Xihua Lu

Bioinspired Lotus-like Self-Illuminous Coating.

The sensitivity of long persistent phosphor materials (LPP) to moisture greatly limits their applications especially in humid environments, which cause the hydrolysis of LPP and shorten their lifetime. In this work, a facile, environmentally friendly, and low-cost method was developed to prevent the infiltration of water or moisture to the LPP by doping LPP with SiO2 nanoparticles to form a superhydrophobic coating. The superhydrophobic coating provided a stable environment to the self-illuminous system, which not only can resist the infiltration of water but also can have good self-cleaning property, similar to the lotus leaf effect. This facile method will be very beneficial for expending further application of LPP especially in high humidity.

Methacrylic acid-triggered phase transition behavior of thermosensitive hydroxypropylcellulose.

Methacrylic acid (MAA)-triggered phase transition of thermosensitive hydroxypropyl cellulose (HPC) was studied. The phase transition temperature of 0.1 wt.% HPC aqueous solutions was dramatically reduced from 41 °C to 8 °C as the MAA concentration increased from 0 wt.% to 4 wt.%. The sharp decrease of HPC phase transition temperature triggered by MAA may be attributed to strong hydrogen bonding between MAA and HPC. It may be proposed that the hydrogen bonding of MAA with HPC restricts the interaction of water with HPC and so reduces the solubility of HPC in water and improves the hydrophobic association of HPC. Furthermore, MAA attaching on HPC polymer chains was polymerized to form surfactant-free PMAA nanogels around ambient temperature when HPC collapsed forming PMAA nanogels. Effect of MAA concentration and polymerization temperature on the size and size distribution of PMAA nanogels was investigated.

Synthesis of surfactant-free hydroxypropylcellulose nanogel and its dual-responsive properties.

Surfactant-free hydroxypropylcellulose (HPC) nanogels were synthesized by using thermo-sensitive HPC as a template to form HPC/PMAA nanoscale complex. The formation mechanism was owing to the interpolymer hydrogen bonding between HPC and PMAA induced phase transition of HPC in aqueous media. The average size of the resulting HPC nanogels ranges from about 98 to 241 nm. It was found that the average size of HPC nanogels changed little with increasing polymerization temperature below 26 °C, whereas it greatly increased above 26 °C. When the concentration of HPC was increased from 0.1 to 0.9 wt.%, the diameter of nanogels decreased firstly and then increased. Besides, an increasing crosslinker BIS concentration led to a reduced size of HPC nanogels, and the nanogels had the narrowest size distribution when its concentration was 0.1 wt.%. In addition to intrinsic thermo-sensitivity, HPC nanogels also display pH-induced phase transition due to pH-responsive PMAA contained in HPC nanogels. Surfactant-free, dual-responsive HPC nanogels would have promising applications in biotechnology and nanomedicine.

Synthesis of surfactant-free hydroxypropyl methylcellulose nanogels for controlled release of insulin.

A facile controlled-release nanogels delivery system has been developed by using hydroxypropyl methylcellulose (HPMC) hybrid nanogels as encapsulation shell materials, which were synthesized by surfactant-free polymerization in aqueous solution. The effects of reaction time and cross-linker concentration on the size of the nanogels have been studied. The results showed that in a certain range, the particle size decreased with increasing reaction time and increasing concentration of cross-linker. Meanwhile, at the feeding ratio 0.05/1 of HPMC/methacrylic acid (MAA), the LCST of prepared nanogels at pH=6 was close to the body temperature, which can be used as sustained insulin delivery system. Besides, the HPMC nanogels loaded with insulin had a high drug loading of 21.3% and a high entrapment efficiency of 95.7%. The release behavior of the insulin nanogels can be adjusted by pH and temperature which will have potential applications in controlled release delivery system.

Preparation of high encapsulation efficiency fragrance microcapsules and their application in textiles

Poly(1,4-butanediol dimethacrylate) microcapsules containing dementholized peppermint oil (DPO) were prepared by interfacial free-radical polymerization. The influence of the composition of the core material on the morphology of the fragrance microcapsules was investigated by scanning electron microscopy (SEM). Response surface methodology (RSM) was applied to optimize the effects of curing temperature, homogenization time, ratio of core/shell and homogenization rate on the encapsulation efficiency. The thermal stability of the fragrance microcapsules was studied by thermogravimetric analysis (TGA). The prepared fragrance microcapsule, under optimal conditions, possessed spherical shape, good thermal stability below 100 °C and high encapsulation efficiency of 91%. In addition, the fragrance microcapsules coated onto cotton fabric displayed good washing durability after 15 cycles, which will be beneficial for their future application in textiles, daily necessities and so on.

In situ synthesis of magnetic poly(N-tert-butyl acrylamide-co-acrylic acid)/Fe3O4 nanogels for magnetic resonance imaging

Poly(N-tert-butylacrylamide-co-acrylic acid)/Fe3O4 (P(TBA-co-AA)/Fe3O4) nanogels have been synthesized successfully by two steps: firstly, poly(N-tert-butylacrylamide-co-acrylic acid) (P(TBA-co-AA)) nanogels were synthesized through emulsion precipitation polymerization by using N-tert-butylacrylamide (TBA) and acrylic acid (AA) as reactive monomers; then P(TBA-co-AA)/Fe3O4 nanogels were synthesized by in situ oxidation of Fe2+ into Fe3O4 nanoparticles inside the networks of the P(TBA-co-AA) nanogels. The prepared P(TBA-co-AA)/Fe3O4 nanogels were about 70 nm in dry state, and 118.9 nm in aqueous solution with a low polydispersity index (PDI) of 0.124. The small size and low PDI of the magnetic nanogels could be applied in living body. Besides, the nanogels had good superparamagnetic property, and high r2 relaxivity value of about 512.01 mM−1 s−1. These magnetic properties endowed the nanogels with a new ability to be applied in T2-style imaging. In short, this work would provide the possibility of using the P(TBA-co-AA)/Fe3O4 nanogels as contrast agents for high resolution of magnetic resonance imaging (MRI).

Coordination-bond-driven fabrication of crack-free photonic crystals

The self-assembled fabrication of large-area opal photonic crystals (PCs) that are free of cracks has remained a challenge which greatly limits the practicality of such a structure in optical and electronic applications. We report a new route in this paper for fabricating centimeter scale crack-free opal PC films in which the latex spheres are bound together through coordination bonds. The elimination of cracks in the PCs is attributed to the formation of metal ion–polymer latex spheres coordination complexes which is confirmed by shifts of the binding energy of the metal ion after the reaction. The coordination bonds enhance the interactions between the polymer latex spheres, which can neutralize the adhesion stress caused by the substrate and tension stress caused by the shrinkage of the latex spheres during the evaporation of solvent. The as-prepared PC films show a uniform diffraction color and excellent reflection properties, which proves that the formation of coordination bonds does not weaken the contrasts of the refractive index or the optical quality of the PCs. This facile fabrication of large area, crack-free opal PCs will offer significant insight into the preparation and applications of PCs in optical devices.

Use of caprylic/capric triglyceride in the encapsulation of dementholized peppermint fragrance leading to smaller and better distributed nanocapsules

Dementholized peppermint (DP) fragrance nanocapsules were prepared through the interfacial polymerization of isophorone diisocyanate (IPDI) and hexamethylene diamine (HMDA) in a nanoemulsion, in which peppermint fragrance added with/without caprylic/capric triglyceride (GTCC) was used as the core material and polyurea as the shell material. The results showed that addition of GTCC can significantly reduce the sizes of nanocapsules and improve the size distribution of the nanocapsules. Under the optimized conditions, the resulting DP-GTCC nanocapsules kept good physical stability, while DP nanocapsule dispersion was physically separated in a short time. The average nanocapsule diameter was 82.8 nm with a narrow size distribution of 0.19. The nanocapsules possessed a high DP fragrance loading of 16% with encapsulation efficiency of 81%. Besides, the addition of GTCC further improved the thermal stability of the core material. DP-GTCC nanocapsule dispersion was very stable and exhibited good transparency at a nanocapsule concentration of 0.2% or less due to its very small size.