共查询到20条相似文献,搜索用时 46 毫秒
1.
PS grafted silica nanoparticles have been prepared by a tandem process that simultaneously employs RAFT polymerization and click chemistry. In a single pot procedure, azide‐modified silica, an alkyne functionalized RAFT agent and styrene are combined to produce the desired product. As deduced by thermal gravimetric and elemental analysis, the grafting density of PS on the silica in the tandem process is intermediate between analogous “grafting to” and “grafting from” techniques for preparing PS brushes on silica. Relative rates of RAFT polymerization and click reaction can be altered to control grafting density.
2.
Subramanian Sundarrajan Kalathur S. V. Srinivasan 《Macromolecular rapid communications》2003,24(12):724-731
A series of poly(acyl sulfides) were synthesized by polycondensation of acid dichlorides with sodium sulfide using tetrabutylammoniumhydrogen sulfate as a phase transfer catalyst. The thermal stability of these polymers was determined by thermogravimetric analysis. A unique phenomenon of exothermic degradation behavior was observed by differential thermal analyses, which is attributed to the energetics of the acylsulfide linkage during the thermal degradation. The mechanism of formation of degradation products was investigated by the pyrolysis–gas chromatography/mass spectrometry (Py‐GC/MS) technique.
3.
Adhesion of immiscible polymers during two‐component injection moulding may be improved by transreactions of properly functionalised components. We performed MC simulations based on the three‐dimensional coarse‐grained bond fluctuation model (BFM) including a thermal interaction potential in with energy to characterise the behaviour of several selected types of chemical reactions, which are governed by activation energies of EA = 0, 1, 3 and 5 kBT. The consumption of reactive monomers for all the reactions in the time interval below the Rouse time τR exhibits a typical crossover from a kinetic‐controlled to a diffusion‐controlled behaviour and can be described by a bimolecular kinetic ansatz.
4.
The gecko adhesion phenomenon has stimulated efforts to produce synthetic patterned dry adhesives. Besides introducing surface patterns on dry adhesives, it is also highly desirable to understand their intrinsic material properties. This communication reports the viscoelastic behavior of non‐patterned epoxy elastomers exhibiting intrinsic adhesion that is much higher than that of elastomers typically used for structure patterning. The diverse molecular origin of the adhesion is revealed through the study of adhesion against various substrates.
5.
A kinetic model of the amphiphilic star block copolymerization is developed. The star polymer species, resulting from star polymerization with dendrimer cores and hydrophobic monomers, are used as macroinitiators and initiate the graft polymerization of the hydrophilic monomers. Analytical expressions for the size distributions for the species formed in every step are derived. The method with monomers added to the reaction system in batches decreases the polydispersity index for the products obtained. It reaches a minimum if the monomer feed quantity is equal in every step. Therefore, the dimension and structure of the amphiphilic star block copolymers produced can be designed by using the proposed kinetic mechanism.
6.
Mihee Heo Jonggi Kim Jin Young Kim Changduk Yang 《Macromolecular rapid communications》2010,31(23):2047-2052
A rod‐coil block copolymer consisting of poly(3‐hexylthiophene) (P3HT) and poly(N‐vinylcarbazole) (PVK) ( P3HT‐ b ‐PVK ) in a single molecular architecture is prepared as the first example for WOLEDs. By obtaining the phase separated domains in thin film of the resulting block copolymer, it is possible to suppress energy transfer from PVK as wide bandgap units to P3HT as low bandgap blocks, yielding dual emissions for white electroluminescence with CIE coordination of (0.34, 0.33).
7.
Summary: The evolution of the photoinduced birefringence in thin films of narrow polymer fractions is studied and compared with the behavior of the non‐fractionated polymer. The Δnind value decreases by increasing the degree of polymerization ( ) within the oligomeric range but becomes independent of molecular weight starting from a of ≈70. Thermal pretreatment of the films results in higher photoinduced birefringence. The films show good stability of the photorecording.
8.
Eun Je Lee Hyeok Moo Lee Yue Li Lan Young Hong Dong Pyo Kim Sung Oh Cho 《Macromolecular rapid communications》2007,28(3):246-251
Unique hierarchical pore structures were fabricated by simply irradiating an electron beam onto silicone grease films. The hierarchical pore structures consisted of micrometer‐sized pores and macroporous walls. Due to the high surface roughness, the hierarchical pore structures exhibited both superhydrophobicity with a water contact angle (CA) of 170° and superhydrophilicity with an extremely low water CA of 3° after the chemical treatment of the surfaces. In addition to the hierarchical pore structures, sponge‐like pore structures were also fabricated by the electron irradiation of silicone grease films.
9.
A novel crosslinked conductive polyaniline (PANI) was prepared by chemically copolymerizing aniline (An) and p‐phenylenediamine (PPDA) with triphenylamine (TPA) as crosslinker, using ammonium peroxydisulfate (APS) as an oxidant. The effects of different preparation conditions on the electrical conductivity of polymers were systematically investigated by adjusting acid kinds, concentration, the ratio of APS/An, the mounts of TPA and PPDA. The crosslinked PANI displayed a conductivity increase of up to 25% compared with the linear one. Their structures were characterized by Fourier‐transformed infrared spectroscopy and X‐ray photoelectron spectroscopy, and the electrical conductivity was also tested by a typical four‐point probe (RTS‐8) technique.
10.
Nawel Khelfallah Nikhil Gunari Karl Fischer Giorgos Gkogkas Nikos Hadjichristidis Manfred Schmidt 《Macromolecular rapid communications》2005,26(21):1693-1697
Summary: Amphiphilic cylindrical brush‐coil block copolymers consisting of a polystyrene coil and a cylindrical brush block with poly(acrylic acid) side chains are prepared by ATRP of t‐butylacrylate from a block comacroinitiator. Upon acidolysis of the poly(t‐butylacrylate), water‐soluble polymers were obtained that were observed to form micelles consisting of 4–5 block copolymers on average in aqueous solution. The star‐like nature of such micelles was clearly visualized by scanning force microscopy.
11.
Aaron C. Jackson Jonathan A. Bartelt Kamil Marczewski Nancy R. Sottos Paul V. Braun 《Macromolecular rapid communications》2011,32(1):82-87
A generalized silica coating scheme is used to functionalize and protect sub‐micron and micron size dicyclopentadiene monomer‐filled capsules and polymer‐protected Grubbs' catalyst particles. These capsules and particles are used for self‐healing of microscale damage in an epoxy‐based polymer. The silica layer both protects the capsules and particles, and limits their aggregation when added to an epoxy matrix, enabling the capsules and particles to be dispersed at high concentrations with little loss of reactivity.
12.
Graft chitosan derivatives (CMCTS‐g‐MAAS and CMCTS‐g‐AAS) were prepared by the graft copolymerization of methacrylic acid sodium (MAAS) and acrylic acid sodium (AAS) onto the etherification product of chitosan‐carboxymethyl chitosan (CMCTS). Their antioxidant activity was estimated as superoxide anion scavengers by chemiluminescence techniques. The derivatives with low grafting percentages have a relatively low 50% inhibition concentration (IC50), which could be related to the fact that they have different contents of hydroxyl and amino groups in the polymer chains.
13.
Jun Ma Zhong‐Zhen Yu Hsu‐Chiang Kuan Arovind Dasari Yiu‐Wing Mai 《Macromolecular rapid communications》2005,26(10):830-833
Summary: A new strategy was developed to prepare disorderly exfoliated nanocomposites, in which a soft siloxane surfactant with a weight‐average molecular weight ( ) of 1 900 was adopted to modify the clay. The modified clay slurry was then mixed with silicone rubber by hand, and exfoliation was achieved. The proposed mechanism thereof was verified by TEM and XRD. The physical entanglement of the soft siloxane surfactant plays a vital role in the diffusion and intercalation of the matrix molecules during the compounding of the slurry‐polymer mixture. This simple method is applicable to other silicone‐based materials reinforced by clay.
14.
Yunze Long Lijuan Zhang Yongjun Ma Zhaojia Chen Nanlin Wang Ze Zhang Meixiang Wan 《Macromolecular rapid communications》2003,24(16):938-942
Camphor sulfonic acid (CSA) doped polyaniline (PANI) nanotubes (175 nm in outer diameter and 120 nm in inner diameter) were synthesized successfully by a self‐assembly method. It is found that the room‐temperature conductivity of an individual PANI nanotube is 30.5 S · cm−1; in particular, the intrinsic resistance of an individual nanotube (30 kΩ) is much smaller than the contact resistance of crossed nanotubes (500 kΩ).
15.
Jun Fu Xiaoshuang Feng Yanchun Han Caiyuan Pan Yuming Yang Binyao Li 《Macromolecular rapid communications》2003,24(8):487-491
A two‐armed polymer with a crown ether core self‐assembles to produce macroporous films with pores perpendicularly reaching through the film down to the substrate. A possible assembling mechanism is discussed. The pore size can be conveniently adjusted by changing the solution concentration. These through‐hole macroporous films provide a template for fabricating an array of Cu nanoparticle aggregates.
16.
A photochemical approach toward the generation of enzyme‐containing redox polymer networks, which are the key material in enzymatic sensors and biofuel cells, is described. The approach is based on the incorporation of photo‐reactive benzophenone groups into the redox polymers. The obtained polymers are then deposited on the surface of glassy carbon electrodes and cross‐linked by illumination with UV light at 365 nm. If this step is done in the presence of the enzyme glucose oxidase, functional electrodes are obtained that yield electrical power upon addition of glucose. This work specifically addresses the question of electrode stability in buffer and demonstrates how slight variations in the chemistry of the redox polymer have a dramatic effect on the electrochemical performance of the electrodes. Different ferrocene‐containing redox polymer networks are synthesized and their properties in physiological buffer are studied.
17.
Summary: Ethylene and 10‐undecen‐1‐ol have been successfully copolymerized by an organically modified montmorillonite (OMMT)‐intercalated metallocene catalyst, Et[Ind]2ZrCl2, activated by methylaluminoxane (MAO). The obtained hydroxy‐functionalized polyethylene (PE‐OH)/OMMT nanocomposites exhibit enhanced structural stability as compared with the neat PE‐based ones, with no significant collapse of the nanocomposite structure being detected by WAXD examination after high‐temperature processing. The simultaneous polyolefin functionalization provides an effective and convenient solution to stabilize the PE/MMT nanocomposite structure formed by in‐situ polymerization.
18.
19.
Summary: A water‐soluble gold nanoparticle aggregate 2 was prepared by chloroauric acid and a polypseudorotaxane 1 of mono‐6‐thio‐β‐cyclodextrin with poly(propylene glycol) bis(2‐aminopropyl ether) ( ≈ 2 000) in the presence of sodium borohydride in N,N‐dimethylformamide (DMF) solution. The investigative results indicated that the gold nanoparticle aggregate 2 might act as an efficient DNA‐cleavage reagent.
20.
Kaimin Chen Yan Zhu Li Li Yan Lu Xuhong Guo 《Macromolecular rapid communications》2010,31(16):1440-1443
Spherical polyelectrolyte brushes consisting of a magnetite/polystyrene nanocomposite core and a poly(acrylic acid) brush shell were prepared by photo‐emulsion polymerization. They are narrowly dispersed, superparamagnetic and redispersible after aggregating by external magnetic field, as determined by transmission electron microscopy, dynamic light scattering, thermal gravimetric analysis and a vibrating sample magnetometer. Magnetic control is thus introduced into nano‐sized spherical polyelectrolyte brushes to achieve recovery and controllable delivery in applications. This approach opens up the way for cost‐effective applications of spherical polyelectrolyte brushes.