检索结果-南通市图书馆

Effects of Shell Composition, Dosage and Alkali Type on the Morphology of Polymer Hollow Microspheres

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2018年第1期36卷 43-48页

作者： Wei Deng Hua-Chao Guo Wei-Li Yu cheng-you kan Key Laboratory of Engineering Dielectrics and Its Application Ministry of Education School of Material Science and Engineering Harbin University of Science and Technology Department of Chemical Engineering Key Laboratory of Advanced Materials of Ministry of Education Tsinghua University

Polymer hollow microspheres were prepared by performing alkali treatment on the multilayer core/shell polymer latex particles containing carboxyl groups. Effects of the shell composition and dosage as well as alkali type on the morphology of the microspheres were investigated. Results showed that in comparison with acrylonitrile（AN） and methacrylic acid（MAA）, using butyl acrylate（BA） as the shell co-monomer decreased the glass transition temperature（T_g） of shell effectively and was beneficial to the formation of uniform and big hollow structure. Along with the increase of the shell dosage, the alkali-treated microspheres sequentially presented porous and hollow morphology, and the size of microspheres increased, while the hollow diameter increased first and then decreased, and the maximum hollow ratio reached 39.5%. Furthermore, the multilayer core/shell microspheres had better tolerance to NH_3·H_2O than to NaOH. When the molar ratio of alkali to methacrylic acid（MR_（alkali/acid）） for Na OH ranged from 1.15 to 1.30 or MRalkali/acid for NH_3·H_2O ranged from 1.30 to 2.00, the regular polymer hollow microspheres could be obtained.

关键词： Hollow microspheres Core-Shell polymer Alkali treatment Morphology

Fabrication of polymeric-Laponite composite hollow microspheres via LBL assembly

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2017年第2期28卷 367-371页

作者： Wei Deng Hua-Chao Guo Guo-An Li cheng-you kan Key Laboratory of Engineering Dielectrics and Its Application Ministry of Education School of Material Science and Engineering Harbin University of Science and Technology Key Laboratory of Advanced Materials of Ministry of Education Department of Chemical Engineering Tsinghua University

Hollow structure microspheres with composite polymeric-Laponite shells were prepared by electrostatic self-assembly of Laponite on the polymeric hollow microspheres in this *** multilayer hydrophilic core/hydrophobic shell polymer latex particles containing carboxyl groups inside were first synthesized via seeded emulsion polymerization,followed by alkali treatment,generating polymeric hollow ***,polyethyleneimine（PEI） and Laponite were alternately electrostatic adsorbed on the prepared polymeric hollow microspheres to form polymeric-Laponite composite hollow *** was indicated that the morphology of alkali-treated microspheres could be tuned through simply altering the dosage of alkali used in the post-treatment *** with the increasing of the coating layers,the zeta potential of microspheres absorbed PEI or Laponite approximately tended to be constant respectively,and the thickness of Laponite layer around the hollow microspheres increased clearly,getting more uniform and ***,the corresponding polymeric-Laponite hollow microspheres showed high pressure resistance ability compared to the polymeric hollow microspheres.

关键词： Composite microspheres Hollow structure Laponite Osmotic swelling LBL assembly

Influences of Electrolytes on the Soap-free Emulsion Copolymerization of St-MMA-AA

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2006年第11期17卷 1503-1506页

作者： Rong Long LI cheng you kan Yi DU Ze Ping LI Department of Chemical Engineering and Key Laboratory of Advanced Materials of Ministry of Education Tsinghua University Beijing 100084

Monodisperse functional polymer microspheres with different particle size and with clean surface were prepared by batch soap-free emulsion polymerization of styrene, methyl methacrylate and acrylic acid in the presence of salts, and the influences of type and amount of electrolytes on polymerization process and particle morphology were investigated. Results showed that there was a critical concentration for different electrolyte to make polymerization process and the resultant emulsion stable, and the particle size increased with the increase of electrolyte concentration. The effect of metal ions was Ca^2＋〉〉K^＋〉Na^＋〉Li^＋, and the effect of haloids was Br〉Cl〉F. Keywords： Electrolyte, soap-free emulsion polymerization, polystyrene, latex particle morphology.

关键词： Electrolyte soap-free emulsion polymerization polystyrene latex particle morphology.

Preparation of sulphonate-containing core/shell latex particles via seeded emulsion copolymerization

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2010年第10期21卷 1259-1262页

作者： Ji Shuai Wang Wei Deng Yun Shen Chen cheng you kan Department of Chemical Engineering and Key Laboratory of Advanced Materials of Ministry of Education Tsinghua University Belting 100084 China

In this study, P（St-MAA） seed latex particles were first prepared via soap-free emulsion polymerization of styrene （St） and methacrylic acid （MAA）, then the seed particles were allowed to swell with St at room temperature, and the P（St-MAA）/P（St- NaSS） core/shell latex particles were then synthesized via seeded emulsion copolymerization of St and sodium styrene sulphonate （NaSS） using AIBN as initiator in the presence of N,N^-methylenebisacrylamide （BAA, water-soluble crosslinker）. Results showed that the polymerization could be carried out smoothly when the ratio of BAA to total monomers was less than 3 mol%, the narrow dispersed P（St-MAA） seed particles with the diameter of 150 nm and the P（St-MAA）/P（St-NaSS） core/shell latexes with the particle size of about 200 nm were synthesized. When the 25/75 mole ratio of NaSS/（St ＋ MAA） and 2 tool% of BAA were used in the seeded emulsion polymerization, the resulted P（St-MAA）/P（St-NaSS） latex product showed a low weight loss after water extraction, and the NaSS unit content in the whole particle and in the shell reached 11.7 mol% and 34.6 mol%, resoectivelv.

关键词： seeded emulsion polymerization Sulphonate-containing particles Sodium styrene sulphonate N,N^-Methylenebisacrylamide

Synthesis of vegetable oil based polyol with cottonseed oil and sorbitol derived from natural source

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2011年第11期22卷 1289-1292页

作者： Lian Kun Jia Li Xiang Gong Wen Jiao Ji cheng you kan Department of Chemical Engineering and Key Labolzttory of Advanced Materials of Education Ministry Tsinghua Universit3 Beijing 100084 China

In order to prepare the polyol with all bio-based components as raw materials,cottonseed oil was first epoxidized by peroxyformic acid generated in situ from hydrogen peroxide and formic acid,and the cottonseed oil based polyols with variable hydroxyl value were then prepared by the ring-opening of epoxidized cottonseed oil with sorbitol,which is a multi-functional hydroxyl compound derived from a natural *** chemical structure of the products was characterized with FTIR analysis, and the residual epoxy oxygen content and hydroxyl value of the polyol versus the ring-opening time were investigated.

关键词： Vegetable oil Sorbitol Polyol Epoxidation Ring opening reaction

Preparation of multihollow P(St-MAA) particles by sequence soap-free/soap emulsion polymerization and followed by stepwise alkali/acid posttreatment

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2007年第6期18卷 741-743页

作者： Rong Long Li cheng you kan Ze Ping Li Yi Du Yan Nan Cui Department of Chemical Engineering and Key Laboratory of Advanced Materials of Ministry of Education Tsinghua UniversityBeijing 100084China

The effects of ionic emulsifier, sodium dodecylbenzene sulfate (SDBS), on the formation of the multihollow structures in sub-micron sized polymer particles produced by alkali/acid posttreatment were investigated. The original latex particles with narrow size distribution were synthesized by a new sequence emulsifier-free/emulsifier emulsion copolymerization of styrene (St) and methacrylic acid (MAA). Results indicated that the pore size decreased and the pore number increased with the increase of SDBS amount, and the morphology of the posttreated latex particles was also significantly influenced by the introducing time of SDBS in the preparation of the original latex particles, and a suitable introducing time was 3 h of polymerization. (c) 2007 cheng you kan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

关键词： multihollow latex particles morphology emulsion polymerization emulsifier

INFLUENCES OF ACID POST-TREATMENT ON THE MORPHOLOGY OF SOAP-FREE P(MMA-EA-MAA)PARTICLES PREPARED BY SEEDED EMULSION POLYMERIZATION

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2005年第5期23卷 479-485页

作者： Kai kang cheng-you kan Yi Du De-shan Liu Department of Chemical Engineering,School of Materials Science and Engineering,Tsinghua University,Beijing 100084,China Tsinghua Univ Dept Chem Engn Sch Mat Sci & Engn Beijing 100084 Peoples R China

Soap-free poly（methyl methacrylate-ethyl acrylate-methacrylic acid） latex particles with narrow size distribution were synthesized by seeded emulsion polymerization, and the porous particles were created by a stepwise alkali/acid treatment method. Effects of acid treatment conditions on the particle morphology were investigated. Results show that one to three pores were formed inside most of particles after post-treatment. At pH 7.0, when the treatment temperature was lower than 70℃, the size of particles and the volume of pores remained almost unchanged, and these two values increased significantly when the temperature was higher than 70℃. Both the particle size and the pore volume decreased with the increase of initial pH value and treatment time in the acid treatment. As the pH was below 4.0 and the treatment time was longer than 180 min, the particles shrunk in size.

关键词： Soap-free emulsion polymerization Particle morphology Porous structure Acid treatment Methyl methacrylate based copolymer.

Protective effect of glucocorticoid-free immunosuppressive regimen in allogenic islet transplantation

在线全文

学校读者我要写书评

暂无评论

Hepatobiliary & Pancreatic Diseases International 2006年第1期5卷 43-47页

作者： cheng-you Du and Er-kan Xu Department of Hepatobiliary Surgery & Liver Transplantation, First Affiliated Hospital, Chongqing University of Medical Sciences, Chongqing 400016, China Department of Hepatobiliary Surgery & Liver Transplantation First Affiliated Hospital Chongqing University of Medical Sciences Chongqing 400016 China. duchengyou@***

BACKGROUND: The most common complication after allogenic islet transplantation is rejection. This study was to evaluate the effect of anti-rejection of glucocorticoid-free immunosuppressive regimen on allogenic islet transplantation. METHODS: Tacrolimus(FK506)+mycophenolate mofetil (MMF) and FK506+MMF+prednisone (Pred) were administered respectively for 2 weeks to inhibit rejection after allogenic islet transplantation in rats, which were compared with the control group. The concentrations of blood glucose, insulin and C-peptide were determined dynamically in recipients and the sites of transplantation were observed morphologically. RESULTS: As compared with the control group without immunosuppressive agents, FK506+MMF and FK506+MMF+Pred could prolong the survival time of grafts significantly. There were many morphologically intact islets in the liver of recipients 2 months after transplantation. Group FK506+MMF kept normal levels of blood glucose, insulin and C-peptide beyond 60 days after transplantation. In contrast, group FK506+MMF+Pred secreted less C-peptide(P<0.05) and maintained a higher level of blood glucose concentration (P<0.01) after the operation. There was no significant difference in insulin concentrations between the two groups. The level of blood glucose beyond the first 2 weeks after drug withdrawal in group FK506+MMF+Pred decreased obviously (P<0.05), and the secretion of insulin　and C-peptide increased. These results were compared with　those the first 2 weeks after transplantation and the first 2　weeks after drug withdrawal. CONCLUSIONS: Both regimens of FK506+MMF and FK506+MMF+Pred could provide effective immunosup-pression. Moreover the combined glucocorticoid-free immunosuppressive strategy of low-dose FK506 and MMF could protect islet grafts in islet transplantation without diabetogenic side-effects.

关键词： immunosuppressive agent islets of langerhans transplantation glucocorticoid rat

反应介质pH值和前驱体用量对PSt/TiO_2复合微球结构形态及TiO_2空心微球形貌的影响

在线全文

学校读者我要写书评

暂无评论

高分子学报 2012年第4期22卷 391-397页

作者：程冠之胡杨邓伟阚成友清华大学化工系教育部先进材料重点实验室北京100084

首先用聚乙烯亚胺(PEI)对粒径为360 nm的单分散无皂聚苯乙烯(PSt)乳胶粒进行修饰,得到表面荷正电的PSt种子乳液,然后将其滴加到溶有钛酸正丁酯(TBT)的乙醇与水的混合介质中,通过溶胶-凝胶(sol-gel)法制备出了核壳结构PSt/TiO2复合微球,... 详细信息

首先用聚乙烯亚胺(PEI)对粒径为360 nm的单分散无皂聚苯乙烯(PSt)乳胶粒进行修饰,得到表面荷正电的PSt种子乳液,然后将其滴加到溶有钛酸正丁酯(TBT)的乙醇与水的混合介质中,通过溶胶-凝胶(sol-gel)法制备出了核壳结构PSt/TiO2复合微球,系统研究了体系pH和TBT用量对复合微球结构形态的影响.研究表明,酸性条件不利于核壳结构PSt/TiO2复合微球的形成;当体系pH值为7.2时,可得到包覆完整、TiO2壳层厚度均一的PSt/TiO2复合微球,此后随着体系pH值的升高,包覆厚度逐渐提高;当pH值升高到11.0时,壳层厚度达到最大,但出现了包覆层不完整的复合微球.在固定聚合体系pH为8.5,EtOH/H2O质量比为100/6,表面修饰PSt种子乳液用量为0.5 g(固含量为4%)的条件下,随着TBT用量从0.01 g增加到0.16 g,复合微球壳层厚度从约0 nm逐渐增加到60 nm;当TBT用量增加到0.32 g时,壳层厚度迅速降至12nm,微球表面变得粗糙,并出现大量未包覆微粒;此后随着TBT用量的增加,包覆层厚度逐渐减少,未包覆微球逐渐增多.结果显示,当复合微球中TiO2包覆层达到一定厚度时,经煅烧后才能得到形貌完整的TiO2中空微球.

关键词： PSt/TiO2复合微球,TiO2中空微球,形态,pH,前驱体