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991.
Aromatic triblock polymers were synthesized, characterized, and tested as protective coatings for stone surfaces. Syntheses were carried out by a ring opening polymerization process from specifically synthesized monomers ((3S)‐6‐methyl‐3‐phenyl‐1,4‐dioxan‐2,5‐dione or 1,4‐benzodioxepin‐3‐methyl‐2,5‐dione) and a perfluoropolyether diol (Fluorolink D10‐H), as chain initiator. Polymers were characterized through spectroscopic and analytical techniques while their stability under photo‐oxidative conditions was tested using a Solar Box. An excellent stability to environmental conditions was noticed with very low degradation during accelerated aging tests up to 1000 h, as detected by FTIR, molecular weight, DSC and weight loss. Furthermore, these polymers formed an excellent protective coating on the stone surface as shown by capillary water absorption test. Finally, as expected, very stable coatings were obtained as shown by aging tests. The stone surface showed negligible changes of color and a good hydrorepellency confirming a good durability of treatments. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43377. 相似文献
992.
993.
994.
A germyl‐bridged lanthanocene chloride, Me2Ge(tBu‐C5H3)2LnCl (Ln = Nd; (Cat‐ Nd ), was prepared and successfully used as single catalyst to initiate the ring‐opening polymerization of ε‐caprolactone (ε‐CL) for the first time. Under mild conditions (60°C,[ε‐CL]/[Ln] = 200, 4 h), Cat‐ Nd efficiently catalyzes the polymerization of ε‐CL, giving poly(ε‐caprolactone) (PCL) with high molecular weight (MW) (>2.5 × 104) in high yield (>95%). The effects of molar ratio of [ε‐CL]/Cat‐Nd, polymerization temperature and time, as well as solvent were determined in detail. When the polymerization is carried out in bulk or in petroleum ether, it gives PCL with higher MW and perfect conversion (100%). The higher catalytic activity of this neodymocene chloride could be ascribed to the bigger atom in the bridge of bridged ring ligands. Some activators, such as NaBPh4, KBH4, AlEt3, and Al(i‐Bu)3, can promote the polymerization of ε‐CL by Cat‐ Nd, which leads to an increase both in the polymerization conversion and in the MW of PCL. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 1212–1217, 2012 相似文献
995.
In this study, a novel well‐defined epoxy mid‐chain functional macromonomer of poly(ε‐caprolactone) (PCL) has been synthesized by ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) and epoxidation on workup with 3‐chloroperoxybenzoic acid. The ROP of ε‐CL monomer in bulk at 110°C, by means of a dihydroxy functional initiator namely, 3‐cyclohexene‐1,1‐dimethanol in conjunction with stannous‐2‐ethylhexanoate, (Sn(Oct)2), yielded a well‐defined PCL with a cyclohexene mid‐chain group. The epoxidation of the cyclohexene (CH) mid‐chain group of PCL was performed using 3‐chloroperoxybenzoic acid. GPC, IR, and 1H‐NMR analyses revealed that a low‐polydispersity macromonomer of PCL with the desired cyclohexene oxide (CHO) functionality at the mid‐chain was obtained. The photoinduced cationic polymerizations of this macromonomer yielded comb‐shaped and graft copolymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
996.
O’Dae Kwon D.K. Kim J.H. Yoon Y.C. Kim Y.H. Jang M.H. Shin 《Microelectronics Journal》2009,40(3):570-573
A new whispering cave mode (WCM), a three-dimensional (3D) case of Lord Rayleigh's 2D whispering gallery modes, based upon 3D total internal reflection is presented, where GaAs quantum well (QW) near-vertical microdisk resonators exhibit a strong carrier-photon coupling for the QW carriers located in the Rayleigh band, generating 2D-to-1D carrier phase transitions of photonic quantum ring (PQR). It is a ‘photonic’ quantum corral effect (PQCE), whose simulation work produces a tangled web pattern of imminent recombinant carriers in picoseconds timescale. The PQCE is responsible for the ultralow threshold currents below 300 nA for a single mode GaAs PQR laser, and a prototype GaN PQR laser with a threshold near and below 1 μA. 相似文献
997.
粘结层对超声马达定子振动特性的影响 总被引:5,自引:1,他引:4
基于环形波型超声马达定子振动有限元模型,详细分析研究了粘结层对超声马达定子振动特性的影响。通过对压电陶瓷机电耦合效应的分析计算,给出了粘结层厚度、粘结材料特性与定子表面质点运动轨迹之间的关系,确定了超声马达粘结层材料特性要求及粘结层厚度的范围。此外,该论文针对由于粘结层的原因引起超声马达定子制作质量不稳定的问题,给出了粘结中所必须注意的问题。研究结果表明:该文的计算模型和分析是准确有效的。 相似文献
998.
Qingjun Zhu Junko N. Kondo Satoshi Inagaki Takashi Tatsumi 《Topics in Catalysis》2009,52(9):1272-1280
Aluminosilicate H/CHA and H/MTF zeolites show remarkably different catalytic activities in the methanol and ethanol transformations
although they have similar pore size of 8-membered ring structures. Moreover, the produced ethylene is further converted on
H/CHA, but H/MTF is not active for the ethylene transformation. The correlations between the distinct catalytic differences
and their intrinsic structural properties, including topology and acidity, are discussed. 相似文献
999.
苗彦 《组合机床与自动化加工技术》2001,1(3):34-35,45
用修配法装置可获得较高的装配精度,修配环修配量的确定是该装置配法的主要问题,本文仅对此进行阐述。 相似文献
1000.
介绍广州地铁二八号线石会区间轨排井的锚索围护结构的施工过程,在地质条件差,雨季地下水丰富,锚索体系部分预应力失效引起基坑变形过大的情况下,利用支护结构本身加强和设置环框梁,既满足了轨排施工需要预留较大孔洞的需要,也保证了基坑安全,为类似支护工程提供参考。 相似文献