The aim of the present work was to develop the crosslinked polymeric nanocapsules for drug delivery from the SiO2 nano-templates via surface-initiated atom transfer radical polymerization (SI-ATRP) technique. The crosslinked polymeric nanocapsules were fabricated via the SI-ATRP of 2-hydroxyethyl acrylate (HEA) from initiator modified silica nano-templates. After the hydroxyl side-groups of the polymer grafted silica nanoparticles (SN@PHEA) were crosslinked with hexamethylene diisocyanate (HDI), the silica templates encapsulated in the crosslinked polymer shells were removed by being etched with HF to produce the crosslinked polymeric nanocapsules. The diameter of the polymeric nanocapsules is in the range of 20–40 nm, characterized by transmission electron microscopy (TEM). 相似文献
A new nanoencapsulation was established in which small nanocapsules with a natural polymeric wall could be fabricated, capsulizing the capsaicin having pungent odor. The new nanoencapsulation is based on a simple coacervation process. In this technique, gelatin was used as the wall material of the nanocapsules, and an insoluble polymer film was formed after cross‐linking reaction. The shell formation mechanism and the effects of the process conditions such as shearing force, the gelatin viscosity, cross‐linking time, and so on, on the particle size of the nanocapsulated capsaicin (NC) agents were discussed. Meanwhile, the morphology and size distribution of the nanocapsules prepared by the most suitable conditions, were analyzed by Fourier transform infrared (FTIR) spectroscopy, laser particle size analyzer, transmission electron microscopy (TEM), and atomic force microscopy (AFM). The NC agents had a mean particle size of about 100 nm. Moreover, the thermal properties of the NC agents were measured by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was demonstrated that the melting point and thermal pyrolysis temperature of the NC agents were improved from 75 to 100°C, 230 to 240°C, 310 to 320°C, and from 450 to 540°C compared with that of the uncovered capsaicin, which were caused by the encapsulation of the cross‐linked gelatin over the surface of the capsaicin. 相似文献
ABA block copolymers of polylactide and poly(ethylene glycol) as amphiphilic bioabsorbable polymers were synthesized by the ring-opening
polymerization of dl- lactide onto poly(ethylene glycol) (PEG 2000 or PEG 6000) and their structures were characterized on the basis of proton
NMR. Biodegradable nanocapsules of an aqueous insulin solution were prepared from the block copolymers and polylactide by
an improved interfacial coacervation technique. The results showed that the diameters of the nanocapsules were mainly dependent
on the ratio of the two chains in the block polymers. The size of the nanocapsules decreased with an increase in the amount
of surfactant used. More insulin solution resulted in an enlargement of the nanocapsules in diameter. In an optimum condition,
biodegradable nanocapsules could be achieved with a size around 250 nm with a narrow distribution. The encapsulation percentages
of insulin were larger in the nanocapsules from the PEG 2000 copolymers than in those from the PEG 6000 analogs and changed
with the ratios of the blocks in the block copolymers.
Received: 17 July 2000 Accepted: 24 November 2000 相似文献
Nimodipine loaded hydroxypropyl-β-cyclodextrin polymeric nanocapsules were prepared by interfacial polyaddition of hydroxypropyl-β-cyclodextrin and isophorone diisocyante in a miniemulsion system. The effects of ultrasonicate times on the preparation of miniemulsion, the total amount of hydroxypropyl-β-cyclodextrin and isophorone diisocyante, and the molar ratio of isophorone diisocyante to hydroxypropyl-β-cyclodextrin on the capsule size and drug release behavior from capsule were investigated. The chitosan based polymeric nanocapsules were prepared as a control to study the effect of hydroxypropyl-β-cyclodextrin molecules in capsule matrix on the drug release. The results indicated that the droplet size of miniemulsion and capsule size decreased with increasing sonicate times. When the total amount of hydroxypropyl-β-cyclodextrin and isophorone diisocyante, and the molar ratio of isophorone diisocyante to hydroxypropyl-β-cyclodextrin were increased, the capsule as well, but the drug release rates from capsules became slower. The drug release behaviors from hydroxypropyl-β-cyclodextrin polymeric nanocapsules were affected by the drug diffusion through the polymer matrix and the formation of inclusion complex between drug and hydroxypropyl-β-cyclodextrin. 相似文献
The fabrication of polymer nanocapsules with tailored dimensions has been accomplished by microemulsion polymerization using different surfactants. 相似文献
A model which successfully predicts many of the qualitative features of the phase separation can be based upon the assumption that the microemulsion particle retains its integrity when diluted with external phase or when mixed with a polymer (which does not complex with the surfactants). In this case, the microemulsion particle behaves thermodynamically in a manner similar to a macromolecule so that one can predict that the polymer—microemulsion phase diagram will have qualitative similarities to that exhibited by the polymer—polymer2-solvent case. Most of the experiments were conducted by following the phase boundaries by measurements of the cloud points of the polymermicroemulsion mixtures. The cloud points of the mixtures were found to be (usually) linear functions of the weight fraction of the added polymer and decreased with increasing molecular weight. Plots of the logarithm of the slopes of these curves against the logarithm of the polymer molecular weight were linear, with a slope designated as β. The values for β for twenty-five systems studied fell within the narrow range of 0.55 ± 0.15. These values were seen to be the same as the Mark—Houwink exponents in the relationship between the intrinsic viscosity and the polymer molecular weight. The reason for this correspondence appears to be that the coacervation occurs at a polymer concentration about equal to the threshold overlap concentration. Ternary phase diagrams with microemulsion particles, brine, and polymer selected as pseudocomponents also exhibit many of the features predicted by the model. The phase boundary asymmetry is in the direction expected and asymptotes with the expected independence upon microemulsion and polymer molecular weights are also demonstrated. In agreement with the model, it is shown that the controlling variable is polymer weight average, rather than z or number average molecular weight. 相似文献
Summary: Polyacrylonitrile (PAN) nanocapsules and nanotubes were selectively synthesized by microemulsion polymerisation using β‐cyclodextrin (β‐CD) as a nanoporogen. Iron(III ) chloride (FeCl3) was used as a structure‐directing agent to fabricate polymer nanotubes. In addition, the average pore size of the PAN nanocapsules and nanotubes could be controlled with the concentration of β‐CD.
(a) TEM image of PAN nanocapsules; (b) SEM image of PAN nanotubes. 相似文献
A new method for the fabrication of Fe(3)O(4) nanoparticles enveloped by polymeric nanocapsules is proposed. This method is characterized by combining a double emulsification with the interfacial coprecipitation of iron salts to form Fe(3)O(4)/polymer composite nanocapsules in a single step. To demonstrate the viability of this approach, methoxy poly(ethylene glycol)-poly(lactide) (MePLEG) was chosen as the shell material for Fe(3)O(4)/MePLEG nanocapsules. In addition to the versatility offered for fabricating nanocapsules with different shell materials, the method was found to be convenient for adjusting the magnetite content of the nanocapsules from 0 to 43%. In addition to their confirmed T(2)-weighted magnetic resonance imaging (MRI) enhancement, the resultant composite nanocapsules display much more obvious acoustic responses than MePLEG nanocapsules in an acoustic investigation. Furthermore, the low toxicity of these composite nanocapsules, as confirmed by our study, combined with their magnetic and acoustic properties ensure that these composite nanocapsules have great potential in acting as ultrasonic/MRI dual contrast agents. 相似文献
The solid photoinitiator Lucirin TPO was encapsulated within a polymer shell by using the miniemulsion process. A solution
of Lucirin TPO in methyl methacrylate (MMA) or butyl acrylate (BA)/MMA mixture was miniemulsified in water followed by a polymerization
process in which phase separation of the Lucirin TPO and the formed polymer led to amorphously solidified Lucirin TPO nanoparticles
encapsulated by polymer. These nanocapsules were freeze-dried and could be redispersed in acidic monomers, which are applied
in polymeric dental adhesives. It is shown by 1H nuclear magnetic resonance spectroscopy that the shell separates the Lucirin TPO, which is sensitive to degradation in acidic
media, from an ambient acidic monomer phase and protects it from fast decomposition. Investigations of the release kinetics
of Lucirin TPO from the nanocapsules reveal that the kinetics are strongly dependent on the composition of the surrounding
continuous phase. 相似文献