Low viscosity and low temperature curing reactive POSS/epoxy hybrid resin with enhanced toughness and comprehensive thermal performance.

The mechanical and high-temperature resistance properties of epoxy resins cured at low temperatures (Tcuring ≤ 100 °C) are often inferior, and the most toughening modification methods for epoxy resins tend to compromise thermal resistance, which significantly limit the practical applications of it. Therefore, this work reported a low viscosity and low-temperature curing epoxy hybrid resin system (OPEP), adopting E-51 as a resin matrix, liquid anhydride (MHHPA) as a curing agent, tertiary amine (DMBA) as a curing accelerator, and reactive octa-epoxy terminated polyhedral oligomeric silsesquioxane (OG-POSS) as a toughening modifier. Results demonstrated that the OPEP system has excellent processability with low viscosity and long processing window period and satisfies the practical requirements of low-temperature curing. The OG-POSS exhibits superior compatibility and reactivity with the resin matrix, and its addition slightly reduces the Eα of the curing reaction and has a certain promotive effect on the curing of epoxy resin. In addition, the curing reaction rate of the OPEP resin complies with the Sesták-Berggren autocatalytic kinetics model. The impact strength, flexural strength, tensile strength, and elongation at break of the OPEP resin reached a maximum of 15.55 kJ m-2, 121.65 MPa, 90.36 MPa, and 2.48%, representing increases of 55.97%, 3.1%, 64.68%, and 26.51% compared to those of the pure resin, respectively. Notably, due to the heat-resistant inorganic silicon cage structure of OG-POSS, the thermal decomposition temperature (Td5), glass transition temperature (Tg), and heat distortion temperature (THDT) of the OPEP0.02 resin were 313.2 °C, 123.7 °C, and 102.0 °C, showing increases of 13.0 °C, 2.3 °C, and 6.8 °C compared to the pure resin, respectively, which is difficult to achieve for the general thermosetting resin toughening modification method. This research utilized organic-inorganic nanohybrid materials (POSS) to optimize the toughness and thermal stability of the resin in a coordinated manner, providing guidance for the preparation of high-performance epoxy resins that cure at low temperatures.

Membership Function-Weighted Non-Linear Fitting Method for Optical-Sensing Modeling and Reconstruction.

Imprecise measurements present universally due to variability in the measurement error. We devised a very simple membership function to evaluate fuzzily the quality of optical sensing with a small dataset, where a normal distribution cannot be assumed. The proposed membership function was further used as a weighting function for non-linear curve fitting under expected mathematical model constraints, namely the membership function-weighted Levenberg⁻Marquardt (MFW-LM) algorithm. The robustness and effectiveness of the MFW-LM algorithm were demonstrated by an optical-sensing simulation and two practical applications. (1) In laser-absorption spectroscopy, molecular spectral line modeling was greatly improved by the method. The measurement uncertainty of temperature and pressure were reduced dramatically, by 53.3% and 43.5%, respectively, compared with the original method. (2) In imaging, a laser beam-profile reconstruction from heavy distorted observations was improved by the method. As the dynamic range of the infrared camera increased from 256 to 415, the detailed resolution of the laser-beam profiles increased by an amazing 360%, achieving high dynamic-range imaging to capture optical signal details. Therefore, the MFW-LM algorithm provides a robust and effective tool for fitting a proper physical model and precision parameters from low-quality data.

Measurement of Atmospheric Dimethyl Sulfide with a Distributed Feedback Interband Cascade Laser.

This paper presents a mid-infrared dimethyl sulfide (CH3SCH3, DMS) sensor based on tunable laser absorption spectroscopy with a distributed feedback interband cascade laser to measure DMS in the atmosphere. Different from previous work, in which only DMS was tested and under pure nitrogen conditions, we measured DMS mixed by common air to establish the actual atmospheric measurement environment. Moreover, we used tunable laser absorption spectroscopy with spectral fitting to enable multi-species (i.e., DMS, CH4, and H2O) measurement simultaneously. Meanwhile, we used empirical mode decomposition and greatly reduced the interference of optical fringes and noise. The sensor performances were evaluated with atmospheric mixture in laboratory conditions. The sensor's measurement uncertainties of DMS, CH4, and H2O were as low as 80 ppb, 20 ppb, and 0.01% with an integration time 1 s, respectively. The sensor possessed a very low detection limit of 9.6 ppb with an integration time of 164 s for DMS, corresponding to an absorbance of 7.4 × 10-6, which showed a good anti-interference ability and stable performance after optical interference removal. We demonstrated that the sensor can be used for DMS measurement, as well as multi-species atmospheric measurements of DMS, H2O, and CH4 simultaneously.

Fusiform micelles from nonlinear poly(ethylene glycol)/polylactide copolymers as biodegradable drug carriers.

PEG-PLA copolymers with dumbbell- and Y-shaped structures are prepared. They can self-assemble from nanoparticles to micro-sized fusiform micellar particles in aqueous solution. In particular the micelles formed by the (PLA)2-PEG-(PLA)2 particles show a better drug loading capacity and encapsulation efficiency than those formed by linear MPEG-PLA. In vitro studies show that the particles formed by Y-shaped copolymers show a particularly quick drug release. The copolymers have good biocompatibility with low cytotoxicity. These unique self-assembled systems thus have many possible biomedical applications, such as a sustained delivery of high-dosed water insoluble drugs, quick effective drugs for trauma, controlled delivery of the oral-administration drugs, and so forth.