidity analysis and dynamic light scatting (DLS) measurement illustrated that PIL-based nanogel solutions presented the phase transform with upper critical solution temperature (UCST) in the range of 5-25 °C. The nanogels were characterized using Fourier transform infrared (FTIR), thermogravimetric analyses (TGA), and scanning electron microscopy (SEM). In addition, BIm-based nanogels could also be used as highly active catalysts in the cycloaddition reaction of CO2 and epoxides. As a result, our attributes build a robust platform suitable for the preparation of polymeric nanomaterials, as well as CO2 conversion.

One-step synthesis of thermosensitive nanogels based on highly cross-linked poly(ionic liquid)s.

A gel for all seasons: Thermosensitive nanogels based on highly cross-linked poly(ionic liquid)s (CLPNs) were prepared in one step by the copolymerization of imidazolium-based monomers with cross-linkers in selective solvents. Reversible nanogel-macrogel transitions of CLPNs in methanol could be achieved by changing the temperature.

Amphiphilic cholic-acid-modified dextran sulfate and its application for the controlled delivery of superoxide dismutase.

A novel amphiphilic and biodegradable polyelectrolyte DS-CA is prepared by the esterification of DS with CA. DS-CA can self-assemble into stable nanoparticles in water. SOD can effectively associate with DS-CA at pH = 5.0 by virtue of electrostatic and hydrophobic interactions. SOD release from the complex nanoparticles is slow at pH = 1.2. The release at pH = 7.4 PBS shows an extended behavior and is tunable by changing the weight ratio of SOD to DS-CA as well as the CA substitution degree. Increasing the CA substitution degree of DS-CA can significantly enhance the cellular uptake of the loaded SOD. This study demonstrates that the amphiphilic DS-CA provides a promising strategy for oral delivery of protein/peptide drugs.

A facile one-step synthesis to cross-linked polymeric nanoparticles as highly active and selective catalysts for cycloaddition of CO2 to epoxides.

A very convenient one-step synthesis to cross-linked polymeric nanoparticles by conventional radical copolymerization without the addition of stabilizers or surfactants was explored. Moreover, these nanoparticles exhibited excellent stability, activity and selectivity in the cycloaddition reaction of CO(2) to epoxides and could be separated from the products easily and reused.