A facile method for fabricating room-temperature-film-formable casein-based hollow nanospheres

"Casein micelle -nanoparticle double cross-linking" triggered stable adhesive, tough CA/MWCNT/PAAm hydrogel wearable strain sensors, for human motion monitoring

Flexible hydrogels have emerged as highly-desirable materials for wearable strain sensors. However, pristine biomass hydrogel systems are limited by their lack of stretchability, self-adhesion, and sensitivity. Here, a novel CA/MWCNT/PAAm double-network conductive hydrogel was developed through integrating casein (CA) micelles and multi-walled carbon nanotubes (MWCNT) into the polyacrylamide (PAAm) network. The resulting hydrogel displayed desired properties such as adhesiveness, toughness, self-healing, and near-infrared photothermal response. In this hybrid system, MWCNT were uniformly dispersed in the presence of casein micelles through hydrogen bonding and electrostatic interactions, favoring its role of nano reinforcement. Moreover, based on the "casein micelle-nanoparticle double cross-linking" mechanism and its double network structure, the prepared hydrogel showed high extensibility (2288 % ± 63 %), fast responsiveness (273 ± 5.13 ms), high sensitivity (GF = 12.46 ± 0.35), and a wide strain range (1-1000 %). Through consistent and repeated electrical inputs, this hydrogel was able to detect including large and small human movements, such as hand, leg, and swallowing motions. The results from this study provide a new way to fabricate bio-based hydrogel sensors with excellent mechanical and electrical properties.

Breathability and Moisture Permeability of Cellulose Nanocrystals Hollow Microsphere Coatings for PET Fabrics

In this study, cellulose nanocrystals hollow microspheres (HMs) were fabricated through Pickering emulsion polymerization, in which hydrophobically modified cellulose nanocrystals (CNCs) acted as Pickering stabilizers. The hollow interior core was prepared by solvent evaporation. This manuscript describes the synthesis of HMs in detail. The hollow structure and nanoscale size of HMs were verified using TEM. The resultant HMs could easily coat self-forming films on the surface of PET fabrics. Additionally, these coatings exhibited superior breathability and moisture permeability properties with a high one-way transport index of 936.33% and a desirable overall moisture management capability of 0.72. Cellulose nanocrystal hollow microsphere coatings could be used as a moisture-wicking functionality agent for finishing fabrics, oil-water separation, and fog harvesting.

Preparation and characterization of homogeneous and enhanced casein protein-based composite films via incorporating cellulose microgel

Gelatin-coupled cellulose (GCC) microgel with whisker-like structure is prepared and used to incorporate into casein (CA) matrix to construct reinforced CA-based composite films by solution casting. The GCC microgel has excellent dispersibility and stability in water, which contributes to the hydrophobicity and significantly reduces the moisture absorption of the composite films, as well as a decrease in the water vapor permeability with an increase of GCC content at different relative humidity is also observed. Compared with pure casein material, the resultant CA-based composite films show more homogeneous and dense cross-sectional structure, and the cleavage temperature of the hydrogen bonds increases by 16 °C. In particular, their tensile strength and Young’s modulus increase by 6 and 3.5 times, respectively. These indicators are superior to that of the nanoparticle enhanced CA-based composite film. Moreover, the light transmittance of the CA-based films at 550 nm is about 88% when GCC content is higher than 9%. The above results could be attributed to the strong hydrogen bonds formed between GCC components and CA matrix, as further confirmed by fourier transform infrared spectra and X-ray diffraction analysis.

Hollow polymer nanocapsules: synthesis, properties, and applications

Hollow polymer nanocapsules (HPNs) have gained tremendous interest in recent years due to their numerous desirable properties compared to their solid counterparts.

Water Absorption Behavior of Polystyrene Particles Prepared by Emulsion Polymerization with Nonionic Emulsifiers and Innovative Easy Synthesis of Hollow Particles

Submicrometer-sized raspberry-like polystyrene (PS) particles, which were prepared by emulsion polymerization with polyoxyethylene nonylphenyl ether nonionic emulsifier (Emulgen 910, HLB 12.2) and potassium persulfate initiator, contained 8.5 vol % (relative to the particle) of water and 5.5 wt % (relative to PS) of Emulgen 910 in the inside. The water absorption decreased the glass transition temperature of the PS particles dispersed in an aqueous medium. The wt % (relative to PS) of the incorporated Emulgen 910 increased with increasing initial Emulgen 910 concentration in the emulsion polymerization, but the wt % (relative to the total Emulgen 910 used) of the incorporated Emulgen 910 was constant at approximately 50% independent of the initial concentration. The vol % (relative to particle) of water increased to 46% by heat treatment at 90 °C for 24 h, which was based on further water absorption, and resulted in spherical hollow particles, where the amount of the incorporated Emulgen 910 remarkably decreased in a short treatment and then remained almost constant during the heat treatment. After another 24 h treatment, the percentage of nonhollow particles increased gradually, which was based on the escape of the water domain together with Emulgen 910 from the inside of the particles. On the other hand, spherical PS particles prepared by emulsifier-free emulsion polymerization did not contain water in the inside and were not changed to hollow ones by a similar heat treatment. From these results, an innovative easy method to synthesize hydrophobic hollow PS particles is proposed.

Hollow Casein-Based Polymeric Nanospheres for Opaque Coatings

Casein-based hollow polymeric sphere were fabricated through emulsifier-free polymerization coupled with alkali swelling approach. Hollow structure and nanoscale size of casein-based polymeric spheres were verified by TEM, AFM, SEM, and UV-vis spectra. The as-obtained hollow spheres were proved exhibiting superior opaque characteristic. Through adjusting the structural parameters, for example, MAA usages and MAA content in seed to core, sphere film showed tunable visible-light transmittance and antiultraviolet property. The formation mechanism of casein-based hollow sphere has been discussed in depth. Worth mentioning, the resultant hollow polymeric sphere can easily form films itself at room temperature, which would open a new possibility of designing opaque coatings in several fields, such as leather, packaging, paper making, biomedical, and special indoor coating applications.