Polymer particles with submicrometer dimensions show promising applications in “bottom-to-top approach” to fabrication of materials with periodic structure, function, and composition. A novel approach to producing such materials is proposed, which employs core-shell particles with specific structures and compositions. We report on the synthesis of core-shell particles using interfacial polymerization and heterocoagulation techniques. The compositions of core-forming material and/or the shell-forming polymers were selectively controlled to be make the cores or the shells rigid or fluid, fluorescent or non-fluorescent, organic or inorganic. Several potential applications of nanocomposite materials obtained from these particles are demonstrated, including three-dimensional optical data storage and optical limiting and switching. 相似文献
A novel UV-curable hyperbranched polyurethane acrylate (HUA) was synthesized and found to polymerize rapidly in the presence of 5 wt.% benzophenone in N2 under UV exposure. The photopolymerization kinetics of HUA was studied by differential photocalorimetry (DPC). Its toughening effect for polypropylene (PP) was investigated by tensile and impact tests of the UV irradiated PP/HUA blends. The morphological structures and thermal behavior were determined by polarized optical microscopy, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The obtained results demonstrate that (1) the maximum photopolymerization rate increases with raising temperature up to 140 °C, whereas decreases at above 150 °C. The activation energy of 19 kJ mol−1 for the photopolymerization was obtained at below 140 °C from the Arrhenius plot, while it is negative at above 150 °C. (2) The incorporation of 5 wt.% HUA greatly improved the notched impact strength of PP matrix with a slight improvement in the tensile strength and without obvious decline in breaking elongation. These results correlate well with SEM observation. (3) During the UV irradiation of PP/HUA blends, PP can be crosslinked/grafted with the cured HUA particles, resulting in the increase of the impact strength of PP matrix. (4) The cured HUA particles in the PP/HUA blends act as heterogeneous nucleation agent for PP, which results in the decrease of spherulite size and less perfection of PP crystals. 相似文献
Polyorganophosphazenes substituted by glycino ethyl ester and allylamine with different ratios were synthesized and their structures were characterized by 1H NMR, 31P NMR and FTIR. Via the crosslink reaction, a novel biodegradable crosslinked polyorganophosphazene material was obtained. DSC and FTIR spectra indicated the occurrence of crosslink. Hydrolysis studies were also performed to compare the crosslinked polymers with linear ones. The co-substituted polyorganophosphazenes with more allylamine at pendant groups exhibited a lower degradation rate than poly[bis(glycino ethyl ester)phosphazene] and crosslinked polyphosphazenes had an even lower degradation rate. SEM photographs characterized the surface of polyphosphazenes films after hydrolytic degradation, confirming that uncrosslinked ones had outstanding hydrolytic evidences at the surface while the crosslinked ones only had sporadic small erosion holes, remaining much smoother. 相似文献
A series of novel organic-inorganic hybrid proton-conducting electrolyte membranes with silane-crosslinked sulfonated poly(aryl ether ketone)(SC-SPAEK) networks was prepared via a simple procedure that includes solution casting and acid treatment. The organosilicon pendants of the silane-grafted SPAEK, which were expected to serve as coupling and crosslinking agents, were found to play a key role in the homogenous dispersion of inorganic particles and improved the performance of hybrid membranes. The hybrid membranes exhibited enhanced proton conductivity, and SC-SPAEK/TiO2-4 showed an extremely high proton conductivity of 0.1472 S/cm at 100℃. The crosslinked hybrid membranes also demonstrated good chemical resistance, oxidative stability, and mechanical properties. The crosslinked hybrid membranes with excellent comprehensive performance may be a promising material for proton exchange membrane fuel cells. 相似文献
In this communication, gold nanoparticles with a tadpole shape were synthesized by a simple aqueous-phase chemical method. The unusual three-dimensional and crystallized structures were demonstrated by TEM, AFM, and HRTEM methods. The SEM and UV-visible absorption measurements and electrophoresis experiments revealed that the tadpoles had novel optical and electrical properties. These attractive structures and properties are expected to find uses in many fields such as electrics, optics, electrochemistry, and biological sensing. 相似文献
A novel approach of measuring the surface roughness of spherical and flat micron-sized drug particles using scanning white-light interferometry was applied to investigate the surface morphology of micron-sized active pharmaceutical ingredients (APIs) and excipient particles used for inhalation aerosols. Bovine serum albumin (BSA) and alpha-lactose monohydrate particles were chosen as model API and excipient particles, respectively. Both BSA and lactose particles were prepared with different degrees of surface corrugation using either controlled spray drying (four samples of BSA) or decantation (two samples of lactose). Particle size distributions were characterized by laser diffraction, and particles were imaged by scanning electron microscopy (SEM). Surface roughness of the BSA and lactose particles was quantified by white-light optical profilometry using vertical scanning interferometry (VSI) at full resolution using a 50x objective lens with 2.0x and 0.5x fields of view for BSA and lactose, respectively. Data were analyzed using Vision software (version 32, WYKO), and surface roughness values are expressed as root-mean-square roughness ( Rrms). Furthermore, data were compared to topographical measurements made using conventional atomic force microscopy. Analysis of the optical profilometry data showed significant variation in BSA roughness ranging from 18.58 +/- 3.80 nm to 110.90 +/- 13.16 nm for the smoothest and roughest BSA particles, respectively, and from 81.20 +/- 15.90 nm to 229.20 +/- 68.20 nm for decanted and normal lactose, respectively. The Rrms values were in good agreement with the AFM-derived values. The particle morphology was similar to SEM and AFM images. In conclusion, scanning white-light interferometry provides a useful complementary tool for rapid evaluation of surface morphology and roughness in particles used for dry powder inhalation formulation. 相似文献
Suspension polymerization has been extensively utilized with vinyl monomers to prepare vinyl‐polymer microparticles (μm size; denoted MPs) with a variety of morphologies and significant applications. However, suspension polymerization of acetylenic monomers has remained a big challenge. This communication reports the first methodology for performing suspension polymerizations of acetylenic monomers, from which optically active microparticles (OAMPs) are constructed exclusively from helical substituted polyacetylenes. Chiral monomer (M1) and achiral monomer (M2) separately underwent suspension polymerization at room temperature in aqueous media in the presence of Rh‐based catalyst with poly(vinyl alcohol) as a stabilizer, providing MPs (200∼700 mm) in high yield (>80%). The obtained OAMPs, both crosslinked and non‐crosslinked, were characterized by SEM, polarimetry, circular dichroism, and UV‐vis spectroscopy. The chiral substituted polyacetylene chains constituting the MPs were found to adopt helices of predominantly one‐handed screw sense, affording the particles with pronounced optical activity. The MPs derived from achiral M2 exhibited optical inactivity. The present study opens up new opportunities for preparing novel (non‐)crosslinked microparticles derived from acetylenic monomers.
The effect of crosslinked poly(methacrylic acid) (c-PMAA) on the polymerization of N-vinylimidazole in aqueous solution was studied using UV, calorimetry, SEM, and TEM. It was established that synthetic lightly crosslinked PMAA samples behaved intermediate between rigid crosslinked PMAA particles functioning as microreactors, and linear conventional PMAA, where template and conventional polymerization in the surrounding solution are integrated. A modified calorimetric technique was used to measure monomer conversion, and to correct for the rapid adsorption process. Rate enhancements up to a factor of 4 were obtained for the c-PMAA's, which were lower than those obtained for linear conventional PMAA, and which slightly decreased with increasing crosslink density of the samples. Template complexes possessed a platelet-like morphology similar to template complexes obtained for linear PMAA. 相似文献
This study describes an environmentally friendly and green synthetic approach for the preparation of poly(aminoethylmethacrylate)-based hydrogels crosslinked through Diels–Alder (DA) reaction in water. This “click” reaction offers the possibility of preparing chemically crosslinked hydrogels in the absence of any catalyst, initiator or coupling agent, thus preserving the biocompatibility of the material. The suitable furan diene was obtained by modifying a methacrylate polymer by its reaction with furfural, a first generation compound derived from renewable resources. Methacrylate-based complementary polymeric dienophiles were also prepared by introducing maleimide groups into the structure. The products obtained at different steps were characterized by FTIR, NMR and TGA techniques. The study of the rheological properties of the hydrogels proved the success of this green “click” synthetic strategy confirming the formation of chemically crosslinked networks by the use of the Diels–Alder reaction. Furthermore, SEM studies revealed promising morphological properties of the ensuing hydrogels in terms of biomedical applications. 相似文献
A series of novel monomethylated salts derived from linear benzobisthiazole was prepared. The push-pull attributes of these new compounds are represented by a quaternised azolium cycle as the acceptor part at one end of the structure and the dialkylamino- or diarylamino-substituted benzene ring as the donor part at the opposite end. Both moieties are connected by a conjugated linker consisting of one or two double bonds. Such dipolar structures are promising candidates for non-linear optical materials. The quantum-chemical indices describing linear and non-linear optical properties were obtained from semi-empirical calculations. The relationships between the chemical structure and non-linear optical properties of the cations studied were obtained. Effective conjugation was confirmed by measuring the optical properties in the UV-VIS region. 相似文献
Colloidal ZnO particles with narrow size distribution were prepared via a sol-gel process by base-catalyzed hydrolysis of zinc acetate. The morphology of ordered arrays of the particles was recorded by SEM. SEM also reveals that these uniform particles were composed of tiny ZnO subunits (singlets) sized of several nanometers. The size of the singlets, which is confirmed by X-ray diffraction and UV-vis absorption spectra, increases as the aging time is prolonged. The size-selective formation of colloids by aggregation of nanosized subunits is proposed to consist of two-stage growth by nucleation of nanosized crystalline primary particles and their subsequent aggregation into polycrystalline secondary colloids. The aggregates are all spherical because the internal rearrangement processes are fast enough. The ZnO colloids, i.e., the aggregates, tend to self-assemble into well-ordered hexagonal close-packed structures. Room-temperature photoluminescence was characterized for green and aged ZnO. 相似文献