The Synthesis, Characterization And Self-assembly Behavior Of The Amphiphilic Copolymers Containing Fluoropropyl Substitute Polyhedral Oligomeric Silsesquioxane (POSS)

The concept of incorporating inorganic (or organometallic) blocks into organic polymers has been widely accepted to obtain the materials with some new and improved properties. Typical POSS molecules possess the nanosized cage-like structures, derived from hydrolysis and condensation of trifunctional organiosilanes with a formula of (RSiO3/2)n,n=6~12,where R can be various types of organic groups, different approaches can be adopted to incorporate POSS molecules into polymers. For instance, the mono-functional POSS monomers can be grafted onto macromolecular chains by co-polymerization or reactive blending whereas the bi-functional POSS monomers will allow ones to incorporate the silsesquioxane building blocks into macromolecular backbones. The multi-functional POSS monomers can be used as curing agents to prepare POSS-containing thermosetting nanocomposites.Fluorinated polyhedral oligomeric silsesquioxanes (FluoroPOSS) are the newest class of POSS compounds. Because they combine both advantages of the fluoro-materials and the organosilicone, it will greatly influence the properties especially the surface hydrophobicity of the target materials when the fluoroPOSS was introduced into them. But because the great difference in chemical structure and composition between the fluoroPOSS and the usual polymer materials, it is difficult to obtain the idea composite by simply physical blending them together. In composites system, getting micro-scaled phase separation act as the key role to obtain a material with outstanding performance. In order to improve the miscibility between the fluoroPOSS and polymer matrix, methods must be done to introduce one or more reactable group into fluoroPOSS molecule, or someamphiphilic copolymers containing fluoroPOSS can be synthesized. All these can make the miscibility between the fluoroPOSS and polymer matrix much better.In this thesis, we successfully synthesis varied functionalized fluoroPOSS monomer or amphiphilic copolymers containing fluoroPOSS. Then these monomers or copolymers were addressed into some thermosets or thermoplastic polymers. With self-assembling mechanism, the phase separation in micro-scale will occur in the polymers'matrix. Atomic force microscopy (AFM), transmission electric microscopy (TEM) and field emission scan electric microscopy (FESEM) were employed to observe the morphologyformed. Due to the low surface energy of the fluorinated materials, the introduction of the fluoroPOSS will greatly improved the hydrophobicity of the polymers'surface. The contact angles on the materials'surface were measured and were further used to calculate the surface energy. The following systems were studied in this thesis.1. the self-assembling behavior of the fluoroPOSS monomers or copolymers in epoxy resinEpoxy resin is a class of thermosets and is widely used for its excellent performance. There have been many report on POSS modified epoxy resin but few on the fluoroPOSS. Because of the difference in the chemical structure between the fluoroPOSS and epoxy resin, macro scale phase separation must be happened when we mix them together. Chemical modification is needed to improve the miscibility between them. Some well defined functionalized fluoroPOSS or amphiphilic copolymers containing fluoroPOSS,for instance, amino-functionalized fluoroPOSS, fluoroPOSS-capped PEO, fluoroPOSS-capped PCL and fluoroPOSS-phenoxy-fluorPOSS, were designed and successfully synthesized.. And these macromonomer or copolymers were further incorporated into the epoxy resin. Due to the amphiphilic characterization of the copolymers, self-assembling would be occurred in epoxy matrix. Adjusting the composition of the copolymers, nanosized phase separation behavior would be obtained. The morphology can be easily fixed via curing reaction and observed by AFM, TEM and SEM. The thermal and mechanical properties can be evaluated by DSC, TGA and DMA.The surface properties of the fluorinated materials are always the interesting area because of their great applied value. After fluoroPOSS introduction, the surface morphology and the hydrophobicity would be greatly influenced. AFM, XPS and contact angle measurement were addressed to value the surface properties of the epoxy resin.2. Functional polymers modified by fluoroPOSSHepta(3,3,3-trifluoropropyl)propylacrylate polyhedral oligomeric silsesquioxane (POSS) was synthesized and used as a monomer of copolymerization to prepare the organic-inorganic poly(N-isopropylacrylamide) (PNIPAM) nanocomposites with POSS content up to 12.5 wt%. The POSS-containing PNIPAM networks can be prepared with N,N'-Methylenebisacrylamide (BIS) as the crosslinking agent. When the organic-inorganic nanocomposites were swollen in water they exhibited the characteristics of hydrogels. With the moderate contents of POSS, the POSS-containing hybrid hydrogels displayed much faster response rates in swelling, deswelling and re-swelling experimentsthan control PNIPAM hydrogel than the PNIPAM hydrogels prepared via the free radical copolymerization of N-isopropylacrylamide (NIPAM) and N,N'-methylenebisacrylamide (viz. the conventional crosslinker). The improved hydrogel properties have been interpreted on the basis of the formation of the nanosized hydrophobic microdomains around the POSS moieties.Polyethyleneimine (PEI) is kind of water-soluble polymer. It is widely used in biomedicine fields for its biocompatibility. Several methods have been employed to improve its hydrophobicity to decrease the physiological toxicity and expend its appliance. There are many amino groups on the PEI chains, and they can react with epoxy group in mild condition. Based on this, fluoroPOSS-capped propyl glycidyl was synthesized. The POSS macromonomer was further applied to modify the PEI. The POSS-PEI compositesshowed the enhanced thermal properties that were proved by the differential scanningcalorimetry (DSC) and thermogravimetric analysis (TGA). The static contact angle measurements indicate that the organic-inorganic nanocomposites displayed a significant enhancement in surface hydrophobicity.3. Synthesis of the telechelic polymer containing fluoroPOSS and its propertiesUsing click chemistry, we designed and synthesis the POSS-PEG-POSS telechelic polymer. Its crystallization behavior was studied by means of DSC and XRD. The results showed that the POSS cages could greatly influence the crystal ability of the PEG chains. With the decrease of the PEG chain's length, the crystal ability decreased significantly. It's the result of the special topology of the telechelic polymer. The POSS rich domain can act as physical crosslink points to limit the crystal behavior the PEG chains. The special topology also influence the solubility of the polymer, in selective solvent such as water, POSS-PEG-POSS can only be swelled but can not be dissolve. Physical gel formed due to the strong interaction between POSS cages.A novel polyrotaxane based on polyhedral oligomeric silsesquioxane (POSS),α-cyclodextrin (α-CD) and poly (ethylene glycol) (PEG) was synthesized in this research work. Pesudorotaxanes were prepared based on alkyne terminated PEG andα-cyclodextrin (α-CD) with different PEG chains length. To prevent the dethreading of theα-CD from the PEG chains, azido-POSS was used as block agent to close the both ends of the pesudorotaxanes via"Click Chemistry", and convert the pesudorotaxanes to the polyrotaxane. X-ray diffraction (XRD) results showed that the channel-type inclusion complexs were formed for all the polyrotaxane, but their crystal structure were slightly different with the corresponding pesudorotaxanes. And the crstalization ability of the polyrotaxanes were decreased with the decreasing of the PEG chains'length, which means that the introduction of the POSS can inflence the crystal behavior of the supramolecules due to its bulky effect. Thermal stability of the polyrotaxane was improved comparing to the pesudorotaxane by introducing the POSS.The amphiphilic tri-block copolymer POSS-PEG-POSS was used as the modifier to improve the temperature response rate of poly(N-isopropylacrylamide) (PNIPAM) hydrogels. The modified PNIPAM hydrogels exhibited temperature-responsive behavior as to the control organic hydrogels. It is identified that all the modified PNIPAM hydrogels displayed much faster response rates in terms of swelling, deswelling and re-swelling experiments than the control PNIPAM hydrogel. The improved hydrogel properties could be interpreted on the basis of the synergetic effect between the hydrophobic parts (POSS) and hydrophilic parts (PEG). Hydrophobic POSS cage will self-assemble due to its immiscibility with other components. Hydrophobic micro-domains can be formed and increase the contact area between the water and PNPAM network. Therefore the response rate can be improved. At the same time, the hydrophilic PEG component can act as channel for water in/out and facilitate the diffusion of water in PNIPAM network. From this aspect, the response rate of hydrogels can also be improved.Combine the reversible addition fragmentation chain transfer (RAFT) and Click chemistry. POSS-PNIPAM-POSS telechelic polymer was synthesized. POSS and PNIPAM are immiscible, the phase separation behavior was observed by AFM. Based on the temperature sensitive properties of the PNIPAM chains, photon correlation spectroscopy (PCS) was employed to study the micelle behavior of the telechelics in dilute solution.