【作者】 薛裕华；

【导师】 冯连芳； 胡国华；

【作者基本信息】 浙江大学 ， 化学工程， 2010， 博士

【摘要】 多面体低聚倍半硅氧烷(Polyhedral Oligomeric Silsesquioxane,简称POSS)是一种具有笼状结构的有机/无机杂化分子。与蒙脱土,二氧化硅等传统的纳米填料不同,POSS具有规整的笼状结构、纳米尺度以及与聚合物良好的相容性,POSS能与聚合物形成真正意义上的分子级复合,提高了聚合物的热稳定性,机械强度,阻燃性,抗氧化,抗老化等性能。开发新型的POSS基聚合物纳米杂化材料具有非常重要的学术意义和实际应用价值。论文首先合成了一系列不同官能团的POSS单体:八乙烯基倍半硅氧烷(OvPOSS),八胺基倍半硅氧烷(OapPOSS),八巯基倍半硅氧烷(OmpPOSS),八苯基倍半硅氧烷(OPS),环氧基倍半硅氧烷(epoxy-POSS),苯磺酰氯基倍半硅氧烷(SC-POSS),单乙烯基倍半硅氧烷(monovinyl-POSS),单巯基倍半硅氧烷(monothiol-POSS)。并用红外光谱(FTIR),核磁共振(NMR),元素分析等对POSS的结构进行了表征。随后以这些POSS为基础,制备POSS基聚合物纳米杂化材料。将POSS引入环氧树脂中,制备了四种不同的环氧树脂/POSS纳米杂化材料;以POSS为核合成了星形聚合物;用紫外光聚合制备了高度交联的POSS多孔材料。最后以POSS为基本结构单元,用模板法制备了定向排列的POSS纳米线和纳米管阵列,用电纺法制备了具有超疏水性能的PMMA/POSS纳米纤维。论文取得了以下创新性研究结果:(1)以OmpPOSS为环氧树脂的固化剂,制备了高透明、高折射率的环氧树脂/OmpPOSS纳米杂化材料。OmpPOSS完全以分子级均匀的分布在环氧树脂基体里。用紫外-可见光对光学性能进行了研究,可见光透过率逾80%,320nm以下的紫外光不能透过,环氧树脂/OmpPOSS杂化材料的折射率高达1.581。用差示扫描量热仪(DSC)研究了固化动力学,用热重分析(TGA)对环氧树脂进行了热分析,OmpPOSS固化的环氧树脂具有较高的热稳定性。(2)用双酚A型环氧树脂(DGEBA)与二氨基二苯甲烷(DDM)和SC-POSS原位聚合制备了环氧树脂/SC-POSS纳米杂化材料,用DSC对固化行为进行了研究,SC-POSS的加入,能使环氧树脂的固化温度显著降低,活化能下降,固化速率明显提高。SC-POSS对环氧树脂的固化具有促进作用。少量POSS的加入能够提高环氧树脂的玻璃化温度T_g。(3)制备了环氧树脂/OvPOSS和环氧树脂/epoxy-POSS纳米杂化材料。OvPOSS与环氧树脂之间没有化学作用,OvPOSS以微晶的形式混在环氧树脂基体里,在EP/OvPOSS纳米杂化材料中出现了明显的相分离。而epoxy-POSS以化学键连在环氧树脂主链上,EP/epoxy-POSS纳米杂化材料没有出现大面积的相分离。研究了POSS对杂化材料机械性能的影响,环氧树脂/epoxy-POSS纳米杂化材料的弯曲模量和弯曲强度都得到了增强。(4)以SC-POSS为核引发剂,以氧化亚铜为催化剂,以2,2联吡啶为配体,通过ATRP合成了一系列POSS为核的PMMA/POSS和PS/POSS的星形聚合物。用GPC对聚合物进行了表征,显示分子量大小随着单体与引发剂的比例的增加而增加。并且分子量分布较窄。(5)用紫外光引发聚合制备高度交联的POSS共聚物。以OvPOSS和OmpPOSS为单体,在紫外光作用下反应,反应过程用UV-VIS实时监控,反应在几分钟内即可完成。用红外和核磁硅谱研究表明,POSS单体之间几乎完全反应,反应转化率高达96.3%。使用SEM观察干燥后共聚物的形貌,冷冻干燥得到了多孔结构的POSS共聚物材料。(6)以POSS为基本构造单元,以多孔氧化铝为模板,制备了大面积的、定向排列、自由挺立的POSS纳米线阵列和POSS纳米管阵列。比较了两种干燥方法得到的纳米线的形态。真空热干燥法得到的POSS纳米线有团聚塌陷现象,而用冷冻干燥得到了自由挺立的POSS纳米线阵列。POSS起始分解温度为354度,在900度下仍然有52.3%的残余量,红外显示煅烧残余物主要为二氧化硅。使用溶液浸润法还成功制备了定向排列的POSS纳米管阵列。(7)以MMA和POSS单体为原料,用自由基聚合的方法合成了一系列PMMA/POSS杂化共聚物,共聚物中POSS的含量从0%到75%。对PMMA/POSS聚合物电纺制得了不同形态的纳米纤维膜。POSS的加入降低了共聚物的表面能,纳米纤维表面的接触角都随着POSS含量的增加而增加。POSS含量50wt%以上的共聚物纤维具有明显的超疏水性能(8)增加聚合物的分子量可以制得没有珠状颗粒(bead-free)的均匀纤维,以高分子量PMMA/50%POSS的共聚物为研究对象在不同浓度下电纺制得了“bead-free”的纳米线纤维,并且纤维表面出现了定向排列的纳米线结构。该纤维的表面结构与自然界的水蜘蛛的腿的结构相似,并且也具有超疏水性能,以PMMA/POSS共聚物纤维为腿部材料,仿制了能自由挺立在水面上的人造水蜘蛛。更多还原

【Abstract】 Polyhedral Oligomeric Silsesquioxane（POSS） was a cage-like Organic/Inorganic hybrid molecular.Unlike clay and silica,POSS has a well-defined and nanoscale structure,it is also compatible with polymers.POSS can composite with polymer at molecular level.POSS modified polymers have enhanced properties. It is very significant to prepare novel polymer/POSS nanohybrids.Firstly,a series of POSS were synthesized,such as OvPOSS,OapPOSS, OmpPOSS,OPS,epoxy-POSS,SC-POSS,monovinyl-POSS and monothiol-POSS. The structures of POSS were characterized by Fourier Transform Infrared（FTIR）, Nuclear Magnetic Resonance（NMR） and element analysis.Then,POSS were used to prepare polymer/POSS nanocomposites.Four kinds of epoxy resin/POSS nanohybrid materials were prepared.PMMA/POSS and PS/POSS star-polymers were synthesized by atom transfer radical polymerization（ATRP） using POSS as a core.A highly-crosslinked three-dimensional（3D） POSS copolymer was prepared from OvPOSS and OmpPOSS via photo-induced thiol-ene Click reaction.Finally, One-dimentional POSS materials were prepared.Free-standing nanowire and nanotube arrays were fabricated via AAO template using POSS as building blocks. PMMA/POSS nanofibers were prepared by electrospinning.This thesis achieved some results as follow:（1） OmpPOSS was used as a curing agent for epoxy resin.Well-defined organic-inorganic Epoxy resins/OmpPOSS nanocomposites were prepared via in-situ copolymerization of diglycidyl ether of bisphenol A（DGEBA） and OmpPOSS.FTIR and NMR were used to characterize the structures before and after curing,which show OmpPOSS reacted with DGEBA completely. EP/OmpPOSS nanocomposite exhibited a featureless morphology and no discernable phase separation was observed,which indicate that OmpPOSS was dispersed at the molecular level in EP matrix.EP/OmpPOSS nanocomposites have well optical properties,it is colorless and highly transparent,and the UV light under 320nm can not transmit.OmpPOSS curing resin also has high refractive index（1.581）.The curing behaviors of epoxy resin/OmpPOSS were researched by DSC.The thermal stability of the result hybrids was characterized by TGA,the decomposition temperature（Td） of the hybrid was 375℃.（2） EP/SC-POSS hybrids were prepared via the polymerization of DGEBA, 4,4’-Diaminodiphenyl- methane（DDM） and SC-POSS.TEM indicated that SC-POSS was dispersed at the molecular level in EP matrix.DSC results showed the curing temperature of the EP/SC-POSS hybrids were much lower than the control EP.The apparent activation energy of hybrid was slightly lower than the control EP.The reaction rate increased when adding the SC-POSS into EP matrix, indicating the promotion effect of POSS cages in EP matrix.（3） EP/OvPOSS and EP/epoxy-POSS hybrids were prepared via the polymerization of DGEBA and 1,5-Diamino-2-methylpentane（Dytek A） in the presence of OvPOSS and epoxy-POSS.The inorganic-organic hybrids containing 1wt%, 2wt%and 3wt%of POSS were obtained.The morphologies of the resulting hybrids were quite dependent on the types of comer organic groups in the POSS monomers.The fine phase-separated structures were obtained in the EP/OvPOSS hybrids,in which the spherical POSS-rich particles（about 0.5μm in diameter） were uniformly dispersed in the continuous epoxy matrix.But the homogeneous morphology was obtained by SEM for EP/epoxy-POSS.EP/POSS hybrids displayed the enchanced initial thermal decomposition temperatures due to the nanodispersion of POSS moieties.The flexural modulus of both EP/OvPOSS and EP/epoxy-POSS hybrids were much higher than the control epoxy resins. Contrasting to the lower flexural strengths of EP/OvPOSS hybrids,the flexural strengths of EP/epoxy-POSS nanocomposites were higher than that of neat epoxy resins.（4） An efficient and versatile method was developed for the synthesis of nano-hybrid star polymers via atom transfer radical polymerization（ATRP） using POSS as a core.SC-POSS was successfully used as an initiator to synthesize star polymers via the "core-first" approach.PMMA/ POSS and PS/POSS nano-hybrid star polymers with controlled molecular weights and relatively narrow molecular distribution were prepared.These hybrid star polymers were further characterized using FTIR,NMR and GPC.（5） A new reaction route was reported to synthesize a highly-crosslinked three-dimensional（3D） POSS copolymer from OvPOSS and OmpPOSS,based on a photo-induced thiol-ene Click reaction.The reaction took place very fast,just in a few minute of UV irradiation.The structure of the resultant polymer was confirmed by solid ²⁹Si NMR analyses and FTIR.The rate of conversion calculated based on the ²⁹Si NMR spectra is as high as 96.3%.The SEM observations indicated that freeze-dried POSS polymer was highly porous. Thermal Gravimetric Analysis（TGA） indicated the POSS polymers have excellent thermal properties.（6） Free-standing organic-inorganic hybrid nanowire and nanotube arrays were fabricated via AAO template using POSS as building blocks.Two kinds of POSS, OmpPOSS and epoxy-POSS,were used in this report.The nanowires and nanotubes were prepared by in-situ polymerization and solvent-wetting method respectively.FTIR indicates that OmpPOSS and epoxy-POSS were completely reacted in the AAO pores.POSS were uniformly dispersed in the hybrid nanowires and nanotubes.The free-standing nanowire arrays were formed via freeze-drying removal of the environmental liquid.POSS nanowires and nanotubes show high glass translation temperature（Tg） and thermal stability.The POSS hybrid nanowires and nonotubes might find applications in catalysis, nanodevices,chemical/biological separation and sensors.（7） Inorganic-Organic hybrid nanofibers of methyl methacrylate（MMA） and POSS copolymers were prepared by electrospinning technology using THF/DMF as the solution.A series of PMMA/POSS random copolymers with POSS content of 0, 20,50 and 75wt%were investigated.The wettability of the fiber mats can be controlled by changing the amount of POSS in the copolymers.Water contact angles of both casting films and electrospun nanofiber mats increased by increasing the POSS content of the copolymers.（8） When increase the molecular of PMMA/POSS copolymer,we got the "Bead-free" fibers.The fibres showed a stride’s leg-like morphology with highly ordered POSS arrangement on the surface,and wire like bundle structure was found within the fibres.The PMMA/POSS mats show superhydrophobic properties.We use this fibres to make an artifical water stride.The artifical water stride,which is much heavier than natural ones,can free-stand on water surface.更多还原