Enhanced Molecular Alignment in Poly‐l‐Lactic Acid Nanotubes Induced via Melt‐Press Template‐Wetting

Molecular ordering in polymers can have a drastic effect on their properties and can be used to induce or enhance functionality. In the case of poly‐l ‐lactic acid (PLLA), which is a widely used polymer in biomedicine, sensors, and actuators, preferential orientation of chains can lead to significantly enhanced electromechanical properties. In this context, template‐wetting is a straightforward method of producing polymer nanostructures, which can lead to some degree of molecular order in the polymer. Template‐wetting of PLLA has not been fully explored, especially in terms of morphological and/or structural characterization. In this work, PLLA nanotubes are grown via a modification of the template‐wetting process, referred to here as melt‐press template‐wetting. The nanotubes are thoroughly characterized with wide‐angle X‐ray diffraction, isothermal differential scanning calorimetry, and polarized light optical microscopy. This characterization indicates that the polymer chains in these PLLA nanotubes are aligned parallel to the cylindrical axis of the nanotube, which may be beneficial in certain applications.     

Self‐Detecting and Self‐Healing Reinforce Elastomer Doped with Aggregation‐Induced Emission Molecules

Most of elastomers for fabrication of comfortable epidermal devices and smart actuators produce responsive signals by the stimuli‐induced deformation. Herein, a dynamic visualization of external stimuli rather than the deformation through synthesis of a self‐healing poly(dimethylsiloxane) (PDMS)‐based elastomer doped with aggregation‐induced emission (AIE) molecules is reported. The self‐healing PDMS‐based elastomer is designed and synthesized through molecule integration of reversible multi‐strength H‐bonds and permanent covalent crosslink sites. The adjustment of the weight ratio of elastic cross‐linker offers tunable mechanical properties of the resultant elastomer. After doping such an elastomer with AIE molecules of 1,1,2,2‐tetrakis(4‐nitrophenyl)ethane, the elastomer composite displays strong on–off fluorescence depending upon mechanical damage and temperatures, which can be used to detect the breaking and self‐healing performances, as well as the temperature change. The strategy described here provides another way to develop smart polymeric elastomers for practical applications.     

Thin Films Bearing Conjugated Polymer Nanoparticles Fabricated by Microliter‐Scale Layer‐by‐Layer Deposition

A conjugated polymer, poly(9,9‐bis(6‐bromohexyl)‐9H‐fluorene‐alt‐1,4‐phenylene), is synthesized, converted to nanoparticles via a nanoprecipitation process, and utilized to fabricate thin films including conjugated polymer nanoparticles. The nanoparticles with surface bromides can be conjugated with an amine‐functionalized dendrimer via a nucleophilic coupling reaction. Thus, when microliter solutions of the particulates are dragged at a constant velocity on substrates alternately in a layer‐by‐layer manner, thin films composed of the nanoparticles and dendrimers can be successfully built up on the substrates. Our results suggest a methodology to control the deposition of thin films bearing conjugated polymer nanoparticles while minimizing processing time and decreasing material consumption.

     

聚合物模板法制备单分散多孔二氧化硅微球

聚合物模板法是实现无机材料高效制备的有效途径.本研究采用交联聚苯乙烯二乙烯基苯聚合物微球为模板,以有机硅源正硅酸四乙酯(TEOS)为前驱体,通过将硅溶胶沉积到多孔聚合物中形成聚合物和二氧化硅的混合物,再经过高温煅烧将聚合物模板去除的方法,可以方便地制备形貌可控的单分散多孔二氧化硅微球.利用扫描电子显微镜(SEM),傅里叶红外光谱仪(FHR),热重分析仪(TGA),X射线衍射仪(XRD),比表面积孔径分布测定仪(BET)对聚合物模板以及制备的二氧化硅微球进行表征.另外,对单分散多孔二氧化硅微球形成机理进行探讨.     

Adaptive Polymeric Coatings with Self‐Reporting and Self‐Healing Dual Functions from Porous Core–Shell Nanostructures

In biological system, early detection and treatment at the same moment is highly required. For synthetic materials, it is demanding to develop materials that possess self‐reporting of early damage and self‐healing simultaneously. This dual function is achieved in this work by introducing an intelligent pH‐responsive coatings based on poly(divinylbenzene)‐graft‐poly(divinylbenzene‐co‐methacrylic acid) (PDVB‐graft‐P(DVB‐co‐AA)) core–shell microspheres as smart components of the polymer coatings for corrosion protection. The key component, synthesized PDVB‐graft‐P(DVB‐co‐AA) core–shell microspheres are porous and pH responsive. The porosity allows for encapsulation of the corrosion inhibitor of benzotriazole and the fluorescent probe, coumarin. Both loading capacities can be up to about 15 wt%. The polymeric coatings doped with the synthesized microspheres can adapt immediately to the varied variation in pH value from the electrochemical corrosion reaction and release active molecules on demand onto the damaged cracks of the coatings on metal surfaces. It leads simultaneously to the dual functions of self‐healing and self‐reporting. The corrosion area can be self‐reported in 6 h, while the substrate can be protected at least for 1 month in 3.5 wt% NaCl solution. These pH‐responsive materials with self‐reporting and self‐healing dual functions are highly expected to have a bright future due to their smart, long‐lasting, recyclable, and multifunctional properties.     

Ferroelectric polymers for non‐volatile memory devices: a review

Ferroelectric memories have attracted great attention for data storage, and ferroelectric polymers have been widely studied with the development of flexible and wearable devices. The multifunctional capabilities, non‐volatile memory state, low power consumption, long durability, fast switching, chemical stability and mechanical flexibility make them good candidates for various memories, such as ferroelectric tunnel junctions and diodes, ferroelectric capacitors, resistive memories and field‐effect transistors. Here, recent advances in the research of these ferroelectric polymer memories are summarized, and challenges in the development of smart electronics are also discussed. © 2020 Society of Chemical Industry     

Flexible Sandwich Structural Strain Sensor Based on Silver Nanowires Decorated with Self‐Healing Substrate

Flexible and stretchable conducting composites that can sense stress or strain are needed for several emerging fields including human motion detection and personalized health monitoring. Silver nanowires (AgNWs) have already been used as conductive networks. However, once a traditional polymer is broken, the conductive network is subsequently destroyed. Integrating high pressure sensitivity and repeatable self‐healing capability into flexible strain sensors represents new advances for high performance strain sensing. Herein, superflexible 3D architectures are fabricated by sandwiching a layer of AgNWs decorated self‐healing polymer between two layers of polydimethylsiloxane, which exhibit good stability, self‐healability, and stretchability. For better mechanical properties, the self‐healing polymer is reinforced with carbon fibers (CFs). The sensors based on self‐healing polymer and AgNWs conductive network show high conductivity and excellent ability to repair both mechanical and electrical damage. They can detect different human motions accurately such as bending and recovering of the forearm and shank, the changes of palm, fist, and fingers. The fracture tensile stress of the reinforced self‐healing polymer (9 wt% CFs) is increased to 10.3 MPa with the elongation at break of 8%. The stretch/release responses under static and dynamic loads of the sensor have a high sensitivity, large sensing range, excellent reliability, and remarkable stability.     

Self‐assembly micelles from novel tri‐armed star C3‐(PS‐b‐PNIPAM) block copolymers for anticancer drug release

Novel tri‐armed star polystyrene‐block‐poly(N‐isopropylacrylamide) block copolymers with trimesic acid as central molecules were synthesized by successive two‐step atom transfer radical polymerization, and confirmed by Fourier‐transform infrared spectra, ¹H nuclear magnetic resonance, and laser light scattering gel chromatography system. The copolymers could self‐assemble into spherical core‐shell micelles in aqueous media independent on drug loading. Physicochemical properties of the blank and drug‐loaded micelles were examined by surface tension, fluorescence spectroscopy, UV‐vis, transmission electron microscope, and dynamic light scattering measurements. The copolymer micelles exhibited thermo‐triggered phase transition, with low critical solution temperature of 33.7 and 34.6°C, varying with copolymer compositions. The critical aggregate concentrations were 11.62 and 47.61 mg L^?1, and hydrodynamic diameters from 200 to 220 nm. Water‐insoluble 10‐hydroxycamptothecine was encapsulated into the micelle aggregates to investigate the change in the resulting physicochemical parameters, thermo‐triggered in vitro drug release, and the applicability as drug targeting release carriers. MTT assays were carried out to uncover cytotoxicity of the newly developed micelle‐based drug formulations. © 2014 American Institute of Chemical Engineers AIChE J, 61: 35–45, 2015     

Application of Nano‐Polymer Emulsion for Inhibiting Shale Self‐Imbibition in Water‐Based Drilling Fluids

In order to effectively solve shale instability problems in the drilling process, the remarkable capillary effect of shale formations cannot be ignored. In this paper, we report the development and characterization of a nano‐polymer emulsion (SDPE) as a shale self‐imbibition control agent in water‐based drilling fluids. Spontaneous imbibition experiments, surface tension measurements, contact angle measurements, particle size distribution analysis, linear swelling tests, and hot‐rolling cuttings dispersion tests were conducted to evaluate the comprehensive performance of SDPE. The results show that the water absorption of shale samples in SDPE emulsions is significantly less than in deionized water. At a concentration of 2.0%, the absorption mass decreased from 7.51 to 2.59%. Reducing the surface tension of the testing fluids, increasing the contact angle of the shale samples, and maintaining the nanoscale size were the important considerations for SDPE to greatly decrease the capillary effect. The low swelling rate and high recovery rate indicate that SDPE also exhibits strong shale hydration inhibition performance. Compared with water‐based drilling fluids without SDPE, drilling fluids with SDPE present higher yield point/plastic viscosity values, and also decrease the filtration loss. Based on our findings, SDPE has the potential to be a good shale self‐imbibition control agent and to help mitigate the shale instability problems.     

A Self‐Healing PAM/CMHPG System for Unconventional Reservoir Stimulation

A hybrid chemically and physically linked polyacrylamide (PAM)/carboxymethyl hydroxypropyl guar gum (CMHPG) system is prepared via a fast and controllable one‐pot strategy. Due to the synergetic effect of the non‐covalent interactions between chains, these systems show improved, balanced mechanical properties. The apparent morphology, storage modulus G′, and loss modulus G″ show that these systems have rapid and almost full recovery ability (the self‐healing efficiency can reach 95%) with several hydrogen‐bonding interactions between two networks. This self‐healing property can cover the shortage of G′, G″, and viscosity loss at high shear force, which will help the system keep enough viscosity to create fractures or carry proppants during the whole fracturing process. Meanwhile, the self‐healing fracturing fluid can be broken easily and flow back to surface with little damage to the fracture conductivity, indicating great potential in unconventional reservoir which is sensitive to the fracturing fluid damage.     

Polymer Self‐Etching for Superhydrophobicity through a Green Hot‐Pressing‐Exfoliation Process: Low and High Adhesion

A green polymer self‐etching strategy for fabricating superhydrophobic surfaces exhibiting low and high adhesion is proposed by using hot‐pressing and exfoliation on a pair of low density polyethylene (LDPE) films. It is demonstrated that the hot‐pressing temperature has significant influence on the surface morphology of LDPE. Effective hot‐pressing temperature for low‐adhesive superhydrophobicity ranges from 109 to 161 °C. Bird's‐nest like micro‐/nanostructures are observed in the unzipped LDPE surfaces compressed at 109 °C, which shows excellent water repellency. LDPE surface compressed at 108 °C demonstrates superhydrophobicity with high adhesion, i.e., a water droplet cannot roll off even when the surface is turned upside down. Furthermore, superhydrophobic vessels are processed and applied to transport water and microdroplets of water losslessly.

     

A Thermo‐ and Moisture‐Responsive Zwitterionic Shape Memory Polymer for Novel Self‐Healable Wound Dressing Applications

Developing wound dressings that have strong adhesion strength without causing any conglutination to the wound site is still challenging. Herein, is proposed that zwitterionic shape memory polymers can be applied as promising candidates for wound dressing. Sulfobetaine methacrylate (SBMA) is copolymerized with 2,3‐dihydroxypropyl methacrylate (DHMA) in the presence of boric acid as a cross‐linking agent. The prepared material exhibits multi‐stimuli responsive shape memory behaviors: it can rapidly return to its initial shape upon heating to 90 °C, and a gradual recovery is also observed by absorbing moisture in humid environments. The shape memory effect can be well adjusted via incorporation of sodium chloride to induce the dissociation of electrostatic interactions between PSBMA chains, leading to reduced transition temperature and faster shape recovery rate. Moreover, the dynamic nature of boron ester bonds and electrostatic interaction endows the material with effective and rapid self‐healing ability. It is also demonstrated that the deployment process of the dressing that a sample with an initially circular shape can perfectly fit and tightly bind to the wound site after moisture‐induced shape recovery. The proposed zwitterionic polymer can possibly extend the application scope of shape memory polymers and pave a new way for the design of wound dressings.     

Self‐healing imidazolium‐based ionene‐polyamide membranes: an experimental study on physical and gas transport properties

A new series of six imidazolium‐based ionenes containing aromatic amide linkages has been developed. These ionene‐polyamides are all constitutional isomers varying in the regiochemistry of the amide linkages (para, meta) and xylyl linkages (ortho, meta, para) along the polymer backbone. The physical properties as well as the gas separation behaviors of the corresponding membranes have been extensively studied. These ionene‐polyamide membranes show excellent thermal and mechanical stabilities, together with self‐healing and shape memory characteristics. Most importantly, [TC‐API(p)‐Xy][Tf₂N] and [IC‐API(m)‐Xy][Tf₂N] membranes (TC, terephthaloyl chloride; API, 1‐(3‐aminopropyl)imidazole; Xy, xylyl; Tf₂N, bis(trifluoromethylsulfonyl) imide; IC, isophthaloyl chloride), where the amide and xylyl linkages are attached at para and meta positions, exhibit superior selectivity for CO₂/CH₄ and CO₂/N₂ gas pairs. We also demonstrate the transport properties and diverse applicability of our newly developed ionene‐polyamides, particularly [TC‐API(p)‐Xy][Tf₂N], for various industrial applications. © 2019 Society of Chemical Industry     

Self‐heating properties of styrene‐butadiene rubber

Rubbers, including styrene‐butadiene rubber (SBR), are well known to be susceptible to self‐heating. SBR is used in a wide range of applications and is often produced in the form of a crumb which is then used to form the final product. The crumb may be transported and stored in large quantities. Self‐heating properties of a SBR crumb have been determined using standard oven methods. The results indicate that self‐heating is a real hazard for SBR crumb. The results are generally consistent with recent measurements by Clothier and Prichard (Combust. Flame 2003; 133 :207–210) for rubber tyre crumb. Copyright © 2005 John Wiley & Sons, Ltd.     

Electric Field‐Induced Light Scattering in Eu‐Doped PMN‐PT Transparent Ceramics

Highly transparent Eu‐doped Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃(PMN‐PT) ferroelectric ceramics were obtained by a two‐stage sintering method. Eu doping play a significant role in the domain structures of PMN‐PT ceramics and resulted in different light scattering responses under electric field. The dielectric behaviors, ferroelectric properties, and domain configurations in the ceramics with increasing Eu doping concentration were studied, which were consistent with the electric field‐induced light scattering responses.     

Self‐healing properties of layer‐by‐layer assembled multilayers

The review is focused on the formation and the self‐healing properties of polymer and hybrid multilayers formed via the layer‐by‐layer approach. In the first part of the review the recent developments in the construction of polymer multilayers are highlighted. In the second part the design and the self‐healing properties of inorganic ? polymer hybrid multilayers are described. It is shown that self‐healing multilayers have a broad spectrum of applications including corrosion protection, as elements of antifouling and antimicrobial coatings and bio‐inspired superhydrophobic interfaces. It is demonstrated that dynamic functional interfaces have a complex hierarchical organization of non‐covalently bonded polymers and colloidal particles. Mechanisms of self‐healing behavior of the multilayers and the role of water and external stimuli (pH, ionic strength and temperature, light) in swelling of multilayers and rearrangement of polymer segments are discussed. Future trends, perspectives and research strategies for the design of ‘smart’ self‐assemblies with self‐healing properties are proposed. © 2015 Society of Chemical Industry