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1.
Masao Kato Takao Shiraga Tatsumi Kimura Takashi Fukuda Hiro Matsuda Hachiro Nakanishi 《先进技术聚合物》2002,13(2):120-126
We synthesized some novel rigid NLO‐active maleimide copolymers bearing DR‐1 moieties ( PMPD , PHSD and PHND ). All copolymers exhibited high Tg's (190~197 °C), good solubilities for common solvents and excellent film‐forming properties. Dependence of film thickness on the d33 value for the poled copolymer films induced by corona poling was investigated and it was demonstrated that in less than thickness of 0.3 µm decrease of the thickness gives rise to remarkable increase in the d33 value. The poled copolymer films exhibited large d33 values (270 × 10?9 esu (film thickness 0.13 µm) for PMPD , 290 × 10?9 esu (0.12 µm) for PHSD and 350 × 10?9 esu (0.08 µm) for PHND ) as well as large r33 values (51.0 pmV?1 for PMPD and 60.4 pmV?1 for PHND ) which are significantly large compared to the value of LiNbO3 (31 pmV?1) as a typical EO material. The d33 values of the poled copolymers were kept constant even after standing 1000h at 80 °C, although a small decrease was observed at an initial stage. Further, the d33 values did not change up to ca. 123 °C upon heating at the rate of 10 °C/min in all cases. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
2.
Naozumi Teramoto Toyoki MotoyamaRyutoku Yosomiya Mitsuhiro Shibata 《European Polymer Journal》2002,38(7):1365-1369
Amylose was etherified with 1-bromopropane in DMSO. The degree of substitution (DS) was varied by altering the feed ratio of 1-bromopropane. The structures of the products were characterized by IR and 1H-NMR spectroscopy. When the molar feed ratio of 1-bromopropane to hydroxyl groups of amylose was beyond 7.5, the hydroxyl groups were completely substituted with propyl ether groups. The etherified amylose with DS 1.9 showed a glass transition temperature (Tg), and that with DS 2.3 or 3.0 showed both Tg and melting temperature (Tm) (DS 3.0 means complete substitution). The etherification imparted melt processability and solubility in nonpolar organic solvent to amylose. 相似文献
3.
Jiaxin Fu Yingxiong Wang Kaizhi Shen Qiang Fu Jie Zhang 《Journal of Polymer Science.Polymer Physics》2019,57(10):598-606
Many experimental results have revealed that the re‐entanglement kinetics of disentangled polymers is much slower than that predicted by tube theory. This retarded recovery of fully entangled state is of practical significance that shear‐induced modification may offer a way to improve processability for a polymer by reducing viscosity. This work tried to figure out the shear‐rate dependence variation of viscosity in the view of evolution of entanglement state through disentanglement and re‐entanglement, aiming to provide fundamental insights into application prospect of shear‐induced modification in preparing “in‐pellet” disentangled polymers prior to final processing. High‐density polyethylene was sheared on a parallel‐plate rotational rheometer with a linearly increased shear rate. Results showed that higher shear rate could induce further disentanglement, resulting in a lower viscosity with a reduction rate up to 93.7%, larger molecular weight between entanglements Me , and longer re‐entanglement time. Additionally, less entanglement would give a larger lamellar thickness of sheared samples after nonisothermal crystallization. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 598–606 相似文献
4.
Masatoshi Hasegawa Daiki Hirano Mari Fujii Misako Haga Eiichiro Takezawa Shinya Yamaguchi Atsushi Ishikawa Takashi Kagayama 《Journal of polymer science. Part A, Polymer chemistry》2013,51(3):575-592
This work presents novel colorless polyimides (PIs) derived from 1R,2S,4S,5R‐cyclohexanetetracarboxylic dianhydride (H″‐PMDA). Isomer effects were also discussed by comparing with PI systems derived from conventional hydrogenated pyromellitic dianhydride, that is, 1S,2R,4S,5R‐cyclohexanetetracarboxylic dianhydride (H‐PMDA). H″‐PMDA was much more reactive with various diamines than H‐PMDA, and the former led to PI precursors with much higher molecular weights. The results can be explained from the quite different steric structures of these isomers. The thermally imidized H″‐PMDA‐based films were colorless regardless of diamines because of inhibited charge‐transfer interaction. In particular, the H″‐PMDA/4,4′‐oxydianiline system simultaneously achieved a very high Tg exceeding 300 °C, high toughness (elongation at break > 70%), and good solution processability. In contrast, the H‐PMDA‐based counterparts were essentially insoluble. The outstanding solubility of the former probably results from disturbed chain stacking by its nonplanar steric structure. An advantage of chemical imidization process is also proposed. In some cases, a copolymerization approach with an aromatic tetracarboxylic dianhydride was effective to improve the thermal expansion property. The results suggest that the H″‐PMDA‐based PI systems can be promising candidates for novel high‐temperature plastic substrate materials in electronic paper displays. A potential application as optical compensation film materials in liquid crystal displays (LCD) is also proposed in this work. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
5.
Direct On‐Surface Patterning of a Crystalline Laminar Covalent Organic Framework Synthesized at Room Temperature 下载免费PDF全文
Alejandro de la Peña Ruigómez David Rodríguez‐San‐Miguel Dr. Kyriakos C. Stylianou Dr. Massimiliano Cavallini Dr. Denis Gentili Dr. Fabiola Liscio Prof. Silvia Milita Dr. Otello Maria Roscioni Dr. Maria Luisa Ruiz‐González Carlos Carbonell Prof. Daniel Maspoch Dr. Rubén Mas‐Ballesté Dr. José Luis Segura Dr. Félix Zamora 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10666-10670
We report herein an efficient, fast, and simple synthesis of an imine‐based covalent organic framework (COF) at room temperature (hereafter, RT‐COF‐1 ). RT‐COF‐1 shows a layered hexagonal structure exhibiting channels, is robust, and is porous to N2 and CO2. The room‐temperature synthesis has enabled us to fabricate and position low‐cost micro‐ and submicropatterns of RT‐COF‐1 on several surfaces, including solid SiO2 substrates and flexible acetate paper, by using lithographically controlled wetting and conventional ink‐jet printing. 相似文献
6.
Luxian Zeng Pengqing Liu Ting Wu Sheng Wang Guangdou Ye Jianjun Xu 《Journal of Macromolecular Science: Physics》2013,52(12):2401-2411
A new type of thermotropic liquid crystalline aromatic poly(ether ester) (PEE) was prepared from 1,3-bis(4′-carboxyphenoxy)benzene, 1,4-diacetoxybenzene, and p-acetoxybenzoic acid through a melt transesterification process. The rheological behavior of blends of poly(phenylene sulfide) (PPS) with PEE was studied using a high-pressure capillary rheometer with the shear rate range of 50 s?1 to 3000 s?1. The results show that according to the range of shear rate, the flow curves of PEE/PPS blends can be divided into three zones: a first shear-thinning zone (n < 1, “n” represents non-Newtonian indexes), a shear-thickening zone (n > 1), and a second shear-thinning zone (n < 1), and the former two zones are more obvious with the increase of PEE content or elevated temperature. In the second shear-thinning zone, the PPS melt is close to a Newtonian fluid at high temperature and high shear rate; meanwhile the non-Newtonian behavior of the PPS melt at high temperature is enhanced with the addition of PEE. The apparent viscosity of PPS melts sharply dropped after adding PEE, especially at relatively low temperature and low shear rate. The curve of apparent viscosity vs. shear rate starts to flatten out after adding PEE, suggesting that the addition of PEE lowers the sensitivity of PPS to shear rate. As the content of PEE increases, the activation energy of the viscous flow, ΔEη, of PPS decreases, which means that adding PEE weakens the temperature sensitivity of the apparent viscosity of the PPS melt. It can clearly be seen that the addition of PEE is beneficial to the processing of PPS. 相似文献
7.
J. C. Abed R. Mercier J. E. McGrath 《Journal of polymer science. Part A, Polymer chemistry》1997,35(6):977-987
Several aromatic dicyanate monomers have been synthesized bearing para-linked strong electron withdrawing groups, such as phenylphosphine oxide, sulfone, and carbonyl. These groups increased the reactivity of the cyanate functional groups and eliminated the need for curing catalysts. However, an undesirable decrease in the processing window between the monomer melting point and the onset of cure was also generally observed. An arylene ether phenyl phosphine oxide system was designed that displayed several attractive characteristics such as a low softening point, a wide processing window, cure with no catalyst, high Tg and high char yield in air, suggesting that these new thermosets might show good fire resistance. The dicyanate ester monomers were synthesized in high yield by reacting various bisphenols with cyanogen bromide in the presence of triethylamine. The high reactivity of the cyanate functional groups required that the cyanation reaction be conducted at temperature below 0°C in order to prevent imidocarbonate side reactions. Proton NMR and FT-IR were used to characterize these monomers. The cyclotrimerization curing process was monitored by the disappearance of the carbon-nitrogen triple bond stretch (2270 cm−1). An optimal cure schedule was determined and the cured polycyanurate networks were characterized by DSC, DMTA, and TGA. Tg values were typically > 250°C and 5% weight loss values were observed by TGA in air above 400°C. Several of the dicyanate monomers with sufficiently large processing windows were cured into single lap shear adhesive bonds onto titanium 6/4 and the measurements are reported herein. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 977–987, 1997 相似文献
8.
Gang Liu Yan‐Hu Li Wan‐Yi Tan Zhi‐Cai He Xiao‐Tie Wang Chi Zhang Prof. Yue‐Qi Mo Prof. Xu‐Hui Zhu Prof. Junbiao Peng Prof. Yong Cao 《化学:亚洲杂志》2012,7(9):2126-2132
A new series of monoammonium‐based organic electrolytes with the tetrafluoroborate (BF4?) counteranion have been synthesized. Replacing the pendant ethyl groups in the fluorenyl unit with 4‐ethoxyphenyl groups dramatically improves both solubility and morphological stability. The characterization of the alcohol‐processable amorphous ionic compounds as an electron‐injection layer in organic light‐emitting diodes (OLEDs) reveals that the organic electrolyte that comprises a rigid linear‐conjugated unit provides better device performance, with respect to its counterpart containing a branched bulky moiety. The capability of these compounds to facilitate electron injection from air‐stable aluminum metal is preliminarily discussed on the basis of the investigations of the electron‐only devices and photovoltaic experiments. 相似文献
9.
《先进技术聚合物》2018,29(2):921-933
This study described approaches for improving the film ductility of colorless cycloaliphatic polyimides (PIs). An unexpected toughening effect was observed when a PI derived from pyromellitic dianhydride (PMDA) and 4,4′‐methylenebis(cyclohexylamine) was modified by copolymerization with a low isophoronediamine (IPDA) content of 5 to 30 mol%, despite there being no film‐forming ability in the homo PMDA/IPDA system. For example, at an IPDA content of 20 mol%, the copolymer showed significantly improved film toughness (maximum elongation at break, εb max = 57%), excellent optical transparency (light transmittance at 400 nm, T400 = 83.7%), and a high glass transition temperature (Tg = 317°C). This toughening effect can be interpreted on the basis of the concept of chain slippage. In this study, the PIs derived from bicyclo[2.2.2]octane‐2,3,5,6‐tetracarboxylic dianhydride (H‐BTA) with various diamines were also systematically investigated to evaluate the potential of H‐BTA‐derived systems. The combinations of H‐BTA with ether‐containing diamines led to highly tough PI films (εb max > 100%) with very high Tgs, strongly contrasting with the results of an earlier study. The observed excellent properties are related to the steric structure of H‐BTA. Our interest also extended to the solution processability. A copolyimide derived from H‐BTA with a sulfone‐containing diamine and an ether‐containing diamine achieved a very high optical transparency (T400 = 86.8%), a very high Tg (313°C), and good ductility (εb max = 51%) while maintaining solution processability. Thus, these approaches enabled us to dramatically improve the ductility of cycloaliphatic PI films that have, to date, been considered brittle. 相似文献
10.
Qingxuan Li Xingzhong Fang Zhen Wang Lianxun Gao Mengxian Ding 《Journal of polymer science. Part A, Polymer chemistry》2003,41(21):3249-3260
2,2′,3,3′‐Oxydiphthalic dianhydride (2,2′,3,3′‐ODPA) and 2,3,3′,4′‐ODPA were synthesized from 3‐chlorophthalic anhydride with 2,3‐xylenol and 3,4‐xylenol, respectively. Their structures were determined via single‐crystal X‐ray diffraction. A series of polyimides derived from isomeric ODPAs with several diamines were prepared in dimethylacetamide (DMAc) with the conventional two‐step method. Matrix‐assisted laser desorption/ionization time‐of‐flight spectra showed that the polymerization of 2,2′,3,3′‐ODPA with 4,4′‐oxydianiline (ODA) has a greater trend to form cyclic oligomers than that of 2,3,3′,4′‐ODPA. Both 2,2′,3,3′‐ODPA and 2,3,3′,4′‐ODPA based polyimides have good solubility in polar aprotic solvents such as DMAc, dimethylformamide, and N‐methylpyrrolidone. The 5% weight‐loss temperatures of all polyimides were obtained near 500 °C in air. Their glass‐transition temperatures measured by dynamic mechanical thermal analysis or differential scanning calorimetry decreased according to the order of polyimides on the basis of 2,2′,3,3′‐ODPA, 2,3,3′,4′‐ODPA, and 3,3′,4,4′‐ODPA. The wide‐angle X‐ray diffraction of all polyimide films from isomeric ODPAs and ODA showed some certain extent of crystallization after stretching. Rheological properties revealed that polyimide (2,3,3′,4′‐ODPA/ODA) has a comparatively lower melt viscosity than its isomers, which indicated its better melt processability. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3249–3260, 2003 相似文献