Summary: The interaction of a polymer bearing β‐cyclodextrin moieties (β‐CD polymer) with poly(acrylamide)s bearing aromatic side chains was investigated by viscometry to study the effect of collectivity (i.e., interactions at multi‐sites) in macromolecular recognition. The formation of inclusion complexes at multi‐sites caused a large difference in the size of interpolymer aggregates, even though the difference in association constants for complexation of native β‐CD with guest moieties was not very much large.
Conceptual illustration for interpolymer aggregates of β‐CD polymer with poly(acrylamide)s bearing naphthyl groups substituted on the (a) 1‐ and (b) 2‐positions (see Scheme 1 ). 相似文献
Two kinds of cyclodextrin/peptide (CD/peptide) hybrids bearing ZnII‐cyclen or cyclen, dansyl and β‐cyclodextrin (β‐CD) units have been synthesized as chemosensors for organic anionic molecules. ZnII‐cyclen serves as a ligand site and β‐CD is a receptor site for guest molecules, while the dansyl unit acts as a fluorescent probe. Examination of the fluorescence behaviors of these CD/peptides suggest that the hybrid containing Zn2+ has larger binding constants with respect to anionic molecules than that without Zn2+.
Macroscopic pH‐responsive self‐assembly is successfully constructed by polyacrylamide(pAAm)‐based gels carrying dansyl (Dns) and β‐cyclodextrin (βCD) residues, which are represented as Dns‐gel and βCD‐gel, respectively. Dns‐gel and βCD‐gel assemble together at pH ≥ 4.0, but disassemble at pH ≤ 3.0. The adhesion strengths for pairs of Dns‐gel/βCD‐gel increase with increasing pH. The fluorescence study on the model system of pAAm modified with 1 mol% Dns moieties (pAAm/Dns) reveals that Dns residues are protonated at a lower pH, which results in the reduction in binding constant (K) for Dns residues and βCD.
In the present paper, the microwave (MW)‐assisted synthesis of the alkaline N‐[3‐(dimethylamino)propyl]methacrylamide ( 4 ) and ‐acrylamide ( 5 ) monomers within minutes is described. The reaction was carried out by mixing and subsequent irradiation of 3‐dimethylamino‐1‐propylamine ( 3 ) and (meth)acrylic acid ( 1 / 2 ) without addition of solvent. After polymerization, the obtained homopolymers ( 6 / 7 ) exhibit lower critical solution temperature (LCST) behavior in water at 35 °C only at pH = 14. The LCST‐behavior can be influenced by N‐oxidation of the tertiary amino group with hydrogen peroxide or by formation of a polymer‐inclusion complex ( 6a ) of 6 and β‐cyclodextrin (β‐CD) by addition of randomly‐methylated β‐CD.
The single‐polymer form factor is determined for branched polymers using a scaling argument in order to recover the low‐Q Porod exponent characteristic of the overall structure. The high‐Q Porod exponent characterizes the local branching structure. An alternative approach based on a high‐Q expansion contains information about functionality, branch length and branch content. The specific case of a starburst dendrimer for which the form factor is known is discussed. The model predictions are compared to small‐angle neutron scattering data from a dilute solution of dendrimer in D2O.
Two novel monovinyl β‐cyclodextrin (β‐CD) monomers are synthesized. Their chemical compositions are characterized by means of element analysis, NMR and FT‐IR spectroscopy. The results show that the synthesis techniques used are convenient and efficient. Using N‐isopropylacrylamide as a comonomer, two novel linear copolymers can also be synthesized.
Self‐stabilized nanoparticles with a temperature‐responsive poly[(N,N‐diethylacrylamide)‐co‐(N,N′‐methylenebisacrylamide)] microgel core and a covalently attached hairy shell were synthesized via a simple nitroxide‐mediated controlled free‐radical aqueous dispersion polymerization, using a poly(sodium acrylate) alkoxyamine macroinitiator. With this method, high solid content, surfactant‐free particle suspensions were prepared, with diameter ranging from 49 to 118 nm at high temperature, and able to reversibly swell with water at low temperature. The proposed method requires a limited number of reagents in a simple polymerization procedure and thus avoids many drawbacks generally encountered in the synthesis of thermally responsive microgel particles.
Interaction of β‐cyclodextrin (β‐CD) with alternating copolymers (pAdMA and pAdPhMA) of sodium maleate with adamantyl (Ad) and with adamantylphenyl (AdPh) vinyl ether has been investigated by several NMR techniques. Comparing the apparent association constants (K) for the polymers with the K for the model compounds, which are determined by the analysis of 1H NMR and isothermal titration calorimetry data, respectively, the selectivities of β‐CD toward Ad and AdPh moieties are contrasting for the model and polymer systems. This phenomenon is described by circular dichroism and 2D NMR as follows; the most stable inclusion complex for the β‐CD/AdPh model system is extremely destabilized for the corresponding polymer system because of competition with hydrophobic interaction between neighboring AdPh moieties.
Methacrylate‐modified β‐cyclodextrin (β‐CD) and methyl methacrylate (MMA) have been radically copolymerized to obtain hydrophobic CD copolymers. The water‐insoluble copolymers are able to form highly stable inclusion complexes with anions of ionic liquids. Surprisingly, the inclusion of the anions in the CD cavity results in a significant change of thermal and solution properties. Furthermore, it can be shown that the structure of the ionic liquid anions influences the coil structure of the copolymers. The obtained results could be proven by means of microcalorimetry, differential scanning calorimetry, and dynamic light scattering.
Summary: We have successfully constructed a redox‐responsible hydrogel system by combination of β‐cyclodextrin (β‐CD), dodecyl‐modified poly(acrylic acid) [p(AA/C12)], and a redox‐responsive guest, ferrocenecarboxylic acid (FCA). In the reduced state of FCA, the ternary mixture exhibited a gel‐like behavior, whereas, in its oxidized state, the mixture exhibited a sol behavior.
Conceptual illustration for the redox‐responsive hydrogel system. 相似文献
Films of an α‐cyclodextrin/poly(ε‐caprolactone) inclusion complex have been successfully prepared and show high transparency and heat resistance in comparison to the pure polymer film. The physical properties, such as transparency, mechanical properties, and thermal stability, of the α‐CD‐PCL‐IC films are found to depend on the α‐cyclodextrin‐to‐polymer stoichiometry.
Well‐dispersed silver nanoparticles were successfully fabricated within poly[(N‐isopropylacrylamide)‐co‐(acrylic acid)] [P(NIPAM‐co‐AA)] microgel particles which were synthesized with different cross‐linking densities. Their structures were studied by field‐emission scanning electron microscopy, transmission electron microscopy, UV‐vis spectroscopy, X‐ray diffraction and FT‐IR spectroscopy. The interactions between the microgel particles and the incorporated silver nanoparticles were investigated by X‐ray photoelectron spectroscopy. The results revealed that there was charge transfer from the carbonyl groups of the microgel particles to the silver nanoparticles. Moreover, as the diameter of the AgNPs decreases, the charge‐transfer efficiency increases accordingly. The P(NIPAM‐co‐AA)/AgNPs hybrid microgel particles were thermoresponsive and their behavior completely reversible with several heating/cooling cycles.
The preparation of novel cationic β‐cyclodextrin polymers (CPβCDs) and its complexes with butylparaben and triclosan were reported in this paper. FT‐IR and two‐dimensional (2D) 1H–1H gradient correlated spectroscopy (gCOSY) NMR spectra confirmed that the antibiotics could be included inside the lipophilic cavities of CPβCDs. The water solubility of the antibiotics was improved significantly after inclusion with CPβCDs. The results also suggest that it was easier for butylparaben, which had relatively small molecular size, to form the complexes with CPβCDs than triclosan. Due to the targeting effect after the inclusion with cationic CPβCDs, the anti‐microbial activity of butylparaben was also enhanced substantially. However, similar improvement was not obvious for triclosan.
A novel supramolecular network has been prepared based on the formation of inclusion complexes between γ‐cyclodextrin and poly(ethylene glycol), in which the PEG chains are interlocked by γ‐CD rings. This PEG/γ‐CD network exhibits good shape memory behavior because of the crosslinked structure. The crosslinked PEG/γ‐CD inclusion complexes and PEG crystallites account for the fixing phase and reversible phase, respectively. The characteristics of the materials have been investigated by 1H NMR spectroscopy, XRD, DSC, DMA, viscosity tests, and swelling measurements.
The reversible addition‐fragmentation chain transfer (RAFT) polymerization of N‐acryloylmorpholine (NAM) is performed using three dithioesters (DT) as chain transfer agents (CTA) that incorporate a morpholine (morpholine‐DT), a biotin (biotin‐DT), or a sugar (sugar‐DT) moiety in the R group. PolyNAM chains of controlled characteristics are synthesized. An unexpected behavior is observed with morpholine‐DT, described as an ‘additional retardation’, which is especially visible when low molar masses are targeted ( < 5 000 g · mol−1). In that particular case, further investigations using MALDI‐TOF mass spectrometry show the presence of terminated intermediate radicals (IRs), which corroborates the assumption based on a specific protection of IR according to the nature of the α‐chain‐end.
A new method was developed to crosslink water‐soluble unsaturated polyester resins prepared from maleic anhydride and poly(ethylene glycol) in water as the solvent. Crosslinking was carried out with various molar ratios of the host‐guest complex consisting of styrene as the guest and methylated β‐cyclodextrin as the host. Polymerizations were performed in water with K2S2O8/Na2S2O5 as free radical initiator at 25 °C. Thermal properties of the networks obtained depend on the amount of styrene incorporated into the polymer.
Acceleration effect of me‐β‐CD during crosslinking of an unsaturated polyester with styrene in water: (a) monomer complexed with me‐β‐CD, and (b) with uncomplexed monomer. 相似文献
Macroporous cross‐linked organic polymer based on N‐acryloxysuccinimide (NAS) and ethylene dimethacrylate (EDMA) was prepared inside 75 µm id fused silica capillary as a functionalizable monolithic stationary phase for chromatographic applications. Succinimide groups on the monolith surface provide reactive sites able to react readily through standard electrophile–nucleophile chemistry. Propargylamine was used to prepare alkyne functionalized poly(NAS‐co‐EDMA). Onto this azido‐reactive polymer surface was grafted β‐cyclodextrin (CD) via a triazole ring utilizing the copper(I)‐catalyzed 1,3‐dipolar cyclo‐addition reaction. Chemical characterization was performed in situ after each synthetic step by means of Raman spectroscopy. Good enantioseparations of flavanone enantiomers, chosen as test chiral compound, were achieved under reversed phase conditions by both capillary electrochromatography and nano‐liquid chromatography (nano‐LC) techniques. These results demonstrate the potentiality and usefulness of click chemistry in the preparation of β‐CD containing chiral organic polymer monolith.
Food‐grade biomaterials, like β‐lactoglobulin, bovine serum albumin, and ovalbumin, can assemble into fibrils. Using the irreversible fibril formation for β‐lactoglobulin, gels can be formed even at protein concentrations of 0.07%. These fibrillar mesostructures form new structuring materials for food and pharmaceutical applications.
TEM micrograph of β‐lg at pH 2, after heating at 80 °C for 10 h and then the pH was adjusted to pH 8. 相似文献
Summary: N‐methacryloyl‐1‐aminopropane ( 1 ), N‐methacryloyl‐1‐aminobutane ( 2 ), N‐methacryloyl‐1‐aminopentane ( 3 ), and N‐methacryloyl‐1‐aminohexane ( 4 ) are synthesized and treated with an aqueous solution of randomly methylated β‐cyclodextrin (Me‐β‐CD) to form the water‐soluble host‐guest complexes 1a – 4a . In case of the aqueous polymerization of the free monomers 1 – 4 the initial polymerization rate increases with increasing water solubility. The opposite effect is observed in the case of the polymerizations of the Me‐β‐CD‐complexed methacrylamide monomers 1a – 4a . The polymerization rates are increased with increasing alkyl chain length of the complexed monomers 1a – 4a and decreasing water solubility of the free monomers 1 – 4 .
Initial polymerization rate v0 of CD‐complexed monomers 1a – 4a (○) vs. water solubilities of monomers 1 – 4 (▪). 相似文献
Summary: We synthesized for the first time novel pH‐responsive polyampholyte microgels consisting of poly(methacrylic acid) and poly(2‐(diethylamino)ethyl methacrylate) (PMAA‐PDEA) that are sterically stabilized with poly(ethylene glycol) methyl ether methacrylate (PEGMEM). These microgels showed enhanced hydrophilic behavior in aqueous medium at low and high pH but become hydrophobic and compact between pH 4 and 6 near the isoelectric point. Dynamic‐light scattering measurements showed that the hydrodynamic radius, Rh of these microgels is approximately 100 nm between pH 4 and 6 and increases to around 140 and 170 nm at pH 2 and 10, respectively. It is evident that the cross‐linked MAA‐DEA microgel that is sterically stabilized with PEGMEM retains the polyampholyte properties in solution.
