Nano‐sized polyacrylonitrile (PAN) colloidal dispersions of 44.6 ± 8.3 nm prepared by the modified emulsion polymerization method are utilized for gas separation. The emulsion (o/w) polymerization ...using organic solvent instead of precipitation polymerization is utilized, and both the size of the colloidal particle and the zeta potential could be controlled by the content of the material constituting emulsion. Thus, the solubility of CO2 is dependent on the zeta potential on the surface of colloids, resulting in that the degree of absorption of CO2 is controllable. Then, N2/CO2 separation experiment is carried out by applying the synthesized PAN colloidal dispersions into a polymer composite. The composite membranes are prepared by adding PAN colloidal dispersions based on poly(vinyl pyrrolidone) (PVP). It is observed that the neat PVP membrane has no separation performance, while the PVP/PAN colloidal composite film shows the improved N2/CO2 selectivity of 17. This improved separation performance is due to the fact that the solubility of CO2 decreased by absorption to specific functional groups, resulting in the enhancement of N2 separation.
Nano‐sized polyacrylonitrile (PAN) particles, approximately 44.6 nm, are utilized for gas separation, where their size and zeta potential are tuned by altering the emulsion formula, which in turn controls carbon dioxide (CO2) absorption levels. PAN particles are incorporated into polymer composites with poly(vinyl pyrrolidone) for N2/CO2 separation, achieving a selectivity of 17 by decreasing CO2 solubility, thereby enhancing nitrogen separation efficiency.
Electronic devices based on a series of synthesized block copolymers are demonstrated. In particular, a block copolymer system with a lamellar structure exhibits unipolar switching behavior. This ...study provides a simple strategy based on the adjustment of the block ratio in block copolymers to control the polymer morphology and thus the electrical and switching properties of polymer‐based memory devices.
A block copolymer that can be thermally cross-linked is synthesized by copolymerization of
N
-phenyl-2-vinylcarbazole
(A)
and trimethyl(2-(4-vinylphenyl)ethynyl)silane
(B)
, followed by a ...deprotection reaction (d-P
BAB
). A triblock copolymer containing carbazole and (trimethylsilyl)ethynyl groups (P
BAB
) is first prepared using potassium naphthalenide in tetrahyrdofuran at −78 °C for 60 min. Well-controlled poly
(A)
and P
BAB
can be obtained under the conditions employed in this anionic block copolymerization. The well-defined d-P
BAB
with thermally cross-linkable ethynyl group is then prepared by the deprotection of the trimethylsilyl group from P
BAB
without side reactions. The thermal cross-linking behavior of d-P
BAB
is investigated using thermogravimetric analysis and differential scanning calorimetry. The d-P
BAB
is cross-linked under different conditions, and it is observed that the d-P
BAB
film heated at 250 °C for 60 min shows excellent solvent resistance and increased film density. In addition, the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of cross-linked d-P
BAB
are estimated to be −5.09 and −1.57 eV, respectively.
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•Block copolymer containing silicon atom is precisely synthesized in a living manner.•Relationship between χ value and self-assembled pattern quality is systemically ...demonstrated.•High-χ block copolymer is able to form the patterns with more improved quality.
Directed self-assembly (DSA) of block copolymers (BCPs) is among the best alternative methods for achieving traditional top-down lithography because BCPs can form well-ordered nanostructures, such as spheres, cylinders, gyroids, and lamellae, with a controlled domain size (d) of 10–50 nm. However, regarding the pattern quality, further development of BCPs to satisfy industrial demands is still necessary. Here, a well-defined BCP, poly(4-(tert-butyldimethylsiloxy)styrene-b-2-vinylpyridine) (P4BDSS-b-P2VP), was synthesized to investigate the relationship between the Flory-Huggins interaction parameter (χ) and the self-assembled pattern quality by comparing it with poly(styrene-b-4-(tert-butyldimethylsiloxy)styrene) (PS-b-P4BDSS). It was confirmed that the higher χ value of P4BDSS-b-P2VP (0.128 at 25 °C) than that of PS-b-P4BDSS (0.0525 at 25 °C) calculated based on small-angle X-ray scattering (SAXS) analysis and Leibler’s mean field theory was beneficial to pattern quality in DSA. The line edge roughness (LER) and line width roughness (LWR) of P4BDSS-b-P2VP were 1.33 and 2.73 nm, respectively, which were lower than those of PS-b-P4BDSS (2.29 and 3.52 nm, respectively).
Abstract
Metformin increased cellular ROS levels in AsPC-1 pancreatic cancer cells, with minimal effect in HDF, human primary dermal fibroblasts. Metformin reduced cellular ATP levels in HDF, but not ...in AsPC-1 cells. Metformin increased AMPK, p-AMPK (Thr172), FOXO3a, p-FOXO3a (Ser413), and MnSOD levels in HDF, but not in AsPC-1 cells. p-AMPK and p-FOXO3a also translocated from the cytosol to the nucleus by metformin in HDF, but not in AsPC-1 cells. Transfection of si-FOXO3a in HDF increased ROS levels, while wt-FOXO3a-transfected AsPC-1 cells decreased ROS levels. Metformin combined with apigenin increased ROS levels dramatically and decreased cell viability in various cancer cells including AsPC-1 cells, with each drug used singly having a minimal effect. Metformin/apigenin combination synergistically decreased mitochondrial membrane potential in AsPC-1 cells but to a lesser extent in HDF cells. Metformin/apigenin combination in AsPC-1 cells increased DNA damage-, apoptosis-, autophagy- and necroptosis-related factors, but not in HDF cells. Oral administration with metformin/apigenin caused dramatic blocks tumor size in AsPC-1-xenografted nude mice. Our results suggest that metformin in cancer cells differentially regulates cellular ROS levels via AMPK-FOXO3a-MnSOD pathway and combination of metformin/apigenin exerts anticancer activity through DNA damage-induced apoptosis, autophagy and necroptosis by cancer cell-specific ROS amplification.
Copolymer composed of two poly(2-vinylpyridine) blocks and one polystyrene block ((P2VP)2–PS) with a PS volume fraction (ΦPS) of 0.44 was synthesized, and their morphologies in bulk and thin films ...were compared to linear block copolymers (BCPs) having a similar ΦPS (PS-b-P2VP). For the symmetric diblock copolymer, a lamellar morphology was observed after thermal annealing, as was expected. However, (P2VP)2–PS in the bulk showed a hexagonally packed cylindrical microdomain morphology with PS forming the cylindrical microdomains in a P2VP matrix. In thin films, after solvent annealing in the vapors of a chloroform/ethanol mixture, the cylindrical microdomain morphology was retained and the microdomains were oriented parallel to the substrate surface. With the addition of ethanol into the annealing solvent, the morphology of (P2VP)2–PS was transformed from a bicontinuous morphology to one with cylindrical microdomains of PS oriented parallel to the substrate. The lamellar microdomain of the PS-b-P2VP copolymer changed to a morphology composed of PS cylindrical microdomains oriented normal to the substrate. The different orientations of the morphologies arise from the preferential interaction of P2VP with the substrate and the mediation of these interactions by the solvent. The morphological evolution of (P2VP)2-PS thin films was also investigated as a function of SVA time to optimize well-defined microstructures where an orientation of the microdomains parallel to the substrate occurred within 180 s. By use of a faceted sapphire substrate having a sawtoothed topography, highly aligned line patterns were achieved.
A novel polymer, poly(2‐(N ‐carbazolyl)ethyl methacrylate) end‐capped with fullerene (PCzMA‐C60), has been synthesized via living anionic polymerization. Electrically programmable flash memory ...devices were easily fabricated with this polymer by using solution coating and metal deposition. This polymer was found in these devices to exhibit bipolar and unipolar switching behaviors with a high ON/OFF current ratio, a long retention time, high reliability, and low power consumption. The excellent properties and easy processability of this polymer open up the possibility of the mass production of high performance nonvolatile memory devices at low cost.
Among the various types of shape changing materials, liquid crystal elastomers (LCEs) have received significant attention as they can undergo programmed and reversible shape transformations. The ...molecular engineering of LCEs is the key to manipulating their phase transition, mechanical properties, and actuation performance. In this work, LCEs containing three different types of butyl groups (n-, iso-, and sec-butyl) in the side chain were synthesized, and the effect of isomeric amine chain extenders on the thermal, mechanical, and actuation properties of the resulting LCEs was investigated. Because of the considerably low reactivity of the sec-butyl group toward the diacrylate in the LC monomer, only a densely crosslinked LCE was synthesized. Most interestingly, the mechanical properties, actuation temperature, and blocking stress of the LCEs comprising isobutyl groups were higher than those of the LCEs comprising n-butyl groups. This difference was attributed to the presence of branches in the LCEs with isobutyl groups, which resulted in a tighter molecular packing and reduced the free volume. Our results suggest a facile and effective method for synthesizing LCEs with tailored mechanical and actuation properties by the choice of chain extenders, which may advance the development of soft actuators for a variety of applications in aerospace, medicine, and optics.
We report high-performance and air-stable organic field-effect transistors (OFETs) fabricated with thermally cross-linked bottlebrush polymers as gate dielectrics. By synthesizing bottlebrush ...polymers with a varying degree of polymerization, we investigate the effect of the density of alkyne functional groups on the on-set cross-linking time (t c) and dielectric properties of the bottlebrush polymer thin films. The bottlebrush polymer with the highest density of alkyne groups shows the lowest t c of 0.6 min, and t c values increase to 0.8, 1, and 30 min as the density of alkyne groups decreases. These t c values are unambiguously shorter than that (t c > 120 min) of the most widely used polymer gate dielectric, poly(methyl methacrylate) (PMMA). The top-gate/bottom-contact OFET fabricated with poly{N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl-alt-5,5′-(2,2′-bithiophene)} and the bottlebrush polymer gate dielectric cross-linked in 1 min shows the highest charge carrier mobility (μ = 0.16 cm2 V–1 s–1) and extended device lifetime (120 h) compared to those of OFETs fabricated with the other bottlebrush polymers and PMMA gate dielectrics. Considering the sufficiently reduced t c (≤1 min) and excellent device properties of bottlebrush polymers, these results demonstrate that thermally cross-linkable bottlebrush polymers without any cross-linking agents would be promising materials for developing high-performance and reliable OFETs fabricated by a high-throughput fabrication method.
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