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Selenium nanoparticles (SeNPs) were synthesized and stabilized by biopolymers, namely, sodium lignosulfonate (LS) and starch sodium octenyl succinate (OSA). The obtained selenium nanoparticles were studied for their catalytic activity in the reduction of a dye (C.I. Basic Blue 9, methylene blue) by sodium borohydride. The SeNPs-OSA and SeNPs-LS nanoparticles were also dispersed in a photosensitive matrix and studied as polymer composites. The research confirmed the catalytic abilities of the prepared SeNPs in the reduction of the organic dye. Mechanical tests on the polymers and their composites showed an improvement in the composites’ strength in all tested cases. An increase in hardness and Young’s modulus values of the filled materials compared to the pure matrix was found as well.

Emulsification is one of the important processes in chemical flooding to mobilize the residual oil in wells following secondary recovery. Oil displacement efficiency is enhanced and volumetric sweep efficiency is increased by engineering the interactions of the supporting chemicals used with the geological formations present in the wells. Polymers and surfactants are often applied to enhanced oil recovery (EOR) as emulsification displacement. However, polymers are limited by poor temperature and salt tolerance, while surfactants have a high cost. In this contribution, we report on the use of lignin nanoparticles (LNPs) as Pickering emulsifiers obtained from enzymatic hydrolysis of lignin powders to apply in EOR. The interfacial activity of LNPs prepared this way is greatly improved, which substantially promotes its emulsification ability. We show that kerosene emulsified with different concentrations of LNPs can form stable Pickering emulsions, and the emulsions can be stored for up to 6 months. In addition, due to the pH responsive character of lignin, rapid oil-water separation can be achieved by alkali demulsification. This enables the reuse of lignin suspension under pH control, which provides a new platform for the application of green and low-cost flooding, employing LNPs in EOR.

Bio-based and biodegradable polymers are essential for a sustainable society. Cellulose is the most abundant biopolymer on earth; however, derivatization is necessary for its processing, which slows down its biodegradability dramatically, e.g. used cigarette filters made from cellulose acetate are barely biodegradable. We developed the first reversible modification of cellulose, which allows processing and guarantees full biodegradation even at high degrees of substitution as the linkers, acetals, can be cleaved first during the degradation process releasing native cellulose that biodegrades in a second step. Acetalization is a versatile platform approach to bio-based and fully degradable cellulose-derivatives, which are characterized by solubility in common organic solvents (alcohols, aromatic and chlorinated solvents), adjustable glass transition temperatures (-48 °C < Tg < 80 °C), young's modulus (1.9 MPa < E < 58 MPa) and contact angle (86°< θ < 124°). In contrast to previously known cellulose modifications, cellulose acetals remain fully degradable as the acetal bond is reversible and undergoes an acidic cleavage under desired conditions, for instance in compost, followed by enzymatic degradation of the remaining cellulose backbone. With climate change and plastic pollution, these new and versatile cellulose acetals provide bio-based and biodegradable alternatives to fossil-based and non-degradable polyolefin plastics, leading to a more sustainable future for our planet.

Imaging and tracing materials inside the body is essential to develop functional materials for personalized therapies, including drug delivering nanocarriers and artificial tissues. Magnetic Resonance Imaging (MRI) is a key whole-body imaging technology, where heteronuclear MRI agents enable background-free, quantitative labeling. However, many MRI agents raised concerns due to environmental pollution and organ accumulation. As a solution, we developed a biodegradable, biocompatible polymer platform for heteronuclear 31P magnetic resonance imaging (MRI). We introduce polyphosphoester colloids for heteronuclear MRI using 31P-nucleus. 31P MRI has been severely hampered by unfavorable magnetic resonance properties of 31P, including intrinsic background and low sensitivity. We overcame these fundamental challenges in imaging of 31P by tailoring molecular and structural features of polymeric colloids. We have synthesized gradient-type polyphosphonate copolymers that self-assemble into well-defined micelles. The gradient leads to favorable MRI characteristics compared with homo- and block copolymers. Background-free imaging and biodegradation were proven in vivo in Manduca sexta. Furthermore, we demonstrate by encapsulation of the potent drug PROTAC ARV-825 that these amphiphilic copolymers can simultaneously deliver hydrophobic drugs and thus enable theranostics. We present a unique platform of biocompatible, degradable polyphosphoesters that inherently act as background-free MRI agents and delivery vehicles.

Initial retention of the bacterium Escherichia coli on model poly(dimethylsiloxane) (PDMS) surfaces was studied as a function of substrate bulk and surface mechanical stiffness values. Our reference PDMS system was designed such that out of the parameters that govern bacterial adhesion only the mechanical stiffness was systematically varied. This was achieved by varying the crosslinking density of PDMS. Following crosslinking, we performed Soxhlet extraction of non-crosslinked, free chains to rule out their effect on bacterial response. Bulk moduli were assessed by dynamic mechanical analysis at 1 rad sec−1 frequency and the values obtained ranged between 0.03 and 1.8 MPa. The increase in crosslink density resulted in increasing surface modulus, as measured by atomic force microscopy, with values ranging between 0.7 and 9 MPa. The number of bacteria retained was then assessed. We observed a decreasing trend with the increase of both bulk and surface mechanical stiffnesses down to a limit corresponding to the Young's modulus of the bacterial cell surface. For higher values than this threshold, the number of retained bacteria remained constant. We tentatively explain this observation by considering conformal overlay of bacterial and material surfaces.

The interface between nucleating agents and polymers plays a pivotal role in heterogeneous cell nucleation in polymer foaming. We describe how interfacial engineering of nucleating particles by polymer shells impacts cell nucleation efficiency in CO2 blown polymer foams. Core–shell nanoparticles (NPs) with a 80 nm silica core and various polymer shells including polystyrene (PS), poly(dimethylsiloxane) (PDMS), poly(methyl methacrylate) (PMMA), and poly(acrylonitrile) (PAN) are prepared and used as heterogeneous nucleation agents to obtain CO2 blown PMMA and PS micro- and nanocellular foams. Fourier transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy are employed to confirm the successful synthesis of core–shell NPs. The cell size and cell density are determined by scanning electron microscopy. Silica NPs grafted with a thin PDMS shell layer exhibit the highest nucleation efficiency values, followed by PAN. The nucleation efficiency of PS- and PMMA-grafted NPs are comparable with the untreated particles and are significantly lower when compared to PDMS and PAN shells. Molecular dynamics simulations (MDS) are employed to better understand CO2 absorption and nucleation, in particular to study the impact of interfacial properties and CO2-philicity. The MDS results show that the incompatibility between particle shell layers and the polymer matrix results in immiscibility at the interface area, which leads to a local accumulation of CO2 at the interfaces. Elevated CO2 concentrations at the interfaces combined with the high interfacial tension (caused by the immiscibility) induce an energetically favorable cell nucleation process. These findings emphasize the importance of interfacial effects on cell nucleation and provide guidance for designing new, highly efficient nucleation agents in nanocellular polymer foaming.

The aerobic composting of biodegradable plastics can be a promising solution to the growing issue of waste accumulation. Therefore, this article offers a review of papers investigating the biodegradability of polyesters (PLA, PHB, PBS and PCL) in home- and industrial composting. Not only the thermal and biodegradation properties are discussed, but also a comparison is made between the different polyesters under the same composting conditions. From this review, it becomes clear that composting shows promise for polyester waste management. However, although several methods for assessing the composting properties of polyester have been developed, the fact that they rarely follow the same standards does not allow for a comparative analysis that would clearly define composting as the most viable solution.

Liquid-releasing artificial skins are made from films made of a smectic liquid-crystal polymer network (LCN) photopolymerized in the presence of a photoactive azobenzene chromophore and a liquid-crystal porogen. The nonreactive porogen phase separates during the polymerization process, and the polymer forms a spongy polymer network filled with liquid. The liquid is excreted from the film when exposed to UV light upon conversion of trans-azobenzene to its cis isomer. Here, localized liquid secretion at preset positions at the polymer film is described. The design principle is based on creating a hybrid molecular architecture with both smectic and nonordered isotropic alignments in a continuous LCN coating. This coating is fabricated by a maskwise photopolymerization of the monomer mixture in the smectic phase, followed by a flood exposure at an elevated temperature above the isotropic state of the unpolymerized region. The smectic regions that polymerized during the maskwise exposure are not affected by the heating needed for the second polymerization step of the isotropic area. Upon activation under light illumination, the embedded liquid is exclusively released from the area with the smectic alignment. This approach reveals films of which the excretion process is reversible. The secreted liquid is reabsorbed spontaneously when azobenzene takes its initial trans-form. This process occurs thermally in time or can be accelerated by light irradiation with visible light.

In this work, we show and discuss the surface structure picture of copper phthalocyanine (CuPc) thin films deposited from trifluoroacetic acid (TFA) solvent onto silicon substrates at ambient conditions by four solution processing methods, namely drop-casting, dip-coating, spin-casting and spray-coating. The CuPc films were studied by AFM, as the main technique, and complemented by micro-Raman spectroscopy. Essentially, such thin films consist of CuPc molecular nanoribbons of a fixed ~1 nm thickness. CuPc molecules are arranged in an in-plane direction and formed in stacks under a defined tilt angle with respect to the substrate surface (monolayer) or underlying CuPc layer (multilayer). The film morphology takes various forms depending on the solution concentration, number of layers, and the deposition method. For instance, the morphology varies from very wide (~600 nm) but flat (~1 nm) ribbons for films prepared by dip-coating to crystallized rod-like features (multi-layered ribbons) when obtained by spray-coating. The factors studied in this paper should be taken into consideration in designing and controlling the criteria for rigorous CuPc film architecture.

In this work, a transparent and free-standing ionic gel as the dielectric layer for polarization switching in leaky ferroelectric thin films is reported. By applying an electric field over an ionic liquid dielectric layer used as an electrostatic field gated capacitor, one can avoid electronic conduction. The association of the electrical double layer with depolarization at the solid-liquid interface contributes to the reversible switching in PbZrxTi1-xO3 (x = 0.6) (PZT). Using such ionic gels, the anisotropic ferroelastic switching from mono-c-domain toward a-domain is studied in PZT grown on CaF2 substrates. Our results demonstrate that an electrostatic field, induced by the free-standing ionic gel, is an effective and promising way to investigate leaky ferroelectrics.

Marine plastic pollution is a worldwide challenge making advances in the field of biodegradable polymer materials necessary. Polylactide (PLA) is a promising biodegradable polymer used in various applications; however, it has a very slow seawater degradability. Herein, we present the first library of PLA derivatives with incorporated “breaking points” to vary the speed of degradation in artificial seawater from years to weeks. Inspired by the fast hydrolysis of ribonucleic acid (RNA) by intramolecular transesterification, we installed phosphoester breaking points with similar hydroxyethoxy side groups into the PLA backbone to accelerate chain scission. Sequence-controlled anionic ring-opening copolymerization of lactide and a cyclic phosphate allowed PLA to be prepared with controlled distances of the breaking points along the backbone. This general concept could be translated to other slowly degrading polymers and thereby be able to prevent additional marine pollution in the future.

Additive manufacturing or, as also called, three-dimensional (3D) printing is considered as a game-changer in replacing traditional processing methods in numerous applications; yet, it has one intrinsic potential weakness related to bonding of layers formed during the printing process. Prior to finding solutions for improvement, a thorough quantitative understanding of the mechanical properties of the interface is needed. Here, a quantitative analysis of the nanomechanical properties in 3D printed photopolymers formed by digital light processing (DLP) stereolithography (SLA) is shown. Mapping of the contact Young's modulus across the layered structure is performed by atomic force microscopy (AFM) with a submicrometer resolution. The peakforce quantitative nanomechanical mapping (PF-QNM) mode was employed in the AFM experiments. The layered specimens were obtained from an acrylate-based resin (PR48, Autodesk), containing also a light-absorbing dye. We observed local depressions with values up to 30% of the maximum stiffness at the interface between the consecutively deposited layers, indicating local depletion of molecular cross-link density. The thickness values of the interfacial layers were approximately 11 μm, which corresponds to ∼ 22% of the total layer thickness (50 μm). We attribute this to heterogeneities of the photopolymerization reaction, related to (1) atmospheric oxygen inhibition and (2) molecular diffusion across the interface. Additionally, a pronounced stiffness decay was observed across each individual layer with a skewed profile. This behavior was rationalized by a spatial variation of the polymer cross-link density related to the variations of light absorption within the layers. This is caused by the presence of light absorbers in the printed material, resulting in a spatial decay of light intensity during photopolymerization.

Magnetosomes produced by magnetotactic bacteria are biological membrane-enveloped magnetic nanoparticles. Extracted magnetosomes having the form of long chains as well as shortened chains with individual magnetosomes were prepared. The morphology (chain sizes) was modified in the sonication process and its impact was studied by transmission electron microscopy and dynamic light scattering. Fast magnetization saturation of magnetosome samples and the Verwey transition were detected by temperature-dependent magnetization measurements. To study the heating response to the applied alternating magnetic field (magnetic hyperthermia) magnetosomes were added into tissue-mimicking phantom. Temperature evolution and specific absorption rate (SAR) were measured and analyzed. It was found that embedding magnetosome chains in gel phantoms lead to a noticeable decrease in the efficiency of heating due to deterioration of Brownian mechanism.

In this work, the morphology, thickness, chemical composition and mechanical properties of the tribofilm formed by a fully formulated CVT fluid are investigated by multiple techniques and linked to the frictional and wear characteristics of a pin-on-disc tribosystem. It is found that the tribosystem shows higher friction and wear when tested at 150 °C than at 80 °C. The main reason is that although the morphology and thickness are similar, the tribofilms formed at different temperatures have different chemical compositions and mechanical properties. The tribofilm formed at 150 °C is Fe richer and has greater hardness and shear strength, which leads to a higher tribochemical wear rate and a greater interfacial shear force.

The properties of suspensions of magnetosomes extracted from magnetotactic bacteria are investigated. By using dynamic light scattering and measuring the dispersion of magnetic susceptibility it is shown that sonicated samples with broken magnetosome chains have qualitatively different behavior in comparison with native samples. This is explained by the presence of flexible chains of magnetosomes in non-sonicated samples which have the qualitative features of magnetic susceptibility predicted by the model of flexible magnetic rods.

A series of thin cyclomatrix polyphosphazene films has been prepared by interfacial polymerization of hexachlorocyclotriphosphazene (HCCP) with an aromatic biphenol. The pKa values of the biphenol used strongly influence the properties of the hyper-cross-linked films formed. 4,4′-Dihydroxybiphenyl (BPH) and 4,4′-dihydroxydiphenyl ether (DHPE) possess pKa values in the range of 9.4-9.6 & 10.0-10.3 for the mono- and di-ionized forms, respectively, and produce films with a lower cross-link density, whereas 4,4′-dihydroxybenzophenone (DHBP) and 4,4′-sulfonyldiphenol (BPS) feature lower pKa values (7.4-7.6 & 8.0-8.2), resulting in films with a higher cross-link density. The difference in cross-link density is reflected in, e.g., the surface morphology and mechanical properties of the films. Mechanical stiffness has been quantitatively assessed by PeakForce QNM AFM. Lower cross-link densities result in Young's moduli with average values of 44-69 MPa, with a sharp distribution, while higher cross-link densities yield broadly distributed Young's moduli with average values of 255-306 MPa, depending on the choice of the biphenol. The surface chemistry of the films was successfully altered by post-functionalization.

Surface-initiated atom transfer radical polymerization (SI-ATRP) was used to graft poly(N-isopropylacrylamide) (PNIPAM) brush layers with a controllable thickness in the 10-nm range from silicon substrates. The rate of polymerization of N-isopropylacrylamide was tuned by the [Cu(II)]0/[Cu(I)]0 ratio between the deactivating and activating species. The polymer layer thickness was characterized by atomic force microscopy (AFM) and ellipsometry. PNIPAM layers with a dry thickness between 5.5 and 16 nm were obtained. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed that the chemical structure is PNIPAM brushes. Analysis of the AFM data showed that our procedure leads to polymer grafts in the "mushroom-to-brush" transition regime.

UV-curable polymer composites are of importance in industry, biomedical applications, scientific fields, and daily life. Outstanding physical properties of polymer composites were achieved with nanoparticles as filler, primarily in enhancing mechanical strength or barrier properties. Structure-property relationships of the resulting nanocomposites are dictated by the polymer-filler molecular architecture, i.e. interactions between polymer matrix and filler, and high surface area to volume ratio of the filler particles. Among monomers, acrylates and methacrylates attracted wide attention due to their ease of polymerization and excellent physicochemical and mechanical properties of the derived polymers. We prepared and photopolymerized two series of formulations containing hydrophobized silica nanofiller (Aerosil R7200) dispersed in 2-hydroxyethyl acrylate (HEA) or polyethylene glycol diacrylate (PEGDA) monomers. We compared selected physical properties of the formulations, both before and after photocuring; specifically the viscosity of formulations and dispersion of the filler in the polymer matrices. Additionally, we estimated the bulk Poisson׳s ratio of the investigated nanocomposites. This article contains data related to the research article entitled "Nanoscale Young׳s modulus and surface morphology in photocurable polyacrylate/nanosilica composites" (Gojzewski et al., 2017) [1].

We studied quantitatively nanomechanical properties (Young’s modulus, adhesion force) and surface morphology of two types of model polymer-nanosilica composites. High-resolution structure-property maps were obtained using atomic force microscopy (AFM) in the non-resonant dynamic imaging mode (Quantitative Imaging, QI) by the collection and evaluation of a large number of force-distance curves. The Derjagin-Muller-Toropov (DMT) mechanical contact theory was applied. Interactions between the filler (Aerosil R7200) and two matrices (based on 2-hydroxyethyl acrylate and polyethylene glycol diacrylate) resulted in the appearance of differences in the interphase structure of the two types of composites. The main goal of the paper was to reveal these differences by determination of the mechanical nature of the polymer-particle interphase through systematic AFM indentations providing excellent mapping details. We focused on how the sub-microstructure of the nanocomposites is influenced by the presence of the varied filler contents. The AFM nanomechanical analysis is supported by a standard AFM imaging and SEM morphological observation as well as polymerization kinetics measurements. Our work serves to give a better understanding of the mechanical behaviour and properties of nanocomposites, particularly at the filler-matrix interphase. The article also discusses the measuring accuracy and possible method errors related to the QI mode in the AFM.

Recent developments in soft matter science provide options to add mobility and motility to polymer films and surfaces. Restrictively, the dynamics in these materials are modulated by a pulsated trigger and the route to autonomous dynamics is still a most intriguing challenge. Here, is the design of a self-sustaining oscillating surface is reported that is fueled by a continuous AC electric field without an intermittent on–off switch. The underlying principle is based on the polarity inversion over the poly(dimethyl siloxane) layer with a 10 nm thick silicon oxide top layer by an integrated tri-electrode structure connected to an alternating power source. In absence of the electric signal, the coating surface is flat. By applying an AC field, the surface corrugates into a sinusoidal morphology and starts oscillating to develop a continuous standing wave. Typically, the oscillation frequency is 0–5 Hz and the modulation depth is 150 nm. The topographical dynamics are analyzed in terms of viscoelastic materials properties and actuation kinetics and are supported by finite element calculations.

Segmented polyurethane elastomers for biomedical applications were synthesized and studied at macroscopic (by mechanical testing) and meso/nanoscopic length scales (by atomic force microscopy, AFM). The polyurethanes are composed of 4,4'-methylenebis(phenyl isocyanate), 1,4-butanediol and an ε-polycaprolactone diol. The stoichiometric ratio of the isocyanate and hydroxyl groups is constant, but the polymer diol to total diol—varies from 0 to 100 %. We show the representative features of the morphology from phase separation to mixed phases, how this is related to the mechanical properties in the bulk and locally, at exposed free surfaces and at the nanoscale. We propose a morphological model considering the molecular structure, the length of hard segments, and the dimensions of both the soft and the hard phases, respectively. Understanding such structure–property relations is pivotal to establishing designer materials and controlling the performance of the final product to achieve optimal properties in polyurethane based medical devices.

International audience; Mesh network structures are visualized by peak force tapping atomic force microscopy on cross-linked poly(dimethylsiloxane) (PDMS) at the nanometer length scale. The images directly capture network mesh structures with mesh diameter values, from 10 to 16 nm at the free surface of PDMS. Perpendicular to the free surface, in cross-sectional areas exposed by cryo-fracturing, similar mesh structures are observed. When exposed to uniaxial stress, the circular mesh features become elongated, showing network deformation at the nanoscale, as a result of mechanical stress. Following Soxhlet solvent extraction the mesh-like appearance remains unchanged, but mesh diameter values decrease, which are attributed to the removal of non-crosslinked chains and silica filler.

Crosslinked poly(urea-siloxane) (PUS) copolymer microspheres with diameters ranging from 0.8 to 1.8 μm with diameter polydispersity indices between 1.15 and 1.60 were synthesized in one-step precipitation polymerization in water-acetone solvent mixtures at room temperature. The spheres were obtained using aminopropyl-terminated siloxanes, isophorone diisocyanate and a tetrafunctional isocyanate crosslinker, employing a systematically varied molar ratio. The length of the siloxanes was controlled to obtain spheres with pre-determined Young's modulus values. Phase separation between soft disiloxane/poly(dimethylsiloxane) segments and hard isophorone bisurea units was observed with an excellent spatial resolution of ∼5 nm using atomic force microscopy (AFM). AFM mapping of the Young's modulus was achieved utilizing the PeakForce Quantitative Nanomechanical Mapping (QNM) mode. This AFM method allowed us to also measure the values of elasticity moduli of individual microspheres, ranging from 200 to 900 MPa. The microspheres can be used as filler to fine-tune the properties of composite materials, particularly with regard to elasticity. The hydrophobicity was also varied as indicated by water contact angle values between 122° - 132°. These features open the possibility of preparing designer composites for a range of applications from coatings to the biomedical field.

In order to produce segmented polyurethane polymers (PU) that can be processed readily into elastomeric thin films, a thermally labile blocking agent was used to form an isocyanate prepolymer and prevent reaction with moisture while facilitating the formation of the polymers by bulk thermal polymerization. The approach is to react a polymeric diol and isocyanate to form a prepolymer, end cap or ‘block’ the isocyanate, combine it with a chain extender, and form films that then thermally polymerize when the blocking agent dissociates and evaporates. A major advantage of this process is that the blocked isocyanate prepolymer is completely stable and unreactive on exposure to incidental moisture. Film polymerization kinetic studies were performed with the blocked isocyanate at a series of temperatures and reaction times. The extent of reaction was followed by proton NMR and the molecular weights of the resulting films were characterized by gel permeation chromatography (GPC). The data indicate how both temperature and reaction time are important for the formation of high molecular weight polyurethanes and that a catalyst is required to facilitate the reaction. Films with high molar masses and excellent mechanical properties were obtained. High resolution quantitative atomic force microscopy (AFM) imaging disclosed interesting features of the polymer morphology at the nanoscale that relate directly to the polymer mechanical properties.

Herein we report a facile and scalable synthesis of highly nitrogen-doped porous carbon materials with tunable morphology. Bio-based imidazolium derivatives made from natural amino acids and dioxo-derivatives are employed as precursors, exhibiting an analogous behavior during carbonization to classical ionic liquids. Utilization of systematically controlled salt templating methods yields nitrogen-doped carbon materials with high surface areas of up to 2650 m 2 g −1 and morphology-engineered structures such as monolithic or highly extended, sheet-like carbons. We believe that the presented approach represents an alternative and sustainable platform towards the rational design of carbon materials possessing controlled nanoporosity and functionality.

Copper phthalocyanine (CuPc) dissolved in trifluoroacetic acid (TFA) is deposited on solid SiO2 surfaces by solvent evaporation. The deposited CuPc aggregates are investigated by atomic force microscopy (AFM). The CuPc deposits were prepared by spin casting, dip coating, and spray deposition. Depending on the amount of deposited CuPc the aggregate morphology ranges from small individual domains to mesh-like multilayers. Each domain/layer consists of many parallel stacks of CuPc molecules with the square, plate-like molecules piled face-wise within each stack. The parallel stacks are attached sideways (i.e., edgewise attachment molecularly) to the substrate forming “nanoribbons” with uniform thickness of about 1 nm and varying width. The thickness reflects the length of a molecular edge, the width the number of stacks. A nucleation and growth model is presented that explains the observed aggregate and multilayer morphologies as result of the combination of nucleation, transport processes and a consequence of the anisotropic intermolecular interactions due to the shape of the CuPc molecule.

A series of segmented polycaprolactone polyurethane (PU) polymers is synthesized. One set of polymers ranges in composition from 0 to 100 wt% hard segments (HSs). The syntheses are carried out in solution and the polymers are melt-processed by compression molding. Another subset of polymers is formed in bulk from a blocked isocyanate prepolymer. The blocked polymer's thermal and mechanical properties are compared with the melt-processed materials. The emphasis in this paper is on the effects of varying the chemical structures of the PUs on their phase structures and physical cross-linking due to nanocrystalline hard domains. The thermal properties indicate that nanophase separation and the formation of hard domains occur at HS contents above ≈8 wt%. Property differences resulting from varying the hard segment amounts are directly related to differences in morphology at the nanoscale. Atomic force microscopy images show that the best elastomeric mechanical properties are found when nanocrystallites are 4–5 nm in size.

A critical complication in handling nanoparticles is the formation of large aggregates when particles are dried e.g. when they need to be transferred from one liquid to another. The particles in these aggregates need to disperse into the destined liquid medium, which has been proven difficult due to the relatively large interfacial interaction forces between nanoparticles. We present a simple method to capture, move and release nanoparticles without the formation of large aggregates. To do so, we employ the co-non-solvency effect of poly(N-isopropylacrylamide) (PNIPAM) brushes in water–ethanol mixtures. In pure water or ethanol, the densely end-anchored macromolecules in the PNIPAM brush stretch and absorb the solvent. We show that under these conditions, the adherence between the PNIPAM brush and a silicon oxide, gold, polystyrene or poly(methyl methacrylate) colloid attached to an atomic force microscopy cantilever is low. In contrast, when the PNIPAM brushes are in a collapsed state in a 30–70 vol% ethanol–water mixture, the adhesion between the brush and the different counter surfaces is high. For potential application, we demonstrate that this difference in adhesion can be utilized to pick up, move and release 900 silicon oxide nanoparticles of diameter 80 nm using only 10 × 10 μm2 PNIPAM brush.

Nanoadhesion on a self-assembled monolayer of 4-methyl-4'-mercaptobiphenyl is measured using a modified atomic force microscope. The dependence of the adhesion force on the loading rate is analyzed with the Dudko-Hummer-Szabo model, and the kinetic and interaction potential parameters for a single terminal group are extracted. The energy and location of the activation barrier suggest that the adhesion is dominated by van der Waals dispersion forces. The humidity effect on the nanoadhesion is also studied. The results are compared with previously measured values for methyl-terminated alkane thiols and the influence of the thiol rigidity on the adhesion force is discussed.

The helical structure of amyloid protofilaments of hen egg white lysozyme was analyzed by small-angle neutron scattering (SANS) and atomic force microscopy (AFM). The structure of these formations in bulk solutions was adequately described by SANS in terms of a simplified model of a helix with spherical structural units. The found main helix parameters (pitch and effective diameter) are consistent with the results of AFM analysis for amyloid fibrils adsorbed on a mica surface. Both methods reveal a strong isotope effect on the structure of amyloid fibrils with respect to the substitution of heavy for light water in the solvent. Specific details responsible for the structural differences when comparing SANS and AFM data are discussed from the viewpoint of methodological aspects, the influence of different (native and adsorbed) amyloid states and sample preparation.

The magnetic properties and hyperthermia effect were studied in solution of magnetosomes obtained by changing conditions during biomineralization of magnetotactic bacteria Magnetospirillum sp.AMB-1. It was shown that adding a higher amount of Wolfe's vitamin solution (WVS) or ferric quinate (FQ) cause increase of the mean diameter from 47 nm (normal condition) up to 52 nm and 58 nm respectively. As a consequence of this change the preparation conditions coercivity and Specific Absorption Rate (SAR) increased up to 20 Oe and 949 W/gFe for sample FQ, respectively. On the other hand the process of cultivation at the changed conditions markedly reduced the cultivation time. Also the isolated chains of magnetosome were shorter containing less amount of magnetosomes too.

Alkanethiols form stable, homogeneous, and well-organized self-assembled monolayers and can be used as lubricants in micro- and nanodevices when sufficiently hydrophobic and resistant to sudden temperature changes. In this paper, we demonstrate a new analysis method which provides a deep physical insight into adhesive interactions and their temperature dependencies at the single molecule level. We have focused on the adhesion between a silicon nitride tip and a 1-decanethiol self-assembled monolayer in the temperature range from 25 to 85 °C. We performed dynamic force spectroscopy measurements and applied theoretical models of adhesive-mechanical interactions and thermally activated unbinding to obtain detailed information on the adhesive interactions. The parameters of the interaction potential describing a single adhesive bond were calculated, and their temperature dependence was discussed. Although the changes of the adhesion force versus temperature are significant and nonmonotonic, the energy of the activation barrier of a single adhesive bond appears temperature independent. We attribute observed changes in the position of the activation barrier to the interplay between the rupture and rebinding of adhesive bonds, as well as to thermal reorganization, in particular the change of the tilt angle of thiol molecules in the self-assembled monolayer.

The anisotropy of several PVA/magnetosome magnetically textured films has been investigated. The thin film synthesized under the influence of a magnetic field (99 mT) shows the typical behavior of an anisotropic material. The results show that the magnetic field applied during the synthesis promotes an orientation of the chains of magnetosomes and permanent textured film is obtained after solidification.

The article describes the influence of the amount and type of organically modified nanosilica (surface and structure modified Aerosil 7200 and surface-modified Aerosil R711) on the photopolymerization kinetics of tetraethylene glycol dimethacrylate and on the physical properties of nanosilica dispersions in the monomer and the polymer matrix. Kinetic measurements showed that silica addition can accelerate or retard the polymerization depending on the silica content; the magnitude of this affect depends on the type of silica modification and can be associated with stability of silica dispersion (as measured by Zeta potential value). The highest reactivity showed compositions containing 4–5 wt.-% of silica and acceleration of the polymerization seems to result mainly from the increase in the propagation rate coefficient. The composites obtained show a uniform dispersion of nanoparticles within the polymer matrix for the silica content at least several wt.-%. The size of aggregates covered with the polymer layer is between 50 and 150 nm for Aerosil R7200 and 75–300 nm for Aerosil R711.

The adhesion force between a silicon nitride tip and a 1-dodecanethiol monolayer have been measured at different loading rates and different humidity. A way to extract the kinetic and interaction potential parameters for a single molecule interaction is demonstrated. The effect of the increase of van der Waals interaction strength per molecule with increasing humidity is explained by assuming a gradual adsorption of water into the tip surface hollows. The study should help in better understanding of the humidity effect on molecular level and in avoiding the underestimation of adhesion forces in micro- and nano-engineering in ambient conditions.

Atomic force microscopy has become an important technique for studying the adhesion of nanometer-sized contacts. However, there is still no good method to quantitatively characterize adhesive interactions. With a modified atomic force microscope, adhesion forces between a silicon nitride tip and a self-assembled monolayer of 1-dodecanethiol on gold(111) have been measured at different loading rates. Adhesion force-versus-loading rate curves revealed two regimes. Various interpretations of the two-regime character, like the existence of an inner transition state in the interaction potential or rebinding processes, are discussed. An explanation related to the cooperativity of individual van der Waals bonds responsible for effective adhesion is proposed. A way to extract the kinetic and interaction potential parameters for an individual van der Waals bond is demonstrated using a microscopic model to the analysis of adhesion force-versus-loading rate dependence.

The adhesion force between silicon nitride tips of an atomic force microscope and different self-assembled thiol monolayers (SAMs) was measured at different loading rates and humidity. SAMs were formed from HS(CH(2))(n)CH(3) with n = 6, 8, 9, 10, 15 and HS(CH(2))(n)OH with n = 6, 9, 11, 16. With a special setup, the loading rate could be increased to 10(7) nN s(-1). For the interaction with two-dimensional crystalline CH(3)-terminated SAMs (nor = 8), two regimes can be distinguished. At loading rates below 10(4)-10(5) nN s(-1), the adhesion force increased proportional to the logarithm of the loading rate. Adhesion is most likely dominated by van der Waals attraction. At higher loading rates, the adhesion forces increased steeper with the logarithm of the loading rate. The specific process limiting separation is not yet identified. On OH-terminated SAMs, the adhesion force was approximately 6 times higher than on the CH(3)-terminated SAMs, even at low humidity. This can partially, but not fully, be explained by hydrogen bridges forming between the hydroxyl groups of the monolayer and silanol groups of the tip. For relative humidity above 10%, the capillary force further increased the adhesion force, which reached a maximum at values of relative humidity between 40% and 80%. Adhesion force versus loading rate (F(ad) versus r(F)) curves increased roughly linearly over the whole range of loading rates. The slope depended on the humidity, and it is correlated with the absolute strength of the capillary force.

A suspension of bacterial magnetosomes was investigated with respect to structural and magnetic properties and hyperthermic measurements. The mean particle diameter of about 35 nm was confirmed by transmission electron microscopy (TEM), X-ray and magnetic analysis. The X-ray powder diffraction peaks of magnetosomes fit very well with standard Fe3O4 reflections. The found value for specific absorption rate (SAR) of 171 W/g at 5 kA/m and 750 kHz means that magnetosomes may be considered as good materials for the biomedical applications in hyperthermia treatments. Moreover, they have biocompatible phospholipid membrane.

In this paper, we describe a method allowing one to perform three-dimensional displacement control in force spectroscopy by atomic force microscopy (AFM). Traditionally, AFM force curves are measured in the normal direction of the contacted surface. The method described can be employed to address not only the magnitude of the measured force but also its direction. We demonstrate the technique using a case study of angle-dependent desorption of a single poly(2-hydroxyethyl methacrylate) (PHEMA) chain from a planar silica surface in an aqueous solution. The chains were end-grafted from the AFM tip in high dilution, enabling single macromolecule pull experiments. Our experiments give evidence of angular dependence of the desorption force of single polymer chains and illustrate the added value of introducing force direction control in AFM.

Two types of silica: precipitated (P, prepared in non-polar media, a new type, submicrometer sized) and fumed (F, nanosized), both unmodified and surface modified are investigated as functional fillers for potential applications in nanocomposites with poly(2-hydroxyethyl methacrylate) matrix. Special attention is paid to the kinetics of composite formation in an in situ photopolymerization process. Silica-containing formulations polymerize faster; this effect is much stronger for silica P having much larger particle size than silica F. Surface treatment leads to further acceleration of the polymerization in case of silica P but to retardation in case of silica F; the effect of modification of the filler surface on properties of composites is different for each of the silicas. The obtained results are discussed in terms of effects of curvature of silica particles, surface properties, solvation cell, interphase region, viscosity changes, and morphology of the resulting composites. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3472–3487

The anisotropy of several PVA/magnetosomes magnetically textured films has been investigated from the point of view of magnetic properties. The thin film synthesized under the influence of a magnetic field (99 mT) shows the typical behavior of an anisotropic material. On sample textured in magnetic field the magnetisation loop measurements were performed in dependence on the direction of the external magnetic field with respect to the texture axis. The results of hysteresis measurements show that the magnetic field applied during the synthesis promotes an orientation of the chains of magnetosomes and permanently textured film is obtained after solidification. The obtained values for magnetic remanence and coercivity were dependent on the external magnetic field orientation and the alignment effect of particle moments may be clearly seen which is in agreement with the theoretical model of magnetic particle chains.