Raspberry-like Particles Research Articles

Golf Ball-like Polymer Particles by Colloidal Etching.

The unique core-corona structure of raspberry-like particles makes it an ideal template for the fabrication of golf ball-like particles by selective removal of the corona particles. However, few types of raspberry-like polymer-polymer core-corona composite particles have been used as the templates, probably because it is relatively difficult to synthesize well-defined raspberry-like polymer-polymer composite particles. We describe, for the first time, the fabrication of golf ball-like polymer particles by colloidal etching of raspberry-like poly(glycidyl methacrylate)-polystyrene (PGMA-PS) composite particles in a tetrahydrofuran (THF)/water medium with a higher THF concentration. Well-defined golf ball-like polymer particles can be obtained within 20 s. The influence of various synthesis parameters including the THF concentration, etching time, and composite particle size on the morphology of the resulting particles has been investigated, which suggests that a sufficient THF concentration is a prerequisite for the rapid formation of the golf ball-like morphology.

Synthesis of Raspberry-like PMMA Particles In a Ternary Solvent Mixture with Binary Initiators.

There is continuing interest in the synthesis of raspberry-like polymer particles, among which most of the reports have tended to focus on polymer composite particles, while there are relatively few examples of polymer particles with a single component. In this study, raspberry-like poly(methyl methacrylate)(PMMA) particles were synthesized by a one-step method in a ternary solvent mixture with binary initiators. The effects of different polymerization parameters, including the solvent composition, the initiator composition, the stabilizer component, the polymerization temperature, the stirring rate, and the nature of the monomer, on the morphology and size of the resulting particles were studied. A plausible mechanism for raspberry-like particle formation was suggested based on the monitoring data of the polymerization kinetics. The raspberry-like PMMA particles have a high dispersion stability in a salty aqueous environment.

Durable, transparent and superhydrophobic coating with temperature-controlled dual-scale roughness by self-assembled raspberry nanoparticles

This study focuses on creating a superhydrophobic, durable, and exceptionally transparent coating with dual-scale roughness by naturally formed raspberry-like particles. This approach facilitates the management of surface roughness at both single and dual scales through variations in surface functionalization temperature. We illustrated that adjusting the temperature of organosilanes functionalization on the surface allows for various reactions, such as the direct grafting of metallic precursors or their polymerization on the surface, resulting in the formation of large raspberry-like particles.We investigated the impact of nanoparticle concentration, functionalization duration, and reaction temperature on surface properties. Our results reveal that a concentration of 1.5 % SiO2 nanoparticles, combined with surface functionalization using TCMS for 4 h at 3 °C, provides the optimal conditions for creating a surface that combines superhydrophobicity, transparency, and acceptable durability. The resulting surface exhibits an impressive contact angle of 158.9°, a sliding angle of 2°, and a transmittance rate of 82 %.Furthermore, the coating demonstrates remarkable resistance to abrasion for up to 35 cycles and can withstand temperatures up to 280 °C. It also offers enhanced protection against UV radiation for 50 h and improved resistance to sand abrasion for up to 30 s, enduring bombardment pressures of up to 6 bars. Moreover, the coating presents several advantages in terms of surface cleaning.

Oleaster (Elaeagnus Angustifolia L.) low-fibrous extract to powder: Drying kinetics analysis

Oleaster's emerging applications in the food and pharmaceutical industries are due to its anti-cancer and pain-relieving properties. Green extraction methods are crucial to ensure drug compatibility to eliminate unwanted substances. This study focuses on the single droplet drying method to simply mimic a spray dryer, investigating how the drying medium controls droplet evolution into particles. Experiments were conducted with low-fibrous oleaster extract at various initial solid concentrations and ambient temperatures (100 °C, 150 °C, and 200 °C). This paper also delves into the influence of temperature on droplet morphology evolution, impacting the final particle's characteristics. The droplet diameter exhibits intricate behavior, involving normal evaporation, abrupt shape, and size changes, and concluding in a sticky solid state. Moreover, the drying process duration extends with higher initial droplet concentrations. The findings recommend using 150 °C and 200 °C as favorable drying temperatures, resulting in raspberry-like particles at high temperatures and shedding light on the oleaster extract drying.

Raspberry-like particle-assisted breath figures method to simultaneously fabricate superhydrophobic surfaces with different adhesions

In this article we introduced a raspberry-like particle-assisted breath figures method to simultaneously fabricate superhydrophobic surfaces with different adhesions. Firstly, SiO2 particles were in situ generated on the surface of styrene copolymer microspheres to form raspberry-like composite particles, and then simply separated the products according to the distribution differences of particles with different structures in the reactor. Finally, the superhydrophobic surface was prepared by breath figures (BF) method. The hydrophobic surfaces prepared by the particles on the wall and bottom of the reactor showed distinct adhesion, the former showed a Cassie-Baxter state with a contact angle of 158° and a sliding angle of 3°, while the latter exhibited a Wenzel state with high adhesion to water droplets. By changing the amount of styrene copolymer microspheres added, the superhydrophobic surface adhesion could be transformed. Meanwhile, the solid-liquid contact mode and the height to width (H/W) of the pores have also been proved to be the key factors affecting the surface adhesion.

Cooperative Synthesis of Raspberry-Like Covalent Organic Framework-Polymer Particles with a Radial Single-Crystal Grain Orientation.

Despite many efforts devoted toward the design of covalent organic frameworks (COFs) at the framework level by selecting the building blocks, their organization in the nano to meso regimes is often neglected. Moreover, the importance of processability for their applications has recently emerged and the synthesis of COF nanostructures without agglomeration is still a challenge. Herein, the first example of hybrid COF-polymer particles for which polymers are used to manipulate the 2D COF growth along a specific direction is reported. The study examines how the nature, chain-end functionality, and molar mass of the polymer influence the shaping of hybrid 2D boronate ester-linked COF-polymer particles. Catechol-poly(N-butyl acrylate) leads to the self-assembly of crystallites into quasi-spherical structures while catechol-poly(N-isopropylacrylamide) mediates the synthesis of raspberry-like COF-polymer particles with radial grain orientation. Scanning and transmission electron microscopies (SEM and TEM) and 4D-STEM-ACOM (automated crystal orientation mapping) highlight the single-crystal character of these domains with one plane family throughout the particles. Interestingly, the presence of PNIPAm on the particle surface allows their drying without co-crystallization and enables their resuspension. Kinetic investigations show that catechol-PnBuA acts as a modulator and catechol-PNIPAm induces a template effect, introducing supramolecular self-assembly properties into particles to create new morphologies with higher structural complexity, beyond the framework level.

Thin coating of silica/polystyrene core-shell nano/microparticles with hierarchical morphology onto polymeric films for fabrication of superhydrophobic surfaces

A novel coating process applied directly onto polymeric films offers a long-term alternative to short-term surface treatment of low surface energy polymers. In this paper, we report (i) an improved synthesis of a coating of raspberry-like particles directly onto polymeric surfaces and (ii) a novel method to obtain films with out-of-the ordinary superhydrophobic and self-cleaning properties. Inspired by the ‘lotus effect’ observed in nature, superhydrophobic surfaces were fabricated by combining dual-scale hierarchical coatings with low surface energy fluoroalkanes. Raspberry-like core-shell microparticles (MPs) composed of polystyrene (PS) core coated with silica (SiO2) shell (SiO2/PS) were synthesized by in situ dispersion polymerization of styrene directly on the surface of corona-treated polypropylene films. The PS MPs covered surface was then coated with SiO2 nano/microparticles (N/MPs) forming a hierarchical morphology on the surface. Biomimicry of the lotus leaf morphology is achieved by the hierarchical structure formed by dual-scale N/MPs that cover both PS particles and bare polypropylene surface, allowing air to be trapped in cavities formed. Adjustment of the diameters of the PS and SiO2 N/MPs allows the surface roughness of the coating to be controlled and optimized. 1H,1H,2H,2H-perfluorododecyltrichlorosilane was applied to lower the surface free energy, allowing the polymeric films to exhibit excellent superhydrophobic properties such as water contact angle above 170° and rolling angle of 0. Here, the application of the hierarchical coating was innovatively improved by direct synthesis of each layer onto the polymeric film. The treated surface portrays self-cleaning—soil placed over the surface is efficiently washed away by water, leaving clean trails. The durability of the microstructure and wetting properties of the coating were investigated. The coated films were observed to withstand a tape peeling test for up to 20 repetitions and sandpaper abrasion (1.96 kPa) for a distance of 2 m while retaining superhydrophobicity.

Synthesis of inorganic/organic raspberry-like composite particles for superhydrophobic and superlipophilic coatings

A facile synthetic route to composite particles with raspberry-like structure was reported, and further led to superhydrophobic and superlipophilic surface by the usage of these composite particles. In this approach, the poly(styrene-co-3-methacryloxypropyl trimethoxysilane) (P(St-MPS)) particles were fabricated by one-step dispersion polymerization. Then, the P(St-MPS)@SiO2 composite particles with raspberry-like structure were obtained by hydrolysis of tetraethoxysilane (TEOS) with (P(St-MPS)) particles under alkaline conditions. The morphology of the (P(St-MPS))@SiO2 composite particles could be controlled by adjusting the ratio of the initial reactants 3-methacryloxypropyl trimethoxysilane (MPS) and styrene (St). A possible mechanism of the morphology changes was also discussed, the reactive siloxane groups of the (P(St-MPS)) particles induce the growth of silica generated by the hydrolysis of tetraethoxysilane (TEOS) on its surface to form raspberry-like structure. In addition, the water contact angle (WCA) of the coating was 152° ± 2°, and the oil contact angle (OCA) of the coating was close to 0°, which demonstrated a superhydrophobic and superlipophilic properties by a rational surface modification of this P(St-MPS)@SiO2 composite particles with raspberry-like structure. Hydrophobic properties could be adjusted by varying the surface morphology of the P(St-MPS)@SiO2 composite particles. The coatings could be used in applications such as self-cleaning and oil-water separation and whole process was carried out under mild conditions and did not involve complex steps.

Effects of particle roughness on the rheology and structure of capillary suspensions

We show that particle roughness leads to changes in the number, shape and resulting capillary force of liquid bridges in capillary suspensions. We created fluorescently labeled, raspberry-like particles with varying roughness by electrostatically adsorbing silica nanoparticles with sizes between 40 nm and 250 nm on silica microparticles. Rougher particles require more liquid to fill the surface asperities before they form pendular bridges, resulting in smaller and weaker bridges. In a system where the effective bridge volume is adjusted, higher particle roughness leads to less clustered networks, which show a higher yield strain for a matching storage modulus compared to the smooth particle networks. This finding suggests that the particle-particle frictional contacts also affects the strength of capillary suspensions. Using asymptotically nonlinear oscillatory rheology, we corroborate the non-cubical power law scaling of the third harmonic in the shear stress response that results from both Hertzian contacts and friction between particles connected by capillary bridges. We demonstrate that the repulsive Hertzian contact parameter A is sensitive to the liquid bridge strength and that roughness appears to shift the relative scaling of the power law exponents from adhesive-controlled friction to load-controlled friction.

High Figure of Merit SPR Sensor Based on Raspberry-Like Silica

To address the problems that the surface plasmon resonance (SPR) sensor is not sensitive enough to detect biomolecules in the refractive index range (RI=1.33-1.34), and the traditional methods to enhance the sensitivity cause the sensor poor bioaffinity, this paper proposed raspberry-like silica assisted high figure of merit (FOM) fiber-optic SPR sensor. The finite element method results show that when the raspberry-like silica is introduced to the SPR sensor, the resonant electric field intensity on the sensor surface is 2.97 times stronger than that of SPR sensors only. Raspberry-like silica particles composed of different noble metals nanoparticles (AuNPs, PtNPs, and CuNPs) were prepared to compare and analyze the effects of different nanoparticles on the sensing performance. The sensing experiments showed that AuNPs raspberry-like silica had the most excellent performance, enabling the sensor to achieve high sensitivity of 5264.3 nm/RIU, which is 2.65 times higher than the Au film SPR sensor. The fitting calculations showed that the AuNPs raspberry-like silica assisted SPR sensor had a high FOM of 42.9 RIU-1, 1.9 times more than the Au film SPR sensor. In addition, the sensor has good temperature stability, repeatability, and generality after the corresponding test. The proposed raspberry-like structure provides a new approach to obtaining both high sensitivity and high FOM for the SPR sensor, which makes the sensor potential for biosensing.

Facile preparation of raspberry-like mesoporous poly(styrene-co-divinylbenzene)/Ag composite particles for antibacterial superhydrophobic surfaces and liquid marbles

Due to their unique properties, raspberry-like colloidal particles (RCPs) have been widely used in various fields. However, a facile, scalable and robust approach of producing raspberry-like colloidal particles remains an ongoing challenge. Herein, raspberry-like mesoporous poly(styrene-co-divinylbenzene) (PSD) polymeric particles were fabricated by one-step dispersion polymerization in the solvent mixture of ethanol and toluene. The morphologies of obtained polymeric particles could be easily tuned from spherical to raspberry-like structure by changing the composition of the solvent mixtures. A rational mechanism for the formation of raspberry-like polymeric particles was also proposed according to the morphological evolution under different copolymerization conditions. With the assitance of the immonilized PVP layer, the raspberry-like PSD colloidal particles can be further functionalized by depositing Ag nanoparticles on the particle surface. The antibacterial activity of raspberry-like PSD/Ag composite particles against E. coli was up to 99.99%. In addition, raspberry-like PSD/Ag composites can be further utilized to construct antibacterial superhydrophobic surface and liquid marbles.

A robust method for the development of mechanically, thermally stable anti-reflective and self-cleaning coatings through in-situ formation of hierarchical raspberry-like mesoporous nanoparticles

A robust formulation was developed to produce anti-reflective and self-cleaning coatings, consisting of hierarchical mesoporous silica, modified mesoporous titania nanoparticles and siloxane resin along with other ingredients. The hierarchical arrangement of nanoparticles by the process of self-assembly along with the polymerization of resin developed hierarchical micro and nanoscale structure on the coated surface because of the in-situ generation of raspberry-like particles during film formation. A systematic study was carried out to investigate the effect of additives on the microstructure, optical property and wettability of the coatings. The optimum composition of the coating has anti-reflective property with maximum transmittance of 99.6% (364 nm) with an absolute increase in transmittance of 5.3% in the wavelength range of 360–600 nm with a contact angle of 140° with water. The addition of Hexamethyldisilazane (HMDS) into the formulation enhanced the hydrophobicity of the coatings by extending the formation of more micro-nano scale structure. Moreover, developed coatings have 5B adhesion, significant humidity resistance, passed the 3H pencil hardness test and are thermally stable up to 250 °C. The developed process is also suitable for low temperature organic substrates, feasible for scale-up production and the stable formulation can be available in a two-pack system.

Engineering the Surface Pattern of Microparticles: From Raspberry-like to Golf Ball-like.

Control of the shape and uniformity of colloid particles is essential for realizing their functionality in various applications. Herein, we report a facile approach for the synthesis of narrowly dispersed anisotropic microparticles with well-defined raspberry-like and golf ball-like surface patterns. First, we demonstrate that hybrid raspberry-like particles can be achieved through a one-pot polymerization method using glycidyl polyhedral oligomeric silsesquioxane (GPOSS) and pentaerythritol tetra(3-mercaptopropionate) (PETMP) as monomers. Varying the polymerization parameters such as catalyst loading, monomer concentration, and the molar ratio of monomers, we are able to regulate the sizes and surface protrusion numbers of these raspberry-like microparticles. The formation mechanism is attributed to a competition balance between thiol-epoxy reaction and thiol-thiol coupling reaction. The former promotes rapid formation of large core particles between PETMP and GPOSS droplets (which can serve as core particles), while the latter allows for generation of surface protrusions by PETMP self-polymerization, leading to the formation of raspberry-like surface patterns. Based on the different POSS contents in the surface protrusions and cores of the raspberry-like microparticles, we demonstrate that they can be used as precursors to produce microporous silica (sub)microparticles with golf ball-like morphology via pyrolysis subsequently. Overall, this work provides a facile yet controllable approach to synthesize narrowly dispersed anisotropic microparticles with diverse surface patterns.

Composite states of wetting

The analytical expressions of liquid–vapor equilibrium contact angles are analyzed in the thermodynamic limit for various simple geometries and arrangements of the substrate, in particular when the latter exhibits two or more scales. It concerns the Wenzel state of wetting when the substrate is completely wet, the Cassie–Baxter state when the liquid hangs over the substrate, but also intermediate states of wetting which are shown to be relevant and in competition with the two other ones. Under a separation of scales hypothesis, a composition rule of contact angles is developed whose interest is illustrated in a close packing setup of raspberry-like particles.

Shape control in seed-mediated synthesis of non-elongated Cu nanoparticles and their optical properties.

Shape and surface chemistry control in copper nanoparticle synthesis is an important research area due to a wide range of developing applications of this material in catalysis, energy conversion, sensing and many others. In addition to being an inexpensive and abundant metal, copper is an attractive photocatalyst due to its optical properties in the visible range. Here, we report a facile, tunable and sustainable methodology for synthesizing Pd-seeded Cu nanoparticles with various shapes, including cubes, spheres, raspberry-like particles and cages stabilized with a bilayer of a cationic surfactant in aqueous media. The experimental and theoretical examination of the optical response in the series of synthesized nanoparticles revealed that the low-energy extinction peak is associated with electronic interband transitions in the metal, in contrast to a widely spread attribution of this peak to a plasmonic response in Cu nanoparticles.

Anomalously Shaped Functional Particles Prepared by Thiol-Isocyanate Off-Stoichiometric Click Dispersion Polymerization.

Anomalously shaped microparticles have attractive advantages in applications. They are usually prepared by chain-growth polymerizations in heterogeneous systems. Recently, thiol-X step-growth polymerizations have been used to produce functional particles with a regular shape but rarely anomalous shapes. Herein, we report the preparation of anomalously shaped particles by thiol-isocyanate dispersion polymerization (Dis.P) in ethanol using polyvinylpyrrolidone (PVP) as a stabilizer and catalyst. Papillae-shaped, raspberry-like, and multibulged particles are prepared by tuning monomer combinations, contents, and feed ratios. Particle morphology evolutions during polymerization are observed by scanning electron microscopy (SEM). Distinct from previous works, particles with residual -SH groups are obtained even with equal moles of monomers added initially. The residue of -SH groups is revealed by Fourier transform infrared spectroscopy (FT-IR) analyses and confirmed by detection with a fluorescent probe containing disulfide linkage. Moreover, fluorescent particle probes are formed by the reaction of excess -NCO groups on particles with fluorescein isothiocyanate isomer I (FITC) and dithioacetal-functionalized perylenediimide (DTPDI). The probes are sensitive in detection of glutathione (GSH) and Hg2+ in water. Hg2+ as low as 1-0.1 ppb is detected using a raspberry-like particle probe with DTPDI.

Spherical probes for simultaneous measurement of rotational and translational diffusion in 3 dimensions

Real time visualization and tracking of colloidal particles with 3D resolution is essential for probing the local structure and dynamics in complex fluids. Although tracking translational motion of spherical particles is well-known, accessing rotational dynamics of such particles remains a great challenge. Here, we report a novel approach of using fluorescently labeled raspberry-like colloids with an optical anisotropy to concurrently track translational and rotational dynamics in 3 dimensions. The raspberry-like particles are coated by a silica layer of adjustable thickness, which allows tuning the surface roughness. The synthesis and applicability of the proposed method is demonstrated by two types of probes: rough and smoothened. The accuracies of measuring Mean Squared (Angular) Displacements are also demonstrated by using these 2 probes dispersed in 2 different solvents. The presented 3D trackable colloids offer a high potential for wide range of applications and studies, such as probing the dynamics of crystallization, phase transitions, biological interactions and the effect of surface roughness on diffusion.

Antifogging UV curable coatings based on hierarchical composite particles through electrostatic interactions

Antifogging UV curable coatings via a two-step spin coating method were successfully fabricated by introduction of raspberry-like particles. Raspberry-like particles were dispersed on the UV coating surface which increase the hydrophilicity of the coating. This UV coating was fabricated by polyester acrylates resin and polyethylene glycol diacrylate. The stability of raspberry-like particles is investigated by dispersing them into water and ethanol. The roughness of raspberry-like particles can be controlled by adjusting the mass ratio. We have investigated the influence of raspberry-like particles on the surface morphology, light transmittance and antifogging performance. Compared with other methods, this method is quite easy to carry out and the raspberry-like particle stability still maintains in the coating and coating hardness increased significantly which is essential for practical uses.

Deformation of raspberry-like polymer composite particles by colloidal fusion

Raspberry-like polymer composite particles with polymer coronas were deformed to core–shell particles through the colloidal fusion method.

Uncontrolled polymerization that occurred during photoinitiated RAFT dispersion polymerization of acrylic monomers promotes the formation of uniform raspberry-like polymer particles

Uniform raspberry-like polymer particles are prepared by a different type of photoinitiated RAFT dispersion polymerization.