Preparation and sustained release of diatomite incorporated and Eudragit L100 coated hydroxypropyl cellulose/chitosan aerogel microspheres.

The drug encapsulation efficiency, release rate and time, sustained release, and stimulus-response of carriers are very important for drug delivery. However, these always cannot obtained for the carrier with a single component. To improve the comprehensive performance of chitosan-based carriers for 5-Fu delivery, diatomite-incorporated hydroxypropyl cellulose/chitosan (DE/HPC/CS) composite aerogel microspheres were fabricated for the release of 5-fluorouracil (5-Fu), and the release performance was regulated with the content of diatomite, pH value, and external coating material. Firstly, the 5-Fu loaded DE/HPC/CS composite aerogel microspheres and Eudragit L100 coated microspheres were prepared with cross-linking followed by freeze-drying, and characterized by SEM, EDS, FTIR, XRD, DSC, TG, and swelling. The obtained aerogel microspheres have a diameter of about 0.5 mm, the weight percentage of F and Si elements on the surface are 0.55 % and 0.78 % respectively. The glass transition temperature increased from 179 °C to 181 °C and 185 °C with the incorporation of DE and coating of Eudragit, and the equilibrium swelling percentage of DE/HPC/CS (1.5:3:2) carriers are 101.52 %, 45.27 %, 67.32 % at pH 1.2, 5.0, 7.4, respectively. Then, the effect of DE content on the drug loading efficiency of DE/HPC/CS@5-Fu was investigated, with the increase of DE content, the highest encapsulation efficiency was 82.6 %. Finally, the release behavior of DE incorporated and Eudragit L100 Coated microspheres were investigated under different pH values, and evaluated with four kinetic models. The results revealed that the release rate of 5-Fu decreased with the increase of DE content, sustained release with extending time and pH-responsive were observed for the Eudragit-coated aerogel microspheres.

Adsorption and Recognition Property of Tyrosine Molecularly Imprinted Polymer Prepared via Electron Beam Irradiation.

To realize the selective separation of L-tyrosine (L-Tyr) and avoid the drawbacks of traditional thermal polymerization, electron beam irradiation polymerization was developed for the fabrication of L-Tyr molecularly imprinted polymers (MIPs). Firstly, L-Tyr MIPs were prepared with methacrylic acid and ethylene glycol dimethacrylate and without an initiator. Then, the influence of absorbed dosage and temperature on the adsorption capacity of L-Tyr, as well as the thermodynamic behavior, were investigated. The maximum adsorption capacity of 10.96 mg/g for MIPs was obtained with an irradiation dosage of 340 kGy under 15 °C, and the ΔH0 and ΔS0 of the adsorption process are -99.79 kJ/mol and -0.31 kJ/mol·K, respectively. In addition, the effect of adsorption time on adsorption performance was evaluated under different initial concentrations, and the kinetic behavior was fitted with four different models. Finally, the recognition property of the obtained MIPs was investigated with L-Tyr and two analogues. The obtained MIPs have an imprinting factor of 5.1 and relatively high selective coefficients of 3.9 and 3.5 against L-tryptophan and L-phenylalanine, respectively. This work not only provided an L-Tyr MIP with high adsorption capacity and selectivity but also provided an effective and clean method for the synthesis of MIPs.

Fabrication and Evaluation of Graphene Oxide/Hydroxypropyl Cellulose/Chitosan Hybrid Aerogel for 5-Fluorouracil Release.

The incorporation of graphene oxide (GO) into a polymeric drug carrier can not only enhance the loading efficiency but also reduce the initial burst and consequently improve the controllability of drug release. Firstly, 5-fluorouracil (5-Fu)-loaded hydroxypropyl cellulose/chitosan (HPC/CS@5-Fu) and GO/HPC/CS@5-Fu aerogels were successfully fabricated through chemical cross-linking with glutaraldehyde. Then, the obtained aerogels were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FITR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TG), and the effect of HPC and GO content on the drug loading (DL) and encapsulation efficiency (EE) for the two aerogels were investigated, respectively. Finally, the drug release behavior of the GO/HPC/CS@5-Fu aerogels with different GO content was evaluated at two different pH values, and four kinds of kinetic models were used to evaluate the release behavior.

Facile and Controllable Preparation of Poly(St-co-MMA)/FA Microspheres Used as Ultra-Lightweight Proppants.

Hydraulic fracturing is an important technology for the exploitation of unconventional oil or gas reservoirs. In order to increase the production of oil or gas, ultra-lightweight proppants with a high compressive strength are highly desirable in hydraulic fracture systems. In this work, a new type of ultra-lightweight proppant, poly(styrene-co-methyl methacrylate)/fly ash (poly(St-co-MMA)/FA) composites with a high compressive strength were prepared via in situ suspension polymerization. The Fourier transform infrared (IR) and X-ray powder diffraction (XRD) analyses confirmed that the poly(St-co-MMA)/FA composites were successfully prepared. The morphology analysis indicated that the composite microspheres show good sphericity, and FA powder was evenly dispersed in the matrix. The apparent density of the microspheres was between 1 and 1.3 g/cm3, which is suitable for hydraulic fracturing. Furthermore, the compressive strength and thermostability were dramatically improved with the incorporation of FA, which could withstand high pressures and temperatures underground. The obtained poly(St-co-MMA)/FA composite microspheres are promising for application as an ultra-lightweight (ULW) proppant in oil or gas exploitation, which provides a new approach for the design of high performance proppants.

Relationship between the Microstructure and Performance of Graphene/Polyethylene Composites Investigated by Positron Annihilation Lifetime Spectroscopy.

The quantitative characterization of microstructure is most desirable for the establishment of structure-property relationships in polymer nanocomposites. In this work, the effects of graphene on the microstructure, mechanical, electrical, and thermal properties of the obtained graphene/polyethylene (PE) composites were investigated. In order to reveal the structure-performance relationship of graphene/PE composites, especially for the effects of the relative free volume fraction (fr) and interfacial interaction intensity (ß), positron annihilation lifetime spectroscopy (PALS) was employed for its quantitative description. The relative free volume fraction fr gives a good explanation of the variation for surface resistivity, melting temperature, and thermal stability, and the variation of tensile strength and thermal conductivity agree well with the results of interfacial interaction intensity ß. The results showed that fr and ß have a significant effect on the properties of the obtained graphene/PE composites, and the effect on the properties was revealed.

Effect of π-π Stacking Interfacial Interaction on the Properties of Graphene/Poly(styrene-b-isoprene-b-styrene) Composites.

Interfacial interaction is one of the most important factors in the construction of high-performance graphene-based elastomer composites. In this paper, graphene/poly (styrene-b-isoprene-b-styrene) (SIS) composites were prepared with solution mixing followed by an evaporation-induced self-assembly process. Various techniques such as scanning electron microscopy, UV-vis absorption spectra, tensile testing, Shore A hardness, surface resistance, thermal conductivity, and thermogravimetric analysis were conducted to characterize the microstructure and properties of the obtained composites. The results showed that the π-π stacking interfacial interaction between phenyl groups of SIS and graphene play an important role in the properties' improvement, and the effect of interfacial interaction on the properties was revealed.