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Self-healing ionic conductors in all solid state without evaporation or leakage offers great potential for the next-generation soft ionotronics. However, it remains challenging to endow ionic conductors with all solid state while keeping their essential features. In this study, an intrinsically conducting polymer is developed as all-solid-state self-healing ionic conductors based on ion-dipole interactions within a fluorinated poly(ionic liquid) copolymer. This unique material possesses good self-healing ability at room temperature (96% of healing efficiency in 24 h), large strain (1800%), optical transparency (96%), and ionic conductivity (1.62 × 10-6 S/cm). The self-healing polymer itself is intrinsically conductive without any additives or fillers, thus it is almost free of evaporation or leaking issues of traditional conducting gels. An alternating-current electroluminescent device with self-healing performance is demonstrated. It is anticipated that this strategy would provide new opportunities for the development of novel self-healing ionotronics.

Herein, we report the first oxygen (O2) and carbon dioxide (CO2) dual gas-switchable thermoresponsive polymers based on a newly synthesized monomer N-(2-fluoroethyl amide)-N-(2-(diethylamino)ethyl) acrylamide, that is, AM(F1EA-DEAE), which bears both O2-switchable fluorinated ethyl amide (F1EA) and CO2-switchable N,N-diethylamino ethyl (DEAE) moieties on its side chain. PolyAM(F1EA-DEAE) samples prepared from reversible addition–fragmentation chain transfer (RAFT) polymerization exhibited good temperature-responsive properties. Their inherent low critical solution temperature (LCST) could be reversibly tuned to different levels by respectively purging O2 or CO2 into its aqueous solution. The O2-treatment shifted LCST to a higher temperature, while the CO2-treatment made the polymer fully water-soluble. The polymer could be readily recovered to its initial state by washing off the trigger gas with an inert gas such as nitrogen. This work provides an effective monomer design approach for the preparation of ...

Gas-responsive polymers have inspired much interest over the past ten years. Gas triggers can interact with functionalities on polymer chains and, thus, modulate their chain structures, architectures, and aggregation states. This review summarizes the latest research progresses in the theme of developing different gas triggers for fine control over some critical properties of polymers, as well as their potential applications in various areas. We focus on the interactions/reactions between gases and gas-responsive functionalities of polymers and highlight some state-of-art developments, which provided good insight and understanding of each particular gas-responsive polymer. We also offer a perspective point of view on future research directions on gas-responsive polymers, both in fundamental studies and in potential application developments.

We report herein a novel approach for preparing CO2- and O2-responsive polymer nanoaggregates. The polymer, synthesized via atom transfer radical polymerization (ATRP), has one hydrophilic poly(ethylene glycol) (PEG) block, and the other hydrophobic block composed of 88 randomly distributed units of CO2-responsive N,N-diethylaminoethyl methacrylate (DEA) and 43 units of O2-responsive 2,2,2-trifluoroethyl methacrylate (FMA). The amphiphilic copolymer self-assembled into vesicular nanoaggregates in water. With O2 bubbling, the vesicles expanded eight times in volume. With CO2 bubbling, the vesicular morphology collapsed and transformed into a small spherical micelle. The dual gas-responsivity significantly expanded the scope in designing stimuli-responsive materials and processes.

Stretchable materials are widely used in various aspects of our daily lives, however, achieving excellent short and long-term damage tolerance in them, i.e., high fracture toughness and fatigue threshold at the same time, remains a challenge. Herein, we report a healable and stretchable material with exceptional damage tolerance based on Al3+ coordinated partiallyamidoximated polyacrylonitrile (Al3+-APAN). Due to the presence of strong coordination bonds and polymer crystalline aggregates, the obtained material exhibits a high fracture toughness of 102.29 ± 5.94 kJ m−2 and a high fatigue threshold of 1.73 ± 0.045 kJ m−2, exceeding those of many natural and synthetic materials. Besides, Al3+-APAN possesses a good tensile strength of up to ∼14 MPa, a high elastic modulus of up to ∼47 MPa, and can be conveniently healed if damaged, thus greatly extending its service time. We believe that this work provides a straightforward strategy to develop tough, healable and stretchable materials with exceptional damage-tolerance for advanced applications such as in protective coatings, wearable electronic devices and soft robotics.

An approach is described for the synthesis of controlled submicron interpenetrating networks with distinct functional features in commodity polymers, based on a mechanism of crazing and polymerization. In this work, ion conductivity was introduced into polyethylene with only minor losses in its mechanical properties, using a highly branched acrylic hydrogel. Control over the porous network developed in the matrix was gained by the addition of a crystallizing nucleating agent, which was used to increase the number and reduce the size of crystallites. Variation of experimental conditions, such as the degree of elongation and applied reaction pressure, produced different morphologies and conductivity for the co-continuous alloy. The samples were deformed in a liquid medium that possessed an affinity for the matrix material, and acted both as a surface-active agent for the crazing, and as a reactant for the conductive phase. Without pressure, deforming by 100% strain yielded a conductivity of 5.67×10⁻⁷ S/cm for the polymer specimen. Simultaneously increasing system pressure while constantly straining a specimen enabled further enhancements in conductivity. As a particular example, elongation of 100% and applied pressure up to 2.76 MPa ensured conductivity nearly equal to that of the pure hydrogel at 4.43×10⁻⁴ S/cm. NSERC

Colorimetric mechanophores, which change color through force-induced covalent bond breakage, have been incorporated into polymer chains to create mechanochromic materials. However, the color change...

This work reports a novel type of reversible shape memory polymers (RSMPs) from commercially available thermoplastic polyolefin elastomers (POEs). Two RSMPs based on Dow Chemical’s POE Engage 8003, Engage 8137, Engage 8180, and olefin block copolymer elastomer Infuse 9007 were prepared by simple blending of the commercial products having different melting temperatures. The multiple and reversible shape memory performances of the as-prepared blends were clearly demonstrated. This work provides a facile and low-cost method for the large-scale preparation of the reversible shape memory materials. It broadens the source of the materials for the design and development of RSMPs.

Objective This study explores the potential role of a highly selective caspase-1 inhibitor, VX-765, on extracellular matrix (ECM) accumulation and inflammation in diabetic nephropathy (DN) and the underlying mechanisms. Methods DN rats, induced via high-fat diet/streptozotocin, were used to assess the effects of VX-765. Parallel experiments were carried out on rat mesangial cell line HBZY-1 exposed to high glucose (HG) to reveal the molecular mechanism of VX-765 in preventing DN. Survival analysis, biochemical parameters and renal oxidative stress of rats were observed, and Western blotting and immunofluorescence were evaluated. In vitro, Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX)1 silencing by RNA interference and quantitative real-time PCR (qPCR) assays were conducted in HBZY-1 cells exposed to HG levels. Key findings In vivo, VX-765 significantly reduced the increase in urine albumin excretion and ECM accumulation. The phosphorylation of nuclear factor kappa-B (NF-κB) and the expression of pro-inflammatory cytokines IL-1β, IL-6 and tumor necrosis factor (TNF)-α were significantly down-regulated. Furthermore, the generation of reactive oxygen species (ROS), phosphorylation of NF-κB and the expression of the NOX1 gene or protein were significantly decreased in HBZY-1 with VX-765 (5 μM) treatment in vitro. Conclusions Our results demonstrated that VX-765 exerts favourable effects on DN via the simultaneous alleviation of systemic metabolic syndrome and down-regulating the renal NOX1/ROS/NF-κB pathway, suggesting that it has therapeutic potential for DN.

This work reports the reversible shape memory polymer (RSMP) by semicrystalline poly(ethylene-co-vinyl acetate) (PEVA) with dynamic covalent polymer networks. The ester linkages in the cross-linked PEVA acted as dynamic covalent bonds in the presence of a transesterification catalyst. This dynamic covalent network imparted the material with good thermal plasticity in a non-flow state at high temperature. The resulting PEVA possessed both the reversible shape memory effect (RSME) and thermadapt property. The thermadapt performance gave little adverse effect on the RSME. This work provides an approach to improve the reprocessability/recyclability of thermoset RSMPs through simple modification of commercially available polymers.

A novel type of comb-branched ethylene/1-octene copolymer elastomers (CPOEs) was synthesized, and their properties were systematically investigated in this work. The polymers had crystalline polyet...

A well-controlled atom transfer radicfal polymerization of methyl acrylate (MA) was realized by mechanical mediation (mechanoATRP) in dimethyl sulfoxide (DMSO, 50% v/v). High conversions of typically over 90% were achieved. The resulting polymers had well-controlled molecular weights and very low dispersities (Đ = 1.03–1.09). No polymerization of MA was observed under various conditions from bulk up to 33.3% DMSO (v/v) solution. It was found that adding an equivalent volume of DMSO with respect to MA activated the polymerization. This finding suggested that DMSO played a crucial role in the mechanoATRP of MA. DMSO not only improved the solubility of CuBr2 complex but also facilitated an electron transfer process in the mechanical reduction of CuBr2. For a proof of the concept, a DMSO analogue acrylate, 2-(methylsulfinyl)ethyl acrylate (MSEA), was also polymerized. In addition, the high chain-end functionality of the polymers collected at ∼95% conversion was confirmed by 1H NMR, MALDI-ToF-MS, and in-situ c...

Controlled synthesis of metal-organic framework (MOF)-based materials with multiple levels of porous structures across different length scales is of great interest in various applications but it still remains challenging. Most of the current strategies are time consuming and labor intensive, and not readily scaled-up. In this work, we introduce a straightforward one-pot fabrication strategy to prepare a robust and flexible hierarchically macro-meso-micro porous HKUST-1/polyvinylidene fluoride (PVDF) composite through solvent evaporation, in which MOF crystallization and polymer precipitation are combined together. The effect of the MOF precursor and the polymer initial amount on the morphology of the final composite was thoroughly studied. The interaction between the MOF and the polymer during the evaporation process is the key factor, which would limit the mobility of the polymer chains and cause instability in the MOF growth, thus endowing the composite with a hierarchically macro-meso-micro porous structure. This "all-in-one" porous structure could enhance the mass transport property of molecules within the composite. The obtained HKUST-1/PVDF composite showed an enhanced CO2 adsorption rate constant of 0.821 min-1 (298 K, 1 bar), which was 3.5 times higher than that of the pristine MOF. In addition, the composite showed an equivalent gas adsorption capacity under all tested pressures and greatly improved water stability.

Mechanoresponsive polymers have garnered significant attention in recent years, due to their great potential application in stress/strain sensing and damage warning. Several reviews of mechanochemistry have been published recently. In this review, we mainly focus on the most established mechanophore, spiropyran (SP), from an engineering perspective. We present a workflow for SP mechanochemistry, applications in various polymeric systems and impacting factors, as well as characterization techniques. Current limitations and future research directions are briefly highlighted in the end. This review aims to offer deep insight into polymer mechanochemistry and provide approaches to study other mechanophores using the example of SP mechanochemistry in polymers.

Polydispersity is inevitable in industrially produced polymers. Established theories of polymer dynamics and rheology, however, were mostly built on monodisperse linear polymers. Dynamics of polydisperse polymers is yet to be fully explored -- especially how chains of different lengths affect the dynamics of one another in a mixture. This study explored the dynamics of bidisperse polymer melts using molecular dynamics and a bead-spring chain model. Binary mixtures between a moderately entangled long-chain species and an unentangled or marginally entangled short-chain species were investigated. We found that adding short chains can significantly accelerate the dynamics of the long chains by substantially lessening their extent of entanglement. Meanwhile, although introducing long chains also hinders the motion of the short chains, it does not qualitatively alter the nature of their dynamics -- unentangled short chains still follow classical Rouse dynamics even in a matrix containing entangled chains. Detailed Rouse mode analysis was used to reveal the effects of entanglement at chain segments of different scales. Stress relaxation following a step shear strain was also studied and semi-empirical mixing rules that predict the linear viscoelasticity of polydisperse polymers based on that of monodisperse systems were evaluated with simulation results., Accepted Manuscript

In the present work, we investigated effects of the dielectric/semiconductor interface modification on the photoelectrical properties of phototransistors comprising a UV responsive semiconductor blend 2,7-dipentyl-[1]benzothieno[2,3-b][1]benzothiophene (C5-BTBT) and a linear unsaturated polyester (L-upe). Using various self-assembly monolayers with different end-groups at the dielectric/semiconductor interface we modulated the drain photocurrent and response times under the UV light illumination of phototransistors. Treatment of the SiO2 dielectric surface with organosilanes led to the variation of the max mobility in the dark 0.10–0.18 cm2 V−1 s−1 and under UV light 0.08–0.50 cm2 V−1 s−1. Interestingly, detailed crystal structure analysis using 2D X-ray diffraction and photoelectrical characterization revealed that mobility in the dark predominantly depends on the alignment of C5-BTBT crystallites at the interface. Under UV light, the mobility increased with the electron withdrawing/donating nature of the SAM end-functional group. Additionally, chemical modification of the SiO2 dielectric surface increased photocurrent relaxation/decay times upon UV light removal while retaining fast response times when exposed to UV light, which enhanced memory properties of fabricated phototransistors (fast UV response = writing and long relaxation = long data storage).

Spiropyran (SP) mechanophore cross-linker was covalently incorporated into two widely used polyolefins, poly(ethylene-vinyl acetate) (EVA) and poly(ethylene-octene) (EOC), through facile cross-linking by peroxide under hot press. It was found that (1'-(2-(methacryloyloxy)ethyl)-3′,3′ dimethylspiro[chromene-2,2'-indolin]-6-yl)methyl methacrylate (SP3) could not be thermally driven to merocyanine (MC) in polyolefins during high temperature cross-linking, which is superior to other types of SP mechanophores used for polymer processing. The force-induced ring-opening reaction of SP-to-MC was demonstrated on SP3-cross-linked EVA. It was found that increasing the SP content resulted in earlier activation and that more MC was driven from SP at a slower strain rate. When held at constant strain, MC gradually reverted to SP. The mechanoactivation of SP was also investigated for SP3-cross-linked EOC. This work represents the first example of color-changeable polyolefins in response to mechanical force and demonstrates the feasibility of applying mechanophores to widely-used commercial polyolefins for stress sensing.

This work reports the first pure hydrocarbon thermoplastic polyolefin material with reversible shape memory effect under stress-free or very small external loading condition. A thermoplastic ethylene/1-octene diblock copolymer with designed chain microstructure was synthesized. The polyolefin material performed not only the conventional one-way multishape memory effects, but also a two-way reversible shape memory effect (RSME). The elongation and contraction induced by oriented crystallization with heating was confirmed as the mechanism of RSME without chemical cross-linking. This work demonstrated that the thermoplastic reversible shape memory could be achieved through careful design of chain microstructure, based on sole hydrocarbon materials such as ethylene-1-octene copolymer.

This paper reports synthesis of the first high internal phase emulsion (HIPE) system with double emulsion (DE) morphology (HIPE-DE). HIPE is a highly concentrated but highly stable emulsion system, which has a dispersed/internal phase fraction over 74vol%. DE represents an emulsion system that hierarchically encapsulates two immiscible phases. The combination of HIPE and DE provides an efficient method for fabrication of complex structures. In this work, HIPE-DE having a water-in-oil-in-water (W/O/W) morphology has been prepared for the first time via a simple one-step emulsification method with poly(2-(diethylamino)ethyl methacrylate) (PDEA) microgel particles as Pickering stabilizer. An oil phase fraction up to 90vol% was achieved by optimizing the microgel concentration in aqueous phase. The mechanism of the DE formation has been elucidated. It was found that while PDEA microgels stabilized the oil droplets in water, small amount protonated DEA monomers acted as surfactant and formed water-containing micelles inside the oil droplets. It was demonstrated that the W/O/W HIPE-DE could be precisely converted into porous polymer structures. With styrene as the oil phase in W/O/W HIPE-DE, porous polystyrene particles were obtained upon polymerization. With dissolved acrylamide as the aqueous phase and toluene as the continuous phase, porous polyacrylamide matrixes were prepared. Elevating temperature required for polymerization did not change the W/O/W HIPE-DE morphologies. This simple approach provides a versatile platform for synthesis of a variety of porous polymer systems.

A UV-A sensitive phototransistor was demonstrated using an organic semiconductor 2,7-dipentyl[1]benzothieno[3,2- b ][1] benzothiophene (C5-BTBT) and a strong electron acceptor 1,5-dichloro-9,10-dintiro-anthracene (2Cl-2NO 2 -Anth) which is not photo-isomerizable. At 0 gate bias the photoresponsivity of the device begins to saturate at an incident power P inc = 1 mW/cm 2 , where a photocurrent-to-dark current ratio ( P ) of P > 10 5 is observed with a photoresponsivity of 9 A/W. The photoresponsivity was increased with the decrease of P inc , reaching 40 A/W at a P inc = 0.0427 mW/cm 2 . A persistent photocurrent with a P > 10 5 was observed for more than 2 h, demonstrating the potential use for rewritable photo memory. By applying a gate voltage program consisting of a reset pulse of −90 V every 2nd data point, the device can perform as a UV sensor or switch at the timescale of 600 ms.

In this work, we study the mechanical activation of a new type of spiropyran mechanophore cross-linker, (1′-(2-(methacryloyloxy)ethyl)-3′,3′-dimethylspiro[chromene-2,2′-indolin]-6-yl)methyl methacrylate ( MA-SP3-MA ) in poly methyl acrylate (PMA), prepared via free radical polymerization. Compared with other SPs, SP3 mechanophore shows two unique features. First, the films exhibit good sensitivity towards mechanical force but not to UV irradiation. Second, the merocyanine (MC)-to-SP reversion in PMA films after relaxation was very fast. Further, the mechanical activation can be repeated for three times but with diminishing of peak color, caused by the damage of overstrained polymer chains. We also observe that increasing SP content leads to stiffer and more rigid elastomer as well as earlier threshold strain for activation point of SP to MC but has little effect on threshold stress for SP activation. This work offers inspirations towards mechanophore design for polymeric materials to broaden the scope of potential applications of mechanophores.

A new type of polymer electrolyte based on gradient copolymers is proposed to resolve the problem of low ionic conductivity faced by polymer electrolytes. A series of random, block, and gradient copolymers of styrene (St) and methyl acrylate (MA) are synthesized by a living radical polymerization method and employed as polymer electrolytes for lithium-ion batteries. The gradient copolymer has gradual change in the monomeric composition along polymer chains. There is no abrupt composition change between the adjacent blocks. This design minimizes possible sharp domain boundaries and generates highly conductive smooth ion pathways. The gradient copolymer gel electrolyte filled with a regular ester electrolyte gives the highest ionic conductivity of 1.20 × 10–3 S cm–1 at room temperature, which meets the requirement of practical applications.

The influence of polymer binders on the UV response of organic thin-film phototransistors (OTF-PTs) is reported. The active channel of the OTF-PTs was fabricated by blending a UV responsive 2,7-dipenty-[1]benzothieno[2,3-b][1]benzothiophene (C5-BTBT) as small molecule semiconductor and a branched unsaturated polyester (B-upe) as dielectric binder (ratio 1:1). To understand the influence of the polymer composition on the photoelectrical properties and UV response of C5-BTBT, control blends were prepared using common dielectric polymers, namely, poly(vinyl acetate) (PVAc), polycarbonate (PC), and polystyrene (PS), for comparison. Thin-film morphology and nanostructure of the C5-BTBT/polymer blends were investigated by means of optical and atomic force microscopy, and powder X-ray diffraction, respectively. Electrical and photoelectrical characteristics of the studied OTF-PTs were evaluated in the dark and under UV illumination with a constant light intensity (P = 3 mW cm(-2), λ = 365 nm), respectively, using two- and three-terminal I-V measurements. Results revealed that the purposely chosen B-upe polymer binder strongly affected the UV response of OTF-PTs. A photocurrent increase of more than 5 orders of magnitude in the subthreshold region was observed with a responsivity as high as 9.7 AW(-1), at VG = 0 V. The photocurrent increase and dramatic shift of VTh,average (∼86 V) were justified by the high number of photogenerated charge carriers upon the high trap density in bulk 8.0 × 10(12) cm(-2) eV(-1) generated by highly dispersed C5-BTBT in B-upe binder. Compared with other devices, the B-upe OTF-PTs had the fastest UV response times (τr1/τr2 = 0.5/6.0) reaching the highest saturated photocurrent (10(6)), at VG = -5 V and VSD = -60 V. The enhanced UV sensing properties of B-upe based OTF-PTs were attributed to a self-induced thin-film morphology. The enlarged interface facilitated the electron withdrawing/donating functional groups in the polymer chains in influencing the photocharge separation, trapping and recombination.

In surface-initiated atom transfer radical polymerization, knowledge of grafting density is of significant interest because it is one of the determining properties of grafted polymer. It is well known that not all of the immobilized initiators can grow into polymer chains. However, little is known about why this happens and what affects the grafting efficiency. The lack of information is partly due to the difficulty in experimental determination of grafting density on flat substrates. To circumvent the problem, Monte Carlo simulation with bond fluctuation model is used in this study to investigate the effects of various reaction conditions on the grafting density. The simulation results show lower grafting density when less deactivator is present. In systems with lower deactivator concentration, the number of monomer added per activation cycle is higher. Coupling this with close proximity of immobilized initiators results in chains initiated at earlier time to shield their neighboring initiator moieties from adding mono­mers, thus lowering the grafting density in such a system. These simulation results also provide an explanation to the seemingly conflicting trend reported in the literatures.

We report the reversible addition–fragmentation chain transfer (RAFT) solution copolymerization of methyl methacrylate (MMA) with a cleavable divinyl comonomer, bis(2-methacryloyl)oxyethyl disulfide (BMAODS). 2-Cyano-2-propyldodecyl trithiocarbonate was used as a RAFT chain transfer agent and 2,2′-azobis(2-methylpropionitrile) as an initiator. The selective cleavage of BMAODS disulfide bonds was used to collect primary chains for the determination of the branching density (BD). The effects of initial monomer concentration, vinyl/divinyl ratio, and primary chain length on the branching and cyclization reactions were thoroughly investigated. It was found that more than 50% pendent double bonds from BMAODS were consumed in cyclization rather than in branching. The BD increased linearly with the conversion up to approximately 60% conversion. The monomer concentration was found to be the most efficient parameter in promoting branching. Increasing divinyl monomer ratio and primary chain length favored cyclizati...

A great challenge in controlled radical polymerization such as atom transfer radical polymerization (ATRP) has been related to keep the livingness and molecular weight control of the reaction at high conversion, especially in bulk polymerization. The objective of this work is to investigate the effects of ultrasound power on the polymerization at high conversion. The initiator for continuous activator regeneration ATRP is used for bulk polymerization of methyl methacrylate (MMA) as the model system. Good livingness and control up to high conversion are obtained through employing ultrasonic waves. By this method, MMA is polymerized in bulk up to “glass state” (88%) at 70°C with polydispersity about 1.2 under an operating frequency of 40 kHz and output power of 100 W. Chain extension reaction proves the livingness of the synthesized polymers at glassy state. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1683–1687, 2016

In this paper, we report the synthesis of oxygen (O2)-switchable thermo-responsive random copolymers based on fluorinated acrylamide monomer homologues: N-(2-fluoroethyl)acrylamide (F1EA), N-(2,2-difluoroethyl)acrylamide (F2EA), and N-(2,2,2-trifluoroethyl)acrylamide (F3EA). Copolymerizing these monomers with N,N-dimethylaminoethyl methacrylate (DMA) via reversible addition–fragmentation chain transfer (RAFT) polymerization yields thermo-responsive random copolymers, which have dual switchability towards O2 and carbon dioxide (CO2). The inherent low critical solution temperature (LCST) of these copolymers can be precisely designed in a wide range of temperatures by varying their chemical compositions. Importantly, this LCST can be reversibly switched to different levels by respectively purging O2 or CO2 into the aqueous solution, and can be recovered to its initial state by washing off the trigger gas. This work provides a versatile and effective approach for the preparation of O2-responsive polymers, with a big operation window of temperature.

MOF particles can be easily collected and re-dispersed in water with the help of a free thermo-responsive polymer. Compared to the polymer grafting approaches reported in the literature, this method requires no chemical reactions and it is highly energy-efficient and environmentally-friendly.

Smart surfaces that can convert external stimuli to changes of surface properties are playing a significant role in both fundamental research and practical applications. However, it is still a challenge to create smart surfaces with good switchability in a facile and controllable way. Herein, a wrinkled smart surface is prepared by a strategy which combines stimuli-responsive polymers and surface wrinkles, where polymers provide surface responsiveness and wrinkles result in enhancement and a regulation effect. A model system composed of the pH-responsive polymer PDEAEMA grafted on the surface of a wrinkled Au/PS bilayer via Au-SH bonding is presented. The contact angle (CA) difference between acidic/basic droplets is found to be much larger for wrinkled surfaces (~117°) than that of flat surfaces (~30°), suggesting that wrinkles can significantly reinforce the switchability of wetting. Moreover, by taking advantage of wrinkles in sample processing and high controllability, we further optimize the wrinkle structure and incorporate asymmetric patterns into the wrinkled smart surface, thereby achieving directional manipulation of acidic and basic droplets/liquids. Due to the excellent capability found in this study, wrinkled smart surfaces may find potential applications in sensors, microfluidics, separation, and smart interfacial design.

Polydispersity quantifies the breadth of polymer molecular weight distribution, making it an important and frequently quoted chain microstructural property for characterization. An explicit expression of such an important variable is desirable for ease of calculation, correlation with experiment data, and/or parameter estimation. A review of published literatures shows that great efforts have been put forth by many researchers to derive these equations for various polymerization mechanisms. In atom transfer radical polymerization (ATRP), polydispersity depends on three factors: monomer conversion, number of monomer addition per activation/deactivation cycle, and amount of dead chains. The existing expressions available in the literature only account for, at most, two of these three factors, with the contribution from dead chains commonly neglected. This assumption results in polydispersity monotonically decreasing with conversion, which is often not observed in experiments. In this work, a new equation fo...

The elastomeric performance of a series of ethylene/1-octene random and block copolymers prepared from living coordination polymerization was studied in this work. All the polymer samples exhibited good toughness. The living random copolymers had better elasticity than commercial metallocene random copolymers. The strain recovery of the living random copolymers was about 90% with an applied strain up to 800%. It was demonstrated that the copolymer elasticity was mainly determined by their block structure, with little influence by their molecular weight. It was also found that either too high or too low content of hard-block content deteriorated the copolymer elastomeric behavior. The diblock copolymer having about 42 wt% hard block content (LBC1) gave the best elasticity among the studied block copolymers and retained the strain recovery about 80% under the applied stain of 600%.

Polymer chain microstructures, such as copolymer composition distribution (CCD) and topology, play an important role in determining materials properties of the polymer products. The design and control of polymer chain microstructures represents an important task in macromolecular reaction engineering. Semi-batch copolymerization with the model-based design of comonomer feeding policies provides a powerful approach enabling precision production of CCD, topology, and their combined structures in controlled radical copolymerization systems. Various novel polymer products with predesigned CCDs and topologies have been successfully prepared by the approach. This article highlights the recent progresses in this area.

We report the design and development of a series of novel ionic liquid polymers (PILs) which possess thermoresponsive properties in organic solvent. The PILs were synthesized via reversible addition–fragmentation chain transfer (RAFT) copolymerization of 1-vinyl-3-butylimidazolium bromide and N-isopropylacrylamide, followed by anion exchange of bromide to amino acid d-alanine. The PILs possessed 0.36–0.76 molar fraction of ionic liquid with number-average molecular weight of 2.70–8.17 kg/mol and polydispersity index ranging between 1.12 and 1.25. The copolymerizations followed first-order reaction kinetics, and they were well-controlled, as indicated by the linear increase of molecular weight with monomer conversion. The PILs were thermoresponsive in acetonitrile with upper critical solution temperatures (UCST) varying from 25.7 to 34.8 °C, owing to the introduction of anion of amino acid. The PILs could be completely precipitated out by lowering the solution temperature. The PIL/acetonitrile solutions we...

Surface-initiated controlled radical polymerization, such as ATRP, has been proven to be a powerful method for preparation of well-controlled functional grafted polymers. There are thousands of experimental works published, by varying polymers, surfaces, and applications. In comparison, theoretical developments are very lacking. Many fundamental questions still remain to be answered. These questions include, but not limited to: What determine the surface initiator efficiency? How many chains per square nanometer can be fully grown? What is the maximum thickness can polymer grow to? If chains are simultaneously grown from surface and solution, which has higher molecular weight? Answers to these questions are most helpful for innovation and further development in this important area. In this work, we employed recently developed theories to explain experimentally observed kinetic profiles of polymer layer thickness growth. What limits the growth of surface chains? Is it the monomer starvation in grafting layer that slow down propagation? Or is it the termination of radicals that stop the chain growth? It was found that no existing models could fully explain the often contradictory experimental observations. It is our hope that this work will provoke further discussions and inspire more effort in resolving the fundamental issues of this area.

Acetylene C2H2gas is one of the most important fault characteristic hydrocarbon gases dissolved in oil immersed power transformer oil. This paper reports the successful preparation and characterization of samarium oxide Sm2O3decorated tin oxide SnO2based sensors with hierarchical rod structure for C2H2gas detection. Pure and Sm2O3decorated SnO2sensing structures were synthesized by a facile hydrothermal method and characterized by XRD, FESEM, TEM, EDS, and XPS measurements, respectively. Planar chemical gas sensors with the synthesis samples were fabricated, and their sensing performances to C2H2gas were systematically performed and automatically recorded by a CGS-1 TP intelligent gas sensing analysis system. The optimum operating temperature of the Sm2O3decorated SnO2based sensor towards 50 μL/L of C2H2is 260°C, and its corresponding response value is 38.12, which is 6 times larger than the pure one. Its response time is about 8–10 s and 10–13 s for recovery time. Meanwhile good stability and reproducibility of the decorated sensor to C2H2gas are also obtained. Furthermore, the proposed sensor exhibits excellent C2H2selectivity among some potential interface gases, like H2and CO gas. All sensing results indicate the sensor fabricated with oxide Sm2O3decorated SnO2nanorods might be a promising candidate for C2H2detection in practice.

Organic thin film transistors (OTFTs) were fabricated for the first time using a semiconductor copolymer of diketopyrrolopyrrole-quarterthiophene (DPP-QT) and unsorted single walled carbon nanotubes (SWCNTs). Three different SWCNTs having different tube diameters, length, and shape were used to investigate the effects of carbon nanotubes’ properties on dispersion of the SWCNTs in DPP-QT polymer, as well as the mobility and current on/off ratio of the OTFTs. The DPP-QT polymer was able to selectively disperse two types of SWCNTs. An optimal SWCNT loading was found to be 1.5–2.5 wt% for these SWCNTs, before the on/off ratio fell below 10 5 due to increased metallic tube content of the film. At this optimal loading, the field effect mobility was improved by a factor of two, with the maximum mobility reaching 1.3 cm 2 V − 1 s − 1 , when the SWCNTs with a short length and small tube diameter were used.

Limonoids produced by citrus are a group of highly bioactive secondary metabolites which provide health benefits for humans. Currently there is a lack of information derived from research on the genetic mechanisms controlling the biosynthesis of limonoids, which has limited the improvement of citrus for high production of limonoids. In this study, the transcriptome sequences of leaves, phloems and seeds of pummelo (Citrus grandis (L.) Osbeck) at different development stages with variances in limonoids contents were used for digital gene expression profiling (DGE) analysis in order to identify the genes corresponding to the biosynthesis of limonoids. Pair-wise comparison of transcriptional profiles between different tissues identified 924 differentially expressed genes commonly shared between them. Expression pattern analysis suggested that 382 genes from three conjunctive groups of K-means clustering could be possibly related to the biosynthesis of limonoids. Correlation analysis with the samples from different genotypes, and different developing tissues of the citrus revealed that the expression of 15 candidate genes were highly correlated with the contents of limonoids. Among them, the cytochrome P450s (CYP450s) and transcriptional factor MYB demonstrated significantly high correlation coefficients, which indicated the importance of those genes on the biosynthesis of limonoids. CiOSC gene encoding the critical enzyme oxidosqualene cyclase (OSC) for biosynthesis of the precursor of triterpene scaffolds was found positively corresponding to the accumulation of limonoids during the development of seeds. Suppressing the expression of CiOSC with VIGS (Virus-induced gene silencing) demonstrated that the level of gene silencing was significantly correlated to the reduction of limonoids contents. The results indicated that the CiOSC gene plays a pivotal role in biosynthesis of limonoids.

A reversibly dispersible/collectable metal-organic framework (MOF) system has been developed. The MOF particles were modified by grafting the thermally switchable copolymers of 2-(2-methoxyethoxy)ethyl methacrylate and oligo(ethylene glycol) methacrylate through a surface-initiated atom transfer radical polymerization (SI-ATRP) approach. The resulted MOF materials preserved their original framework structure and could be readily dispersed in water at room temperature to form stable dispersions. The dispersed MOF particles could also be re-collected by heating the dispersions to above the lower critical solution temperature (LCST) of the grafted copolymer. The dispersion and collection processes were reversible.

Chemical product engineering represents an emerging discipline rooted to chemical engineering. Its core content of research lies in precision production of chemical structures. Polymer products contain complex structures at multiple scales. Polymerization processes, to a large extent, determine polymer chain microstructures and morphologies. In the recent years, we developed various polymerization processes and produced polymers having precisely designed chain microstructures. These polymer products showed high performances and superior material properties in targeted applications. Our methodology employs kinetic modeling combined with reactor technologies, based on extensive mechanistic research on polymerization mechanisms. In controlled/living radical(co)polymeri-zation, we developed a novel model-based computer-programed semi-batch copolymerization technology that allows unprecedented precise control over end-to-end copolymer composition of individual chains. In catalytic polymerization of olefins, we developed a reactor technology for in-situ production of polyolefin alloys. This paper provides a brief summary of the recent advances in the polymer product engineering researches.

Controlled radical polymerization (CRP) such as atom transfer radical polymerization (ATRP) is often conducted in solution processes and stopped at medium monomer conversions to yield well controlled polymer samples. A great challenge lies in running bulk CRP up to high conversions but still retaining system livingness and molecular weight control. In this work, we demonstrate the achievement of good living and well controlled high-conversion bulk ATRP by means of design and optimizing polymerization thermal histories. The initiator-for-continues-activator-regeneration (ICAR) ATRP of methyl methacrylate (MMA) is used as a model system. Employing step functions in temperature, MMA conversions are pushed up to 98% and the PMMA samples possess polydispersities

The controlled synthesis of narrowly distributed low molecular weight polymers with functionalization possibilities is of great industrial interests. Although living polymerization allows for control over polymer architecture, the production of low molecular weight polymers with low polydispersities via living polymerization systems is challenged by the use of large amounts of catalysts and broadening in molecular weight distribution. This review addresses the synthesis of narrowly distributed, functional, low molecular weight polyethylene and polyethylene mimics. The review is structured for quick identification of relevant systems for the production of specific polymer architectures with specific cost, efficiency, and safety concerns.

Copolymer composition distribution (CCD) is an important parameter of chain microstructure that has significant impact on the material properties of polymer products. Controlled/living radical poly...

Methyl methacrylate (MMA) was polymerized in bulk via atom transfer radical polymerization (ATRP) with azobis(isobutyronitrile) (AIBN) and tert-butyl peroxybenzoate (TBPB) as initiator for continuous activator regeneration (ICAR). The ATRP was first carried out up to high conversion at 70 °C. When the system reached its glass state at about 94%, the polymerization temperature was elevated to 120 °C to maximize the conversion. Livingness of the ICAR ATRP process and control of polymer molecular weight at high conversion were carefully examined to elucidate the mechanisms of diffusion-controlled reactions. The “gel effect” started at about 50% conversion, and it was accompanied by molecular weight distribution broadening. A dramatic increase in polydispersity was observed at above 90% conversion. The loss of control over molecular weight was caused by diffusion-controlled deactivation, which could be reduced to some extent by increasing deactivator concentration. However, despite the loss of control at high...

A theory for polymer molecular weight distribution (MWD) in atom transfer radical polymerization (ATRP) has been derived by using analogy to a series of continuous stirred tank reactors (CSTRs). This approach relates one activation cycle in ATRP to one reactor in CSTRs. The derived MWD expression includes effect of radical termination and allows detailed investigation on the factors that determine the polymer distribution, namely the level of “control” and “livingness.” The level of control means the average number of activation cycles experienced by individual chains. The degree of livingness is quantified by the fraction of terminated chains. It was found that the effect of livingness and control on MWD is complex. Large number of activation cycles does not guarantee a narrow distribution. There exists an optimum value of activation cycles to achieve the lowest polydispersity by balancing the control (achieved by increasing activation cycles) with the loss of livingness (also caused by increasing activation cycles). The distribution for ATRP is in-between Poisson and Flory distributions, determined by the level of control and livingness. In general, having high degree of livingness and maintaining control are both necessary conditions to obtain narrow MWD. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 639–651

A nonpercolating network of non-covalently functionalized single-walled carbon nanotubes was embedded within air-stable poly[5,5′-bis(3-dodecyl-2-thienyl)-2,2′-bithiophene] (PQT-12) thin films for the purpose of enhancing the field-effect mobility in thin-film transistors. The host polymer was used to stabilize the nanotubes in suspension through π-orbital overlap caused by simple application of ultrasonication. The stable nanotube suspension was cast into two different device architectures, both of which exhibited excellent on/off ratios ranging from 105 to 106 and dramatically improved mobilities compared with pristine PQT-12 semiconductor. A single-layer film with nanotubes embedded throughout was easy to fabricate and had mobility up to 0.34 cm2/Vs, an enhancement of over 3× compared with PQT-12. Placing the nanotubes closer to the dielectric surface in a dual-layer approach resulted in a mobility improvement of up to six times (0.58 cm2/Vs). The effects of the nanotube content on the polymer interaction within the suspension, film morphology, and electrical properties were investigated as well.

Lactone is a common structural motif in biologically active natural products. However, the metabolic instability of lactone significantly reduces their in vivo potency. In the present investigation, a new strategy to improve the metabolic stability of lactone was provided by the design of α-fluoro ether as a novel bioisostere of lactone. The effectiveness of the α-fluoro ether/lactone replacement was validated by the discovery of (20S,21S)-21-fluorocamptothecins as hydrolytically stable topoisomerase I inhibitors. A highly potent camptothecin derivative, 8l, was successfully identified, which showed excellent in vitro and in vivo antitumor activities and represents a promising lead for the discovery of novel antitumor agents. Interestingly, this study also provided a new structure-activity relationship for the C21-carbonyl group of camptothecin, which has been regarded as an essential pharmacophore. Our results revealed that the conserved C21-carbonyl group can be replaced by a fluorine substituent. α-Fluoro ether may have general application in improving the metabolic stability of lactone.

A kinetic model was developed for the living copolymerization of ethylene/1-octene using the fluorinated FI-Ti catalyst system, bis[N-(3-methylsalicylidene)-2,3,4,5,6-pentafluoroanilinato] TiCl2/dried methylaluminoxane is presented. The model was first validated by batch polymerization experiments. Kinetic parameters were estimated from the model correlations with online ethylene consumption rates and end-of-batch copolymer molecular weight. The model was then used to calculate the microstructural properties of ethylene/1-octene copolymers with controlled composition profiles (uniform, diblock, and step triblock), which were synthesized using sequential comonomer feeding policies in semibatch copolymerization. The synthesized block copolymers had the exact composition distributions and molecular weights as the model simulated. It was demonstrated that the polymer chain microstructure in the living copolymerization of olefins could be precisely regulated by using semibatch comonomer feeding policies. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4686–4695, 2013