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91.
A series of block copolymers composed of a fixed length of an (ar-vinylbenzyl)trimethylammonium chloride (Q) block (the number average degree of polymerization of the Q block, DPn,Q=57) and varying lengths of an N,N-dimethylvinylbenzylamine (A) block (the number average degrees of polymerization of the A blocks, DPn,A, ranging 11-50) were prepared by reversible addition-fragmentation chain transfer (RAFT) radical polymerization, and their pH-dependent micellization was characterized by potentiometric titration, 1H NMR spectroscopy, dynamic and static light scattering, and fluorescence techniques as a function of the A block length. At pH<5.5, the A block is fully protonated, and hence the block copolymers act as a simple polyelectrolyte, dissolving molecularly in acidic water. At pH>7, the A block becomes deprotonated, and thereby the block copolymers aggregate into a micelle composed of hydrophobic microdomains formed from the deprotonated A blocks. Results of light scattering and fluorescence measurements indicated that the micellization behavior depended strongly on the length of the A block. The number of polymer chains comprising one micelle (i.e. mean aggregation number, Nagg) increased from 3 to 12 as DPn,A increased from 11 to 50 at pH 10.0. In the case of a random copolymer of Q and A with an A/Q molar ratio similar to that of a block copolymer with DPn,A=50, Nagg∼1 (i.e. unimolecular micelle) was confirmed by static light scattering at pH 10.0. 相似文献
92.
93.
Kamalesh Prasad Shozaburo Mine Yoshiro Kaneko Jun-ichi Kadokawa 《Polymer Bulletin》2010,64(4):341-349
Cellulose-based ionic porous material compatibilized with polymeric ionic liquid was prepared by means of templating technique using oil/ionic liquid emulsion in the presence of sorbitane monooleate. In situ polymerization of a mixture of polymerizable ionic liquids, 1-(3-acryloyloxypropyl)-3-methylimidazolium and 1-(3-acryloyloxypropyl)-3-vinylimidazolium bromides was first performed in a solution of cellulose in a solvent of an ionic liquid, 1-butyl-3-methylimidazolium chloride. The sonication of the mixture coexisting with corn oil and sorbitan monooleate, followed by the successive treatment with methanol, acetone, and hexane gave the porous material. The material thus obtained was characterized by the FT-IR, TGA, XRD, and SEM measurements. The SEM images of the material showed the morphology of the porosity with the pore sizes of around 0.15–1.3 μm accompanied with the smaller sizes of 30–70 nm. 相似文献
94.
Yoshiro Tahara Satoshi Kosuge Shin-ichi Sawada Yoshihiro Sasaki Kazunari Akiyoshi 《Reactive and Functional Polymers》2013,73(7):958-964
Polysaccharide nanogels are one of the most attractive carriers for drug delivery systems. Nanogels encapsulate proteins in their hydrated polymer networks, and minimize the denaturation of proteins. In this study, we demonstrated the cross-linking of acryloyl group-modified polysaccharide nanogels via photopolymerization, which allowed the formation of novel hydrogel particles and macrogels. The mechanical properties of the resultant hydrogels depended on the concentrations of the nanogels and the cross-linkers. The most significant property of the nanogel-cross-linked hydrogel was the ability to encapsulate insulin via hydrophobic interactions. After incubation of the hydrogel containing insulin in water, the hydrogel was degraded by hydrolysis, and insulin was gradually released from the hydrogels over a period of 1 week. According to these results, this nanogel-cross-linked hydrogel prepared via photopolymerization has potential for innovative biomaterials. 相似文献
95.
TiC–C eutectic (2,761°C) and WC–C peritectic (2,749°C) fixed points were investigated to compare their potential as high-temperature
thermometric reference points. Two TiC–C and three WC–C fixed-point cells were constructed, and the melting and freezing plateaux
were evaluated by means of radiation thermometry. The repeatability of the TiC–C eutectic within a day was 60 mK with a melting
range roughly 200 mK. The repeatability of the melting temperature of the WC–C peritectic within 1 day was 17 mK with a melting
range of ∼70 mK. The repeatability of the freezing temperature of the WC–C peritectic was 21 mK with a freezing range less
than 20 mK. One of the TiC–C cells was constructed from a TiC and graphite powder mixture. The filling showed the reaction
with the graphite crucible was suppressed and the ingot contained less voids, although the lack of high-purity TiC powder
poses a problem. The WC–C cells were easily constructed, like metal–carbon eutectic cells, without any evident reaction with
the crucible. From these results, it is concluded that the WC–C peritectic has more potential than the TiC–C eutectic as a
high-temperature reference point. The investigation of the purification of the TiC–C cell during filling and the plateau observation
are also reported. 相似文献
96.
The effect of diluents on isotactic polypropylene (iPP) membrane formation via thermally induced phase separation was investigated. The diluents were methyl salicylate (MS), diphenyl ether (DPE), and diphenylmethane (DPM). The cloud-point curve was shifted to a lower temperature in the order iPP–MS, iPP–DPE, and iPP–DPM, whereas the crystallization temperature was not influenced so much by diluent type. Droplet-growth processes were investigated under two conditions: quenching the polymer solution at the desired temperature and cooling at a constant rate. Although droplet sizes were in the order iPP–MS, iPP–DPE, and iPP–DPM in both cases, the difference was more pronounced with the constant cooling rate condition. Scanning electron microscopy indicated that interconnected structures were obtained when the polymer solution was quenched in ice water. The effect of the diluents on these structures was observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 169–177, 2001 相似文献
97.
Takano Y Sakai H Watanabe E Ideguchi-Ohma N Jayawardena CK Arai K Asawa Y Nakano Y Shuda Y Sakamoto Y Terashima T 《Journal of electron microscopy》2003,52(6):573-580
The mechanism whereby a region-specific deposition of the two types of cementum (cellular cementum and acellular extrinsic fibre cementum) is regulated on the growing root surface was tested using bisphosphonate-affected teeth of young rats and guinea pigs. The animals were injected subcutaneously with 8 or 10 mg P x kg body weight(-1) x day(-1) of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) for 1 or 2 weeks. In rat molars, HEBP prevented mineralization of newly formed root dentin matrix and totally inhibited de novo deposition of acellular extrinsic fibre cementum. Instead, thick cellular cementum was induced on the non-mineralized root dentin surface, irrespective of the position of the root. In both animals, cellular cementum was also induced on the non-mineralized surface of root analogue dentin in HEBP-affected incisors, where only acellular extrinsic fibre cementum is deposited under normal conditions. In normal rat molars, dentin sialoprotein (DSP) was concentrated along the dentin-cellular cementum border, but not that of dentin and acellular extrinsic fibre cementum. In HEBP-affected rat incisors, DSP was shown to penetrate through the non-mineralized dentin into the surrounding tissues, but not through the mineralized portions. These data suggest that, at the site of cellular cementum formation, putative inducing factors for cellular cementum might diffuse into the periodontal space through the newly deposited mantle dentin matrix before it is mineralized. At earlier stages of root formation, mantle dentin might mineralize more promptly not to allow such diffusion. The timing of mineralization of mantle dentin matrix might be the key determinant of the types of the cementum deposited on the growing root surface. 相似文献
98.
99.
Fuyuki Shimojo 《Science and Technology of Advanced Materials》2007,8(6):504-510
First-principles studies of the proton dynamics in perovskite oxides and the water adsorption on various oxide surfaces are briefly reviewed. Recent progress in the study of the microscopic mechanism of the proton absorption from perovskite oxide surfaces is also presented. It is shown that dopant ions on the surface and oxygen vacancies in the inside just below the surface play an important role for the proton absorption, while oxygen vacancies on the surface are influential for the dissociative adsorption of water molecules. 相似文献
100.
The resistive transition to the superconducting (SC) state in -(ET)2NH4Hg(SCN)4 was studied under magnetic fields applied parallel to the conducting plane. The SC state is divided into three regions: (1) temperature-dependent resistive region, (2) zero-resistive region, and (3) temperature-independent resistive region. We observed twofold symmetry in the resistance under an in-plane magnetic field near the midpoint of the SC transition, which indicates that the upper critical field 0
H
c2 has the same twofold symmetry. This in-plane anisotropy can be ascribed to the crystal structure. 相似文献