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11.
A two-step swelling procedure was adopted to synthesize mono-dispersed and highly cross-linked poly (St-divinylbenzene) particles
with PSt micro-spheres (1.80 μm in diameter). The PSt micro-spheres were prepared by a dispersion polymerization method and
used as seeds. The effects of monomer concentration, ratio of ethanol to water, swelling reagents, crosslinking reagents,
swelling temperature and agitation speed on particle size were investigated in detail. The morphologies and size distributions
of these micro-spheres were examined by SEM and particle size analysis (PSA). The T
g of the micro-spheres was measured by DSC. The results indicate that the particles (6.20 μm in diameter) exhibit excellent
mono dispersed property and high crosslinking degree when the concentration of the swelling reagent was 25%, the concentration
of the crosslinking reagents was 23%, the swelling temperature was 30°C and the stirring speed was 150 r/min.
__________
Translated from Chinese Journal of Applied Chemistry, 2007, 24(11): 1289–1294 相似文献
12.
Chengzhi Qi Mingyang Wang Qihu Qian Jianjie Chen 《Moscow University Mechanics Bulletin》2008,63(5):113-121
The formation mechanisms for the structural hierarchy in geological media are discussed. It is shown that the formation of such a hierarchy is caused by certain external and internal circumstances. The first ones consist in the fact that, because of external actions, the Earth’s poles continuously execute the translational and rotational motions responsible for a regular structure of rock fracture and for the appearance of the scale factor √2. The second ones consist in the fact that, under the action of many random factors and because of external actions, during the formation of geological media there appear dissipative structures and, hence, some self-similar fractal structures are formed. 相似文献
13.
Guobao Zhang Jianming Zhang Shenguo Wang Deyan Shen 《Journal of Polymer Science.Polymer Physics》2003,41(1):23-30
Blends of amorphous poly(DL‐lactide) (DL‐PLA) and crystalline poly(L‐lactide) (PLLA) with poly(methyl methacrylate) (PMMA) were prepared by both solution/precipitation and solution‐casting film methods. The miscibility, crystallization behavior, and component interaction of these blends were examined by differential scanning calorimetry. Only one glass‐transition temperature (Tg) was found in the DL‐PLA/PMMA solution/precipitation blends, indicating miscibility in this system. Two isolated Tg's appeared in the DL‐PLA/PMMA solution‐casting film blends, suggesting two segregated phases in the blend system, but evidence showed that two components were partially miscible. In the PLLA/PMMA blend, the crystallization of PLLA was greatly restricted by amorphous PMMA. Once the thermal history of the blend was destroyed, PLLA and PMMA were miscible. The Tg composition relationship for both DL‐PLA/PMMA and PLLA/PMMA miscible systems obeyed the Gordon–Taylor equation. Experiment results indicated that there is no more favorable trend of DL‐PLA to form miscible blends with PMMA than PLLA when PLLA is in the amorphous state. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 23–30, 2003 相似文献
14.
Howard Robinson 《Acta Analytica》2005,20(3):7-10
Nicholas Nathan tries to resist the current version of the causal argument for sense-data in two ways. First he suggests that,
on what he considers to be the correct re-construction of the argument, it equivocates on the sense of proximate cause. Second
he defends a form of disjunctivism, by claiming that there might be an extra mechanism involved in producing veridical hallucination,
that is not present in perception. I argue that Nathan’s reconstruction of the argument is not the appropriate one, and that,
properly interpreted, the argument does not equivocate on proximate cause. Furthermore, I claim that his postulation of a
modified mechanism for hallucinations is implausibly ad hoc. 相似文献
15.
Yu‐Hsiang Hu Chuh‐Yung Chen Chen‐Chien Wang Yao‐Hui Huang Shao‐Ping Wang 《Journal of polymer science. Part A, Polymer chemistry》2004,42(19):4976-4993
The bulk polymerization of styrene initiated by ?‐caprolactam (CL) and n‐dodecyl mercaptan (RSH) has been explored. This novel polymerization system shows living characteristics. For example, the molecular weight of the resulting polymers increases with conversion, and the system has the ability to form diblock copolymers and so forth. The polymer chain end contains thiol and lactam structures, which we have investigated with Fourier transform infrared, 1H NMR, and 13C NMR techniques. Electron spin resonance spectra and theoretical calculations by the Hartree–Fock methods have been used to examine the mechanism. The results reveal that the initial polymerization starts from thiol via a chain‐transfer reaction, and the propagation proceeds by the insertion of a monomer between the terminal group and the intermediate structure of lactam. Finally, the polymerization kinetics have been examined. The polymerization rate varies linearly with the concentration of CL and RSH, and this confirms the mechanism. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4976–4993, 2004 相似文献
16.
T. Brian Cavitt Brian Phillips Charles E. Hoyle Bo Pan Sukhendu B. Hait Kalyanaraman Viswanathan Sonny Jnsson 《Journal of polymer science. Part A, Polymer chemistry》2004,42(16):4009-4015
Three‐component photoinitiators comprised of an N‐arylphthalimide, a diarylketone, and a tertiary amine were investigated for their initiation efficiency of acrylate polymerization. The use of an electron‐deficient N‐arylphthalimide resulted in a greater acrylate polymerization rate than an electron‐rich N‐arylphthalimide. Triplet energies of each N‐arylphthalimide, determined from their phosphorescence spectra, and the respective rate constants for triplet quenching by the N‐arylphthalimide derivatives (acquired via laser flash photolysis) indicated that an electron–proton transfer from an intermediate radical species to the N‐arylphthalimide (not energy transfer from triplet sensitization) is responsible for generating the initiating radicals under the conditions and species concentrations used for polymerization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4009–4015, 2004 相似文献
17.
Fang‐Jung Huang Tzong‐Liu Wang 《Journal of polymer science. Part A, Polymer chemistry》2004,42(2):290-302
Liquid‐crystalline, segmented polyurethanes with methoxy–biphenyl mesogens pendant on the chain extender were synthesized by the conventional prepolymer technique and esterification reaction. Two, side‐chain, liquid‐crystalline (SCLC) polyurethanes with mesogens having spacers of six and eight methylene units were prepared. The structures of the mesogenic units and SCLC polyurethanes were confirmed by Fourier transform infrared spectroscopy and 1H NMR. Polymer properties were also examined by solubility tests, water uptakes, and inherent viscosity measurements. Differential scanning calorimetry studies indicated that the transition temperature of the isotropic to the liquid‐crystalline phase decreased with increasing spacer length. Wide‐angle X‐ray diffraction (WAXD) studies revealed the existence of liquid‐crystalline phases for both SCLC polyurethanes. Polarized optical microscopic investigations further confirmed the thermotropic liquid‐crystalline behaviors and nematic mesophases of both samples. Thermogravimetric analysis displayed better thermal stabilities for both SCLC polymers and indicated that the presence of mesogenic side chains may increase the thermal stability of segmented polyurethanes. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 290–302, 2004 相似文献
18.
Qi Wang Huaxiang Yang Zhiqiang Fan Hong Xu 《Journal of polymer science. Part A, Polymer chemistry》2004,42(5):1093-1099
Ethylisobutylaluminoxane (EBAO) and its analogues were synthesized by a reaction between an triethylaluminum (Et3Al)/triisobutylaluminum (i‐Bu3Al) mixture and 4‐fluorobenzeneboronic acid, phenylboronic acid, or n‐butaneboronic acid and subsequent hydrolysis with water. They were used as cocatalysts in ethylene polymerization catalyzed by an iron complex {[(ArN?C(Me))2C5H3N]FeCl2, where Ar is 2,6‐diisopropylphenyl}. Polyethylene with a high molecular weight and a narrow molecular weight distribution was prepared with modified EBAOs, and the performance of the iron complex at high polymerization temperatures was greatly improved. The activators for the iron complex also affected the polymerization activity and the molecular weight of the resultant polyethylene. It was suggested that the stereo and electronic effects of the substitute groups of aluminoxane contributed to the improved performance of the new activators. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1093–1099, 2004 相似文献
19.
Chun‐Yan Hong Ye‐Zi You Cai‐Yuan Pan 《Journal of polymer science. Part A, Polymer chemistry》2004,42(19):4873-4881
Well‐defined diblock and triblock copolymers composed of poly(N‐isopropylacrylamide) (PNIPAM) and poly(ethylene oxide) (PEO) were successfully synthesized through the reversible addition–fragmentation chain transfer polymerization of N‐isopropylacrylamide (NIPAM) with PEO capped with one or two dithiobenzoyl groups as a macrotransfer agent. 1H NMR, Fourier transform infrared, and gel permeation chromatography instruments were used to characterize the block copolymers obtained. The results showed that the diblock and triblock copolymers had well‐defined structures and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.2), and the molecular weight of the PNIPAM block in the diblock and triblock copolymers could be controlled by the initial molar ratio of NIPAM to dithiobenzoate‐terminated PEO and the NIPAM conversion. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4873–4881, 2004 相似文献
20.
Hongchao Li Yufeng Hu Yanguang Zhang Dongge Ma Lixiang Wang Xiabin Jing Fosong Wang 《Journal of polymer science. Part A, Polymer chemistry》2004,42(16):3947-3953
A conjugated poly(p‐CN‐phenylenevinylene) (PCNPV) containing both electron‐donating triphenylamine units and electron‐withdrawing cyano groups was prepared via Knoevenagel condensation in a good yield. Gel permeation chromatography suggested that the soluble polymer had a very high weight‐average molecular weight of 309,000. A bright and saturated red emission was observed under UV excitation in solution and film. Cyclic voltammetry showed that the polymer presented quasi‐reversible oxidation with a relatively low potential because of the triphenylamine unit. A single‐layer indium tin oxide/PCNPV/Mg–Ag device emitted a bright red light (633 nm). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3947–3953, 2004 相似文献