Concepts,processing, and recent developments in encapsulating essential oils

By the virtue of their olfactory, physicochemical, and biological characteristics, essential oils (EOs) have drawn wide attention as additives in daily chemicals like perfume or personal care products. Nevertheless, they are physicochemically unstable and susceptible to degradation or loss. Microencapsulation offers a feasible strategy to stabilize and prolong release of EO. This review summarizes the recognized benefits and functional properties of various preparation and characterization methods, wherein innovative fabrication strategies and their formation mechanisms are especially emphasized. Progress in combining detecting/measuring technologies with kinetic modelling are discussed, to give an integral approach of controlling the dynamic release of encapsulated EOs. Moreover, new development trends of EOs capsules are also highlighted.     

Effect of SiO2 on rheology,morphology, thermal,and mechanical properties of high thermal stable epoxy foam

A series of highly thermostable epoxy foams with diglycidyl ether of bisphenol‐A and bisphenol‐S epoxy resin (DGEBA/DGEBS), 4,4′‐diaminodiphenyl sulfone (DDS) as curing agent have been successfully prepared through a two‐step process. Dynamic and steady shear rheological measurements of the DGEBA/DGEBS/DDS reacting mixture are performed. The results indicate all samples present an extremely rapid increase in viscosities after a critical time. The gel time measured by the crossover of tan δ is independent of frequency. The influence of SiO₂ content on morphology, thermal, and mechanical properties of epoxy foams has also been investigated. Due to the heterogeneous nucleation of SiO₂, the pore morphology with a bimodal size distribution is observed when the content of SiO₂ is above 5 wt %. Dynamic mechanical analysis (DMA) reveals that pure epoxy foam possesses a high glass transition temperature (206°C). The maximum of specific compressive strength can be up to 0.0253 MPa m³ kg^?1 at around 1.0 wt % SiO₂. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40068.     

Effect of graft copolymer matrix prepared by reversible addition–fragmentation chain transfer and atom transfer radical polymerization on the electro‐optical properties of polymer‐dispersed liquid crystals

A type of graft macroinitiator, synthesized by reversible addition–fragmentation chain transfer (RAFT) and atom transfer radical polymerization, was employed to prepare polymer‐dispersed liquid crystals (PDLCs) with graft copolymer matrix; meanwhile, a linear macroinitiator was also synthesized via RAFT polymerization. The effect of linear and graft macroinitiators on the electro‐optical (EO) properties of the PDLCs was investigated. The results showed that the graft macroinitiator could make a large difference to the EO properties of the PDLCs. The memory effect was reduced remarkably, but the driving voltage increased and transmittance decreased. A possible mechanism is presented. © 2014 Society of Chemical Industry     

The effect of photoinitiator concentration and structures of RAFT macroinitiators on the memory effect of polymer dispersed liquid crystals

The article aimed to decrease the memory effect of polymer dispersed liquid crystals (PDLCs) films, reversible additional‐fragmental chain transfer (RAFT) polymerization was used to synthesize RAFT‐polystyrene (RAFT‐PS), which was a kind of RAFT macroinitiators and used to prepare PDLCs via photo polymerization induced phase separation (PIPS). Different RAFT agents were used to synthesize RAFT‐PS. The effect of photoinitiator concentration on the memory effect of these PDLCs was investigated, and the effect of structures of RAFT macroinitiators on the memory effect of the PDLCs was also discussed. The results showed that PDLC films with higher photoinitiator concentration and polymer matrix which had two rigid chains in two ends showed lower memory effect, which could be reduced from 10.9% to 2.5% in this experiment. POLYM. ENG. SCI., 55:8–13, 2015. © 2014 Society of Plastics Engineers     

The improvement of electro‐optical properties of polymer‐dispersed liquid crystals with graft copolymer matrix synthesized by reversible addition–fragmentation chain transfer and atom transfer radical polymerization

Aiming to decrease the memory effect of polymer‐dispersed liquid crystals (PDLCs), a type of graft macroinitiator, synthesized by reversible addition–fragmentation chain transfer and atom transfer radical polymerization, was employed to prepare PDLCs with graft copolymer matrix in our previous work. Compared with linear copolymer matrix PDLCs prepared using a linear macroinitiator, it was found that, although low‐memory‐effect PDLCs were obtained, the driving voltage and transmittance of the PDLCs were unfortunately sacrificed to some extent. Thus, it is necessary to improve the electro‐optical properties of PDLCs on the basis of the original research performed by us. In the work reported in this article, a kind of linear macroinitiator with high refractive index and another graft macroinitiator with flexible branched chains were employed to prepare PDLCs. The results showed that by using mixed macroinitiators, the electro‐optical properties of PDLCs could be improved, and a possible mechanism is proposed.     

Micelle‐Enhanced Bioorthogonal Labeling of Genetically Encoded Azido Groups on the Lipid‐Embedded Surface of a GPCR

Genetically encoded p‐azido‐phenylalanine (azF) residues in G protein‐coupled receptors (GPCRs) can be targeted with dibenzocyclooctyne‐modified (DIBO‐modified) fluorescent probes by means of strain‐promoted [3+2] azide–alkyne cycloaddition (SpAAC). Here we show that azF residues situated on the transmembrane surfaces of detergent‐solubilized receptors exhibit up to 1000‐fold rate enhancement relative to azF residues on water‐exposed surfaces. We show that the amphipathic moment of the labeling reagent, consisting of hydrophobic DIBO coupled to hydrophilic Alexa dye, results in strong partitioning of the DIBO group into the hydrocarbon core of the detergent micelle and consequently high local reactant concentrations. The observed rate constant for the micelleenhanced SpAAC is comparable with those of the fastest bioorthogonal labeling reactions known. Targeting hydrophobic regions of membrane proteins by use of micelle‐enhanced SpAAC should expand the utility of bioorthogonal labeling strategies.     

3D Hierarchical Bi<Subscript>2</Subscript>S<Subscript>3</Subscript> Nanostructures by Polyvinylpyrrolidone (PVP) and Chloride Ion-Assisted Synthesis and Their Photodetecting Properties

A solvothermal method has been employed to synthesize bismuth sulfide (Bi₂S₃) with three-dimensional (3D) hierarchical architectures. The influences of different types of surfactants and Cl^? species on the size and morphology were investigated. A possible formation mechanism was also proposed on the basis of time-dependent experiments. The photoresponse properties show that the conductivity of Bi₂S₃ micro-flowers is significantly enhanced and the photocurrent is approximately two orders of magnitude larger than the dark current. The response and decay times are estimated to be 142 and 151 ms, respectively. It is expected that hierarchical architectures Bi₂S₃ may provide a new pathway to develop advanced nanomaterial for high-speed and high-sensitivity photoelectrical switches and photodetecting devices.     

La/Al-SBA-15催化剂的制备及催化合成棕榈酸甲酯

以Al-SBA-15为载体,浸渍法制备La/Al-SBA-15改性介孔分子筛催化剂。通过红外光谱分析、X射线多晶衍射、N2吸附-脱附、扫描电子显微镜和透射电子显微镜等分析方法对催化剂进行表征。X射线多晶衍射表明,La/Al-SBA-15催化剂具有典型的一维六方介孔结构;红外光谱中显示出La—O键590 cm-1特征峰,表明La元素通过键合进入分子筛;N2吸附-脱附分析表明,La/Al-SBA-15催化剂的孔道分布均匀,平均孔径为2.15 nm。以La/Al-SBA-15催化剂合成棕榈酸甲酯,在n(棕榈酸)∶n(甲醇)=1∶20、催化剂用量为0.250 g(即为棕榈酸质量的5%)和反应时间330 min条件下,棕榈酸甲酯酯化率达79.48%。