New nanoassemblies were instantaneously prepared by mixing two aqueous solutions, one containing a beta-cyclodextrin polymer (pbetaCD), and the other a hydrophobically modified by alkyl chains dextran (MD). The formation mechanism and the inner structure of these nanoassemblies were analysed using surface tension measurements and (1)H NMR spectroscopy. The effect of a hydrophobic guest molecule, such as benzophenone (BZ), on the formation and stability of the nanoassemblies was also evaluated. MD exhibited the typical behaviour of a soluble amphiphilic molecule and adsorbed at the air/water interface. Whereas the injection of native beta-CDs in the solution beneath the adsorbed MD monolayer did not produce any change in the surface tension, that of the pbetaCD resulted in an increase in the surface tension, indicating the desorption of the polymer from the interface. This result accounts for a cooperative effect of beta-CDs linked together in the pbetaCD polymer on dextran desorption. The presence of benzophenone in the system hindered the sequestration of dextran alkyl moieties by beta-CD in the polymer without impeding the formation of associative nanoassemblies of 100-200 nm. (1)H NMR investigations demonstrated that, in the BZ-loaded nanoassemblies, the hydrophobic molecule was mainly located into the cyclodextrin cavities. 相似文献
Nanoassemblies (NAs) with sizes ranging from 60 to 160nm were spontaneously formed in water after mixing a host polymer (polymerized cyclodextrin (pβ-CD)) and a guest polymer (dextran grafted with lauroyl side chains (MD)). The combination of microscopy, dynamic light scattering (DLS), nuclear magnetic resonance ((1)H NMR), isothermal titration calorimetry (ITC) and molecular modelling was used to investigate the parameters which govern the association between MD and pβ-CD. Remarkably, when pβ-CD was progressively added to a solution of MD, NAs with a well-defined diameter were spontaneously formed and their diameter was constant whatever the composition of the system. According to NMR data, almost all the alkyl chains of MD were included into CDs' cavities of the polymer when the molar ratio lauroyl chain (C(12))/CD was ?1. The hydrophobic interaction between C(12) and the hydrophobic cavities of CDs appears as the main driving force for NAs' formation, with a minor contribution arising from van der Waals' interactions. The inclusion of C(12) into β-CD cavities is almost a completely enthalpy-driven process, whereas the MD-C(12)/pβ-CD interaction was found to be an entropy-driven process. Major conclusions which can be drawn from these studies are that the interactions between the two polymers are restricted neither by the MD substitution yield, nor by the micellization of MD. The simultaneous effects of several CD linked together in pβ-CD and of many alkyl chains grafted on dextran were necessary to generate these stable NAs. 相似文献
The preparation of nonspherical materials composed of separated multicomponents by droplet‐based microfluidics remains a challenge. Based on polymerization‐induced phase separation and droplet coalescence in microfluidics, we prepared emulsions of variously shaped PAM/PEG core/shell droplets and hydrogels composed of two separated components, which show flexible and transformable hierarchical structures and microarchitectures. We find that AM/PEG aqueous droplets form a core/shell structure after polymerization resulting from phase separation. Thus multicore/shell droplets are easily produced by coalescence of core/shell structures. By changing the polymerization temperature and the flow rate, the morphology of the multicore droplets and the hydrogel can be easily adjusted. The hydrogels exhibit apparent anisotropy and different protein release rates depending on their structures. The preparation technique is simple and versatile and the resulting hydrogels have potential applications in many fields. 相似文献
Particles constructed by chiral polymers (defined as PCPs) have emerged as a rapidly expanding research field in recent years because of their potentially wide‐ranging applications in asymmetric catalysis, enantioselective crystallization, enantioselective release, amongst many others. The particles show considerable optical activity, due to the chirality of the corresponding polymers from which the particles are derived. This review article presents an overview on PCPs with emphasis on our group's recent achievements in the preparation of PCPs derived from optically active helical polymers and their applications. PCPs can be prepared via emulsion polymerization, precipitation polymerization, and suspension polymerization by starting from monomers. Emulsification of preformed chiral polymers and self‐assembly approaches also can lead to PCPs. Chiral polymer‐based core/shell particles, hollow particles, and magnetic particles are also covered because of their remarkable properties and significant potential applications.
Free‐base and nickel porphyrin–diaminopurine conjugates were formed by hydrogen‐bond directed assembly on single‐stranded oligothymidine templates of different lengths into helical multiporphyrin nanoassemblies with highly modular structural and chiroptical properties. Large red‐shifts of the Soret band in the UV/Vis spectroscopy confirmed strong electronic coupling among assembled porphyrin–diaminopurine units. Slow annealing rates yielded preferentially right‐handed nanostructures, whereas fast annealing yielded left‐handed nanostructures. Time‐dependent DFT simulations of UV/Vis and CD spectra for model porphyrin clusters templated on the canonical B‐DNA and its enantiomeric form, were employed to confirm the origin of observed chiroptical properties and to assign the helicity of porphyrin nanoassemblies. Molar CD and CD anisotropy g factors of dialyzed templated porphyrin nanoassemblies showed very high chiroptical anisotropy. The DNA‐templated porphyrin nanoassemblies displayed high thermal and pH stability. The structure and handedness of all assemblies was preserved at temperatures up to +85 °C and pH between 3 and 12. High‐resolution transition electron microscopy confirmed formation of DNA‐templated nickel(II) porphyrin nanoassemblies and their self‐assembly into helical fibrils with micrometer lengths. 相似文献
The aim of this paper was to study the associations between a neutral β-cyclodextrin polymer and amphiphilic dextrans substituted with two kinds of groups able to make inclusion complexes with β-cyclodextrin. The first kind of substituent is purely hydrophobic (dodecyl C12 or adamantyl Ada groups) and the second one, cyclohexancarboxylic acid group CHX, brings pH-dependent charge density on the dextran chains. Synthesis and characterization of the di-substituted dextrans have been detailed in a first part where it has been shown that the incorporation of CHX groups (up to 7 mol.%) did not modify the self assembling properties of the amphiphilic dextrans. Affinity of the amphiphilic dextrans for β-cyclodextrin polymer has been studied by different methods including isothermal titration calorimetry, dynamic light scattering and zeta potential. An original pH sensitive behaviour has been obtained for polymer–polymer associations at low concentrations. Nanoassemblies are formed at pH around 4 which are destabilized at lower pH and swollen into soluble aggregates at higher pH. The nanoassemblies formed at pH 4 have also been evidenced by transmission electron microscopy and have revealed a spherical shape of few hundred nanometers. 相似文献
Thermoresponsive polymers change their physical properties as the temperature is changed and have found extensive use in a number of fields, especially in tissue engineering and in the development of drug delivery systems. The synthesis of a novel core–shell nanogel composed of N‐isopropylacrylamide and sulfobetaine by reversible addition fragmentation chain transfer polymerization is reported. The core–shell architecture of the nanogels is confirmed using energy dispersive X‐ray spectroscopy in scanning transmission electron microscopy. These nanogels exhibit dual thermoresponsive behavior, i.e., the core of the nanogel exhibits lower critical solution temperature, while the shell displays upper critical solution temperature behavior. Transition temperatures can be easily tuned by changing the molecular weight of the constituent polymer. These nanogels can be efficiently used in temperature‐triggered delivery of therapeutic proteins and drugs. 相似文献
An acrylic polymer with pendent adamantyl groups was synthesized and its properties in an aqueous solution with a β-cyclodextrin (βCD) epichlorhydrin polymer examined. Viscosity properties of precursor and modified polymers show differences at low concentrations, but not at higher concentration probably due to very important hydrogen bonds which prevent the formation of intermolecular hydrophobic bonds. The association of both complementary polymers through the inclusion of adamantyl groups is evidenced by phases separation occurrence. Phase diagrams were established at two different concentrations of polymers. We have shown a maximal association of both polymers at these two concentrations, for the same ratio βCD moles/adamantyl groups: 2.4. Salt addition favors this association and displaces the two phases zone to smaller concentrations of modified polymer. Further, 4-nitrophenol can be extracted by the concentrated phase resulting from mixture of solutions of guest and host polymers, pointing out the availability of the associated phase to trap organic molecules. 相似文献
We present a facile strategy to prepare the molecularly imprinted polymers layer on the surface of Fe3O4 nanoparticles with core‐shell structure via sol–gel condensation for recognition and enrichment of triclosan. The Fe3O4 nanoparticles were first synthesized by a solvothermal method. Then, template triclosan was self‐assembled with the functional monomer 3‐aminopropyltriethoxysilane on the silica‐coated Fe3O4 nanoparticles in the presence of ethanol and water. Finally, the molecularly imprinted polymers were formed on the surface of silica‐coated Fe3O4 nanoparticles to obtain the product. The morphology, magnetic susceptibility, adsorption, and recognition property of magnetic molecularly imprinted polymers were characterized using transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffractometry, vibrating sample magnetometry, and re‐binding experiments. The magnetic molecularly imprinted polymers showed binding sites with good accessibility, fast adsorption rate, and high adsorption capacity (218.34 μg/g) to triclosan. The selectivity of magnetic molecularly imprinted polymers was evaluated by the rebinding capability of triclosan and two other structural analogues (phenol and p‐chlorophenol) in a mixed solution and good selectivity with an imprinting factor of 2.46 was obtained. The application of triclosan removal in environmental samples was demonstrated. 相似文献