1、Application of Sum frequency generation vibrational spectroscopy in charactering polymer surface聚合物表面和界面的表征和頻振動光譜 Reporter： Tan Jiaojun2012-12-10ContentsPage03070918Why1What2How3If, Then? 4Lack of surface selectivity!BackgroundAES ATR XPSIRQuasi-surface!Principle Principal and phenomenon of SFGSum f

2、requency spectrum system(5 main units)PrincipleSignal detectorPicosecond pulsed laser 10 Hz 1064nm1064 nm355 nmHarmonic unitSample AreaSignal Mono-chromatorFrequency multiplica-tionVis(532nm)UV ISPrinciple AppearanceFunctionsMono-layerNo damageInterface specicStructure Orientation Crystallize(Stress

3、-induced)Environmental responseBlends behaviorSFG in polymer characterAdvantageFunctionsSample preparation Attention: 1.Spin coating、injection; 2.Clean surface（sample & substrate） by piranha solution.Jie Wang , Zoltan Paszti. J. Am. Chem. Soc.,2002,124(24), pp 701670231.Character composition and str

4、ucture of surfaceFig IR a and b spectra of LDPE and UHMWPE, c and d of LDPE and e CLDPE .Analysis16cm-1Orientational angles of CH2 LDPE = 55 4 UHMWPE = 45 4SFG surface vibrational spectra of LDPE and UHMWPEAnalysis1.Character composition and structure of surface. Indicating that surface is dominated

5、 by OCH3 rather than polyethylene, though the amount of additives added is so small that they cannot be detected by IR and Raman spectroscopies. 2926？OCH3Jie Wang , Zoltan Paszti. J. Am. Chem. Soc.,2002,124(24), pp 701670231.Character composition and structure of surfaceAnalysisDISCUSSION對低密度基乙烯來講，由

6、于其支化結(jié)構(gòu)，表面上都是隨意取向的鏈段，柔性較高。超高密度聚乙烯是在ZN催化劑下合稱的，能夠高度結(jié)晶，形成有序結(jié)構(gòu)，同時形成的是片晶。片晶的厚度為10nm，鏈長大約為1-10mm,這就意味著形成的是折疊鏈模型，這就表明在表面有很多剛性基團。為了解釋超高密度聚乙烯的藍移現(xiàn)象，筆者有做了固態(tài)PE和液態(tài)PE的SFG，結(jié)果表明固態(tài)的SFG有更高的波數(shù)，這是因為聚合物中剛性鏈或鏈段所致的。這說明高密度聚乙烯表面有大量剛性的鏈段。Fig. 3.SFG spectra of APP and IPP as a function of temperature upon coolingD.Graciasa, D.

7、 Zhang. Chemical Physics, 1999, 13(245):277284Analysis2. Glass transition of the PP surfaces Fig.The ratio of the strengths of the CH2symmetric stretch to the CH3symmetric stretch for APP and IPP as a function of temperature.Semicrystalline polymerAmorphous polymer Analysis2. Glass transition of the

8、 PP surfaces BlendsPSPMMAbenzene ringmethylYi Liu, Marie C.messer. J. Phys. Chem. B, 2003, 107 (36):97749779Blends: (A)fMMA= 0.03; (B)fMMA= 0.06; (C)fMMA= 0.09; (D)fMMA= 0.11.PSPMMAAnalysis3. Structures and Segregation of PS/PMMA BlendsPSPMMAPSPMMAFigure Water contact-angle of blends before (o) and

9、after () annealing.Figure SFG of blends.Samples were annealed in a vacuum at 150 for 20 hYi Liu, Marie C.messer. J. Phys. Chem. B, 2003, 107 (36):97749779Analysis3. Structures and Segregation of PS/PMMA BlendsAnalysis4. Environmental responseProspectSFG have been used successfully to probe buried in

10、terfac in various fields of research. But there are many prolems to be solved:1. IRIRvisible spectroscopy2. doubly resonant SFG spectroscopy molecular chirality3. development of high-power tuneable laser sourcesThank you！-TJJ原理IR-visible sum frequency generation spectroscopy uses two laser beams tha

11、t overlap at a surface of a material or the interface between two materials. An output beam is generated at a frequency of the sum of the two input beams. The two input beams have to be able to access the surface, and the output beam needs to be able to leave the surface to be picked up by a detecto

12、r.2One of the beams is a visible wavelength laser held at a constant frequency and the other is a tunable infrared laser. By tuning the IR laser, the system can scan over resonances and obtain the vibrational spectrum of the interfacial region.1As a nonlinear optical process, the polarization which

13、generates the output depends on the electric fields of the two input beams.As a second-order nonlinear process, SFG is dependent on the 2nd order susceptibility (2). The fact that the 2nd order susceptibility, a third rank tensor, becomes zero incentrosymmetricmedia, limits what samples are accessib

14、le for SFG. Centrosymmetric media include the bulk of gases, liquids, and most solids under the assumption of the electric-dipole approximation, which neglects the signal generated by multipoles and magnetic moments.2At an interface between two different materials or two centrosymmetric media, the i

15、nversion symmetry is broken and an SFG signal can be generated. This suggests that the resulting spectra represent a thin layer of molecules. A signal is found when there is a net polar orientation.23Sum frequency generation spectroscopy(SFG) is a technique used to analyze surfaces and interfaces. T

16、his nonlinear laser spectroscopy method was developed in 1987 and rapidly applied to deduce the composition, orientation distributions, and some structural information of molecules at gassolid, gasliquid and liquidsolid interfaces. In a typical SFG setup, two laser beams mix at a surface and generate an output beam with a frequency equal to the sum of the two input frequencies. SFG has advantages in its ability to be monola