Synthesis and characterization of a novel liquid crystalline star‐shaped polymer based on α‐CD core via ATRP

Well‐defined side‐chain liquid crystalline star‐shaped polymers were synthesized with a combination of the “core‐first” method and atom transfer radical polymerization (ATRP). Firstly, the functionalized macroinitiator based on the α‐Cyclodextrins (α‐CD) bearing functional bromide groups was synthesized, confirmed by ¹H‐NMR, MALDI‐TOF, and FTIR analysis. Secondly, the side‐chain liquid crystalline arms poly[6‐(4‐methoxy‐4‐oxy‐azobenzene) hexyl methacrylate] (PMMAzo) were prepared by ATRP. The characterization of the star polymers were performed with ¹H‐NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM). It was found that the liquid crystalline behavior of the star polymer α‐CD‐PMMAzo_n was similar to that of the linear homopolymer. The phase‐transition temperatures from the smectic to nematic phase and from the nematic to isotropic phase increased as the molecular weight increased for most of these samples. All star‐shaped polymers show photoresponsive isomerization under the irradiation with Ultraviolet light. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

连铸板坯表面星状裂纹的形成与控制

研究了连铸成品板坯表面的微裂纹缺陷－板坯表面星状纹的特征、形成机理、影响因素及解决措施。     

Advanced star tracker design using the charge injection device

Future space vehicles will require high-performance sensors for pointing, control, and attitude determination. When combined with unique acquisition and tracking concepts, star trackers that use a charge injection device (CID) offer high accuracy and rate tracking capability and result in decreased spatial noise and minimum size, weight, and power. Tests of a CID breadboard tracker have demonstrated an accuracy of 1 part in 17,000. This is equivalent to 1.7 arc sec for an 8° field of view. Use of flight-quality hardware and improved test equipment are expected to improve performance by a factor of approximately two.     

Net Operations (Ⅱ)-The Iterated Addition Operation of Petri Nets

This paper presents the iterated addition operation of Petri nets and discusses its application in analysis and synthesis of cycle type systems and star type systems.A group of necessary and sufficient conditions for analysis of structural properties is obtained.In addition sufficient conditions for general systems are obtained.     

双向HFC网电缆网建设

在HFC网络建设中，传统树枝型电缆网结构在双向传输中存在很多问题。采用星型结构，集中供电、集中分配入户的网络结构可以解决干扰、上行信号均衡、对用户进行有效管理等问题。     

星型聚合物的合成方法综述

概述了星型聚合物的特点和应用，较详细地介绍了星型聚合物的3种合成方法：活性阴离子聚合法、活性阳离子聚合法和活性自由基聚合法。     

Graft copolymers and high‐molecular‐weight star‐like polymers by atom transfer radical polymerization

Grafting of tert‐butyl acrylate (tBuA), methyl methacrylate (MMA), and styrene (St) monomers (M) by Cu(I)‐mediated ATRP from polystyrene (PSt) macroinitiator (M_n = 5620, polydispersity index, PDI = 1.12), containing initiating 2‐bromopropionyloxy groups (I) (bound to 34% of aromatic cores; 11 groups per backbone), was performed using conditions suitable for the respective homopolymerizations. The preparation of PSt‐g‐PtBuA in bulk using an initial molar ratio [M]₀/[I]₀ = 140 had a controlled character up to M_n = (132–148) × 10³ (PDI = 1.08–1.16). With MMA and St and using the same [M]₀/[I]₀, preliminary experiments were made; the higher the monomer conversion, the broader was the distribution of molecular weight of the products. Graft copolymerizations of all these monomers at [M]₀/[I]₀ = 840 or 1680 were successfully conducted up to high conversions. Low‐polydispersity copolymers, with very long side chains, in fact star‐like copolymers, were obtained mainly by tuning the deactivator amount in the reaction mixture. (PSt‐g‐PtBuA, DP_n,sc (DP of side chain) = 665, PDI = 1.24; PSt‐g‐PMMA, DP_n,sc = 670, PDI = 1.43; PSt‐g‐PSt, DP_n,sc = 324, PDI = 1.11). Total suppression of intermolecular coupling was achieved here. However, the low concentrations of initiator required long reaction times, leading sometimes to formation of a small amount (～5%) of low‐molecular‐weight polymer fraction. This concomitant process is discussed, and some measures for its prevention are proposed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3662–3672, 2006     

反射型单模光纤星形耦合器

本文介绍光纤局部区域网构网的一种关键器件——由2×2光纤耦合器和光纤环组成的反射型单模光纤星形耦合器的构造方法及特点。对光纤环的反射特性与耦合特性关系作理论分析。最后,报道了研制的反射型单模光纤8端口星形耦合器的实验结果。     

Melt electrospinning writing of three‐dimensional star poly(ϵ‐caprolactone) scaffolds

In the last decade, the melt‐electrospinning technique has gained attention for the production of highly porous microfibrous tissue engineering scaffolds. The possibility of processing polymers without the use of organic solvents is one of the main advantages over solution electrospinning. In this study, computer‐controlled melt‐electrospinning of a commercial poly(?‐caprolactone) and of two batches with different molecular weights of a three‐arm star poly(?‐caprolactone) by means of a screw‐extruder‐based additive manufacturing system is reported. Experimental parameters such as processing temperature, extrusion flow rate and applied voltage were studied and optimized in order to obtain non‐woven meshes with uniform fibre morphology. Applying the optimized parameters, three‐dimensional scaffolds were produced using a layer‐by‐layer approach (0 ? 90° lay‐down pattern). © 2013 Society of Chemical Industry