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1、浙江理工大学硕士学位论文和频振动光谱研究聚合物表面结构及其形成机理姓名：薛东武申请学位级别：硕士专业：应用化学指导教师：王新平20090310摘 要聚合物的表面性能是由其表面结构决定。表面结构包括表面的化学组成与结构及微纳米几何结构。而要达到对聚合物表面结构进行设计与控制的能力，则必须对表面层分子的化学物理性质，表面层的聚集态结构及表面结构的形成及其控制因素等进行充分研究。然而现有表征手段难以取得表面分子链或基团的结构与取向等微观结构信息，而且对材料表面结构的形成及其影响因素研究很少。本论文利用具有准单分子层界面敏感性与获取丰富的界面分子结构与取向信息及原位研究能力的和频振动光谱(SFG，sl
2、im frequency generation vibrational spectroscopy)技术为主要研究手段，结合其他表征手段研究聚合物溶液固化过程中表面结构的形成及对应的表面性能，并研究所形成的表面结构与固化过程、聚合物溶液性质之间的关系。得到以下结论：(1)对甲基丙烯酸丁酯(BMA)与甲基丙烯酸十二氟庚酯(DFHMA)的无规共聚物(poly(BMACODFHMA)的研究发现：浇铸与旋涂两种固化方式对高含氟量的共聚物膜表面结构影响很小，而对低含氟量共聚物影响很大。低含氟量时旋涂膜比浇铸膜具有更低的表面能，旋涂膜表面的含氟组分浓度要高于浇铸膜。对于低含氟量的共聚物，浇铸时表面结构形成为
3、熵控制，在分子链由舒展状态到收缩状态时，含氟组分被包埋在无规线团内部，无法有效离析。而旋涂成膜时，离心外力作用削弱了熵对分子链的控制，含氟组分可以离析到表面，因此具有更低表面能。(2)SFG研究表明对于聚甲基丙烯酸丁酯(PBMA)与聚甲基丙烯酸甲酯(PMMA)，不同固化方式得到的膜表面结构(分子链构象与侧链取向)存在明显差别。浇铸成膜时高分子主链与侧链可以做有效的紧密堆积，侧链有序性更好且更垂直于膜表面。旋涂成膜时固化时间短，分子链与基团来不及调整，分子链与侧链不如浇铸时紧密堆积，亲水酯基更易与水相互作用，致使旋涂膜的水接触角下降。(3)对于PBMA与PMMA均聚物的旋涂膜，在玻璃化温度以上2
4、0的热处理时，分子链间缠结的存在起到了瞬时交联的作用，无法使旋涂膜的表面结构与浇铸膜一致。在粘流温度以上热处理时，分子链充分自由运动，可以完成从疏松到致密的分子链构象的转变，导致侧链的取向与堆积程度趋向浇铸成膜时的状态，从而使表面结构与浇铸膜一致。(4)对甲基丙烯酸甲酯(MMA)与甲基丙烯酸2全氟辛基乙酯(FMA)的二嵌段共聚物PMMAl“-bPFMAn溶液气液界面结构研究发现：在临界胶束浓度(CMC)以上，PFMA长度较短时，PFMA段排布在气液界面上，PMMA段则溶解在溶液本体中。当PFMA段I长为10时，表面的吸附量变大与较强的胶束稳定性使得溶液气液界面上会形成以PFMA为核，PMMA为
5、冠的二维表面聚集体。(5)嵌段结构(二嵌段与三嵌段)影响着含氟共聚物环己酮溶液的气液界面结构。三嵌段共聚物PFMA-bPMMA-bPFMA更有利于降低环己酮溶液的表面张力。三嵌段共聚物PFMA-bPMMAbPFMA中间段PMMA长度同样会影响环己酮溶液的气液界面结构。详细的界面结构差别及与溶液表面张力之间的联系有待进一步研究。关键词：和频振动光谱聚合物表面结构 表面结构形成气液界面结构llAbstractPolymer surface properties depend on its surface structureHowever,the formation ofchemical struc
6、tures on polymer surfaces during processing remains largely unstudied and poorlyunderstood despite the immense importance of the surface chemical structure in practicalapplications，especially when compared to the vast theoretical and empirical literature availableon bulk structuresThere is thus a fu
7、ndamental interest regarding the nature of the formationmechanism of the chemical structure on the surface of a polymer filmIn this paper,polymer surface structure and propertiesbotll in the solid state and insolutionwere investigated by contact angle measurement,surface tension measurements，X-rayph
8、otoelectron spectroscopy(xPs)，and sum frequency generation vibrational spectroscopy(SFG)which has unique ability to probe the molecular spectroscopy and molecular group orientation atsubmolecular levelThe effect of film-forming methods and polymer solution properties on filmsurface structure formati
9、on Was also exploredFilmforming techniques(cast and spin-coating)ale known to regulate the surface structureof random copolymers composed of butyl methacrylate 03MA)and dodecafluorheptylmethylacrylate(DFHMA)It made a great influence on the formation of surface structure for thecopolymers with low DF
10、HMA contents，whereas no effect was found for the copolymers谢t11lligh DFHMA contentThe results，based on thermodynamic considerations，demonstrated t11atthe random copolymer chain conformation at the solutionair interface greatly affected thesurface structure of the resulting film，thereby determining t
11、he surface segregation of fluorinatedmoieties on films obtained by various filmforming techniquesWhen the fluorinated monomercontent of the copolymer solution Was low,entropic forces dominated the interracial structure，with the perfluoroalkyl groups unable to migrate to the solutionair interface and
12、 thus becomingburied in a randomcoil chain conformationWhen employing this copolymer solution for filmpreparation by spincoating，the copolymer chains in solution were likely extended due tocentrifugal forces，thereby weakening the entropy effect of the polymer chainsConsequently，this resulted in the
13、segregation of the fluorinated moieties on the film surfaceFor the filmsprepared by casting，the perfluoroalkyl groups were，similar to those in solution，incapable ofsegregating at the film surface and were thus buried in the random-coil chainsWhen thecopolymers contained hi曲content of DFHMA，the migra
14、tion of perfluoroalkyl groups at theIIIsolutionair interface was controlled by enthalpic forces，and the perfluoroalkyl groupssegregated at the surface of the film regardless of the film-forming techniqueSurface structures of poly(butyl methacrylate)(PBMA)and ply(methyl methacrylate(PMMA)were also af
15、fected by filmforming techniquesSFG result showed better surfacecompact chain alignment and packing of the ester side chain were formed when the film prepareby casting than that prepared by spin-coating，which resulted in spincoated film surface havinghigher surface energyThe surface structure of spi
16、ncoated PBMA and PMMA film could notchange when it Was annealed above the Tg(glass transition temperature)since chain activity Waslow due to chain entangleWhen the annealing temperature Was above Tf(viscous flowtemperature)，the chain conformation on the surface of spincoated film could be changed to thestate which Was same as the chain conformation on the film prepared by castingThe reason wasattributed to the increased chain act
