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1、聚合物/离子液体溶液和动态共价键凝胶的流变行为,报告人:刘付永2013-11-09,大纲,1、聚合物/离子液体溶液的流变行为2、动态共价键凝胶的流变行为,2,聚合物/离子液体溶液的流变行为,背景介绍,聚合物:(Polymer)是指具有非常大的分子量的化合物,分子间由结构单位、或单体经由共价键连接在一起的相对分子量在一万以上的化合物。,3,离子液体:(ionic liquids)一种由阴阳离子构成,在室温或接近室温(低于100)下呈液态的有机盐。,聚合物/离子液体溶液的流变行为,能溶解纤维素水洗回收绿色环保,电解质高电导率不挥发,Armand,M.et al.,Nat.Mater.2009,4,
2、聚合物/离子液体溶液的流变行为,聚环氧乙烷:(PEO)环氧乙烷开环聚合而成的线型聚醚,即可溶解于水,也可溶解于很多有机溶剂,两亲性高分子。小分子量的叫聚乙二醇(PEG),具有很好的生物相容性。,Torimoto,T.et al.,Adv.Mater.2010,Rodriguez,H.;et al.PCCP 2009,PEO 与不同ILs的亲和性不同,5,动态共价键凝胶的流变行为,背景介绍,动态共价键:(Dynamic Covalent Bonds)是一类可逆共价键,它们能在一定的环境条件下打开并建立起原料与产物分子间的热力学平衡反应,产物分子与原料分子始终处在一种持续的平衡中,原料和产物共存。
3、,动态共价键化学与超分子化学有相似处:结合是可逆的;不稳定网络;存在一种平衡。,动态共价键化学断裂和形成慢;化学作用;键能大,稳定。,超分子化学断裂和形成快;物理作用;键能小,不稳定。,动态共价键化学与超分子化学不同之处,6,动态共价键凝胶的流变行为,动态共价键的应用,自愈合凝胶,Imato K,et al.,Angew.Chem.Int.Ed.,2012.,Lehn,J.M,et al.,Chem.Commun.2007,功能凝胶,靶向给药,Caixia Ding,et al.Biomacromolecules.2010,7,动态共价键凝胶的流变行为,Dynamic covalent bon
4、ds:酰腙键,Deng GH,et al.,Macromolecules,2010,1191.,流变特性以及背后的分子机理:凝胶化反应动力学机械性能自愈合机理,8,A2=B3,凝胶化反应动力学,tgel as a function of 1/A20,k1 0.03 s-1 M-1,(HAc=13.0 v%),k1 0.003-0.043 s-1 M-1,(HAc=13.0 v%),(HAc=4.8-16.7 v%),G,G“Vs.time for samples with different HAc,second-order reaction,动态共价键凝胶的流变行为,9,Pre-gelati
5、on:At gel point:Post-gelation:,Three steps and corresponding scaling laws,Martin,J.E.;et al.,Phys.Rev.Lett.1988,2620Peyrelasse,J.;et al.Phys.Rev.E 1996,6126,cg=3.7 wt%,=1.5,n=0.75,z=2.5,dynamic covalent bonds are similar to the physical cross-links,10,Mechanical Properties of Well-Developed Gels wit
6、h High Gelator Concentration,Effect of Temperature on the equilibrium modulus(Ge),G and G vs.at different T.(cgelator=10.4 wt%,HAc=13.0 v%),The solid curves are the predictions of the Maxwell model:,G0 is equilibrium modulus.is a frequency at which G=G”,kd=cross,kd=0.1 s-1 at 125 Ckd=0.01 s-1 at 100
7、 C,Kd=10-5 s-1 at 25 C Keq=k1/kd3000 M-1,k1 0.03 s-1 M-1,11,NMR analysis,Keq=8000 M-1,Table S1.Concentration of groups of reactors and products,12,Tensile Properties of Gels at Low T,Engineering stress(eng)against extension ratio(=l/l0),eng against.The solid curve is the prediction of classical mode
8、l with Ge=0.052 MPa,All four samples clearly obey the neo-Hookean relationship,up to=3(300%stretch),13,14,Self-Healing of Well-Developed Gels,eng against for the gel self-healed different times.,eng against the gel self-healed different times with the cross-section coated with HAc after cutting off.
9、,HAc works as a catalyst to accelerate the acylhydrazone bond formation,15,动态共价键凝胶的流变行为,15,转变过程中的动态时间扫描,凝胶的pH值响应,经历一次完整转变后可以基本恢复到初始的模量,转变前和转变后凝胶的动态频率扫描,16,小 结,凝胶化反应可以近似为2级反应;凝胶化过程中粘度-时间标度、平台模量-浓度标度、临界凝胶指数3者相互关系符合Winter-Chambon凝胶理论。动态凝胶网络的末端松弛符合简单的Maxwell模型,凝胶在200%应变范围内的应力-应变曲线符合近胡克固体行为;切断后的凝胶材料可以在24小时内自愈合恢复到初始强度,如果切口涂抹冰醋酸,经过8小时能修复到初始强度。,Liu,F.;Li,F.;Deng,G.;Chen,Y.;Zhang,B.;Zhang,J.;Liu,C.-Y.Macromolecules 2012,45,(3),1636-1645.,17,致谢!,18,中国科学院化学研究所,谢 谢!,19,