AFM Phase Images Research Articles

Investigation on the Curing and Thermal Properties of Epoxy/Amine/Phthalonitrile Blend.

The bisphenol A-type phthalonitrile (BAPH) was blended with the classic epoxy system E51/DDS to prepare the epoxy/phthalonitrile thermoset. The curing kinetics were investigated by differential scanning calorimetry (DSC) using the isoconversional principle, and the average activation energy (Eα) of the E51/DDS curing reaction was found to decrease from 87 kJ/mol to 68.6 kJ/mol. Combining the results of the rheological study, the promoting effect of phthalonitrile on the crosslink of epoxy/amine is confirmed. The curing reaction of the blended resin was characterized using FTIR, and the results showed that BAPH could react with DDS. The thermal behaviors of the thermosets were investigated via DMA and TGA. The glass transition temperature (Tg) is found to increase from 181 °C to 195 °C. The char yield increases from 16% to 59.6% at 800 °C in a N2 atmosphere, which is higher than the calculated value based on the proportional principle. The AFM phase images show that there is no phase separation in the cured thermoset. The results imply that the cured epoxy/amine/phthalonitrile blend is probably a kind of copolymer. The real-time TG-MS indicated that the pyrolysis of the thermoset can be divided into two relatively independent stages, which can be assigned to the cleavage of the E51/DDS network, and the phthalocyanine/triazine/isoindoline, respectively.

Nanoscale mechanical and thermal properties of a multilayer polyethylene film with varying densities

Various atomic force microscopy methods for the imaging and measurement of the modulus of polyethylene (PE) layers in a five-layer multilayer film are described. The film includes linear low-density polyethylene (LLDPE) products with densities ranging from 0.940 to 0.912 gm/cm3. Conventional TappingMode AFM phase imaging can reveal the layers but is sensitive to measurement conditions. PeakForce Tapping AFM using quantitative nanomechanics (QNM) mode can resolve all five layers based on at least three different signals – stiffness mapping, penetration, and energy dissipation. In particular, the difference is statistically significant for the modulus and penetration data. This is remarkable considering that the method is sensitive to density differences of only 0.004 density units. Quasistatic AFM indentation was also done using the same probe and peak load. Here we see the effect of time dependence on the mechanical properties, where the slower interaction times yield estimated moduli much closer to the long-time moduli measured in bulk tensile experiments, compared to the value obtained at much higher frequency using PeakForce Tapping AFM. Nano-thermal analysis of the same five-layer film using heated tip technology can also discriminate the layers statistically, based on softening temperature, which shows excellent correlation with bulk properties.

Carboxylated acrylonitrile butadiene-natural rubber latex blends with methyl methacrylate grafted natural rubber latex: mechanical properties and morphology.

Commercially available carboxylated acrylonitrile butadiene latex (XNBR) was physically blended with natural rubber latex (NR) at varying blend ratios to investigate its effect on the mechanical properties and morphology. Methyl methacrylate grafted natural rubber latex (MG) was added to the latex blends as a third polymer to study whether it could enhance the mechanical properties of the latex blend films. It was found that the tensile strength of the blend films irrespective of composition decreased when the two latexes were blended as compared to the virgin latex films. The modulus 300 decreased while the elongation at break and tear strength of the blend films increased gradually as the ratio of NR increased in the blend films. It was found that the MG did not enhance the mechanical properties of the XNBR/NR blend films under the current experimental condition. AFM phase imaging analysis revealed enhanced polymer distribution and evidence of NR-MG-XNBR interactions.

Investigation on flexible and thermally crosslinked bis-piperidinium-PPO anion exchange membrane (AEM) for electro-kinetic desalination and acid recovery

We investigate a facile solution phase di-cationic cross-linking strategy to fabricate anion exchange membrane (AEM) with efficient electro-kinetic desalination (EKD) attributes from brackish water. The cross-linked membranes showed transmembrane potential up to 55.60 mV and counter-ion transport number of ⁓0.97, respectively. Ionic conductivities (κm) and mechanical stability attributes were improved than un-crosslinked pristine counterpart and confirmed by electrochemical impedance spectroscopy (EIS) and stress-strain analysis, respectively. The chemical and morphological attributes are confirmed by 1H NMR, XPS and FE-SEM analysis, membranes were dense in nature with homogenous phase morphology as confirmed by dye-impregnation method and AFM phase imaging. The higher di-cationic cross-linkable precursor improved κm by ⁓ 30% (from 6.82 to 10.30 mS cm−1) at 30 °C. Moreover, the EKD performance was evaluated for continuous operation time ≥4000min. Appreciable current efficiency and power consumption of 90% and 0.99 kWh kg−1 was realised with ≥95% salt removal in 270min at 2.0V/cell pair. Furthermore, acid recovery was evaluated via. diffusion dialysis at 30 °C and 45 °C and results are corroborated. High proton dialysis coefficient (vH+) and separation factor (Sf) of 0.015–0.019 m h−1 and 10–75 was found. The paradigms suggest membranes suitability for EKD and acid repurposing via. diffusion dialysis. Finally, the alkaline stability attributes, hydroxide conduction dynamics and degradation of AEM was probed using EIS technique in detailed manner for 360 h and discussed.

Deep learning to establish structure property relationships of impact copolymers from AFM phase images

Deep learning to establish structure property relationships of impact copolymers from AFM phase images

Internally cross-linked poly (2,6-dimethyl-1,4-phenylene ether) based anion exchange membrane for recovery of different acids by diffusion dialysis

Acid recovery from acidic waste is a critical issue to be focused on nowadays. Chemical approaches for recovery are not commercially viable and energy intensive to save the environment. Here, we report internally cross-linked poly (2,6-dimethyl-1,4-phenylene ether) (PPE) based anion exchange membranes (AEMs) for acid recovery by diffusion dialysis, prepared via quick grafting of N-methyl-4-piperidone using ultrasonication. The prepared AEMs are assessed for their physicochemical parameters and depicted water uptake (WU) and ion-exchange capacity (IEC) in the range 22.00%–31.00% and 0.64 meq/g–2.18 meq/g respectively for Cl−1, NO3− and SO42− ions. AEMs were investigated for recovery of hydrochloric acid (HCl), nitric acid (HNO3) and sulphuric acid (H2SO4) from simulated effluent based on their proton diffusion coefficient (UH+), separation factor (S) and recovery efficiency (Ƞ). These membranes illustrated the proton diffusion coefficient as high as 0.065 m h−1 and enhanced separation factor values up to 132 at 27 °C. Recovery performance for different acids is corroborated based on unique self-organized membrane structure, studied using AFM phase imaging and cumulative influence of bulk diffusion coefficient, ion-exchange capacity, and hydration radii of Cl−1, NO3− and SO42− ions. The acid recovery efficiency illustrated the trend HCl > HNO3 > H2SO4. The hydrate (–OH) functionality with a non-overlapping set of lone pairs on oxygen enhances the proton mobility via Grotthuss mechanism inside the membrane matrix and provides a cradle-like pathway for high proton mobility. The results are pronounced for fabricated membranes compared to commercially available standards for acid recovery via diffusion dialysis.

Preparation of composite anion-exchange membrane with acid-blocking performance for brine reclamation by bipolar membrane electrodialysis

It has been realized the proton leakage behavior of anion-exchange membrane (AEM) seriously influences the practical applications of bipolar membrane electrodialysis (BMED), for example, the reclamation of brine. In this work, a concept of composite AEM, coating a thin acid-blocking layer bearing weak base functional groups onto a strong base AEM substrate, is put forward to alleviate the membrane conductivity deterioration due to the endowment of acid-blocking property. Above all, Poly(vinylidene fluoride)-graft-Poly[2-(N,N-dimethylamino) ethyl methacrylate] (PVDF-g-PDMAEMA which embraces significant hydrophilic differences between the side and main chains is synthesized by atom transfer radical polymerization (ATRP) and used for preparing the acid-blocking layer by solvent evaporation. Subsequently, series of experiments for measuring the water uptake, the acid adsorption, the current-voltage curve and transport number are performed to optimize the ion-exchange capacity of as-synthesized membrane material. Furthermore, as-prepared acid-blocking layer is coated onto the a strong base AEM substrate fabricated from the blend of PVDF and cross-linking PDMAEMA to prepare the supposed composite AEM. SEM observation clearly demonstrates the bilayer structure and good adhesion therein. AFM phase image confirms the formation of microphase separation morphology in which the hydrophilic channel used for ion transport looks uniform, continuous and well-connected. The ED-based acid concentration and BMED-based brine reclamation experiments show as-prepared composite AEM has an excellent acid-blocking performance and acceptable membrane resistance in comparison with the conventional AEM and even the commercial acid-blocking AEM. This indicates that the proposed AEM-preparing strategy may contribute to beating the trade-off effect between acid-blocking performance and membrane conductivity.

Direct Correlation of Single-Particle Motion to Amorphous Microstructural Components of Semicrystalline Poly(ethylene oxide) Electrolytic Films.

Semicrystalline polymers constitute some of the most widely used materials in the world, and their functional properties are intimately connected to their structure on a range of length scales. Many of these properties depend on the micro- and nanoscale heterogeneous distribution of crystalline and amorphous phases, but this renders the interpretation of ensemble averaged measurements challenging. We use superlocalized widefield single-particle tracking in conjunction with AFM phase imaging to correlate the crystalline morphology of lithium-triflate-doped poly(ethylene oxide) thin films to the motion of individual fluorescent probes at the nanoscale. The results demonstrate that probe motion is intrinsically isotropic in amorphous regions and that, without altering this intrinsic diffusivity, closely spaced, often parallel, crystallite fibers anisotropically constrain probe motion along intercalating amorphous channels. This constraint is emphasized by the agreement between crystallite and anisotropic probe trajectory orientations. This constraint is also emphasized by the extent of the trajectory confinement correlated to the width of the measured gaps between adjacent crystallites. This study illustrates with direct nanoscale correlations how controlled and periodic arrangement of crystalline domains is a promising design principle for mass transport in semicrystalline polymer materials without compromising their mechanical stability.

Topographical and mechanical properties of liposome surfaces harboring Na,K-ATPase by means of atomic force microscopy.

In this study, we obtained unprecedented AFM images of the Na,K-ATPase (NKA) pump after being reconstituted into DPPC and DPPC:DPPE liposomes. The mechanical properties observed in the phase images were associated with protrusions correlated to NKA microdomains, which are the darker areas seen in the AFM phase images. Protrusions in the DPPC-NKA proteoliposomes ranged from 38 to 115 nm, with 74 ± 21 nm diameter and 2.1 ± 1.4 nm height. DPPC:DPPE-NKA proteoliposomes showed protrusions from 21 to 78 nm, with 38 ± 16 nm diameter and 0.7 ± 0.5 nm height. We have estimated the presence of annular lipids in the microdomains considering that the areas of the protrusions should contain αβ oligomers and annular phospholipids. For DPPC-NKA proteoliposomes, we hypothesize that 40 phospholipids surround an (αβ)2 dimer and 46 phospholipids are present for the DPPC:DPPE-NKA proteoliposomes in an αβ monomer. Catalytic activity measurements of both lipid compositions of proteoliposomes harboring NKA provide strong evidence regarding the protein orientation in the biomembrane. AFM data suggest that DPPC-NKA proteoliposomes are also rightside-out protein orientated, where the protrusions have an average height of 2.1 nm, while for DPPC:DPPE-NKA proteoliposomes, the majority of the protein reconstituted should be inside-out orientated, where the protrusions' average height is 0.5 nm. This result corroborates with the enzymatic analysis, where 61% and 91% of the enzymatic activity was recovered, respectively. Thus, a new application of AFM as a tool for the determination of topological features of protrusions in proteoliposomes has been brought to the scientific community, in addition to revealing the distinct catalytic orientation of enzymes present in the biomembranes model.

Semiconducting Polymer Thin Films Used in Organic Solar Cells: A Scanning Tunneling Microscopy Study

AbstractThe widely used semiconducting polymers poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) (PH1000), poly(3‐hexylthiophene‐2,5‐diyl) (P3HT), and Poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]] (PTB7) for organic photovoltaic (OPV) cells, are deposited on highly ordered pyrolytic graphite substrates and investigated by scanning tunneling microscopy (STM) under the liquid/solid interface technique. PEDOT:PSS film morphology shows an ellipsoidal shape of PEDOT surrounded by PSS with 4 nm size. STM images of P3HT reveal that films tend to form well‐defined crystalline domains with an average interchain distance around 1.41 nm and chain length ≈41 nm. PTB7 chains are self‐aggregated by using chlorobenzene as solvent; however, when using 1‐phenyloctane with 3% of 1,8‐diiodooctane, these chains show a worm‐like pattern with a distance of ≈2 nm between backbone chains and a chain length of ≈90 nm. For P3HT and PTB7 based OPVs, local J–V plots are determined from photoconductive atomic force microscopy (pc‐AFM) measurements and fitted with the modified Mott−Gurney equation, the reached parameters are correlated with those achieved from the macroscopic J–V graphs. Active films of OPVs cells based on PTB7 are also analyzed by using AFM phase imaging showing domains size of 80–120 nm. This current STM analysis can elucidate some new important insights on polymer film formation and morphology and therefore, their influence on the OPV performance.

Anion-exchange membrane with ion-nanochannels to beat trade-off between membrane conductivity and acid blocking performance for waste acid reclamation

The bottleneck for the reclamation of low concentration waste acid by electrodialysis (ED) is the proton leakage through anion exchange membranes (AEMs). In order to reject acid without compromising conductivity, we have designed and prepared a series of weak base AEMs with ion-nanochannels through introducing weak base groups. Various weak base groups of different carbon chain lengths and grafting densities were linked onto the Polysulfone skeleton as side chains. Fourier transform infrared spectra provided proof of the successful synthesis of chloromethylated polysulfone (CMPS) and the corresponding AEMs with designated chemical compositions. Thermo-gravimetric analysis showed their thermal stabilities were high enough for ED applications. AFM phase images and a two-phase model confirmed the formation of a microphase-separated structure and the corresponding ion-nanochannels because of the polarity difference between hydrophilic side chains and hydrophobic skeletons. Subsequently, the effects of side chain lengths and ion exchange capacity on the properties of prepared AEMs, including conductivity, water uptake, permselectivity and acid blocking performance, were explored in detail. Lastly, the acid concentration behavior and electrodialytic transport properties of a typical AEM sample were investigated and compared to those of commercial AEMs. Experimental results have shown that the as-prepared AEM exhibited an outstanding performance in membrane conductivity, surface homogeneity, and the rejection of acid. Accordingly, it is reasonable to believe that the confinement effect in the formed ion-nanochannels simultaneously contributes to the reduction of membrane water uptake, the enhancement of the Donnan exclusion for protons, and the facilitated transport for counter-ions. Therefore, the synthesized membranes are promising for the applications in waste acid reclamation by ED.

Determining Material-Specific Morphology of Bulk-Heterojunction Organic Solar Cells Using AFM Phase Imaging

A technique for determining the material-specific morphology of a polymer–fullerene blend is presented. This technique is applied to solution processed bulk-heterojunction organic solar cells with different weight ratios of polymer–fullerene blend using the PTB7:PCBM material system. Optical and electrical characterizations show that the light absorption increases for larger polymer (PTB7) content, while the fill factor of the fabricated solar cells is improved for larger fullerene (PCBM) content. The material-specific morphologies of polymer–fullerene bulk-heterojunctions are measured by employing AFM phase imaging. The measured AFM phase images reveal that fullerene material forms flake-like clusters which are embedded in the polymer network. The size of the flakes is increasing with larger content of fullerene material. By correlating the optical and electrical properties with the measured bulk-heterojunction morphologies, the relation between bulk-heterojunction structure and solar cell performances i...

Low temperature microwave processing of silicone resin coatings containing microwave susceptors

Microwave (MW) processing was used to cure a sol-gel type silicone resin coating that normally requires thermal curing over 250°C. The study focused on coatings applied on polycarbonate and poly(methyl methacrylate) substrates and processing temperatures did not exceed 100°C when using Silicone Carbide, Carbon, and Aluminium susceptors at 5% concentration by weight. Heating performance of the susceptors in bulk silicone resin matrix as well as in thin layers was compared.The results presented show that the heating response of the additives measured in bulk was significant. However, results for thin layers indicated that the effects of MW heating on the coatings containing the susceptors were limited, and samples microwaved at 800W for 4h imparted insignificant increase of the coating hardness.This outcome was supported by AFM Phase images which revealed no distinctive layer near the susceptor particles. This suggests that the heat dissipation to the substrate and air with limited heating performance of the susceptors does not allow for an effective in-situ curing in thin layer.

Morphology and tensile properties of model thermoplastic polyurethanes with MDI/butanediol based monodisperse hard segments

ABSTRACTMorphology and tensile properties of model thermoplastic polyurethanes (TPUs) containing polyisobutylene (PIB) or poly(tetramethylene oxide) (PTMO) based soft segment and 4,4‐methylene bis(phenyl isocyanate) (MDI) and 1,4‐butanediol (BDO) based monodisperse hard segments (HSs), consisting of exactly two to four MDI units extended by BDO, were investigated. Using FT‐IR spectroscopy, increased hydrogen bonded CO fraction was observed in model TPUs as the HS size increased. The hydrogen bonded CO fraction was higher in PIB based TPUs compared with PTMO based TPUs, indicating higher phase separation in PIB based TPUs. The morphology of TPUs was investigated using AFM phase imaging, which showed ribbon‐like or interconnected hard domains in PTMO based model TPUs and randomly dispersed hard domains in PIB based model TPUs. SAXS revealed that the degree of phase separation in the model TPUs was higher than in their polydisperse analogues. Domain spacing as well as interfacial thickness increased with the increasing HS size, and both values were higher in PTMO based TPUs. The tensile analysis indicated that model TPUs exhibited higher modulus and slightly higher elongation compared with their polydisperse analogues. Only in PTMO based model TPUs, strain induced crystallization was observed above 300% elongation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2485–2493

Stabilization of the polymer electrolyte/lithium metal electrode interface with increased ion conduction using PEO polymer/low molecular weight PE-b-PEO diblock copolymer composite bi-layer films

A method of stabilizing the interface of PEO polymer electrolytes with respect to lithium metal, using a composite bi-layered, hybrid film is described. This method utilizes a low molecular weight PE-b-PEO diblock copolymer having a general chemical formula of H-(CH2)32-(O-CH2CH2)10-OH that can be positioned at the PEO polymer electrolyte surface. These hybrid films are fabricated by making a thin layer of the PE-b-PEO materials by solvent casting and then casting a second layer of standard PEO polymer electrolyte on the PE-b-PEO film. This PE-b-PEO layer adheres to the polymer electrolyte surface, making a stabilized interface with lithium. This hybrid system not only stabilize the lithium/polymer electrolyte interface but also has the desirable property of increasing ion conduction by almost three orders of magnitude over a standard PEO polymer electrolyte system. The stabilization of the lithium/polymer electrolyte interface and the increase in ionic conduction has been studied by using AC impedance spectroscopy, AFM phase imaging, and attenuated total reflection IR, which allow the mechanism for stabilization and increased ionic conduction to be discussed.

Ultra-flexible nanocarriers for enhanced topical delivery of a highly lipophilic antioxidative molecule for skin cancer chemoprevention

PurposeIn this study, we developed cationic ultra-flexible nanocarriers (UltraFLEX-Nano) to surmount the skin barrier structure and to potentiate the topical delivery of a highly lipophilic antioxidative diindolylmethane derivative (DIM-D) for the inhibition of UV-induced DNA damage and skin carcinogenesis. MethodsUltraFLEX-Nano was prepared with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dioleoyl-3-trimethylammonium-propane, cholesterol and tween-80 by ethanolic injection method; was characterized by Differential Scanning Calorimetric (DSC), Fourier Transform Infrared (FT-IR) and Atomic Force Microscopic (phase-imaging) analyses and permeation studies were performed in dermatomed human skin. The efficacy of DIM-D-UltraFLEX-Nano for skin cancer chemoprevention was evaluated in UVB-induced skin cancer model in vivo. ResultsDIM-D-UltraFLEX-Nano formed a stable mono-dispersion (110.50±0.71nm) with >90% encapsulation of DIM-D that was supported by HPLC, DSC, FT-IR and AFM phase imaging. The blank formulation was non-toxic to human embryonic kidney cells. UltraFLEX-Nano was vastly deformable and highly permeable across the stratum corneum; there was significant (p<0.01) skin deposition of DIM-D for UltraFLEX-Nano that was superior to PEG solution (13.83-fold). DIM-D-UltraFLEX-Nano pretreatment delayed the onset of UVB-induced tumorigenesis (2 weeks) and reduced (p<0.05) the number of tumors observed in SKH-1 mice (3.33-fold), which was comparable to pretreatment with sunscreen (SPF30). Also, DIM-D-UltraFLEX-Nano caused decrease (p<0.05) in UV-induced DNA damage (8-hydroxydeoxyguanosine), skin inflammation (PCNA), epidermal hyperplasia (c-myc, CyclinD1), immunosuppression (IL10), cell survival (AKT), metastasis (Vimentin, MMP-9, TIMP1) but increase in apoptosis (p53 and p21). ConclusionUltraFLEX-Nano was efficient in enhancing the topical delivery of DIM-D. DIM-D-UltraFLEX-Nano was efficacious in delaying skin tumor incidence and multiplicity in SKH mice comparable to sunscreen (SPF30).

Improving uniformity and nanostructure of solution-processed thin films using ultrasonic substrate vibration post treatment (SVPT)

The main goal of this paper is to introduce a novel mechanical method herein terms as substrate vibration post treatment (SVPT) technique, powered by ultrasonic vibration imposed on the substrate to enhance the characteristics and functionality of spun-on thin films or thin films made by similar casting techniques, such as drop and dip coating. In this technique, the as-casted wet films are placed on a substrate vibrated by an ultrasonic transducer with controlled power and duration to improve the film characteristics, such as uniformity and nanostructure. The performance of this technique is examined on spun-on PEDOT: PSS thin films used in polymer and perovskite solar cells and unprecedented results are presented. We first explore the influence of the vibration duration time on the characteristics of the films made by pristine PEDOT: PSS solution, where it is found that the optimized vibration duration for the pristine PEDOT: PSS film is about 10s, resulting in significant increase in the film electrical conductivity and lowered thickness and roughness. In order to further test the generality and merit of the method, thin films made using PEDOT: PSS solution modified with various types of surfactants and cured by the SVPT are studied. The results show that the application of the SVPT method combined with surfactant modification leads to an impressive twelve-fold increase in the conductivity of the PEDOT: PSS thin films compared with that of the pristine non-vibrated PEDOT: PSS thin films. The sole effect of the SVPT is a four-fold increase in the conductivity of pristine PEDOT: PSS film compared with that of the non-vibrated film. This remarkable enhancement in conductivity is further explained by the AFM phase images of PEDOT: PSS films, showing that the ultrasonic energy could loosen the Coulomb forces between PEDOT and PSS chains, resulting in phase separation and localized reordering of the conducting PEDOT chains leading to an increase in the electrical conductivity of the film. Highly conductive PEDOT: PSS thin film is a viable candidate as electrodes in emerging solution-processed solar cells.

Nanoparticle distribution in NR/BR blend

The distribution of carbon black (CB) nanoparticles in natural rubber/polybutadiene (NR/BR) blend was evaluated by DSC and AFM. The restriction of BR due to the interaction between BR and CB was smaller than that of NR from the glass transition behavior. The AFM phase images of NR/BR blend with and without CB were observed at various at 370 kHz. The phase-separated structures of NR/BR blend with and without CB were observed at the temperature range of 20 °C, which corresponded to glassy NR and rubbery BR phases. The dispersion state of CB in NR/BR blend has been characterized by histogram analysis of AFM phase images. The CB was existed in NR-rich domain and in the interface phase.

Investigation of morphology and physical properties of modified PEDOT: PSS films made via in-situ grafting method

PEDOT: PSS is one of the most suitable conducting polymeric materials for the fabrication of transparent flexible thin film electrodes using a solution-processed method. However, its rather low conductivity impedes its wide application. This work is an attempt to explain the relationship between the nano-structure of PEDOT and PSS phases and the electrical conductivity of the PEDOT: PSS film and to increase the film conductivity by employing a novel grafting or doping technique. Unprecedented results are shown on the application of a novel technique in which grafted spun-on PEDOT: PSS thin films are prepared by adding various dosages of anphiphilic tertiary amine PEGO to the pristine PEDOT: PSS aqueous solution. Results on the structure, thickness, roughness, wettability, transmittance and conductivity of the modified films are presented and discussed. The AFM phase images reveal that the addition of PEGO to PEDOT:PSS results in positive phase separation in PEDOT: PSS film, which facilitates the formation of 3D conducting networks of PEDOT chains, resulting in conductivity enhancement. Moreover, we show that the modified PEDOT: PSS films have an improved transmittance and wettability compared with the pristine PEDOT: PSS films. Addition of PEGO also results in a decrease in film roughness and thickness. Overall, the PEGO grafted PEDOT: PSS film fabricated in this work shows superior optoelectronic properties compared to pristine PEDOT: PSS film.

Molecular Disorder in Prestrained Nanocomposites: Effects of Processing on Durability of Thermally-Active Ethylene-Vinyl Acetate | PyChol | Multiwall Carbon Nanotubes

AbstractIn situ temperature-resolved Near-edge X-ray Absorption Fine Structure (NEXAFS) measurements were performed on thermo-active ethylene-vinyl acetate (EVA) – multiwall carbon nanotube (MWCNT) composites 12 months following synthesis, and compared with spectra acquired shortly after synthesis to examine aging effects on non-covalent interactions. Room temperature spectra revealed no difference between unstrained and strained composites, suggesting relaxation. Further, energy shifts in π* C=C resonances indicated a change in π–π interactions between MWCNT walls and chemical dispersant, supported also by AFM phase imaging. Temperature-resolved NEXAFS analysis showed a lack of interaction between nanotubes and polymeric chains, suggesting the chemical dispersant unlatched from MWCNT walls. The extent of this effect is finally quantified through a comparative study of spectral trends.