Controlled Synthesis of Branched Polystyrene via Free Radical Polymerization of Novel Chain Transfer Monomer

Cui-Ping Li,Jia-Qiang Wang,Jun Lin,Yan Shi,Zhi-Feng Fu 한국고분자학회 2011 Macromolecular Research Vol.19 No.8

The free radical polymerization of styrene was carried out in the presence of a new found chain transfer monomer, p-vinyl benzene sulfonyl chloride (VBSC), which possesses both a chain transfer group and a polymerizable double bond. Branched polystyrene was formed during the polymerization, as indicated by multi-peaks gel permeation chromatography (GPC) curves of the products, the increase in the number-average molecular weight and molecular weight distribution along with monomer conversions. The structure of the obtained polystyrene was analyzed by 1H nuclear magnetic resonance (NMR) spectroscopy. The results showed that with increasing VBSC in the feed, the degree of branching and VBSC unit in the copolymer increased and a shortest polystyrene arm arose from the highest VBSC content in the feed, suggesting that the composition and structure of the branched polystyrenes could be tuned by the amount of VBSC in the feed. By tracing the structure change in the copolymer at various stages of polymerization, the main polymerization process can be regarded as the copolymerization of VBSC with styrene first and then chain transfer to polymeric radical to form branched polystyrene. This strategy is facile and less expensive than the other method.

Controlled Synthesis of Branched Polystyrene via RAFT Technique in the Presence of Chain Transfer Monomer p-Vinyl Benzene Sulfonyl Chloride

Cui-Ping Li,Jia-Qiang Wang,Yan Shi,Zan Liu,Jun Lin,Zhi-Feng Fu 한국고분자학회 2012 Macromolecular Research Vol.20 No.8

Branched polystyrene was first obtained via a reversible addition-fragmentation chain transfer (RAFT)process in the presence of chain transfer monomer p-vinyl benzene sulfonyl chloride (VBSC) in benzene at 60 oC with 2-(ethoxycarbonyl)prop-2-yl dithiobenzoate as the RAFT agent and 2,2-azobisisobutyronitrile as an initiator. During the RAFT polymerization, VBSC played the role of branching agent. It could not only copolymerized but also acted as a chain transfer agent due to the polymerizable vinyl group and sulfonyl chloride chain transfer group in the VBSC. Gel permeation chromatography (GPC) traces demonstrated that the number-average molecular weights and molecular weight distributions increased along with monomer conversion. Compared with the RAFT process without VBSC, the resulting polymers had broad molecular weight distributions and the sulfonyl functionality of the resultant polymer at the branching point, indicating the formation of branched polystyrene. The structure of the obtained polystyrene was further analyzed by proton nuclear magnetic resonance (1H NMR) spectroscopy. The findings indicated that the branched polystyrene was mainly formed via the RAFT copolymerization of VBSC and styrene firstly to form polystyrene bearing pendant sulfonyl chloride group, and then the pendant sulfonyl chloride group acted as the chain transfer agent to generate the branched structure. In addition, the degree of branching and VBSC unit in copolymer increased along with the VBSC in the feed, implying that composition and structure of the branched polystyrenes could be tuned by the amount of VBSC in the feed.

Aldol-Like Carbon-Carbon Condensation for Pyridyl Substituted Chlorins

Jia-Zhu Li,Young Key Shim,Bing-Cun Cui,Jin-Jun Wang 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.7

Experimental and Numerical Research on Process Formability in Magnetic Pulse Forming of AZ31 Magnesium Alloy Sheets

Jun-Rui Xu,Jun-Jia Cui,Guangyong Sun,Yan-Rong Li,Chun-Feng Li 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

The plain strain of AZ31 magnesium alloy sheet in magnetic pulse forming was investigated by numerical simulation and experimental method. Combination of uniform pressure coil and Holmberg's specimen was employed to evaluate the plain strain of AZ31 sheet. The numerical simulation for magnetic pulse plain strain of AZ31 sheet is performed by means of ANSYS FEA software. The magnetic flux density of uniform pressure coil was distributed uniformly, especially at the center of gauged area of AZ31 sheet directly in relation to the deformation behavior of AZ31 sheet. The velocity of typical point increases as increasing energy, and the more position closes to the center of sheet the higher velocity achieves. The forming height is increased with increasing discharge voltage. Compared with C=768 μF and C=1536 μF, the capacitance of 1152 μF is more effective for forming, which is confirmed by experiments. The peak velocity at the center of sheet is about 105 m/s. The major strains of magnetic pulse plane strain lie approximately in the strain ranges of 5.83-6.45%. However, the 3.22-3.82% (major strain) are the limit strains in quasi-static condition. The experimental results indicate that the major strain of AZ31 sheet improves about 75% compared with the quasi-static case.

Three 1-(4-Hydroxyphenyl)-1H-1,2,4-triazole-based Cd(II) Coordination Polymers Directed by Aromatic Polycarboxylate Coligands

Xiao-Jun Zhao,En-Cui Yang,Fang Jia, 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.11

The reactions of 1-(4-hydroxyphenyl)-1H-1,2,4-triazole (hptrz) and inorganic Cd(II) salts with different aromatic polycarboxylic acids in mixed-solvent led to the formation of three new crystalline coordination polymers, {[Cd(H2O)2(hptrz)(Hbtc)]n·CH3OH·H2O} 1, [Cd2(H2O)2(hptrz)2(tp)2]n 2, and {[Cd(H2O)2(hptrz)- (OH-ip)]n·DMF·H2O} 3 (H3btc = 1,3,5-benzenetricarboxylic acid, H2tp = terephthalic acid, and OH-H2ip = 5- hydroxyisophthalic acid), which were fully characterized by elemental analysis, IR spectroscopy, single crystal X-ray crystallography, thermogravimertric analysis and luminescence spectra. Structure determination revealed that one-dimensional (1-D) polymeric chains for 1 and 3, and 2-D layered structure for 2 are significantly directed by the coordination mode of the carboxylate groups from aromatic coligands. In contrast, the terminal hptrz ligand affords its uncoordinated phenolic OH group to form classical H-bond interactions with coordinated water and/or carboxylate groups, which are responsible for the formation of 3-D supramolecular networks. In addition, the three solid coordination polymers with considerable thermal stability present strong hptrz-based fluorescence emissions at room temperature.

Aldol-Like Carbon-Carbon Condensation for Pyridyl Substituted Chlorins

Li, Jia-Zhu,Cui, Bing-Cun,Wang, Jin-Jun,Shim, Young-Key Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.7

Three 1-(4-Hydroxyphenyl)-1H-1,2,4-triazole-based Cd(II) Coordination Polymers Directed by Aromatic Polycarboxylate Coligands

Yang, En-Cui,Jia, Fang,Wang, Xiu-Guang,Zhao, Xiao-Jun Korean Chemical Society 2008 Bulletin of the Korean Chemical Society Vol.29 No.11

Isolation and Preliminary Identification of a Novel Microorganism Producing Aspartame from Soil Samples

Jian Dong Cui,Ya Nan Zhang,Gui Xia Zhao,Shi Ru Jia,Guo Qun Zhao,Si Zhang,Jun Lu 한국식품과학회 2010 Food Science and Biotechnology Vol.19 No.2

To develop a new method for producing aspartame (APM), a simple and efficient strategy for the isolation of certain microorganisms producing APM from soil samples was designed. A newly strain with secreting certain specific dipeptidase to directly synthesize APM from the substrates of L-aspartic acid (L-Asp) and Lphenylalanine methyl ester (L-PM) without protection for amino acid side chains was screened from soil samples. APM concentration in reaction mixture was quantified by high performance liquid chromatography (HPLC), yield reached 0.015 g/L. Examination of the general morphological characteristics and data from the sequence analysis of the rDNA-ITS gene led to identification of the isolate as a strain of fungal endophyte spp. The newly isolated strain had a high potential for application in industrial processes for APM production. In particular, this new method was low cost for synthesis of APM during the reaction due to avoiding protection for amino acid side chains and optical resolution of the mixtures. As we known it, this is first report that a newly strain with a high potential for selective synthesis of the APM was isolated from soil.

Life-Cycle Reliability Evaluation of Semi-Rigid Materials Based on Modulus Degradation Model

Jiupeng Zhang,Shengchao Cui,Jun Cai,Jianzhong Pei,Yanshun Jia 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.6

The dynamic modulus of semi-rigid material is one of the important material parameters widely used in the design and evaluate ofasphalt pavement, which has a great effect on the reliability, healthy condition and service life of pavement. To show the three-phasedegradation process of dynamic modulus accurately and calculate the time-dependent reliability based on fatigue damage, thedegradation models based on non-linear fatigue damage and improved Wei-bull distribution modulus degradation are established andtestified in this paper, considering the threshold of normalized modulus. Then the reliability models based on the two abovedegradation process models are evaluated. Finally, the reliability analysis procedure is established using Monte Carlo (MC) methodand the corresponding calculation is conducted using Matlab. Cement stabilized macadam is used as an example in this paper. Results show that non-linear fatigue damage and improved Wei-bull distribution modulus degradation models can indicate threephasedegradation process of semi-rigid material modulus better and the reliability based on the proposed two models was moreaccurate to the actual situation.

Microstructure design and energy transfer in Gd2(WO4)3: Yb3+/Er3+ phosphors

Wang Yunfeng,Chen Jun,Wei Xiaoyu,Cui Shaobo,Jia Xiao 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.78 No.9

Rare-earth-doped upconverison luminescent (UCL) materials have wide application prospects in the feld of nanoptoelectronics technology. However, achieving highly efficient UCL materials is still a big challenge due to the serious nonradiative energy loss in the host materials. In this research, Gd2(WO4)3: Yb3+, Er3+ inverse opal photonic crystals (IOPCs) were prepared using a polymethylmethacrylate (PMMA) template-assisted method, and the efects of modulations of the IOPC structure on UC emission properties of Er3+ were investigated systemically. As a result, the emission intensity of 2 H11/2- 4 I15/2 in IOPC was found to be suppressed 37.4%, and the radiative lifetimes of 4 S3/2- 4 I15/2 were prolonged 1.55 times. The effects of the doping concentration on the reciprocal of fluorescence lifetimes of 4 S3/2- 4 I15/2 between the IOPC and the reference (REF) samples showed that the cross-energy transfer (CET) rate and the electronic transition rate were greatly inhibited, which could be due to the effect of the modulation of the effective index on the radiative transition rate and on the decrease of nonradiative transition rate caused by periodic thin-walled structure of IOPC. The power-dependent UC emission properties validated the supposition that the IOPC structure could be effectively suppressed the local thermal effect and thermal quenching. This research presents a further step in the exploration of the new kind of UCL materials with high luminous efficiency.