Polymers, Volume 9, Issue 1 (January 2017) – 30 articles

There is an increasing interest in applying the technology of electrospinning for making ultrafine fibers from biopolymers for food-grade applications, and using pullulan (PUL) as a carrier to improve the electrospinnability of proteins and other naturally occurring polyelectrolytes. In this study, PUL solutions containing NaCl or Na₃C₆H₅O₇ at different concentrations were electrospun. The inclusion of salts interrupted the hydrogen bonding and altered solution properties, such as viscosity, electric conductivity, and surface tension, as well as physical properties of fibers thus obtained, such as appearance, size, and melting point. The exogenous Na⁺ associated to the oxygen in the C6 position of PUL as suggested by FTIR measurement and was maintained during electrospinning. Bead-free PUL fibers could be electrospun from PUL solution (8%, w/v) in the presence of a 0.20 M NaCl (124 ± 34 nm) or 0.05 M Na₃C₆H₅O₇ (154 ± 36 nm). The further increase of NaCl or Na₃C₆H₅O₇ resulted in fibers that were flat with larger diameter sizes and defects. SEM also showed excess salt adhering on the surfaces of PUL fibers. Since most food processing is not carried out in pure water, information obtained through the present research is useful for the development of electrospinning biopolymers for food-grade applications. Full article

In this study, seven thermoresponsive methacrylate terpolymers with the same molar mass (MM) and composition but various architectures were successfully synthesized using group transfer polymerization (GTP). These terpolymers were based on tri(ethylene glycol) methyl ether methacrylate (TEGMA, A unit), n-butyl methacrylate (BuMA, B unit), and 2-(dimethylamino)ethyl methacrylate (DMAEMA, C unit). Along with the more common ABC, ACB, BAC, and statistical architectures, three diblock terpolymers were also synthesized and investigated for the first time, namely (AB)C, A(BC), and B(AC); where the units in the brackets are randomly copolymerized. Two BC diblock copolymers were also synthesized for comparison. Their hydrodynamic diameters and their effective pK_as were determined by dynamic light scattering (DLS) and hydrogen ion titrations, respectively. The self-assembly behavior of the copolymers was also visualized by transmission electron microscopy (TEM). Both dilute and concentrated aqueous copolymer solutions were extensively studied by visual tests and their cloud points (CP) and gel points were determined. It is proven that the aqueous solution properties of the copolymers, with specific interest in their thermoresponsive properties, are influenced by the architecture, with the ABC and A(BC) ones to show clear sol-gel transition. Full article

Camellia sinensis, which is obtained from green tea extract (GTE), has been widely used in therapy owing to the antioxidant, chemoprotective, and anti-inflammatory activities of its chemical components. However, GTE is an unstable compound, and may undergo reactions that lead to a reduction or loss of its effectiveness and even its degradation. Hence, an attractive approach to overcome this problem to protect the GTE is its incorporation into liquid crystalline systems (LCS) that are drug delivery nanostructured systems with different rheological properties, since LCS have both fluid liquid and crystalline solid properties. Therefore, the aim of this study was to develop and characterize GTE-loaded LCS composed of polyoxypropylene (5) polyoxyethylene (20) cetyl alcohol, avocado oil, and water (F25E, F29E, and F32E) with different rheological properties and to determine their anti-inflammatory efficacy. Polarized light microscopy revealed that the formulations F25, F29, and F32 showed hexagonal, cubic, and lamellar liquid crystalline mesophases, respectively. Rheological studies showed that F32 is a viscous Newtonian liquid, while F25 and F29 are dilatant and pseudoplastic non-Newtonian fluids, respectively. All GTE-loaded LCS behaved as pseudoplastic with thixotropy; furthermore, the presence of GTE increased the S values and decreased the n values, especially in F29, indicating that this LCS has the most organized structure. Mechanical and bioadhesive properties of GTE-unloaded and -loaded LCS corroborated the rheological data, showing that F29 had the highest mechanical and bioadhesive values. Finally, in vivo inflammation assay revealed that the less elastic and consistent LCS, F25E and F32E presented statistically the same anti-inflammatory activity compared to the positive control, decreasing significantly the paw edema after 4 h; whereas, the most structured and elastic LCS, F29E, strongly limited the potential effects of GTE. Thereby, the development of drug delivery systems with suitable rheological properties may enhance GTE bioavailability, enabling its administration via the skin for the treatment of inflammation. Full article

⁶⁰Co γ-ray irradiation-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization at room temperature with 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the chain transfer agent was first applied to acrylonitrile (AN) polymerization, providing a “green” platform for preparing polyacrylonitrile (PAN)-based carbon fibers using an environment-friendly energy source. Various effects of dose rate, molar ratio of the monomer to the chain transfer agent, monomer concentration and reaction time on the AN polymerization behaviors were performed to improve the controllability of molecular the weight and molecular weight distribution of the obtained PAN. The feature of the controlled polymerization was proven by the first-order kinetics, linear increase of the molecular weight with the monomer conversion and a successful chain-extension experiment. The molecular weight and molecular weight distribution of PAN were characterized by size exclusion chromatography (SEC). ¹H NMR and Matrix assisted laser desorption ionization/time of flight mass spectra (MALDI-TOF-MS) confirmed the chain-end functionality of PAN, which also was supported by the successful chain-extension experiments of original PANs with acrylonitrile and styrene as the second monomers respectively. Full article

Biodegradable stents made of poly-l-lactic acid (PLLA) have a promising prospect thanks to high biocompatibility and a favorable biodegradation period. However, due to the low stiffness of PLLA, polymeric stents have a lower radial stiffness and larger foreshortening. Furthermore, a stent is a tiny meshed tube, hence, it is difficult to make a polymeric stent. In the present study, a finite element analysis-based optimization method combined with Kriging surrogate modeling is firstly proposed to optimize the stent structure and stent microinjection molding process, so as to improve the stent mechanical properties and microinjection molding quality, respectively. The Kriging surrogate models are constructed to formulate the approximate mathematical relationships between the design variables and design objectives. Expected improvement is employed to balance local and global search to find the global optimal design. As an example, the polymeric ART18Z stent was investigated. The mechanical properties of stent expansion in a stenotic artery and the molding quality were improved after optimization. Numerical results demonstrate the proposed optimization method can be used for the computationally measurable optimality of stent structure design and stent microinjection molding process. Full article

Microwave absorbing materials (MAMs) are paving the way for exciting applications in electromagnetic (EM) pollution precaution and national defense security, as they offer an advanced alternative to conventional reflection principles to fundamentally eliminate the EM waves. Conjugated polymer (CP)-based composites appear as a promising kind of MAM with the desirable features of low density and high performance. In this review, we introduce the theory of microwave absorption and summarize recent advances in the fabrication of CP-based MAMs, including rational design of the microstructure of pure conjugated polymers and tunable chemical integration with magnetic ferrites, magnetic metals, transition metal oxides, and carbon materials. The key point of enhancing microwave absorption in CP-based MAMs is to regulate their EM properties, improve matching of characteristic impedance, and create diversified loss mechanisms. The examples presented in this review will provide new insights into the design and preparation of CP-based composites that can satisfy the high demands of the oncoming generation of MAMs. Full article

The influence of short-term water absorption on the mechanical properties of halloysite nanotubes-multi layer graphene reinforced polyester hybrid nanocomposites has been investigated. The addition of nano-fillers significantly increased the flexural strength, tensile strength, and impact strength in dry and wet conditions. After short-term water exposure, the maximum microhardness, tensile, flexural and impact toughness values were observed at 0.1 wt % multi-layer graphene (MLG). The microhardness increased up to 50.3%, tensile strength increased up to 40% and flexural strength increased up to 44%. Compared to dry samples, the fracture toughness and surface roughness of all types of produced nanocomposites were increased that may be attributed to the plasticization effect. Scanning electron microscopy revealed that the main failure mechanism is caused by the weakening of the nano-filler-matrix interface induced by water absorption. It was further observed that synergistic effects were not effective at a concentration of 0.1 wt % to produce considerable improvement in the mechanical properties of the produced hybrid nanocomposites. Full article

We employ H₂/Ar low-damage plasma treatment (H₂/Ar-LDPT) to reduce graphene oxide (GO) coating on a polymer substrate—polyethylene terephthalate (PET)—with the assistance of atomic hydrogen (H_α) at low temperature of 70 °C. Four-point probing and ultraviolet-visible (UV-Vis) spectroscopy demonstrate that the conductivity and transmittance can be controlled by varying the H₂/Ar flow rate, treatment time, and radio-frequency (RF) power. Optical emission spectroscopy reveals that the H_α intensity depends on these processing parameters, which influence the removal of oxidative functional groups (confirmed via X-ray photoelectron spectroscopy) to yield reduced GO (rGO). To further improve the conductivity while maintaining high transmittance, we introduce silver nanowires (AgNWs) between rGO and a PET substrate to obtain a hybrid rGO/AgNWs/PET with a sheet resistance of ~100 Ω/sq and 81% transmittance. In addition, the hybrid rGO/AgNWs thin film also shows high flexibility and durability and is suitable for flexible and wearable electronics applications. Full article

Nitrogen doped carbon materials as electrodes of supercapacitors have attracted abundant attention. Herein, we demonstrated a method to synthesize N-doped macroporous carbon materials (NMC) with continuous channels and large size pores carbonized from polyaniline using multiporous silica beads as sacrificial templates to act as electrode materials in supercapacitors. By the nice carbonized process, i.e., pre-carbonization at 400 °C and then pyrolysis at 700/800/900/1000 °C, NMC replicas with high BET specific surface areas exhibit excellent stability and recyclability as well as superb capacitance behavior (~413 F $\cdot$ g⁻¹) in alkaline electrolyte. This research may provide a method to synthesize macroporous materials with continuous channels and hierarchical pores to enhance the infiltration and mass transfer not only used as electrode, but also as catalyst somewhere micro- or mesopores do not work well. Full article

This review summarizes the most widely used mechanisms in memory devices based on conjugated polymers, such as charge transfer, space charge traps, and filament conduction. In addition, recent studies of conjugated polymers for memory device applications are also reviewed, discussed, and differentiated based on the mechanisms and structural design. Moreover, the electrical conditions of conjugated polymers can be further fine-tuned by careful design and synthesis based on the switching mechanisms. The review also emphasizes and demonstrates the structure-memory properties relationship of donor-acceptor conjugated polymers for advanced memory device applications. Full article

Long-timescale molecular dynamics simulations were performed to estimate the actual physical nature of a united-atom model of polyethylene (PE). Several scaling laws for representative polymer properties are compared to theoretical predictions. Internal structure results indicate a clear departure from theoretical predictions that assume ideal chain statics. Chain motion deviates from predictions that assume ideal motion of short chains. With regard to linear viscoelasticity, the presence or absence of entanglements strongly affects the duration of the theoretical behavior. Overall, the results indicate that Gaussian statics and dynamics are not necessarily established for real atomistic models of PE. Moreover, the actual physical nature should be carefully considered when using atomistic models for applications that expect typical polymer behaviors. Full article

Bio-based polymer foams have been gaining immense attention in recent years due to their positive contribution towards reducing the global carbon footprint, lightweighting, and enhancing sustainability. Currently, polylactic acid (PLA) remains the most abundant commercially consumed biopolymer, but suffers from major drawbacks such as slow crystallization rate and poor melt processability. However, blending of PLA with a secondary polymer would enhance the crystallization rate and the thermal properties based on their compatibility. This study investigates the physical and compatibilized blends of PLA/poly (butylene succinate-co-adipate) (PBSA) processed via supercritical fluid-assisted (ScF) injection molding technology using nitrogen (N₂) as a facile physical blowing agent. Furthermore, this study aims at understanding the effect of blending and ScF foaming of PLA/PBSA on crystallinity, melting, and viscoelastic behavior. Results show that compatibilization, upon addition of triphenyl phosphite (TPP), led to an increase in molecular weight and a shift in melting temperature. Additionally, the glass transition temperature (T_g) obtained from the tanδ curve was observed to be in agreement with the T_g value predicted by the Gordon–Taylor equation, further confirming the compatibility of PLA and PBSA. The compatibilization of ScF-foamed PLA–PBSA was found to have an increased crystallinity and storage modulus compared to their physically foamed counterparts. Full article

Chitosan is a natural polymer that has been widely utilized for many purposes in the food, textile, agriculture, water treatment, cosmetic and pharmaceutical industries. Based on its characteristics, including biodegradability, non-toxicity and antimicrobial properties, it has been employed effectively in wound healing applications. Importantly, however, it is necessary to improve chitosan’s capacities by combination with zinc oxide (ZnO), titanium dioxide (TiO₂) and silver (Ag) nanoparticles (NPs). In this review of many of the latest research papers, we take a closer look at the antibacterial effectiveness of chitosan combined with ZnO, TiO₂ and Ag NPs and also evaluate the specific wound healing application potentials. Full article

Polymeric materials display distinguished characteristics which stem from the interplay of phenomena at various length and time scales. Further development of polymer systems critically relies on a comprehensive understanding of the fundamentals of their hierarchical structure and behaviors. As such, the inherent multiscale nature of polymer systems is only reflected by a multiscale analysis which accounts for all important mechanisms. Since multiscale modelling is a rapidly growing multidisciplinary field, the emerging possibilities and challenges can be of a truly diverse nature. The present review attempts to provide a rather comprehensive overview of the recent developments in the field of multiscale modelling and simulation of polymeric materials. In order to understand the characteristics of the building blocks of multiscale methods, first a brief review of some significant computational methods at individual length and time scales is provided. These methods cover quantum mechanical scale, atomistic domain (Monte Carlo and molecular dynamics), mesoscopic scale (Brownian dynamics, dissipative particle dynamics, and lattice Boltzmann method), and finally macroscopic realm (finite element and volume methods). Afterwards, different prescriptions to envelope these methods in a multiscale strategy are discussed in details. Sequential, concurrent, and adaptive resolution schemes are presented along with the latest updates and ongoing challenges in research. In sequential methods, various systematic coarse-graining and backmapping approaches are addressed. For the concurrent strategy, we aimed to introduce the fundamentals and significant methods including the handshaking concept, energy-based, and force-based coupling approaches. Although such methods are very popular in metals and carbon nanomaterials, their use in polymeric materials is still limited. We have illustrated their applications in polymer science by several examples hoping for raising attention towards the existing possibilities. The relatively new adaptive resolution schemes are then covered including their advantages and shortcomings. Finally, some novel ideas in order to extend the reaches of atomistic techniques are reviewed. We conclude the review by outlining the existing challenges and possibilities for future research. Full article

The synthesis and photoluminescence properties of crystal crosslinked gels (CCGs) with an aggregation-induced emission (AIE) active crosslinker derived from tetraphenylethene (TPE) is discussed in this article. The CCG was prepared from a metal organic framework (MOF) with large pore aperture to allow the penetration of TPE crosslinker. The obtained CCG possessed a rectangular shape originated from the parent MOF, KUMOF. The CCG showed stimuli-responsive photoluminescence behavior depending on the swelling degree, thus the photoluminescence intensity was higher at higher swelling degree. By changing the solvent, water content, or ionic strength, the photoluminescence intensity was controllable, accompanying the change of swelling degree. Moreover, emission color tuning was also achieved by the introduction of luminescent rare earth ions to form a coordination bonding with residual carboxylate inside the CCG. Full article

In this paper, the influence of the molecular structure of polylactide (PLA)—characterised by its molar mass and content of d-lactide isomer—on the molecular ordering and α’–α form transition during fibre manufacturing by the wet spinning method is described. Fibres were studied by wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Additionally, the physical and mechanical properties of the fibres were determined. This study also examines the preliminary molecular ordering and crystallisation of PLA fibres at various draw ratios. The performed experiments clearly show the dependence of the molecular ordering of PLA on the molar mass and d-lactide content during the wet spinning process. The fibres manufactured from PLA with the lowest content of d-lactide and the lowest molar mass were characterised by a higher tendency for crystallisation and a higher possibility to undergo the disorder-to-order phase transition (α’ to α form). The structural changes in PLA explain the observed changes in the physical and mechanical properties of the obtained fibres. Full article

Understanding the lateral variations in the elemental and chemical state of constituents induced by electrochemical reactions at nanoscales is crucial for the advancement of electrochemical materials science. This requires in situ studies to provide observables that contribute to both modeling beyond the phenomenological level and exactly transducing the functionally relevant quantities. A range of X-ray coherent diffraction imaging (CDI) approaches have recently been proposed for imaging beyond the diffraction limit with potentially dramatic improvements in time resolution with chemical sensitivity. In this paper, we report a selection of ptychography results obtained in situ during the electrodeposition of a metal–polymer nanocomposite. Our selection includes dynamic imaging during electrochemically driven growth complemented with absorption and phase spectroscopy with high lateral resolution. We demonstrate the onset of morphological instability feature formation and correlate the chemical state of Mn with the local growth rate controlled by the current density distribution resulting from morphological evolution. Full article

Radical solvent-free suspension polymerization of styrene with 3-mercapto hexyl-methacrylate (MHM) as the branching monomer has been carried out using 2,2′-azobisisobutyronitrile (AIBN) as the initiator to prepare branched polymer beads of high purity. The molecular weight and branching structure of the polymers have been characterized by triple detection size exclusion chromatography (TD-SEC), proton nuclear magnetic resonance spectroscopy (¹H-NMR), and Fourier transform infrared spectroscopy (FTIR). The glass transition temperature and rheological properties have been measured by using differential scanning calorimetry (DSC) and rotational rheometry. At mole ratios of MHM to AIBN less than 1.0, gelation was successfully avoided and branched polystyrene beads were prepared in the absence of any solvent. Branched polystyrene has a relatively higher molecular weight and narrower polydispersity (M_w.MALLS = 1,036,000 g·mol⁻¹, M_w/M_n = 7.76) than those obtained in solution polymerization. Compared with their linear analogues, lower glass transition temperature and decreased chain entanglement were observed in the presently obtained branched polystyrene because of the effects of branching. Full article

We investigate the conformational properties of polymers in ionic microgels in the presence of salt ions by molecular dynamics simulations and analytical theory. A microgel particle consists of coarse-grained linear polymers, which are tetra-functionally crosslinked. Counterions and salt ions are taken into account explicitly, and charge-charge interactions are described by the Coulomb potential. By varying the charge interaction strength and salt concentration, we characterize the swelling of the polyelectrolytes and the charge distribution. In particular, we determine the amount of trapped mobile charges inside the microgel and the Debye screening length. Moreover, we analyze the polymer extension theoretically in terms of the tension blob model taking into account counterions and salt ions implicitly by the Debye–Hückel model. Our studies reveal a strong dependence of the amount of ions absorbed in the interior of the microgel on the electrostatic interaction strength, which is related to the degree of the gel swelling. This implies a dependence of the inverse Debye screening length κ on the ion concentration; we find a power-law increase of κ with the Coulomb interaction strength with the exponent $3/5$ for a salt-free microgel and an exponent $1/2$ for moderate salt concentrations. Additionally, the radial dependence of polymer conformations and ion distributions is addressed. Full article

Carbon nanotubes (CNTs) are attractive nanostructures that serve as multifunctional transporters in biomedical applications, especially in the field of cancer therapy and diagnosis. Owing to their easily tunable nature and remarkable properties, numerous functionalizations and treatments of CNTs have been attempted for their utilization as hybrid nano-carriers in the delivery of various anticancer drugs, genes, proteins, and immunotherapeutic molecules. In this review, we discuss the current advances in the applications of CNT-based novel delivery systems with an emphasis on the various functionalizations of CNTs. We also highlight recent findings that demonstrate their important roles in cancer imaging applications, demonstrating their potential as unique agents with high-level ultrasonic emission, strong Raman scattering resonance, and magnetic properties. Full article

Composites of LDPE filled with different amounts of graphene nanoplatelets (GnP) were prepared in form of films by means of precoating technique and single screw melt-extrusion using two types of screws, compression and mixing. This manufacturing process imposes strong anisotropy on the sample’s morphology, in which the nanoplatelets become oriented along the extrusion direction. Such orientation of GnP in LDPE matrix is confirmed by scanning electron microscopy observations and it yields unique electrical properties. As compared to pure LDPE, significant reductions of the through-plane conductivity are found for the composites at relatively low electric fields (<20 kV/mm) at low filler concentrations. Above the field level of 20 kV/mm, a crossover effect is observed that results in a strong field dependency of the conductivity where the non-linear behavior starts to dominate. Moreover, differential scanning calorimetry (DSC) results indicate a decrease in polymer crystallinity of the composite matrix with increasing filler content, whereas thermogravimetric (TG) analysis shows a slight increase in the material’s thermal stability. Application of GnP also leads to improvement of mechanical properties, manifested by the increase of Young’s modulus and tensile strength in both types of samples. Full article

A new hybrid material for the removal of polycyclic aromatic hydrocarbons (PAH) from water was prepared by the polymerization of pentynyl beta-cyclodextrin (PyβCD) and silica micro-particles (SMP). Phenanthrene, being one of the important members of the PAH family and a potential risk for environmental pollution, was selected for this study. Results show that phenanthrene removal efficiency of the SMP was improved significantly after hybridization with PyβCD-polymer. Approximately 50% of the phenanthrene was removed in the first 60 min and more than 95% was removed in less than 7 h when 25 mL of the 2 ppm aqueous phenanthrene solution was incubated with the 100 mg of SMP-PyβCD-polymer material. Infrared spectroscopy and thermal gravimetric analysis show that the enhanced efficiency of the SMP-PyβCD-polymer compared to the unmodified SMP was due to the formation of the inclusion complexation of phenanthrene with the PyβCD. These results indicate that SMP-PyβCD polymers have a potential to be applied as molecular filters in water purification systems and also for waste water treatment. Full article

In the electrospinning process, a modified parallel electrode method (MPEM), conducted by placing a positively charged ring between the needle and the parallel electrode collector, was used to fabricate highly aligned carbon nanotubes/polyacrylonitrile (CNTs/PAN) composite nanofibers. Characterizations of the samples—such as morphology, the degree of alignment, and mechanical and conductive properties—were investigated by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), universal testing machine, high-resistance meter, and other methods. The results showed the MPEM could improve the alignment and uniformity of electrospun CNTs/PAN composite nanofibers, and enhance their mechanical and conductive properties. This meant the successful preparation of highly aligned CNT-reinforced PAN nanofibers with enhanced physical properties, suggesting their potential application in appliances and communication areas. Full article

The main objective of this study was to determine the effect of biochemical modification of epoxy adhesive compounds on the mechanical properties of a cured adhesive exposed to various climatic factors. The epoxy adhesive was modified by lyophilized fungal metabolites and prepared by three methods. Additionally, the adhesive compound specimens were seasoned for two months at a temperature of 50 °C and 50% humidity in a climate test chamber, Espec SH 661. The tensile strength tests of the adhesive compounds were performed using a Zwick/Roell Z150 testing machine in compliance with the DIN EN ISO 527-1 standard. The examination of the adhesive specimens was performed using two microscopes: a LEO 912AB transmission electron microscope equipped with Quantax 200 for EDS X-ray spectroscopy and a Zeiss 510 META confocal microscope coupled to an AxioVert 200M. The experiments involved the use of a CT Skyscan 1172 tomograph. The results revealed that some mechanical properties of the modified adhesives were significantly affected by both the method of preparation of the adhesive compound and the content of the modifying agent. In addition, it was found that seasoning of the modified adhesives does not lead to a decrease in some of their mechanical properties. Full article

A significant amount of academic and industrial research efforts are devoted to the encapsulation of active substances within micro- or nanocarriers. The ultimate goal of core–shell systems is the protection of the encapsulated substance from the environment, and its controlled and targeted release. This can be accomplished by employing “stimuli-responsive” materials as constituents of the capsule shell. Among a wide range of factors that induce the release of the core material, we focus herein on the light stimulus. In polymers, this feature can be achieved introducing a photo-sensitive segment, whose activation leads to either rupture or modification of the diffusive properties of the capsule shell, allowing the delivery of the encapsulated material. Micro- and nano-encapsulation techniques are constantly spreading towards wider application fields, and many different active molecules have been encapsulated, such as additives for food-packaging, pesticides, dyes, pharmaceutics, fragrances and flavors or cosmetics. Herein, a review on the latest and most challenging polymer-based micro- and nano-sized hollow carriers exhibiting a light-responsive release behavior is presented. A special focus is put on systems activated by wavelengths less harmful for living organisms (mainly in the ultraviolet, visible and infrared range), as well as on different preparation techniques, namely liposomes, self-assembly, layer-by-layer, and interfacial polymerization. Full article

Electromechanical, adhesion, and viscoelastic properties of polymers and polymer nanocomposites (PNCs) are of interest for additive manufacturing (AM) and flexible electronics. Development/optimization of inks for AM is complex, expensive, and substrate/interface dependent. This study investigates properties of free standing films of a thermoplastic polyurethane (TPU) polymer and an Ag–carbon black (Ag-CB) TPU PNC in a lightly loaded low strain compression contact as a rough measure of their suitability for AM. The TPU exhibited high hysteresis and a large viscoelastic response, and sufficient dwell time was needed for polymer chain relaxation and measurable adhesion. A new discovery is that large enough contact area is needed to allow longer time constant polymer ordering in the contact that led to higher adhesion and better performance/reliability. This has previously unknown implications for interface size relative to polymer chain length in AM design. The standard linear model was found to be a good fit for the viscoelastic behavior of the TPU. The PNC exhibited no adhesion (new result), low electrical resistance, and relatively small viscoelastic response. This implies potential for AM electrical trace as well as switch applications. Full article

In this paper, we investigate the effects of gamma (γ) radiation on the spectral and mplified spontaneous emission (ASE) properties of two conjugated polymers (CPs) viz., poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH–PPV) (CPM) and poly{[2-[2′,5′-bis(2″-ethylhexyloxy)phenyl]-1,4-phenylenevinylene]-co-[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene]} (BEHP-co-MEH–PPV) (BMP) in tetrahydrofuran (THF). Gamma irradiation strongly affected the photophysical properties of these CPs. To explore these changes, gamma radiation, in the range of 2–50 kGy, was used to maintain the temperature at 5 °C constant for all doses at a dose rate of 12.67 kGy/h, using a ⁶⁰Co gamma ray. The ASE profiles of the CPs in THF were obtained under the high power excitation of a Nd:YAG laser (355 nm), pre- and post-radiation. The result revealed a dramatic blue shift of the fluorescence and the ASE spectra after gamma irradiation. This shift in the luminescence and ASE spectra could be a response to the conformational disorders such as gamma irradiation-induced polymer crosslinking, which was verified using Raman spectra, FTIR, and swelling experiments. This could be the first report on the effect of gamma radiation on the ASE properties of conjugated polymers. Full article

In this paper, a novel method for preparing nanoparticle-polymer hybrid adsorbent was established. Laponite was dispersed in distilled water to form Laponite nanoparticles. These nanoparticles were pre-adsorbed by 2-acrylamido-2-methylpropane-sulfonic acid (AMPS) to improve their dispersion stability in chitosan solution. The nanoparticle-polymer hybrid adsorbent was prepared by copolymerization of chitosan, acrylamide, acrylic acid, AMPS, and Laponite nanoparticles. Four adsorbents were obtained and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller adsorption (BET). Additionally, the uptake capacities of Cu²⁺ using different samples were studied. Compared to the adsorbent without chitosan and Laponite components, the maximum uptake of the hybrid adsorbent increased from 0.58 to 1.28 mmol·g⁻¹ and the adsorption equilibrium time of it decreased from more than 75 min to less than 35 min, which indicated that the addition of chitosan and Laponite could greatly increase the adsorption rate and capacity of polymer adsorbent. The effects of different experimental parameters—such as initial pH, temperature, and equilibrium Cu²⁺ concentration—on the adsorption capacities were studied. Desorption study indicated that this hybrid adsorbent was easy to be regenerated. Full article

Compared to unhealthy UV or γ-ray and high-energy-consumption thermal external stimuli, the promising light emitting diode (LED) external stimulus has some outstanding technological merits such as narrow wavelength distribution, low heat generation and energy consumption, and safety for human beings. In this work, a novel reversible addition-fragmentation transfer (RAFT) polymerization system for acrylonitrile (AN) was developed under the irradiation of blue LED light at room temperature, using 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as a novel radical initiator and 2-cyanoprop-2-yl-1-dithionaphthalate (CPDN) as the typical chain transfer agent. Well-defined polyacrylonitrile (PAN) with a controlled molecular weight and narrow molecular weight distribution was successfully synthesized. This strategy may provide another effective method for scientific researchers or the industrial community to synthesize a PAN-based precursor of carbon fibers. Full article