Preparation, Characterization And Properties Of Polymer/POSS Nano-hybrid Materials

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.