Recent work in structure–processing relationships of polymer semiconductors have demonstrated the versatility and control of thin-film microstructure offered by meniscus-guided coating (MGC) techniques. Here, we analyze the qualitative and quantitative aspects of solution shearing, a model MGC method, using coating blades augmented with arrays of pillars. The pillars induce local regions of high strain rates—both shear and extensional—not otherwise possible with unmodified blades, and we use fluid mechanical simulations to model and study a variety of pillar spacings and densities. We then perform a statistical analysis of 130 simulation variables to find correlations with three dependent variables of interest: thin-film degree of crystallinity and transistor field-effect mobilities for charge-transport parallel (μpara) and perpendicular (μperp) to the coating direction. Our study suggests that simple fluid mechanical models can reproduce substantive correlations between the induced fluid flow and important performance metrics, providing a methodology for optimizing blade design.

Additive manufacturing (AM) has made long strides in the recent past and rapidly evolved into a promising alternative in specific applications. The aircraft industry is not an exception to this. The true just-intime production possibility is critical for the aircraft maintenance industries, though the lack of material freedom is a major hurdle. Several fire-retardant materials were investigated for AM in the aerospace context, but mainly for fused deposition modeling (FDM). The material consolidation constraints in FDM led to the expansion to the use of selective laser sintering (SLS) to some extent. Nevertheless, the material options are still limited, proprietary, and lack scientific insights into the material consolidation mechanics. Attempts are made in this paper to fill this gap, evaluating a new fire-retardant material for processing by SLS. Experiments conducted to ascertain the material, process, structure, and consolidation relationships indicated energy density levels 0.062–0.070 J/mm2 with laser power 13 W and scan speed varied slightly around 390 mm/s to give the best laser sintering and mechanical property results in polyetherimide powders.

Nowadays, theranostics drug delivery systems (DDSs) with imaging and therapy bi-functions have been regarded as a future orientation for imaging-guided cancer therapy. To achieve high imaging quality, a donor–acceptor (D–A)/Förster resonance energy transfer (FRET) bi-adjustment strategy is carried out for designing dual-colored DDSs with amplified aggregation-induced emission (AIE) behavior for imaging-guided cocktail cancer therapy in this study. In detail, four AIE-active conjugated polymers P-1 to P-4 are synthesized via the Suzuki reaction. Noteworthily, the D–A-type structure is applied in tuning the fluorescence color from orange (P-1) to far-red/near-infrared (P-2), while the intramolecular FRET process further enhanced the fluorescence signal for six times (P-3). Afterwards, P-3-based amphipathic polymer P-4 further acts as a drug carrier in preparing doxorubicin (Dox)- and curcumin (Cur)-loaded polymer dots (Pdots) (Dox-loaded Pdots as PDox and Cur-loaded Pdots as PCur). PDox + PCur DDS is successfully applied in imaging-guided cocktail cancer therapy to give obviously higher in vivo anticancer efficacy compared with single PDox or PCur. In addition, the drug-loaded Pdots also exhibit higher biocompatibility compared with free drugs. This work provides a novel D–A/FRET bi-adjustment strategy for developing high efficiency imaging-guided cocktail DDSs in cancer therapy.

Poly(phthalaldehyde) (pPHA) and copolymers with aliphatic aldehydes were investigated as dry-develop, positive-tone photoresist. Exposure of the films loaded with a photoacid generator to 248 nm radiation creates an acid that depolymerizes the polymer into volatile monomers, allowing the development of features by vaporization rather than solution-based processes. By controlling the acid content, the vaporization rate of the reaction products, and the degree of liquid formation of the decomposed polymer, control of spatial resolution and the quality of polyaldehyde dry-develop photoresist was achieved. Heat, vacuum, and forced convection were evaluated as development techniques in determining the resist sensitivity, contrast, and resolution. Forced convection of heated nitrogen was the most controllable development method for pPHA films. Five-micron lines and spaces were printed. Poly(aldehyde) copolymer resins had slightly lower spatial resolution but were able to be developed faster due to higher vapor pressure of the depolymerized monomers. Cold photo-exposures and development were used to prevent detrimental liquid formation of the decomposed copolymers. In addition to exploring new dry-development methods that have not been tested before, these findings offer insights into designing better material systems and optimizing processes for dry-develop photoresists.

Boronic ester bonds can be reversibly formed between phenylboronic acid (PBA) and triol moieties. Here, we aim at a glucose-induced shape-memory effect by implementing such bonds as temporary netpoints, which are cleavable by glucose and by minimizing the volume change upon stimulation by a porous cryogel structure. The polymer system consisted of a semi-interpenetrating network (semi-IPN) architecture, in which the triol moieties were part of the permanent network and the PBA moieties were located in the linear polymer diffused into the semi-IPN. In an alkaline medium (pH = 10), the swelling ratio was approximately 35, independent of Cglu varied between 0 and 300 mg/dL. In bending experiments, shape fixity Rf ≈ 80% and shape recovery Rr ≈ 100% from five programming/recovery cycles could be determined. Rr was a function of Cglu in the range from 0 to 300 mg/dL, which accords with the fluctuation range of Cglu in human blood. In this way, the shape-memory hydrogels could play a role in future diabetes treatment options.

In this paper, we use finite element analysis (FEA) to study the linear viscoelastic response of polyurea, a type of hard–soft block copolymer. A Niblack's algorithm-based technique employed on atomic force microscopy images provides geometry inputs for the FEA model, while the viscoelastic master curves of the soft matrix are obtained via a combination of dynamic mechanical analysis data and molecular dynamic (MD) estimations. In this microstructural image-based FEA framework, we introduce an interphase area of altered properties between the hard and soft domains. Both spatial and property distributions of this interphase area affect the viscoelastic response of the copolymer system. To quantitatively investigate the impact of structural and property features of the interphase on the energy storage and dissipation of a system during linear perturbation, we develop a statistical descriptor representation of the interphase region related to physical parameters. Utilizing decision-tree and random forest concepts from machine learning, we apply a ranking algorithm to identify the most significant features for four different mechanical response descriptors. Results show that the total interphase volume fraction and shifting factor distributions in the interphase area dominate the magnitude of the tan δ peak, whereas the magnitudes of the shifting factors primarily affect the tan δ peak location in frequency space. This method allows us to readily identify the dominant features impacting individual properties and paves the way for material design of hard–soft block copolymer systems.

Vast improvements have been made to the capabilities of advanced manufacturing (AM), yet there are still limitations on which materials can effectively be used in the technology. To this end, parts created using AM would benefit from the ability to be developed from feedstock materials incorporating additional functionality. A common three-dimensional (3D) printing polymer, acrylonitrile butadiene styrene, was combined with bismuth and polyvinylidene fluoride via a solvent treatment to fabricate multifunctional composite materials for AM. Composites of varying weight percent loadings were extruded into filaments, which were subsequently 3D printed into blocks via fused filament fabrication. Investigating the material properties demonstrated that in addition to the printed blocks successfully performing as radiation shields, the chemical, thermal, and mechanical properties are suitable for AM. Thus, this work demonstrates that it is possible to enhance AM components with augmented capabilities while not significantly altering the material properties which make AM possible.

Hydrogels have gained recent attention for biomedical applications because of their large water content, which imparts biocompatibility. However, their mechanical properties can be limiting. There has been significant recent interest in the strength and fracture toughness of hydrogel materials in addition to their stiffness and time-dependent behavior. Hydrogels can fail in a brittle manner, although they are extremely compliant. In this work, the failure and fracture of hydrogels are examined using a compression test of spherical hydrogel particles. Spheres of commercially available polyacrylamide–potassium polyacrylate were hydrated and tested to failure in compression as a function of loading rate. The spheres exhibited little relaxation when compressed to small fixed displacements. The distributions of strength values obtained were examined in a particle fracture framework previously used for brittle ceramics. There was loading rate dependence apparent in the measured peak force and calculated peak strength values, but the data fell on a single empirical distribution function of strength for the hydrogels regardless of loading rate. Strength values for these hydrogels were mostly in the range of 0.05–0.3 MPa, illustrating the challenges using hydrogels for mechanically demanding applications such as tissue engineering.

In this work, filament based on ɛ-polycaprolactone (PCL) and containing the bioactive ceramics nanohydroxyapatite (nHap) and Laponite® (Lap) was prepared by the extrusion process. To obtain the material, a mass ratio of 89:10:1 (PCL:nHap:Lap) was used, and structural and morphological characterization was realized. In addition, cytotoxicity (using Allium cepa bulbs) and viability tests on L929 cells also were performed. The results showed that filament (diameter of 1.79 ± 0.17 mm) presented a good dispersion of nHap and Lap into polymeric matrices. Fourier transform infrared spectroscopy identified typical bands at 1720, 1091, and 1045 cm−1 addressed to PCL and nHAp, In addition, Lap was identified through dispersive energy system and X-ray diffraction analyses. All filaments did not exhibit cytotoxic effects.

The quality of the polymer raw material used in plastic processing methods is an important characteristic because it is one of the main factors in producing quality products. Therefore, the characterization of polymeric pellets in the polymer processing industry is very important to avoid using inferior materials. In general, differences in the interiors of polymeric pellets reflect differences in their densities. In this study, a high-sensitivity magnetic levitation method was used to characterize the polymeric pellets in four different occasions. The device used has a high sensitivity that can distinguish minute differences as small as of 0.0041 g/cm3 in density between different samples. In addition, the method can obtain a sample's density without knowing the weight and volume of the sample. This method can be used to characterize materials by testing only a single pellet, which is very useful for polymeric pellet characterization.

Bioactive dressings which can treat any kind of chronic or acute wounds and can fully replace the conventional gauzes and superabsorbent dressings have proven to be a future market of wound care products in recent times. These dressings are multifunctional, which can effectively combat the wound infection, remove the exudate, promote angiogenesis, and protect the wound from external trauma. Proper selection of bioactive and polymer defines its efficiency. Current research unveils the therapeutic efficacy of curcumin–honey-loaded multilayered polyvinyl alcohol/cellulose acetate electrospun nanofibrous mats as an interactive bioactive wound dressing material. Scanning electron microscopy and Fourier transform infrared spectroscopy analysis infers uniform encapsulation and chemical compatibility of herbal actives and polymer, inside the nanofibrous layers. The as-spun mat shows potential resistance towards Escherichia coli and ∼90% antioxidant activity against diphenyl-picrylhydrazyl (DPPH)–free radical. Additionally, water absorbency, water vapor transmission rate, and wettability analysis show quick and excellent absorption with controlled transmission of wound exudate.

Ab initio design of polymer nanocomposite materials for high breakdown strength requires prediction of localized trap states at the polymer–filler interface. Systematic first-principles calculations of realistic interfaces can be challenging, particularly for amorphous polymers and fillers that necessitate the calculation of ensembles of large unit cells with hundreds of atoms. We present a computational approach for automatically generating reasonable structures for amorphous polymer–filler interfaces, combining classical molecular dynamics and Monte Carlo simulations. We identify trap states by analyzing the localization of electronic eigenstates calculated using density functional theory on ensembles of interface structures, clearly distinguishing shallow trap states from delocalized band-edge states. Applying this approach to silica–polyethylene interfaces as an initial example, we find under-coordination and distorted coordination structures at amorphous silica surfaces contribute a combination of deep and shallow traps at these interfaces, whereas polyethylene does not generate localized interfacial states.

The tensile yield strength of high-density polyethylene using instrumented indentation tests with a flat-ended cylindrical indenter was evaluated. The variation in the field expressed by stress and strain beneath the flat-ended cylindrical indenter is investigated using a new expanding cavity model to study the relation between tension and indentation. This model starts from the separation of forces into the compressive force on the material and the frictional one, which is generated during indentation on the sides of indenter. The authors propose a method to correct the frictional force based on the saturation of indentation hardening and obtain load–depth curve with compressive component only. For conversion of indentation force and displacement, our new representation model is applied. By modifying Johnson's model, the new assumption of conservation of indentation plastic volume is suggested. This model proves and supports conventional relations of the strain rates between indentation and tension theoretically. These are verified through the experiments: instrumented indentation and uniaxial tensile test. The authors find a good agreement between the tensile yield strengths at various strain rates.

Nanocomposites of polyvinylidene fluoride loaded with various amounts of γ-Fe2O nanoparticles, with an average size ranging between 20 and 40 nm, have been obtained by melt mixing and investigated using various experimental techniques [Superconducting Quantum Interference Device, Mössbauer, and Thermogravimetric Analysis]. Magnetic and Mössbauer measurements confirmed the presence of maghemite and a trace of a paramagnetic iron compound. Magnetic data are consistent with a blocking temperature close to room temperature (RT), showing a decrease in the coercive field as the temperature is increased. A weak exchange bias was noticed in all nanocomposites investigated at all temperatures and tentatively ascribed to surface spin disorder. The temperature dependence of the coercive field obeys the Kneller law. The nanocomposites exhibit superparamagnetic behavior near RT. Most magnetic measurements have been performed below the blocking temperature, revealing thus a complex behavior. The dependence of the mass loss derivative versus temperature, as obtained by thermogravimetric analysis, exhibits a single peak due to the thermal degradation of the polymeric matrix. A weak increase in the thermal stability of the polymeric matrix upon loading with maghemite is reported.

Polymer nanocomposites possess unique sets of properties that make them suitable for different applications, including structural and flame-retardant material, electromagnetic wave reflector, sensors, thin film transistor, flexible display, and many more. The properties of these nanocomposite are dependent on nanofiller dispersion and bonding with polymer matrix (i.e. particle-matrix interaction). Thermography is a non-destructive method that may be used to gain insight into dispersion and particle-matrix interaction. Infrared (IR) radiation emitted from these nanomaterial polymer composite depends on the emissivity of the individual components. In addition, during flash heating and cooling, different thermal conductivity of components in the nanocomposite can influence pixel intensity differently in the IR image or video being captured. We have used an economical mid wavelength IR camera Fluke RSE600 equipped with a close-up macro lens and algorithm based on MATLAB image processing toolbox to analyse dispersion, voids and thermal diffusivity of patented graphene polymer nanocomposite materials (G-PMC) in micro-scale. These G-PMCs can act as a standard material to determine the potential of our IR thermography technique due to their homogeneity and lack of impurity due to unique fabrication process. Thermal diffusivity and dispersion of nanoparticles in our G-PMCs was estimated after irradiation with a xenon flash lamp by spatially mapping transient IR radiations from different G-PMCs using the Fluke RSE600 thermal imager. Results from thermography experiments were compared with scanning electron microscope (SEM) and Raman spectroscopy results. Micro-scale thermography was able to detect millimetre scale thermal diffusivity variation in the injection molded G-PMC samples and relate it to change in dispersion of nanofillers, unlike SEM and Raman, where micro-scale measurements could not determine the reason behind millimetre scale property variation. We believe this low cost, fast, micro-scale, non-destructive technique will provide valuable insight into functional polymer nanocomposite fabrication and corresponding electrical and thermal properties.

Fused deposition modelling (FDM) type of 3D printing is widely used for manufacturing complex shaped polymer products. Recently, the metal/polymer composite products can be made by 3D printer using metal/polymer composite filament. Now, we are planning to develop a new manufacturing process of the thermoelectric (TE) elements or modules by combining the FDM-type 3D printing and the degreasing-sintering process. In this work, we focused on the degreasing-sintering process of the mixture of Mg2Si and polylactic acid (PLA) powders. Mg2Si compound powder was synthesized by a liquid-solid phase reaction (LSPR) method. The powder mixtures of Mg2Si, Al and PLA were pressed and heated in a pulse discharge sintering (PDS) chamber under a vacuum in various degreasing conditions. Following the degreasing, the sintering of Mg2Si was carried out in the same PDS chamber at various starting sintering temperatures. Sintered density, Seebeck coefficient and electrical resistivity of the consolidated Mg2Si were measured and the power factor as a TE performance was estimated from the TE properties. The optimum conditions of degreasing-sintering process maximizing the sintered density and the TE performance of Al-doped Mg2Si were investigated. Furthermore, the influences of the additive amount of Al on the sintered density and the TE performance of Mg2Si fabricated via the optimized degreasing-sintering process were investigated.