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The film formation step of latexes constitutes one of the challenges of these environmentally friendly waterborne polymers, as the high glass transition (TG) polymers needed to produce hard films to be used as coatings will not produce coherent films at low temperature. This issue has been dealt by the use of temporary plasticizers added with the objective to reduce the TG of the polymers during film formation, while being released to the atmosphere afterwards. The main problem of these temporary plasticizers is their volatile organic nature, which is not recommended for the environment. Therefore, different strategies have been proposed to overcome their massive use. One of them is the use of hydroplasticization, as water, abundant in latexes, can effectively act as plasticizer for certain types of polymers. In this work, the effect of three different grafted hydroplasticizers has been checked in a (meth)acrylate copolymer, concluding that itaconic acid showed the best performance as seen by its low minimum film-formation temperature, just slightly modified water resistance and better mechanical properties of the films containing itaconic acid. Furthermore, film formation monitoring has been carried out by Differential Scanning Calorimety (DSC), showing that itaconic acid is able to retain more strongly the water molecules during the water losing process, improving its hydroplasticization capacity.

Nanostructured hematite (α-Fe₂O₃) films exhibit significant potential for energy, environmental, and medical applications. In the present work, a large-scale spray coating deposition method, scanning electron microscopy, and in situ grazing-incidence small-angle X-ray scattering are combined to investigate the structure formation mechanism of pure poly(styrene)-b-poly(4-vinyl pyridine) (PS-b-P4VP) and hybrid PS-b-P4VP/FeCl₃ films during and after spray deposition. Under the film deposition conditions specified in this experiment, a layered pure PS-b-P4VP film, a sponge-like hybrid PS-b-P4VP/FeCl₃ film, and a porous α-Fe 2 O 3 film are obtained upon completion of the deposition. The morphological differences between the investigated pure PS-b-P4VP and hybrid PS-b-P4VP/FeCl₃ films result from the interplay among the complexation between FeCl₃ and P4VP segments, the crystallization of the P4VP segment, and the surface diffusion of the FeCl 3 species. The findings of this work can offer both experimental and theoretical guidance for designing spray-deposited block copolymer and hybrid films.

The use of polymer latexes for high‐performance coatings is challenging as the properties required to allow for film formation at reasonable temperatures tend to result in films with relatively poor mechanical properties. In this review, routes to overcome this so‐called film‐formation dilemma are discussed. First, the use of coalescing agents, focusing in particular on more recent approaches to minimize the use of volatile organic compounds (VOCs), is reviewed. Subsequently, approaches that utilize hybrid latexes are considered. This includes the use of high/low Tg latex blends, nanocomposites that include a second, non‐polymeric phase, and multiphase latexes. Finally, the use of crosslinking technologies is considered, with a focus on necessary developments to reduce environmental impact. The review concludes with a summary and a discussion of possible future directions for research. Achieving high‐performance waterborne coatings is challenging as the properties required to allow for film formation at reasonable temperatures tend to result in films with relatively poor mechanical properties. In this review, routes to overcome this so‐called film‐formation dilemma (volatile organic compound [VOC]‐free diffusion promotors, structural reinforcement, and chemical and physical crosslinking) are discussed.

Mainly due to environmental aims, petroleum-based plastics are being replaced by natural polymers. In the last decades, starch has been evaluated in its film-forming ability for applications in the food packaging area. Characteristics of the starch film matrices, the film formation methods, and physicochemical properties of the starch films are reviewed in this paper. The influences of different components added in casting methods and thermoplastic processes have been also analyzed. Comparison of mechanical properties of newly prepared starch films and stored films reveals that the recrystallization phenomenon made the films more rigid and less stretchable. These effects can be inhibited by adding other polymers to the starch matrix. Other approaches to improve the starch films’ properties are the reinforcement by adding organic or inorganic fillers to the starch matrix as well as the addition of functional compounds. In this way starch films have improved mechanical and barrier properties and can act as a bioactive packaging. Physicochemical properties of the starch films showed a great variability depending on the compounds added to the matrix and the processing method. Nevertheless, dry methods are more recommendable for film manufacturing because of the greater feasibility of the industrial process. In this sense, a better understanding of the nano and microstructural changes occurring in the matrices and their impact on the film properties is required.

Natural rubber (NR) films with different natural networks—concentrated NR (CNR), deproteinized NR (DPNR), and small rubber particles (SRP)—are investigated to explore the relationship between network structure and film properties using atomic force microscopy (AFM) in PeakForce Quantitative Nanomechanics (QNM) mode. Nitrogen content, gel content, and particle size distribution analyses reveal distinct network topologies in each latex type. Mechanical testing shows variations in tensile strength and crosslink density. AFM analysis provides insights into the crosslink network structures within the pre‐vulcanized latex film. It is found that DPNR and CNR films have a uniform distribution of crosslink networks, with DPNR exhibiting higher Young's modulus values. In contrast, SRP shows varying Young's modulus values, suggesting poor coalescence arising from a harder particle surface and a softer rubber core in an inhomogeneous network structure intrinsic to the non‐rubber components (NRCs) make‐up of SRP latex. This study highlights the pivotal role of natural network structures formed by NRCs in determining the ultimate properties of latex films, which has significant implications for the rubber industry, particularly in the production of latex‐dipped products, medical devices, and bioengineering applications.

Emulsion polymerized latex-based pressure-sensitive adhesives (PSAs) are more environmentally benign because they are synthesized in water but often underperform compared to their solution polymerized counterparts. Studies have shown a simultaneous improvement in the tack, and peel and shear strength of various acrylic PSAs upon the addition of cellulose nanocrystals (CNCs). This work uses atomic force microscopy (AFM) to examine the role of CNCs in (i) the coalescence of hydrophobic 2-ethyl hexyl acrylate/n-butyl acrylate/methyl methacrylate (EHA/BA/MMA) latex films and (ii) as adhesion modifiers over multiple length scales. Thin films with varying solids content and CNC loading were prepared by spin coating. AFM revealed that CNCs lowered the solids content threshold for latex particle coalescence during film formation. This improved the cohesive strength of the films, which was directly reflected in the increased shear strength of the EHA/BA/MMA PSAs with increasing CNC loading. Colloidal probe AFM indicated that the nano-adhesion of thicker continuous latex films increased with CNC loading when measured over small contact areas where the effect of surface roughness was negligible. Conversely, the beneficial effects of the CNCs on macroscopic PSA tack and peel strength were outweighed by the effects of increased surface roughness with increasing CNC loading over larger surface areas. This highlights that CNCs can improve both cohesive and adhesive PSA properties; however, the effects are most pronounced when the CNCs interact favourably with the latex polymer and are uniformly dispersed throughout the adhesive film. This article is part of the theme issue ‘Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 1)’.

Electrochemical discharge machining (ECDM) is a nonconventional micromachining suitable for glass machining. Repeatability and dimensional inaccuracy issues are the biggest barriers to industrial applications. It is found through the literature survey that gas film is the most responsible parameter for the reproducibility and dimensional accuracy of the process. Ultrasonic vibration and magnetic field assistance, individually and combined, both ways affect the machining efficiency and dimensional accuracy. However, no research has been carried out to pinpoint the control of these advancements on the gas film geometry in detail. In this article, a comparative evaluation of gas film characteristics has been carried out with ultrasonic vibration, magnetic field, and combining both. The gas film attributes, such as formation mechanism, speed, stability, and width, were studied through current and voltage signals. The gas film formation time was reduced by approx. 23% at an applied voltage of 60 V with ultrasonic-assisted ECDM under a magnetic field compared to conventional ECDM. The geometry of the gas film was discovered to impact machining efficiency, accuracy, and work surface quality directly. The depth of penetration (DOP) and hole circularity were increased with a markable reduction in hole overcut (HOC) with ultrasonic-assisted ECDM under a magnetic field.

Hemicellulose, one of the most abundant biopolymers next to cellulose, has been considered as a potential substitute to synthetic polymers. Film casting from water is the most basic route for material applications of xylan. However, depending on plant sources and separation methods, xylans do not always form films and the related mechanism is unclear, which significantly hinders their material applications. We extensively characterized various fractions of bagasse xylan to understand the molecular features promoting the film formation. The side groups of xylans or impurities contributed to the prevention of excessive aggregation or crystallization of xylan molecules, leading to the film-forming capacity. However, once the film is formed, the side groups do not seem to be necessarily contributing to the mechanical resistance.

Recently, organic–inorganic halide perovskites have sparked tremendous research interest because of their ground‐breaking photovoltaic performance. The crystallization process and crystal shape of perovskites have striking impacts on their optoelectronic properties. Polycrystalline films and single crystals are two main forms of perovskites. Currently, perovskite thin films have been under intensive investigation while studies of perovskite single crystals are just in their infancy. This review article is concentrated upon the control of perovskite structures and growth, which are intimately correlated for improvements of not only solar cells but also light‐emitting diodes, lasers, and photodetectors. We begin with the survey of the film formation process of perovskites including deposition methods and morphological optimization avenues. Strategies such as the use of additives, thermal annealing, solvent annealing, atmospheric control, and solvent engineering have been successfully employed to yield high‐quality perovskite films. Next, we turn to summarize the shape evolution of perovskites single crystals from three‐dimensional large sized single crystals, two‐dimensional nanoplates, one‐dimensional nanowires, to zero‐dimensional quantum dots. Siginificant functions of perovskites single crystals are highlighted, which benefit fundamental studies of intrinsic photophysics. Then, the growth mechanisms of the previously mentioned perovskite crystals are unveiled. Lastly, perspectives for structure and growth control of perovskites are outlined towards high‐performance (opto)electronic devices. The development of structures and growth of organic–inorganic halide perovskites in forms of polycrystalline films and single crystals is reviewed, which is directed towards the optimization of their optoelectronic performance. A key is to implement a fine control of film morphology and crystal growth of perovskites.

In this research, ethyl cellulose films were prepared by a simple, easy, controlled one-pot method using either ethanol or ethyl lactate as solvents, the films being formed at 6 °C. Titanium dioxide nanoparticles were incorporated to improve the oxygen transmission and water vapour transmission rates of the obtained films. This method used no plasticizers, and flexible materials with good mechanical properties were obtained. The resulting solvent-free and transparent ethyl cellulose films exhibited good mechanical properties and unique free-shapable properties. The obtained materials had similar properties to those reported in the literature, where plasticizers were incorporated into ethyl cellulose films with an elastic modulus of 528 MPa. Contact angles showed the hydrophobic nature of all the prepared materials, with contact angles between 80 and 108°. Micrographs showed the smooth surfaces of the prepared samples and porous intersections with honeycomb-like structures. The oxygen and water vapor transmission rates were the lowest for the ethyl cellulose films prepared in ethyl lactate, these being 615 cm3·m−2·day−1 and 7.8 gm−2·day−1, respectively, showing that the films have promise for food packaging applications.