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.
A chiral polymeric micelle is described, formed from the self‐assembly of TPPS and PEG114‐b‐P(4VP)38 in aqueous media based on their electrostatic interaction. The self‐assembly behavior is studied by DLS, SLS, TEM, UV‐vis absorption spectroscopy, and CD spectroscopy. The experimental results indicate that the resultant hybrid spherical micelles with a hybrid P(4VP)/TPPS core and a PEG shell show chiral signatures. In addition, the chiral micelles have a large dimension and biphasic segregated structure because of the formation of H‐aggregates and J‐aggregates in the micellar core.
Densities and viscosities of a series of blends of poly(ethylene glycol) (PEG) and poly(ethylene glycol‐ran‐propylene glycol) (PEG‐ran‐PPG) were measured at a temperature above the melting point. The density and viscosity data were fitted with analytical functions involving the volume fraction of PEG, ϕPEG. Stress relaxation curves for the pure components and blends were obtained through Monte Carlo (MC) simulations. A typical stress relaxation curve exhibits a fast mode that represents energetic‐interactions‐driven motion and a slow mode that originates from the entropy‐driven motion. Flory–Huggins interaction parameters (χ) for the blends are much smaller than the critical values (χcritical). The calculation of χ and χcritical provides important clues for polymer blend processing.
Thermosensitive poly(N‐isopropylacrylamide) (PNIPAm)‐coated gold nanoparticles (AuNPs) were prepared by self‐assembly of the azobenzene‐terminated PNIPAm on the surface of the α‐cyclodextrin (α‐CD)‐capped AuNPs via the host–guest molecular recognition between α‐CD and azobenzene. Reversible attachment–detachment of azobenzene‐terminated PNIPAm on the surface of α‐CD‐capped AuNPs was achieved when subjected to visible and UV light irradiation alternately, which endowed thermosensitive AuNPs with tunable smart properties.
Highly efficient formation of poly(propylene carbonate) can be achieved in the coupling of CO2 and propylene oxide assisted by 4‐(N,N‐dimethylamino)pyridine (DMAP) and catalyzed with salen chromium(III) chloride by using DMAP/Cr ratios of less than 2. Under these conditions a possible backbiting mechanism is suppressed, leading to only minor amounts of cyclic carbonate as a side product.
Polymerizations of methyl methacrylate with (α‐diimine)nickel(II)/methylaluminoxane (MAO) and (pyridyl bis(imine))iron(II) and (pyridyl bis(imine))cobalt(II)/MAO are reported. Effects of structural variation of the ligand on the activities of catalysts and polymer microstructure are described. The catalyst systems gave syndio‐rich poly(methyl methacrylate). The α‐diimine system showed much higher activity than the pyridyl bis(imine) systems under similar polymerization conditions.
Self‐assembled hollow nanosphere composites of polyaniline and Au nanoparticles (PANI‐p‐TSA/Au) were chemically synthesized from solutions containing p‐toluenesulfonic acid (p‐TSA) with the addition of gold chloride trihydrate as the oxidant. The composite materials were characterized by SEM, TEM, and a range of spectroscopic methods. Spectroscopic characterizations confirmed that the polymeric product is a form of doped PANI, while electron diffraction and X‐ray diffraction showed that elemental Au was present in the PANI‐p‐TSA/Au nanocomposites. The room temperature electrical conductivity of the PANI‐p‐TSA/Au nanocomposites was two orders of magnitude greater than a PANI‐p‐TSA obtained in the presence of ammonium persulfate as the oxidant under the same conditions.
Novel linear poly(NIPA‐co‐CL) copolymers have been synthesized by radical copolymerization of N‐isopropylacrylamide (NIPA) and 2‐methylene‐1,3‐dioxepane (MDO). The structure of copolymers was confirmed by 1H NMR and IR spectroscopy. Cross‐linked poly(NIPA‐co‐CL) hydrogels have also been prepared in toluene using N,N′‐methylenebisacrylamide as cross‐linking agent. The hydrogels thus obtained exhibit good temperature response and are biodegradable in the presence of proteinase K.
Temperature influence on the enzymatic degradation by proteinase K of poly(NIPA‐co‐CL) hydrogel (G‐60). 相似文献
PEGylated click polypeptides ( PEG‐CP s) containing α‐amino side groups as well as PEG segments are designed for selective endotoxin removal from protein solutions. The PEG‐CP s are synthesized via copper‐free thermal click copolymerization from aspartic (or glutamic) acid‐based dialkyne and diazide monomers (containing free amino side groups) and alkyne‐terminated mPEGs or dialkyne‐terminated PEGs. Microwave‐assisting technology is introduced into thermal click chemistry to improve the reaction efficiency. The monomers and polymers are fully characterized using NMR, XPS, and MALDI‐TOF MS. After immobilizing the PEGylated click polypeptides onto polystyrene microspheres, the adsorbents exhibit good endotoxin removal selectivity from BSA solutions.
Polybutadienes (PBs) are found to form inclusion complexes with cyclodextrins (CDs) stereoselectively to give crystalline compounds in bulk. These complexes have been isolated and characterized by means of 1H NMR and 13C CP/MAS NMR spectroscopy, and X‐ray diffraction. Although α‐CD did not form inclusion complexes with any kinds of PBs in aqueous solutions, α‐CD did form inclusion complexes with PBs having 1,4‐cis‐ and 1,4‐trans‐butadiene units in bulk by heating at 100 °C. On the other hand, PB having 79% of a 1,2‐structure did not form inclusion complexes with α‐CD. The yield of the inclusion complexes increases with an increase in the content of the 1,4‐cis‐structure of PB and decreases with the molecular weights of the PBs.
Reactions between the ethylene groups in the backbone of conjugated polymers under UV illumination and heat treatment result in the cross‐linking of the main polymer chains. The cross‐linking leads to two simultaneous results in the polymer: excellent solvent resistance and increased bandgap. Using this reaction, three‐color polymer light‐emitting diodes (PLEDs) with a multi‐layer structure can be easily realized by a dry photo‐pattern in an active‐gas‐free environment. Multi‐layer blue devices with dramatically enhanced efficiency can also be achieved conveniently.
A novel pH‐responsive polymer vesicle obtained by the aqueous self‐assembly of carboxy‐terminated hyperbranched polyesters is reported. The synthesis is very simple, just a one‐step esterification of the commercially available hydroxy‐terminated hyperbranched polyester of Boltorn Hx (x = 20, 30, 40) with succinic anhydride. The vesicle size can be controlled from 200 nm to 10 µm by simply adjusting the solution pH as well as the degrees of branching (or generation).
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.
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.
Summary: Borane reacts with TDM by a sequence of insertion and disproportionation reactions to yield tris‐(trimethylsilylmethyl)borane. No further addition of TDM occurs. Triallylborane and tris‐(4‐methoxyphenylethyl)borane initiate the copolymerization of TDM and dimethylsulfoxonium methylide. The reactions afford TMS‐substituted polymethylene oligomers. The resultant poly(methylidene‐co‐TMSmethylidene) random copolymers arise from incorporation of TMSmethylidene (CHSiMe3) and methylidene (CH2) groups into the growing polymer chain one carbon at a time.
Trialkylborane‐catalyzed copolymerization of trimethylsilyl diazomethane and dimethylsulfoxonium methylide. 相似文献
Miniemulsion polymerization with an amphiphilic poly(acrylic acid)‐block‐polystyrene reversible addition–fragmentation chain transfer agent as a surfactant and polymerization mediator is used to synthesize highly uniform nanocapsules. The nanocapsules with uniform structures, which include particle size, shell thickness, and shape symmetry, could be achieved by the post‐addition of a small amount of sodium dodecyl sulfate. Although the solid particles seem unavoidable, the ‘pure’ uniform core–shell structures are easily collected by centrifugation.
Interaction of cyclodextrins (CDs) with an alternating copolymer of sodium maleate and dodecyl vinyl ether (pC12MA), which forms micelle‐like aggregates in aqueous media, is investigated by several NMR techniques to explore the competition of the complexation of CDs with the dodecyl (C12) groups and the self‐association of the C12 groups. 1H NMR and two‐dimensional nuclear Overhauser effect spectroscopy data demonstrate that α‐CD interacts significantly with the C12 groups in pC12MA but β‐ or γ‐CD does not, which indicates that the competition with self‐association of the C12 groups enhances the selectivity towards α‐CD. Furthermore, the binding isotherm prepared using 1H NMR data exhibits a sigmoidal curve, which is indicative of cooperative complexation of α‐CD with pC12MA.
Summary: Well‐defined pentablock copolymers of styrene–[1]dimethylsilaferrocenophane–methyl methacrylate (PMMA‐b‐PFS‐b‐PS‐b‐PFS‐b‐PMMA) are synthesized using lithium naphthalide as initiator and a 1,1‐dimethylsilacyclobutane‐mediated 1,1‐diphenylethylene (DPE) end‐capping technique. Annealing under various conditions followed by analysis by transmission electron microscopy revealed good phase separation by the copolymers and the presence of ordered microstructures, such as spheres‐on/in‐spheres, and spheres‐on/in‐lamellae micromorphologies.
Structure of the styrene–[1]dimethylsilaferrocenophane–methyl methacrylate pentablock copolymers. 相似文献
Summary: Experimental and modeling studies of addition–fragmentation chain transfer (AFCT) during radical polymerization of methyl methacrylate in the presence of poly(methyl methacrylate) macromonomer with 2‐carbomethoxy‐2‐propenyl ω‐ends (PMMA‐CO2Me) at 60 °C are reported. The results revealed that AFCT involving PMMA‐CO2Me formed in situ during methyl methacrylate polymerization has a negligible effect on the molecular weight distribution.
Summary: Novel hyperbranched poly(amine‐ester) (HPAE) cross‐linked films were prepared by cross‐linking the terminal hydroxyl groups of HPAE using glutaraldehyde (GA). Atom force microscope and scanning electron microscope revealed their smooth surfaces, dense and homogenous matrices. Property characterizations indicated that these cross‐linked films had good hydrophilicity, relative low protein adsorption, and high tensile strength. Also, their swelling behavior varied with the solvent.
Structure of the hyperbranched poly(amine‐ester). 相似文献
