The Crystallization and Melting Behaviors of PDLA-b-PBS-b-PDLA Tri-block Copolymers

In this study,the poly(D-lactide)-block-poly(butylene succinate)-block-poly(D-lactide)(PDLA-b-PBS-b-PDLA)triblock copolymers with a fixed length of PBS and various lengths of PDLA are synthesized,and the crystallization behaviors of the PDLA and PBS blocks are investigated.Although both the crystallization behaviors of PBS and PDLA blocks depend on composition,they exhibit different variations.For the PDLA block,its crystallization behaviors are mainly influenced by temperature and block length.The crystallization signals of PDLA block appear in the B-D 2-2 specimen,and these signals get enhanced with PDLA block length.The crystallization rates tend to decrease with increasing PDLA block lendth during crystallizing at 90 and 100°C.Crystallizing at higher temperature,the crystallization rates increase at first and then decrease with block length.The crystallization rates decrease as elevating the crystallization temperature.The melting temperatures of PDLA blocks increase with block lengths and crystallization temperatures.For the PBS block,its crystallization behaviors are mainly controlled by the nucleation and confinement from PDLA block.The crystallization and melting enthalpies as well as the crystallization and melting temperatures of PBS block reduce as a longer PDLA block has been copolymerized,while the crystallization rates of the PBS block exhibit unique component dependence,and the highest rate is observed in the B-D 2-2 specimen.The Avrami exponent of PBS crystallites is reduced as a longer PDLA block is incorporated or the sample is crystallized at higher temperature.This investigation provides a convenient route to tune the crystallization behavior of PBS and PLA.     

Insights into the interactions between DNA and an infinite clamp-like copper (II) complex

Transition Metal Chemistry - A Cu(II) complex [Cu2(phen)2(NAB)2(HO)]n (phen?=?1, 10-phenanthroline and NABH?=?p-N, N-(2-hydroxyethyl)amino benzoic acid) was synthesized, and...     

Copolymer synthesis of poly(L-lactide-b-DMS-L-lactide) via the ring opening polymerization of L-lactide in the presence of α,ω-hydroxylpropyl-terminated PDMS macroinitiator

Various amounts of hydroxy terminated PDMS were linked into PLLA chains via in-situ ring opening polymerization at a very low content of SnOt₂. The ¹H and FTIR spectra provided evidence for the incorporation of the PDMS in the PLLA chains. The molecular weights, T_g, T_m, crystallinity and the heats of fusion decreased as the feed mole ratio of PDMS/LLA in the block copolymer increased. The molecular weight distribution broadened as the content of the PDMS increased, due the occurrence of two initiation and propagation mechanisms. Linking PDMS into the PLLA chains improved its thermal stability. © 1996 John Wiley & Sons, Inc.     

Effects of guanidinium cations on structural,optoelectronic and photovoltaic properties of perovskites

Guanidinium (GA) cations are intentionally introduced in MAPbl3 perovskite by considering its potential capability of stabilizing the material through plenty of...     

Upper Bound Shakedown Analysis of Plates Utilizing the C1 Natural Element Method

This paper proposes a numerical solution method for upper bound shakedown analysis of perfectly elasto-plastic thin plates by employing the C1 natural element m...     

真空条件下LiCl溶液蒸发量随浓度变化规律研究

除湿溶液再生是除湿空调系统的核心过程,为了提高除湿溶液再生效率,以蒸发量作为评价标准,在不同的真空度下对不同浓度LiCl溶液进行再生。对不同再生条件下,溶液的再生情况进行数学模拟及实验研究,并将模拟结果与实验结果进行对比分析,结果表明,实验结果同模拟结果具有相同的变化趋势。在6 kPa和8 kPa的压强下,LiCl溶液的蒸发量随浓度的增大先上升后下降,而在1 kPa的压强下,LiCl溶液的蒸发量随浓度的增大呈现出先下降再升高接着又下降的趋势。     

Single top partner production in the tZ channel at eγ collision in the littlest Higgs model with T-parity

Introducing the top partner is a common way to cancel the largest quadratically divergent contribution to the Higgs mass induced by the top quark. In this work, we study single top partner production in the tZ channel at eγ collision in the littlest Higgs model with T-parity(LHT). Since it is well known that polarized beams can enhance the cross section, we analyze the signal via polarized electron beams,and photon beams. we have selected two decay modes for comparison, based on the leptonic or the hadronic decays of the W and Z from the top partner. We then construct a detailed detector simulation, and choose a set of cuts to enhance signal significance. For mode A(B), the capacity for exclusion in this process at s~(1/2)=3TeV is comparable to the current experimental limits with L=1000(500) fb~(-1). If the integrated luminosity can be increased to 3000 fb~(-1), the top partner mass+mTcan be excluded up to 1350(1440) GeV at 2σ level. We also considered the initial state radiation effect, and find that this effect reduces the excluding ability of the eγ collision on the the top partner mass by approximately 10 GeV. Moreover, the ability to exclude the LHT parameter space at eγ collision complements the existing research.     

In-situ SiN combined with etch-stop barrier structure for high-frequency AlGaN/GaN HEMT

The etch-stop structure including the in-situ SiN and AlGaN/GaN barrier is proposed for high frequency applications.The etch-stop process is realized by placing an in-situ SiN layer on the top of the thin AlGaN barrier.F-based etching can be self-terminated after removing SiN,leaving the AlGaN barrier in the gate region.With this in-situ SiN and thin barrier etch-stop structure,the short channel effect can be suppressed,meanwhile achieving highly precisely controlled and low damage etching process.The device shows a maximum drain current of 1022 mA/mm,a peak transconductance of 459 mS/mm,and a maximum oscillation frequency(fmax)of 248 GHz.     

A new inorganic–organic hybrid compound constructed from polyoxoanions and rare earth coordination complexes

A new chainlike polymer, Na[Ce(dipic)(H₂O)₃]₂ [CrMo₆H₆O₂₄] · 13H₂O (H₂dipic = pyridine-2,6-dicarboxylic acid) (1), has been synthesized and characterized by elemental analysis; IR and XPS spectroscopy, TG analysis, and single-crystal X-ray diffraction. Compound (1) is built up of Anderon-type polyoxoanions as structural motifs and cerium–dipic coordination fragments as linkers to yield an unprecedented one-dimensional chain. Such chains are further in close contact forming a three-dimensional supramolecular framework with channels via extensive hydrogen-bonding interactions among polyoxoanions, dipic ligands and water molecules. Furthermore, the magnetic properties of compound (1) have been studied by measuring their magnetic susceptibility in the temperature range 2–300 K.