Structure-Property Relationships of CO2 Absorbing Core-Shell Microparticles with Encapsulated Ionic Liquid.

The demand for new ionic liquid (IL)-based systems to selectively sequester carbon dioxide from gas mixtures has prompted the development of individual components involving the tailored design of IL themselves or solid-supported materials that provide excellent gas permeability of the overall material as well as the ability to incorporate large amounts of ionic liquid. In this work, novel IL-encapsulated microparticles comprising a cross-linked copolymer shell of ß-myrcene and styrene and a hydrophilic core of the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) are proposed as viable materials for CO2 capture. Water-in-oil (w/o) emulsion polymerization of different mass ratios of ß-myrcene to styrene (i.e. 100/0, 70/30, 50/50, 0/100) yielded IL-encapsulated microparticles, where the encapsulation efficiency of [EMIM][DCA] was dependent on the copolymer shell composition. Thermal analysis using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed that both thermal stability and glass transition temperatures depend on the mass ratio of ß-myrcene to styrene. Images from scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the microparticle shell morphology as well as measure the particle size perimeter. Particle sizes were found to be between 5 and 44 µm. CO2 sorption experiments were conducted gravimetrically using TGA instrumentation. Interestingly, a trade-off between CO2 absorption capacity and ionic liquid encapsulation was observed. While increasing the ß-myrcene content within the microparticle shell increases the amount of encapsulated [EMIM][DCA], the observed CO2 absorption capacity did not increase as expected due to reduced porosity compared to microparticles with higher styrene content in the microparticle shell. [EMIM][DCA] microcapsules with a 50/50 weight ratio of ß-myrcene/styrene showed the best synergistic effect between spherical particle diameter (32.2 µm), pore size (0.75 µm), and high CO2 sorption capacity of ∼0.5 mmol CO2/g sample within a short absorption period of 20 min. Therefore, core-shell microcapsules composed of ß-myrcene and styrene are envisioned as a promising material for CO2 sequestration applications.

The Impacts of Polyisoprene Physical Interactions on Sorting of Single-Wall Carbon Nanotubes.

Conjugated polymer sorting is currently the best method to select large-diameter single-walled carbon nanotubes (SWCNTs) with tunable narrow chirality in the adaption of highly desired electronics applications. The acceleration on conjugated polymers-SWCNTs interaction with long-term stability through different molecular designs; for example, longer alkyl side-chains or conjugation moieties have been extensively developed in recent years. However, the importance of the macromolecules with abundant van der Waals (VDW) interaction in the conjugated-based block copolymer system acting during SWCNTs sorting is not clearly demonstrated. In this work, a conjugated diblock copolymer involving polyisoprene (PI) and highly dense π-interaction of poly (9,9-dioctylfluorene) (PFO) is utilized to investigate the impact of natural rubber PI physical interaction on sorting effectiveness and stability. Through the rational design of diblock copolymer, PFO with ≈1200 isoprene units can remarkably enhance SWCNTs sorting ability and selected few chiralities with a diameter of ≈0.83-1.1 nm and highly stable solution for more than 1 year. The introduction of long-chain PI system is attributed not only to form weak VDW force with SWCNTs and strengthen the wrapping of PFO around the semiconducting SWCNTs but also to act as a barrier among nanotubes to prevent reaggregation of sorted SWCNTs.

Improving the Lifetime of CsPbBr3 Perovskite in Water Using Self-Healing and Transparent Elastic Polymer Matrix.

This study developed a simple and efficient strategy to stabilize inorganic halide perovskite CsPbX3 at high relative humidity by embedding it into the matrix with elastic and self-healing features. The polymer matrix has a naturally hydrophobic characteristic of n-butyl acrylate segment (n-BA) and cross-linkable and healable moiety from N-(hydroxymethyl) acrylamide segment (NMA). It was chosen due to the provisions of both a surrounding protective layer for inorganic perovskite and elastic, as well as healing ability to the whole organic-inorganic composite. This fabricated CsPbBr3/PBA-co-PNMA composite was demonstrated to stably persist against the suffering from hydrolysis of perovskites when exposed to a high moisture environment. The PL intensity of the composite after crosslinking was found to be relatively stable after 30 days of exposure to air. Upon water immersion, the PL intensity of composite only showed a decrease of 32% after the first 6 h, then remained stable for 6 h afterward. Furthermore, this fabricated composite was not only flexible and relatively transparent but also exhibited excellent self-healing capability in ambient conditions (T = 25°C), in which the self-healing efficiency after 24 h was above 40%. The tensile strength and stretching ability of 5 wt% perovskite content in the random copolymer were observed to be 3.8 MPa and 553.5% respectively. Overall, flexible and self-healing properties combining with high luminescence characteristics are very promising materials for next-generation soft optical devices.

Exploitation of Thermoresponsive Switching Organic Field-Effect Transistors.

In this work, a novel thermoresponsive switching transistor is developed through the rational design of active materials based on the typical field-effect transistor (FET) device configuration, where the active material is composed of a blend of a thermal expansion polymer and a polymeric semiconductor. Herein, polyethylene (PE) is employed as the thermal expansion polymer because of its high volume expansion coefficient near its melting point (90-130 °C), which similarly corresponds to the overheating point that would cause damage or cause fire in the devices. It is revealed that owing to the thermistor property of PE, the FET characteristics of the derived device will be largely decreased at high temperatures (100-120 °C). It is because the high volume expansion of PE at such high temperature (near its T m) effectively increases the distance of the crystalline domains of poly(3-hexylthiophene-2,5-diyl) to result in a great inhibition of current. Besides, the performance of this device will recover back to its original value after cooling from 120 to 30 °C owing to the volume contraction of PE. The reversible FET characteristics with temperature manifest the good thermal sensitivity of the PE-based device. Our results demonstrate a facile and promising approach for the development of next-generation overheating shutdown switches for electrical circuits.

Iodine-loaded metal organic framework as growth-triggered antimicrobial agent.

Zeolitic imidazolate framework-8 (ZIF-8) is one of easily available metal organic frameworks because of its facile preparation via mixing aqueous solutions of zinc nitrate and 2-methylimidazole. It turned into a very effective pH-responsive bactericide after loading with iodine. Approximately, 0.9g of iodine could be readily loaded into one gram of ZIF-8 from iodine dissolved n-heptane solution. Both Gram-negative Escherichia coli and Gram-positive Staphylococcus epidermidis and Staphylococcus aureus could be very effectively killed by iodine loaded ZIF-8 (ZIF-8@I) at pH6.0 within 3min. In contrast, at pH above 7.0, no appreciable antimicrobial activity could be detected. The bacteria killing effect is resulted from the iodine released from ZIF-8@I disintegrated at acidic pH. ZIF-8@I coated surface also showed its acidic pH-triggered antimicrobial activity against deposited bacterial cells. The antimicrobial activity of ZIF-8@I against actively grown bacterial lawns on a pH neutral agar plate was also observed. The result demonstrates that iodine was released from the disintegrated ZIF-8@I to kill bacteria in response to the bacterial growth-induced pH lowering.

Bactericidal magnetic nanoparticles with iodine loaded on surface grafted poly(N-vinylpyrrolidone).

Bactericidal magnetic nanoparticles were prepared by complexing iodine with poly(N-vinylpyrrolidone) (PVP) grown at the surface of silica coated magnetic nanoparticles (MNPs) via surface-initiated atom transfer radical polymerization (SI-ATRP). Approximately, 10 mg of iodine could be loaded onto one gram of the PVP-grafted MNPs to form bactericidal MNPs@PVP-I. At a concentration of 5 g L-1, MNPs@PVP-I could achieve 100% bactericidal rate for both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus with a concentration of ∼1 × 1010 CFU mL-1 within 3 min. After being used for killing the bacteria in solution, the bactericidal rate of the MNPs@PVP-I decreased to <10% due to the consumption of iodine. The bactericidal rate could be tuned back to 100% when the used MNPs@PVP-I was recharged in a 15 g L-1 iodine solution for 12 h. The as-prepared bactericidal MNPs@PVP-I could be reused at least 4 times with 100% bactericidal rate by repeatedly recharging it with iodine.