A novel approach, i.e., ultrasonic irradiation, was used to prepare polyaniline/nanocrystalline TiO 2 composite particles. Polymerization of aniline proceeded under ultrasonic irradiation in the presence of nanocrystalline TiO 2 . The aggregation of nano TiO 2 can be reduced under ultrasonic irradiation, and the nanoparticles can be redispersed in the aqueous solution. The polyaniline deposits on the surface of the nanoparticle, which leads to a coreshell structure. The resulting polyaniline/nano TiO 2 composite particles are spherical, and the sizes vary with the content of TiO 2 . The polyaniline/nano TiO 2 composite particles prepared by the conventional stirring method have a "raspberry" aggregate structure, which is different from that obtained through ultrasonic irradiation. The presence of nanocrystalline TiO 2 strengthens the UV absorption of polyaniline and leads to a blue shift of the π-polaron absorption of polyaniline. Ultrasound can enhance the doping level. When polyaniline deposits on the surface of nano TiO 2 , the crystalline behavior of polyaniline is hampered and the degree of crystallinity decreases. With increased TiO 2 content, the H-bonding interaction is strengthened and the characteristic peaks of benzoid and quinoid are shifted. X-ray photoelectron spectroscopy (XPS) shows that the ratio of the number of Ti and N atoms (Ti/N) on the surface is lower than that in the bulk. This is strong evidence for a polyanilineencapsulated nano TiO 2 structure. The conductivity of the composites obtained through ultrasonic irradiation decreases with increasing TiO 2 content. Ultrasonic irradiation contributes to the increase in the conductivity compared with conventional stirring. When the content of polyaniline decreases to ∼10%, the conductivity of composite still remains at 10 -1 S•cm -1 . Ultrasonic irradiation provides us a new way to prepare 0-3-dimensional conducting polymer/nanocrystalline particle composites.
NR/GE composites were prepared by an ultrasonically‐assisted latex mixing and in situ reduction process. Graphene oxide was dispersed in NRL using an ultrasonic field and was then reduced in situ, followed by latex coagulation to obtain the NR/GE masterbatch. The results show that the process produces a much better dispersion and exfoliation of GE in the matrix and contributes to an increase in the tensile strength compared to conventional direct mixing. Compared to pure rubber, the tensile strength and tear strength for NR/(2 wt.‐%)GE composites were increased by ≈47 and 50%, respectively. With increasing GE content, the maximum torque, crosslink density, elastic modulus, and thermal conductivity of NR/GE composites were found to increase. magnified image
Vulcanized graphene/natural rubber composites with a conductive segregated network exhibiting good electrical conductivity, water vapor permeability and high mechanical strength are prepared by self-assembly in latex and static hot pressing. The composite exhibits a percolation threshold of $0.62 vol% and a conductivity of 0.03 S m À1 at a content of 1.78 vol%, which is $5 orders of magnitude higher than that of the composites made by conventional methods at the same loading fraction.
A desirable microenvironment is essential for wound healing, in which an ideal moisture content is one of the most important factors. The fundamental function and requirement for wound dressings is to keep the wound at an optimal moisture. Here, we prepared serial polyurethane (PU) membrane dressings with graded water vapor transmission rates (WVTRs), and the optimal WVTR of the dressing for wound healing was identified by both in vitro and in vivo studies. It was found that the dressing with a WVTR of 2028.3 ± 237.8 g/m2·24 h was able to maintain an optimal moisture content for the proliferation and regular function of epidermal cells and fibroblasts in a three-dimensional culture model. Moreover, the dressing with this optimal WTVR was found to be able to promote wound healing in a mouse skin wound model. Our finds may be helpful in the design of wound dressing for wound regeneration in the future.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.