Abstract: Interest in the stimuli-responsive polymers has been going on for decades, and a lot of work has been dedicated to the development of environmentally sensitive macromolecules that can be crafted into novel responsive carrier materials. This article reviews the state-of-the art in smart responsive carriers for controlled drug delivery applications. And the preparation methods of different responsive materials, sustained and controlled release performance are summarized. The significance and future of smart responsive materials are also commented.
Abstract: Poly acrylic acid (PAA) was synthesized by solution polymerization. We analysed that MBA dosage, acrylic acid percentage, neutralization degree and surface crosslink have affections on PAA, mainly about three properties (including 0.9%NaCl solution's absorptivity, absorptivity under 2068Pa, and holding ability of moisture). The experimental evidence obtained that lower acrylic acid percentage is helpful to these three properties. Indexes increase at first and then decrease with neutralization degree raise. MBA dosage is against to absorptivity and retention capability, but useful to absorptivity under pressure. Scanning electron microscopy (SEM) was used to observe the surface of the PAA powder, and prove that surface crosslink promote form a kind of honeycomb structure. Under the optimum synthetic conditions, the absorptivity of 0.9%NaCl solution is 58.8 times, retention capability is 38.4 times, and absorptivity under 2068Pa is 33.6 times.
Abstract: PVA/PVP-assisted hydrothermal method was used to prepare single-crystal pre-perovskite PbTiO3 (PP-PT) nanofibers, in which polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) acted as surfactants. Subsequently, poly (vinylidene fluoride)/ pre-perovskite PbTiO3 nanofibers (PVDF/PP-PT) nanocomposite thin films were successfully fabricated by a spin-coating method. The test results showed that PP-PT nanofibers had a good distribution in PVDF matrix. Moreover, α-phase coexisted with β-phase in the PVDF and PVDF/PP-PT nanocomposite thin films. The dielectric properties of the PVDF/PP-PT nanocomposite thin films were measured as a function of frequency in the range of 5 kHz to 5 MHz. It is worth noting that the dielectric constant of nanocomposite thin films increased with increasing the weight ratio of PP-PT nanofibers in the low frequency range. By contrast, the dielectric constant of PVDF/PP-PT nanocomposite thin film which contained 20% PP-PT nanofibers was 43.7% larger than that of pure PVDF thin film (εr = 6.77) at 5 kHz, and the loss tangent was ~0.03.
Abstract: Since the first paper by Keddie et al. published on 1994 , the glass transition of polymer systems on surface/thin film has been an active research field and attracted many groups interests. Numerous works have been done, in both experimental and computation approaches, to investigate this subject. In this paper we reviewed the milestone findings in the last twenty years. Generally with only minor disagreements in the mechanism all the mainstream works are consistent in the conclusions that: 1) Geometric confinement in thin film or on surface reduces the glass transition temperature Tg comparing to the bulk behavior; 2) For supported film the substrate-film interaction is critical and its effect may surpass the geometry effects and rise increase on Tg; 3) Chain mobility and molecular weight are critical but the detailed phenomena vary with systems. Notwithstanding the achievement has been made, due to the controversy of glass transition itself and technology limitation on characterization on glass transitions on thin film, the research in this field is still a long-marching effort and breakthrough findings are expected for the development in materials science and engineering and feedback knowledge to understand the glass transition on the theoretical base.
Abstract: This paper gives an introduction to the synthetic methods of gold nanoparticles, such as reduction method, template method and seed growth method. The reduction technique includes green reduction, template reduction and organic small molecules method. In addition, the applications of gold nanoparticles in nanoprobes, drug delivery systems, photonic crystals, etc. are discussed, and an outlook for the gold nanoparticles is also made.
Abstract: The YAG:Ce3+, Gd3+/La3+ yellow phosphors were prepared by co-precipitation method with 0.1mol/L ammonium bicarbonate and aqueous ammonia as precipitants, and the crystal structure, morphology, luminescent properties were investigated. The results indicated that the emission peaks of the YAG:Ce3+, Gd3+/La3+ were redshifted from 535nm to 545.5nm /547nm, and the relative emission intensity declined from 330nm to 145/132 with doping content of Gd3+ /La3+ increased from 0 to 0.9mol at room temperature. Compared with Gd-doping phosphors, the redshift of La3+-doping phosphor was larger and the relative emission intensity declined more quickly. Compared with YAG:Ce3+, the thermal quenching characteristics of YAG:Ce,Gd and YAG:Ce,La were noticeably worse when the temperature increased, but the extents of peak wavelength redshifts were almost the same, about is 7-8nm in the experimental temperature range (50-200°C), have little relation with the doping concentration change. Doping concentrations of Gd or La couldn't be too high, and the suitable concentration was less than 0.6mol at the regulating color temperature and color index.
Abstract: Multifunctional Ag2S-Ag heterogeneous porous nanorods were synthesised by the irradiation of microwave in 210s .The nanorods were characterized by scanning electron microscopic (SEM) and X-ray diffraction (XRD). The photocatalytic activity for degradation of crystal violet and the lowest detectable limit of crystal violet are tested. Results show that the degradation rate of crystal violet can reach almost 100% within 50 min, the detection limit of crystal violet as low as 1×10-6 M. They indicate that the Ag2S-Ag heterogeneous porous nanorods would be a promising material for environmental protection.
Abstract: In order to study how the heavy metal pollution disseminates in urban surface soil and to recognize its evolutive pattern, this paper provides a model with time variable based on Euler method which could avoid the shortcoming of the traditional constant time assumption. We establish a set of spatial-temporal equations and derive their analytical solutions by 3-order Fourier transform.
Abstract: To ensure the normal operation of the electronic components, packaging technology is widely used in the production process of semiconductors, such as stand-alone device, LSI, super LSI, etc. This approach makes a lot of wasted components stay intact and reused. This paper uses laser cutting technology to remove material from PCB resin potting material, establishes the mathematical model of electronic potting materials, designs precision CNC laser cutting equipment for removing potting material under different circumstance. Using precision laser cutting technique, the resin potting material of waste PCB circuit can be removed, so as to expose entirely electronic components and all the solder joints. The technology has high economic benefit by ensuring electronic component function intact for reuse and improving the utilization rate of resource.