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Due to environmental concerns, some of the conventional halogenated flame retardants have been banned. In this context, both the industrial and academics have made efforts to develop more eco-friendly and sustainable flame retardant materials. Among new flame retardants, bio-based groups have attracted plenty of attention. In this review, varied types of bio-based flame retardants are systematically described, including the structural characteristics, flame retardant behaviors, and an overview of flame retardant mechanism. Recent research progress on various bio-based materials such as flame retardants (e.g., chitosan, lignin, phytic acid, polydopamine, Tannic acid, β-cyclodextrin, etc.) applied to different polymers are adequately summarized. Finally, the opportunities and challenges for the future development of bio-based flame retardants are briefly outlooked. post-print 7047 KB

Liquid mixtures composed of colloidal particles and much smaller non-adsorbing linear homopolymers can undergo a gelation transition due to polymer-mediated depletion forces. We now show that the addition of linear polymers to suspensions of soft colloids having the same hydrodynamic size yields a liquid-to-gel-to-re-entrant liquid transition. In particular, the dynamic state diagram of 1,4-polybutadiene star-linear polymer mixtures was determined with the help of linear viscoelastic and small angle X-ray scattering experiments. While keeping the star polymers below their nominal overlap concentration, a gel was formed upon increasing the linear polymer content. Further addition of linear chains yielded a re-entrant liquid. This unexpected behavior was rationalized by the interplay of three possible phenomena: (i) depletion interactions, driven by the size disparity between the stars and the polymer length scale which is the mesh size of this entanglement network; (ii) colloidal deswelling due to the increased osmotic pressure exerted onto the stars; and (iii) a concomitant progressive suppression of depletion efficiency on increasing polymer concentration due to reduced mesh size, hence a smaller range of attraction. Our results unveil an exciting new way to tailor the flow of soft colloids and highlight a largely unexplored path to engineer soft colloidal mixtures., Comment: 27 pages, 5 figures

Among the various renewable energy sources, wind energy offers an effective solution to the energy providers. Onshore wind turbines are generally designed for sites with low wind resources, while offshore wind turbines can be more efficient in producing energy thanks to their longer blades that provide more than 10 MW of rated power. Offshore wind turbine blades are subjected to significantly higher stresses and harsh environmental conditions. Therefore, hybrid composites composed of carbon and glass fibers can offer cost-effective and long-lasting solutions for wind turbine blade manufacturers. Turbine blades are connected with main spars through bolted connections and high interlaminar stresses occurring during the drilling process can cause to delamination in the composites. To prevent catastrophic failure related to defective machining, the drilling process must be performed meticulously and all machining-related results must be analyzed step by step. In this paper, dry drilling properties of hybrid glass-carbon fiber laminate epoxy matrix composites were examined experimentally in order to contribute to the wind energy sector. The results showed that the delamination factor could be decreased with higher cutting speeds or lower feed rates. Besides, higher feed levels caused higher thrust forces on the tool body.

External gear pumps are used in fluid transport systems because of their tight clearances and accurate flow control. These tight clearances are a challenge for numerical studies in terms of spatial discretization. In earlier work, the flow of a viscous fluid in an external gear pump is computed using the finite element method (FEM). An element size based on the respective distance between boundaries is proposed. In this study, results based on the earlier work are compared to extrusion experiments of EPDM. The aim of this study is not only to validate the numerical simulations, but also to determine what material characteristics need to be taken into account for an accurate output prediction of the external gear pump. Especially the introduction of shear-thinning behavior results in an improvement of the amplitude of the pressure difference fluctuation. Taking into account compressibility, alters the torque fluctuation in such a way that it mimics the experiments. Unfortunately, the fluctuation in torque still has a too high amplitude. Eventually, simulations are performed including shear-thinning behavior, a temperature- and pressure-dependent viscosity, and compressibility. The effect of measuring the material behavior using oscillatory or shear experiments is shown. Furthermore, the simulations are applied to a second EPDM. Finally, different processing conditions are tested. For the simulations, only qualitative agreement is found, possibly as a result of the no slip boundary condition.

Recent years have seen rapid growth in utilizing vegetable oils to derive a wide variety of bio-based chemicals and polymer materials to replace petroleum-based chemicals and polymer materials for minimizing environmental impact. Castor oil is a renewable resource and an important platform chemical. The interest in preparation of bio-based chemicals and polymer materials using castor oil as raw material has been increasing. Castor-oil-based chemicals mainly include biodiesel fuels, lubricants, plasticizers and polyols, while castor-oil-based polymers mainly include polyurethane, polyesters, resin, elastomers and cross-linked polymers. With this in mind, the present review summarizes and analyzes castor-oil-based chemicals and polymers in a wide range of industries and provides a perspective on future utilization.

Polypropylene film is the most important organic dielectric in capacitor technology; however, applications such as power electronic devices require more miniaturized capacitors and thinner dielectric films. The commercial biaxially oriented polypropylene film is losing the advantage of its high breakdown strength as it becomes thinner. This work carefully studies the breakdown strength of the film between 1 and 5 microns. The breakdown strength drops rapidly and hardly ensures that the capacitor reaches a volumetric energy density of 2 J/cm3. Differential scanning calorimetry, X-ray, and SEM analyses showed that this phenomenon has nothing to do with the crystallographic orientation and crystallinity of the film but is closely related to the non-uniform fibers and many voids produced by overstretching the film. Measures must be taken to avoid their premature breakdown due to high local electric fields. An improvement below 5 microns will maintain a high energy density and the important application of polypropylene films in capacitors. Without destroying the physical properties of commercial films, this work employs the ALD oxide coating scheme to augment the dielectric strength of a BOPP in the thickness range below 5 μm, especially its high temperature performance. Therefore, the problem of the reduction in dielectric strength and energy density caused by BOPP thinning can be alleviated.

Lightweight, scalable, mechanically flexible conductive polymer composite was always desirable for electromagnetic interference (EMI) shielding applications. In this work, we showcased a novel approach to the superior EMI shielding composite materials by orchestrating the multilayered structure and synergistic system. The asymmetric structure with the carbonyl irons (CI)-rich Ti3C2Tx/poly(vinylidene fluoride) (PVDF) magneto-electric layer jointly behind the Ti3C2Tx nanosheets filled PVDF layer was designed and fabricated in aid of a facile but efficient magnetic field-induced method and was then hot-pressed into multilayer structured film. Ti3C2Tx nanosheets were excluded by CI agglomeration layer in asymmetric film to form the complete 3D electrical conductive skeletons. Based on this strategy, EMI shielding properties of the asymmetric multilayer structured composite was superior to the homogeneous blend and sandwiched or alternating layered composites. In addition, an increase in CI content in the composite referred to the thickening of CI-rich layers, making it gain the most powerful EMI SE values, i.e. 42.8 dB for DCMP20-10 film (20 wt% CI, 10 wt% Ti3C2Tx) at 0.4 mm thickness. More importantly, the composite transformed from a reflection type to an absorption dominating EMI shielding material due to the multireflections and magneto-electric synergism in the CI-rich Ti3C2Tx/PVDF layers. Meanwhile, the EMI SE of the composites can be adjusted by not only increase of the overall thickness, but also the layer number of m-DCMP sheets. The thickness specific EMI SE was calculated as 165.25 dB mm−1 for 4-sheet composite film, a record high value amongst the high efficiency polymer-based EMI shielding materials. This method offered an alternative protocol for preferential integration of excellent EMI shielding performance with high mechanical performance in CPC materials.

A new device and procedure for the in situ quantification of the extent of the self-healing and the kinetics of self-healing of polymeric materials were proposed. The device consisted of flowing an inert gas below the sample placed in a hermetically closed chamber. When the sample was perforated/damaged, the gas passed through the hole made in the polymeric material and the gas flow rate declined as the self-healing was produced. Once the gas flow rate stopped, the self-healing was completed. The proposed method was simple, quick, and reproducible, and several in situ self-healing experiments at different temperatures could be performed in the same sample. As a proof of concept, the new device and method have been used for measuring the self-healing ability of different polyurethanes.

The presence of certain proteins in biofluids such as synovial fluid, blood plasma, and saliva gives these fluids non-Newtonian viscoelastic properties. The amount of these protein macromolecules in biofluids is an important biomarker for the diagnosis of various health conditions, including Alzheimer’s disease, cardiovascular disorders, and joint quality. However, existing technologies for measuring the behavior of macromolecules in biofluids have limitations, such as long turnaround times, complex protocols, and insufficient sensitivity. To address these issues, we propose non-contact, optical Brillouin and Raman spectroscopy to assess the viscoelasticity and chemistry of non-Newtonian solutions, respectively, at different temperatures in several minutes. In this work, bovine and human serum albumin solution-based biopolymers were studied to obtain both their collective dynamics and molecular chemical evolution across heat-driven phase transitions at various protein concentrations. The observed phase transitions at elevated temperatures could be fully delayed in heated biopolymers by appropriately raising the level of protein concentration. The non-contact optical monitoring of viscoelastic and chemical property evolution could represent novel potential mechano-chemical biomarkers for disease diagnosis and subsequent treatment applications, including hyperthermia.

Lightweight materials, such as polymers and composites, are increasingly used in the automotive and aerospace industries. Recently, there has been an increase in the use of these materials, especially in electric vehicles. However, these materials cannot shield sensitive electronics from electromagnetic interference (EMI). The current work investigates the EMI performance of these lightweight materials using an experimental setup based on the ASTM D4935-99 standard and EMI simulation using the ANSYS HFSS. This work studies how metal coating from zinc and aluminum bronze can improve the shielding performance of polymer-based materials, such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), and polyphthalamide (PPA). Based on the findings of this study, a thin coating (50 μm) of Zn on the surface of PPS and a thin coating of 5 μm and 10 μm of Al-Bronze, respectively, on the surface of PEEK and PPA have indicated an increase in the shielding effectiveness (SE) when subjected to EMI. The shielding effectiveness significantly increased from 7 dB for the uncoated polymer to approximately 40 dB at low frequencies and up to approximately 60 dB at high frequencies for coated polymers. Finally, various approaches are recommended for improving the SE of polymeric materials under the influence of EMI.

Grant PID2020-114694RB-I00 funded by MCIN/AEI 10.13039/501100011033. M.T.-O. is Fellow FPU of Ministry of Universities [grant FPU20/0045]., The following supporting information can be downloaded at: https:// www.mdpi.com/article/10.3390/polym15071726/s1, The main target of bone tissue engineering is to design biomaterials that support bone regeneration and vascularization. Nanostructured membranes of (MMA)1-co-(HEMA)1/(MA)3- co-(HEA)2 loaded with 5% wt of SiO2-nanoparticles (Si-M) were doped with zinc (Zn-Si-M) or doxycycline (Dox-Si-M). Critical bone defects were effectuated on six New Zealand-bred rabbit skulls and then they were covered with the membranes. After six weeks, a histological analysis (toluidine blue technique) was employed to determine bone cell population as osteoblasts, osteoclasts, osteo- cytes, M1 and M2 macrophages and vasculature. Membranes covering the bone defect determined a higher count of bone cells and blood vessels than in the sham group at the top regions of the defect. Pro-inflammatory M1 appeared in a higher number in the top regions than in the bottom regions, when Si-M and Dox-Si-M were used. Samples treated with Dox-Si-M showed a higher amount of anti-inflammatory and pro-regenerative M2 macrophages. The M1/M2 ratio obtained its lowest value in the absence of membranes. On the top regions, osteoblasts were more abundant when using Si-M and Zn-Si-M. Osteoclasts were equally distributed at the central and lateral regions. The sham group and samples treated with Zn-Si-M attained a higher number of osteocytes at the top regions. A preferential osteoconductive, osteoinductive and angiogenic clinical environment was created in the vicinity of the membrane placed on critical bone defects., MCIN/AEI, FPU of Ministry of Universities FPU20/0045

The free energy of crystallization of monomeric hard spheres as well as their thermodynamically stable polymorph have been known for several decades. In this work, we present semianalytical calculations of the free energy of crystallization of freely-jointed polymers of hard spheres as well as of the free energy difference between the hexagonal closed packed (HCP) and face-centered cubic (FCC) polymorphs. The phase transition (crystallization) is driven by an increase in translational entropy that is larger than the loss of conformational entropy of chains in the crystal with respect to chains in the initial amorphous phase. The conformational entropic advantage of the HCP polymer crystal over the FCC one is found to be ΔschHCP−FCC≈0.331×10−5k per monomer (expressed in terms of Boltzmann’s constant k). This slight conformational entropic advantage of the HCP crystal of chains is by far insufficient to compensate for the larger translational entropic advantage of the FCC crystal, which is predicted to be the stable one. The calculated overall thermodynamic advantage of the FCC over the HCP polymorph is supported by a recent Monte Carlo (MC) simulation on a very large system of 54 chains of 1000 hard sphere monomers. Semianalytical calculations using results from this MC simulation yield in addition a value of the total crystallization entropy for linear, fully flexible, athermal polymers of Δs≈0.93k per monomer.

This paper considers the synthesis of a novel nanocomposite based on reduced graphene oxide and oxidized carbon nanotubes modified with polyaniline and phenol-formaldehyde resin and developed through the carbonization of a pristine aerogel. It was tested as an efficient adsorbent to purify aquatic media from toxic Pb(II). Diagnostic assessment of the samples was carried out through X-ray diffractometry, Raman spectroscopy, thermogravimetry, scanning and transmission electron microscopy, and infrared spectroscopy. The carbonized aerogel was found to preserve the carbon framework structure. The sample porosity was estimated through nitrogen adsorption at 77 K. It was found that the carbonized aerogel predominantly represented a mesoporous material having a specific surface area of 315 m2/g. After carbonization, an increase in smaller micropores occurred. According to the electron images, the highly porous structure of the carbonized composite was preserved. The adsorption capacity of the carbonized material was studied for liquid-phase Pb(II) extraction in static mode. The experiment results showed that the maximum Pb(II) adsorption capacity of the carbonized aerogel was 185 mg/g (at pH 6.0). The results of the desorption studies showed a very low desorption rate (0.3%) at pH 6.5 and a rate of about 40% in a strongly acidic medium.

In this study, three copolymers of poly(methyl methacrylate) and poly(butyl acrylate) (PMMA-co-PBA) latex containing 1-octyl-3 methylimidazolium hexafluorophosphate (C8mimPF6), cellulose nanocrystals (CNCs), and C8mimPF6-CNCs were successfully synthesized through mini emulsion polymerization. These novel composites were each coated on mild steel panels and tested for their anti-corrosion performance by immersion of the coated samples in 3.5 wt% sodium chloride (NaCl) solution over a certain period. The synergistic anti-corrosion effects of the C8mimPF6-CNCs sample led to the highest coating resistance, charge transfer resistance, and corrosion inhibition efficiency and the lowest diffusion coefficient and corrosion rate. The proposed synergistic mechanism revealed that CNCs enhanced the barrier effect of the coating while C8mimPF6 inhibited corrosion when released.

Construction adhesives are usually polymers that have been modified to achieve specific properties so that they can be used under various loading conditions. An attempt was made to estimate the effect of fatigue loading on the temperature of an adhesive material by further physically modifying the basic adhesive composition used in the research. The temperature of the materials during the tests was recorded using a thermal imaging camera and a thermoelectric thermometer. For most materials tested at 20 Hz, an increase in the number of load cycles corresponded to an increase in the temperature of the samples. For a frequency of 30 Hz, after the temperature increased by a certain value, the temperature of the modified samples recorded with the thermal imaging camera decreased. Fatigue loading caused an increase of the temperature of all tested polymeric materials. Observation of the sample during testing with a thermal imaging camera allows a simple identification of the areas with the highest temperature and can be much more useful in practice than recording temperatures with a thermocouple thermometer, as thermocouples need to be properly positioned before testing.

Poly(ethylene oxide) (PEO) is one of the most famous polymer electrolytes; however, its low conductivity and capacity have prevented its commercial applications. This study utilizes carboxymethyl starch (CMS) and oxidative carboxymethyl cellulose (OCMC) natural polymers with a high potential to dissolve lithium ions (Li+) in to help PEO ionic conductivity. The semi-interpenetrating polymer networks (semi-IPNs) consist of crosslinked poly(ethylene glycol) methyl ether methacrylate (PEGMA) with poly(ethylene glycol) diallyl (PEGDA) and free CMS/OCMC chains. Effect of increasing the amount of natural polymer on the electrochemical properties of semi-IPNs is investigated. Semi-IPN CMS50% and semi-IPN OCMC50% deliver excellent results such as high conductivity (in order 10-2 Scm-1) at room temperature, electrochemical stability window higher than 4.5 V, high Li+ transfer number, high discharge capacities (191 and 203 mAh g–1 with capacity retention of 85 and 88.5% after 100 cycles at 0.2 C, respectively), and stable cyclic behavior.

Facile strategy enabling the fabrication of carbon dots (CDs) with favorable performance useful for various applications is highly desirable. Here, we report the fabrication of highly fluorescent carbon dots (CDs) towards sensitive metal ion detection, brightly fluorescent printing pattern, as well as green flame retardants for synthetic polymeric materials. CDs are synthesized by solvothermal treatment of polypropylene carbonate (PPC) with ethylenediamine, and the quantum yield of CDs could increase from 30 to 86% by further adding trace of citric acid. The abundant functional groups on the surface of CDs allow CDs well incorporated into polymers to form CD-loaded polystyrene (PS) microspheres, which are employed to construct fluorescent supraballs via triphase microfluidic technique and used as “inks” for uniform fluorescent patterns. Interestingly, the resultant CDs show good flame retardancy for highly flammable polymeric foams and fibers. The CDs surpass previously reported flame-retardant additives, to show excellent combustion resistance that the addition of 20 wt% CDs causes 75% decrease in the peak of heat release rate (P-HRR) for polyurethane (PU) foams. Significantly, a molecular dynamics simulation process for PU/CDs combustion is constructed. This work may spur the preparation and application of high-performance carbon-based nanomaterials.

We demonstrate here a novel method for the design of liquid crystals (LCs) via the cyclization of mesogens by flexible chains. For two azobenzene-4,4’-dicarboxylate derivatives, the cyclic dimer, cyclic bis(tetraethylene glycol azobenzene-4,4′-dicarboxylate) (CBTAD), shows LC properties with smectic A phase, while its linear counterpart, bis(2-(2’-hydroxyethyloxy)ethyl azobenzene-4,4′-dicarboxylate (BHAD), has no LC phase. The difference is ascribed to the shackling effect from the cyclic topology, which leads to the much smaller entropy change during phase transitions and increases the isotropic temperature greatly for cyclics. In addition, the trans-to-cis isomerization of azobenzene groups under UV-light is also limited in CBTAD. With the reversible isomerization of azobenzene groups, CBTAD showed interesting isothermal phase transition behaviors, where the LC phase disappeared upon photoirradiation of 365 nm UV-light, and recovered when the UV-light was off. Combined with the smectic LC nature, a novel UV-light tuned visible light regulator was designed, by simply placing CBTAD in two glass plates. The scattered phase of smectic LC was utilized as the “OFF” state for light passage, while the UV-light induced isotropic phase was utilized as the “ON” state. The shackling effect outlined here should be applicable for the design of cyclic LC oligomers/polymers with special properties.

Polymer-based thermally conductive composites have attracted tremendous interest in thermal management of electronics. However, it remains challenging to achieve high thermal conductivity partly because the difficulty to obtain favorable distribution and orientation of conductive fillers within the polymer matrix. Herein, networked boron nitride (BN) conductive pathway was realized within the poly (lactic acid) (PLA) matrix, via regenerated cellulose (RC)-assisted assembly of BN on Pickering emulsion interface based on the noncovalent interaction, followed by solvent evaporation and hot-compressing. The strong noncovalent interactions between BN and RC were found critical to enhance the wettability and stability of BN in aqueous media with a lowest mass ratio of 1:40 of RC and BN. The obtained PLA/BN composites feature a thermal conductivity of 1.06 W/mK at 28.4 wt% BN loading, representing an enhancement of 430% comparing to neat PLA, and the crystallinity of the composites could increase significantly from 11.7% (neat PLA) to 43.7%. This simple, environmentally friendly and effective strategy could be easily extended for effective construction of thermally conductive composites.

Designing of hetero-atomic doped carbon-based systems through pyrolysis of abundant element organic precursors is a novel approach to construct rational porous carbon materials. Herein, a highly-cross-linked triazine polymer is employed to fabricate N, P co-doped porous carbon (A-TDP-12) with tunable active nitrogen in the carbon framework for simultaneous enhancement of CO2 capture capability and Supercapacitance (SC). The synthesized A-TDP-12 possesses a typical hierarchically porous framework (micro-pores and meso-pores) with a large surface area (1332 m2 g−1) and a rich content of N (7.89 atomic %) and P (0.74 atomic %). It delivers a CO2 adsorption capacity of 1.52 and 5.68 mmol g−1 at 1 and 5 bar, respectively, with almost no decay after successive 8 recycles. In 6 M KOH aqueous electrolyte, A-TDP-12 exhibits a superior specific capacitance of 172.7 F g−1 at a current density of 1 A g−1. Even at a high current density of 10 A g−1, 80% of its initial capacity still remains. This work not only offers a novel strategy for fabricating promising adsorbents and electrodes for CO2 uptake and SCs, but also provides new insights into design of porous carbon material for related applications.

Halloysite nanotubes (HNTs) have been considered as a promising flame retardant fillers for polymers. In this work, the polyhedral oligomericsilsesquioxane (POSS) containing amino group was covalently grafted on the surface of HNTs with 3-(2,3-epoxypropoxy)propytrimethoxysilane as a chemical bridge. The POSS modified HNTs (HNTs-POSS) dispersed uniformly in the thermoplastic polyurethane (TPU) matrix and endowed TPU nanocomposites with enhanced tensile properties and fire safety. Cone calorimeter tests revealed that the introduction of 2 wt% HNTs-POSS to TPU matrix remarkably reduced the peak of heat release rate (PHRR) and total heat release (THR) by 60.0% and 18.3%, respectively. In addition, the peak CO production rate and total smoke release (TSR) could be significantly suppressed by the addition of HNTs-POSS. The well dispersed HNTs in combination with the ceramified silicon network from the thermal decomposition of POSS contributed to the formation of a continuous and compact char layer, exhibiting a tortuous effect by inhibiting heat diffusion and evaporation of volatile gaseous. In addition, the released crystal water from HNTs could dilute the combustible volatiles and then decline the combustion intensity. The tensile tests demonstrated that introduction of 2 wt% HNTs-POSS would enhance the maximum stress of TPU nanocomposite with a slight decrease of elongation at break. The combination of HNTs and POSS through the construction of effective interfacial interactions provides a feasible way to effectively enhance the fire safety of TPU nanocomposites without scarifying ductility.

Macromolecule nanocrystal network and strong interfacial interaction are always beneficial to enhance the mechanical property of polymer-based nanocomposites. Poly (vinyl alcohol) (PVA), a typical biocompatible semicrystalline polymer, is an ideal candidate for preparing high performance polymer-based nanocomposites. However, the rich hydrogen bonds between PVA matrix and graphene oxide (GO) can disrupt the formation of PVA nanocrystal network. Thus, it remains a great challenge to achieve both strong and tough PVA-GO nanocomposites. Herein, by introducing a novel Janus-like amphiphilic graphene oxide (JGO), both of hydrogen bonding and interfacial crystallization have been constructed between JGO sheets and PVA matrix. Benefiting from amphiphilic interfacial interaction and the enhanced crystal network, both PVA-JGO dried films and their swollen hydrogels films show superior mechanical properties than those of traditional PVA-GO nanocomposites. PVA-JGO dried films exhibit a 264% improvement of toughness at a JGO loading of 1wt%. Meanwhile, the corresponding PVA-JGO swollen hydrogel films display simultaneous improvement of nearly 8 times increase of tensile strength and 20 times increase of toughness compared to traditional PVA-GO nanocomposite. This work indicates multiple interfacial interactions and macromolecule crystal networks can be concurrent in PVA nanocomposites by innovative modification of nanofillers, providing a new strategy to construct PVA nanocomposites with high strength and high toughness. The integration of outstanding mechanical and swelling resistance properties on PVA-JGO nanocomposite films render their promising applications, such as packaging and toughening hydrogel materials.

Microporous organic polymers with high surface area are widely used in many applications. Among them, hypercrosslinked polymers have been extensively concerned because of their simple processes and low-cost reagents. However, due to most state-of-the-art strategies for HCPs based on condensation reactions, the release of small molecules such as hydrochloric acid and methanol involved in such strategies brings about new hazards to environment. Herein, we propose a method for fabrication of hypercrosslinked polymers via self-addition polymerization of divinyl benzene and its crosslinking with polar aromatic molecules. The hypercrosslinked polyDVB-based products are demonstrated by Friedel-Crafts addition reaction of double bonds on DVB that can connect adjacent phenyl rings of aromatic molecules to form the crosslinked networks. The HCPDVB-CB obtained in 1-chlorobutane as solvent has a high micropore content and displays high surface area up to 931 m2/g. Following this finding, DVB is used as a novel external crosslinker for knitting polar aromatic molecules. When L-phenylalanine and bisphenol A are used as the aromatic units, the obtained HCP(Phe-DVB) and HCP(BPA-DVB) could reach surface area of 612 m2/g and 471 m2/g, and have hydrogen uptake of 0.62 wt% and 0.58 wt% at 77 K and 1.13 bar by comparison with HCPDVB-CB having hydrogen uptake of 0.30 wt%, respectively.

The polymorphic transition of trans−1,4−polyisoprene (TPI) during stretching was investigated by in−situ wide−angle X−ray diffraction and Fourier transform infrared spectroscopy. The influences of the initial structure, stretching temperature, and strain rate on the contents of different crystal modifications (α, β) were explored. The results confirm that the α−β transition occurs during stretching of TPI that only contains α crystal (α-TPI). When the stress is relaxed, the β crystal formed during stretching remains, which indicates that the transition is irreversible. On the other hand, stretching of TPI that only contains β crystal (β-TPI) results in orientated β crystal. No β−α transition occurs during stretching. The different structures of stretched α−TPI and β-TPI exclude the previously proposed “melting−recrystallization mechanism”. The α−β transition depends significantly on temperature and strain rate, indicating the transition is governed both by thermodynamics and kinetics. Our results support a solid−solid transition mechanism rather than a melting−recrystallization mechanism. The irreversible nature of the transition is attributed to the metastability of the β phase in the unstretched state. Different from the “β phases” that appear in polymers with stress-induced reversible transitions, e.g. poly(butylene terephthalate) and poly(butylene succinate), the stability of β phase in TPI is high that can be long-lived. The strain rate dependence of α−β transition hinders the determination of critical stress for the transition. It further indicates that the local stress within the sample is more heterogeneous at higher strain rates.

Benzobisthiazole polymer with resonance-assisted hydrogen bonds (RAHBs) has been synthesized for both organic field-effect transistor and polymer solar cell applications. The properties of the hydrogen bonded polymer are compared with the reference polymer without RAHBs. Single-crystal X-ray diffraction analyses of the building block reveal that the RAHB interactions are formed between the carbamate hydrogen and imine nitrogen of the thiazoles. The hydrogen donor and acceptor are connected by π-conjugated molecular framework and the hydrogen-bridged quasi aromatic rings lock the conformation of the building block. The building block adopted a layered sandwich packing in crystal instead of slipped herringbone stacking which was often found in the crystal of benzobisthiazole derivatives. The polymer PCBTZ-TT with RAHBs showed deeper HOMO/LUMO energy level (about 0.2 eV) than reference polymer. The PCBTZ-TT demonstrated the hole mobility of 0.96 cm2 V-1 s-1 in field-effect transistor devices and achieved power conversion efficiency of 13.6% in solar cell devices with Y6 as acceptor without any additive.

Comb-like polymers with pendant-like perfluorocarbon side chains self-assemble into smectic lamellae and have been extensively used as water-repellent, hydrophobic coating materials characterized by large water contact angles (θ > 120°). As poly(perfluorooctyl acrylate) films are “apparently hydrophobic” (θ > 120°), the interaction of such materials and water molecules has been largely overlooked. To unravel the molecular-level interactions between water and apparently hydrophobic polymers, specular and off-specular neutron scattering experiments were conducted at defined osmotic pressure ΠH2O. The poly{2-[(perfluorooctylethyl)carbamate]ethyl} acrylate (PFAUr-C8), which had a carbamate linker, transitioned to another lamellar phase at 89 °C. At T = 25 °C; the lamellar periodicity of PFAUr-C8 slightly increased with decreasing osmotic pressure, while the vertical correlation length increased. However, the poly[(perfluorooctyl)ethyl] acrylate (PFA-C8) that did not contain a carbamate linker directly transitioned to a disordered phase at 84 °C. The lamellar periodicity of PFA-C8 was largely independent of the osmotic pressure, suggesting that PFA-C8 was poorly hydrated. Remarkably, the vertical correlation length decreased with decreasing osmotic pressure. Because hydration facilitated by the linker modulated the smectic lamellae of the poly(perfluoroalkyl acrylate), water molecules could be used to optimize the self-assembly of apparently hydrophobic liquid crystalline polymers. Self-assembled smectic lamellae of comb-like polymers with pendant-like perfluorocarbon side chains have been extensively used as water-repellent, hydrophobic coating materials, which are characterized by large water contact angles (θ > 120°). By measuring off-specular neutron scattering under defined osmotic pressures, we unraveled that such “apparently hydrophobic” materials interact with water and adapt the inter-lamellar correlation. This suggested that water molecules could be used to optimize the self-assembly of hydrophobic liquid crystalline polymers.

There is a requirement for the development of methods for the preparation of well-controlled polymers with aggregation-induced emission (AIE) properties. This requirement directed this current work towards a robust synthetic route, which would be applicable for preparation in water and the presence of many types of functional groups. Herein, aqueous Cu-mediated living radical polymerization (LRP) has been optimized to provide facile and rapid access to a diverse range of water-soluble AIE polymers at sub-ambient temperatures. Homo-, block and statistical copolymerization all proceeded to a near full monomer conversion (≥99%) within 1 or 2 h and exhibited narrow dispersity, even when DP was targeted up to 1000. This excellent control associated with this polymerisation technique and the high-end group fidelity achieved were further demonstrated by linear first order kinetics and successful in situ block copolymerization, respectively. Fine-tuning the monomer sequence and composition of poly(N-isopropylacrylamide) (PNIPAM) copolymers allows for different lower critical solution temperature (LCST) and fluorescent thermoresponsive nanoparticles, which spontaneously self-assembled to varying sizes in water as determined by a combination of techniques (DLS, SAXS and TEM). Additionally, the fluorescence intensity was demonstrated to depend on the polymer concentration, architecture of the side chains and temperature. Particularly, PNIPAM-containing polymers were resistant to reduction in thermo-induced emission. The good biocompatibility, photostability and high specificity make them promising candidates as lysosome-specific probes for application in bioimaging.

Three alternating conjugated polymers, namely PFTP, PCzTP, and PSiTP, which combine a thieno[3,4-b]pyrazine (TP) unit with different benzene-based donor units such as 9,9-dioctylfluorene, 9-heptadecyl-9H-carbazole and 5,5-dioctyl-5H-dibenzo[b,d]silole, were synthesized in good yield (> 85%) and high molecular weight up to Mn = 58 200 via direct arylation polymerization (DArP). All resultant polymers exhibit moderate bandgap of about 1.80 eV and strong deep red/near-infrared emitting in the solid state. Among them, the PSiTP-based electroluminescence (EL) devices with an architecture of ITO/PEDOT:PSS/PTAA/emitting layer/TPBi/LiF/Al give the best performance with a maximum luminance of 2543 cd/m2 at 478 mA/cm2. This work expands the application scope of high-performance conjugated polymers that can be synthesized by DArP.

In this study, graphene nanoplatelets (GNPs) were synthesized from graphite by a liquid-phase exfoliation (layer separation) method, and their surfaces were functionalized with poly(glycidyl methacrylate) (PGMA) by using the rotatingbed plasma-enhanced chemical vapor deposition (PECVD) method. Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and thermogravimetric (TGA) analyses were performed to characterize the unmodified (u-GNP) and modified GNP (PGMA-GNP). Epoxy nanocomposites were prepared with both types of GNPs at different loading levels (0.1–2% by weight). The role of the surface modification of the GNPs on the mechanical, thermal, electrical conductivity, contact angle, water sorption, and corrosion properties of the epoxy nanocomposite coatings was also investigated. Consequently, the tensile strength and Young’s modulus of the epoxy resin (ER)/PGMA-GNP nanocomposites were enhanced by 10.2–20 and 3.3–18.4%, respectively, as compared to the ER/u-GNP composites. Moreover, the nanocomposites prepared with PGMA-GNP had better water sorption and wettability properties than those prepared with u-GNP, but lower electrical conductivity. The corrosion test results showed that the addition of GNPs to epoxy effectively improved the corrosion resistance of the epoxy composites in high salinity, basic, and acidic environments.

Recently, Coordination Polymers (CPs) have been widely utilized as energy storage materials for reversible Lithium-Ion Batteries (LIBs) benefiting from their tunable building blocks and adjusted electrochemical properties. However, the unsatisfied electrochemical behavior of CPs with poor conductivity and sluggish ion transport kinetics is still a bottle-neck for their large-scale energy storage applications in LIBs. Herein, we display the rational fabrication of a conductive Sn-based coordination polymer (Sn-DHTPA) via judiciously choosing suitable building units. The Sn-DHTPA is employed as anode for LIBs, exhibiting superior reversible storage capacity of 1142.6 mA h g−1 at 0.1 A g−1 after 100 cycles and impressive rate storage capability of 287.7 mA h g−1 at 20 A g−1. More importantly, a robust cycling performance of 205.5 mA h g−1 at an extra-high current density of 20 A g−1 are observed without remarkable capacity-fading up to 1000 cycles. The behavior superiority of Sn-DHTPA is related to its advanced architecture with abundant lithium storage sites, high electrical conductivity and rapid lithium transport. A series of ex-situ characterizations reveal that the impressive lithium storage capacity is contributed by the redox active sites of both the aromatic linker and metal center related to in-situ generated metallic nanoparticles dispersed in the skeleton.

The development of light-mediated controlled radical polymerization has benefited from the discovery of novel photocatalysts, which could allow a precise light control over the polymerization process and the production of well-defined polymers. Here, we introduce oxygen-doped anthanthrene (ODA) as effective organic photocatalysts for photoinduced energy/electron transfer reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization. ODA phtocatalysts featur strong visible light absorption (e455 nm up to 2.4 x 104 M–1cm–1), ease-of-synthesis, a certain oxygen-tolerance, and high stability, which enables the photo-regulated RAFT polymerization with extremely low catalyst loading (0.1-10 ppm) and excellent control under visible light or sunlight. Furthermore, this organocatalytic living radical process is adaptable to the polymerization of a range of monomers including methyl methacrylate, butyl acrylate, styrene, and N,N-dimethyl acrylamide, and also the synthesis of diblock and decablock copolymers under metal-free conditions.

Reversible addition–fragmentation chain-transfer (RAFT) polymerization has been widely exploited to produce homogeneous and living polymer networks for advanced material design. In this work, we incorporate silica nanoparticles (SNPs) into a RAFT polymerization system to prepare a series of photocurable composite resins. These resins are applied to stereolithographic 3D printing to produce composite materials with enhanced mechanical properties. Relatively high loadings of SNPs (30 wt%) within the resins are achieved, allowing an increase in the 3D printed composite material tensile strength by 165% while simultaneously increasing the fracture toughness by 168%, compared with the pristine polymer materials. In addition, the inclusion of small amounts (1 wt%) of RAFT agent into the 3D printing resins also provide efficient control over thermomechanical, tensile, and fracture properties of the resulting materials. In particular, 3D printed SNP composite materials containing 30 wt% SNPs and 1 wt% RAFT show a 37% increase in elongation at break values and a 60% increase in tensile strength compared with free radical polymerization-based counterparts. The increased ductility of composite materials imparted via RAFT agent addition has not been reported and could provide a useful tool for optimizing the performance of composite materials prepared by 3D printing. Additionally, photoinduced reactivation of thiocarbonylthio groups provides access to spatially controlled post-printing functionalization of the surface of the composite materials. As such, RAFT-mediated 3D printing of composite resins is shown to be an effective strategy for developing composite materials with arbitrary combinations of well-defined mechanical properties and diverse chemical functionalities for material post-modification.

Sulfobetainic polymers were synthesized by polymeranalogous reaction of new amino celluloses starting from cellulose tosylate. To obtain different amino celluloses as starting building blocks, a comprehensive study with a selection of asymmetric and symmetric N-alkylated diamines was performed. For reaction with asymmetric diamines, it turned out that the primary amino moiety reacts preferably. Derivatives thus obtained consist in a neutral main structural unit and a cationic side structural unit, which is not described up to now. In order to investigate the reactivity of the amino celluloses 6-deoxy-6-(N,N,N′,N′-tetramethylethylenediamino) cellulose was used as uniform starting material for the design of novel polyampholytes by conversion with 1,3-propansultone. Detailed structure characterization was implemented by means of 1D and 2D-NMR spectroscopy.

Optimizing the properties of electrospun polymer-perovskite nanofibers is considered essential for improving the performance of flexible optoelectronic devices. Here, the influence of electrospinning setup parameters (i.e., electrical voltage, collector type (planar or rotary), rotation speed, as well as process time) on the properties (i.e., external structure, perovskite crystallinity, optical properties, thermal properties, the shrinkage ratio, mechanical properties, and long-term stability) of electrospun polyvinylpyrrolidone nanofibers modified with cesium lead iodide nanocrystals has been studied. The results have shown that the structure of nanofibers is related to the electrical voltage, collector rotation speed, and process duration. Perovskite crystallinity and light absorption have improved by increasing the electrical voltage or/and the process time. The polymer’s glass transition temperature is affected by the embedded perovskite and the collector’s rotation speed. The shrinkage ratio and mechanical properties of nanofibers have been controlled by the rotation speed and the electrical voltage. The shrinkage is caused by the stress created in the nanofibers during the electrospinning process. The best mechanical properties can be noticed with the rotary collector at a rotational speed of 500--750 rpm. Nanofibers have shown good long-term stability and high thermal stability. The long-term stability is inversely proportional to the value of the electrical voltage.

Polymer flooding is one of the techniques used to enhance oil recovery from depleted hydrocarbon reservoirs. Although this technology is popular for this application, the shearing effect in the injection process causes poor performance, which is an obstacle to meeting the needs of the formation. An experimental evaluation of the rheological properties, viscoelasticity, hydrodynamic size, static adsorption, and seepage characteristics of the associated polymer solution before and after shearing was conducted to determine the influence of shearing on the polymer solution. The results show that the effect of shear on the polymer was irreversible, and the properties of the polymer solution damaged by shear were attenuated. After the critical associating concentration, the associated polymer can recover its solution properties through hydrophobic association, which can improve the shear resistance of the polymer solution and make its own rheological law and reduce the viscoelastic change. Although the hydrodynamic size, viscoelasticity, and adsorption capacity of the polymer solution after shear failure decreased, strong flow resistance during porous media seepage and mobility control was achieved. Improving the shear resistance of the polymer solution by increasing the intermolecular force is proposed to develop new polymer systems for subsequent oil displacement.

The dynamic light scattering method was successfully applied to determine the molar mass of nitrocellulose. The methodology of nitrocellulose fractionation in acetonic solutions is described in detail; six polymer fractions with monomodal distribution were obtained. It was shown that the unfractionated colloxylin with polymodal molar mass distribution had mass average molecular mass values of 87.3 ± 14.1, 28.3 ± 7.3, and 0.54 ± 0.17 kDa when investigated by the dynamic light scattering method. The viscometric method only provided integral viscosity average molar mass equal to 56.7 ± 5.8 kDa.

Functionalisation of technological nanopores and investigation of their transport properties have attracted considerable interest from scientific as from technological point of view, among others due to their potential regarding molecular transport design. Asymmetric design of nanopore structure and functionalisation is expected to trigger increased and directed transport of ionic species. Based on this motivation, we demonstrate a layer-selective polymer functionalisation in a mesoporous double layer thin film to generate nanoscale step gradient architectures with asymmetric charge distribution by taking advantage of co-condensation and polymer modification techniques. Thereby, mesoporous silica and co-condensed mesoporous amino silica thin films are combined to double layered films with a film thickness of 300 – 400 nm in both sequential arrangements, respectively. Iniferter initiated polymerisation is used to selectively functionalise only the amino silica layer with polymers such as poly(2-(methacryloyloxy)ethyltrimethylammonium chloride) (PMETAC) in a grafting from approach. Investigation of the ionic pore accessibility of the mesoporous double layered films before and after layer-selective polymer functionalisation shows that the ionic pore accessibility is dominated by the bottom layer when overcoming the electrostatic repulsion of the top layer.

A conical-shaped atmospheric pressure plasma jet (CS-APPJ) was developed to overcome a standard limitation of APPJs, which is their small treatment area. The CS-APPJs increase the treatment area but use the same gas flow. In the present work, polypropylene samples were treated by CS-APPJ and characterized by scanning electron microscope (SEM), the contact angle, Fourier-transformed infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was observed that the treatment co-occurs on the face directly in contact with the plasma and on the opposite face (OF) of the samples, i.e., no contact. However, the treatment changed the chemical composition on each side; the OF is rougher than the direct contact face (DCF), probably due to the oxygen groups in excess at the DCF and nitrogen in quantity at the OF. Although simultaneous treatment of both sides of the sample occurs for most atmospheric plasma treatments, this phenomenon is not explored in the literature.

Efforts to mitigate the effects of feral cats through the management of remnant or reintroduced populations of threatened species, are often unsuccessful due to predation by control-averse feral cats, or 'problem individuals'. In order to target these animals, we have developed the Population Protecting Implant (PPI). PPIs are designed to be implanted subcutaneously in a native animal. If the animal is preyed upon, and the implant ingested by a feral cat, release of a toxic payload is triggered in the acidic stomach environment and the problem individual is eliminated. We introduce the first toxic implant incorporating the poison sodium fluoroacetate. Manufactured via fluidised-bed spray coating, toxic implants exhibited uniform reverse enteric coatings and low intra-batch variation. Toxic implants were found to exhibit favourable stability at subcutaneous pH in vitro, and rapidly release their toxic payload in vitro at gastric pH. However, limited stability was demonstrated in rats in vivo (similar to 39-230 d), due to the use of a filament scaffold to enable coating and was likely exacerbated by metachromatic interactions caused by 1080. This work highlights that future development of the PPIs should primarily focus on removal of the filament scaffold, to afford implants with increased in vivo stability. Refereed/Peer-reviewed

The heterogeneous structure that exists in virtually all hydrogels has a significant influence on the resulting strength and toughness. While the internal structure has been observed with electron microscopy, it is difficult to measure the in situ local polymer concentration in the native swollen state. In this study, a modified microelectrode technique (MET) was employed to measure the Donnan potential of a heterogeneous hydrogel with a phase-separated structure. With this method, we succeeded in observing quantitative in situ polymer concentrations ranging from 10.2 mu mol/L to several hundred mmol/L. From the obtained concentration profiles, we could successfully evaluate the internal phase-separated structure with a resolution of less than 0.8 mu m. Using MET, we could estimate the average activity coefficient of the hydrogel, and we found a difference in concentration between the dense and sparse phases. We demonstrate that MET is a powerful method that can locally and quantitatively measure the polyelectrolyte concentration distribution within hydrogels. Furthermore, this method can be applied to cells and organs in vivo due to their similarities with polyelectrolytes. Enabling the in situ determination of the internal structures of biomaterials could have important implications toward the characterization of damaged and diseased tissues on the local scale.

Both shape memory and self-healing polymers have received significant attention from the materials science community. The former, for their application as actuators, self-deployable structures, and medical devices; and the latter, for extending the lifetime of polymeric products. Both effects can be stimulated by heat, which makes resistive heating a practical approach to trigger these effects. Here we show a conductive polyketone polymer and carbon nanotube composite with cross-links based on the thermo-reversible furan/maleimide Diels–Alder chemistry. This approach resulted in products with efficient electroactive shape memory effect, shape reprogrammability, and self-healing. They exhibit electroactive shape memory behavior with recovery ratios of about 0.9; requiring less than a minute for shape recovery; electroactive self-healing behavior able to repair microcracks and almost fully recover their mechanical properties; requiring a voltage in the order of tens of volts for both shape memory and self-healing effects. To the best of our knowledge, this is the first report of electroactive self-healing shape memory polymer composites that use covalent reversible Diels–Alder linkages, which yield robust solvent-resistant polymer networks without jeopardizing their reprocessability. These responsive polymers may be ideal for soft robotics and actuators. They are also a step toward sustainable materials by allowing an increased lifetime of use and reprocessability.

We, herein, report the fabrication of light-scattering switches from polymer microsphere-filled liquid crystals (PFLCs) using pseudopeptidic bottlebrush polymers. A simple method of precipitation o...