Macrocyclic Oligomeric Silsesquioxane: Synthesis, Functionalization And Their Use To Prepare Organic And Inorganic Hybrid Polymer

In recent years, the organic-inorganic composites have attracted considerable interest since this class of materials can possess the comprehensive properties from the organic and inorganic components. The organic-inorganic hybrids can display excellent and comprehensive properties via the synergism of organic and inorganic components. A typical polyhedral oligomeric silsesquioxanes molecule is composed of cage or macrocyclic like Si-O framework and several organic groups covalently bonded to each Si atom, one or more of which is reactive. The well-defined nanostructures and organometallic features of POSS inspire one to incorporate this class of nano-building blocks into organic polymers to afford organic-inorganic hybrids with improved properties. It is proposed that the following two strategies are adopted to suppress the occurrence of the macroscopic phase separation in the composite systems.1. Thermosets were modified by MOSS molecules containing twelve epoxy groups synthesized by hydrosilylation reaction with allyl glycidyl ether. The formation of hybrid composites for epoxy thermosets and polybenzoxazinewere studied by transmission electronic microscopy(TEM).Mechanical Propertywere studied by dynamic mechanic analysis(DMA) and the thermal stabilities were investigated by thermogravimetric analysis.2. Synthesized a twenty-four-membered MOSS macromer bearing twelve 2-chloropropionate moieties and the macromer was used as a macroinitiator for the atom transfer radical polymerization of N-isopropylacrylamide(NIPAAm) to afford the organic-inorganic macrocyclic molecular brushes. The purpose of this work is twofold: i) explored the synthesis of the organic-inorganic macrocyclic molecular brushes with inorganic macrocyclic molecule as the backbone and PNIPAAm as side chains. ii) investigated the effect of the organic-inorganic macrocyclic brush architectures on the thermoresponsive and self-assembly behavior of PNIPAAm. To the best of our knowledge, there has been no precedent report on the studies on the organic-inorganic PNIPAAm macrocyclic brushes. The morphology and thermoresponsive behavior of the organic-inorganic macrocyclic molecular brushes were addressed on the basis of the results of transmission electronic microscopy(TEM), micro-differential scanning calorimetry(Micro-DSC), UV-vis spectroscopy and dynamic laser scattering(DLS).4. An efficient route to design large macrocyclic copolymer brushes decorated with polystyrene(PS) and polycaprolactone(PCL) thither side chains. The strategy is based on the synthesis of bi-functionalized macrocyclic oligomeric silsesquioxane(MOSS). The novel 24-membered bi-functionalized MOSS was employed as a macroinitiator for the reversible addition-fragmentation chain transfer(RAFT) polymerization of styrene(PS) and ring opening polymerization of ε-caprolactone(PCL) as thither side chains. The organic–inorganic macrocyclic molecular brushes were characterized by means of nuclear magnetic resonance spectroscopy(NMR) and gel permeation chromatography(GPC). Differential scanning calorimetry(DSC) shows that the PCL and PS chains are phase separation but restrict each other in thermal transition behavior.5. Studies on the synthesis MOSS-[PCL-b-PVPy] circular diblock brushes and study self-assembly behavior deeply. Well-defined amphiphilic diblock copolymers circular brushes of MOSS-[PCL-b-PVPy] were synthesized by combining ROP and xanthate-mediated RAFT polymerization. The chemical structure was supported by 1H NMR, 29 Si NMR spectroscopy and mass spectrum. The molecular weight and polydispersity were characterized by Gel permeation chromatography(GPC) that showed the polymerization of NVP was in a living and controlled manner. Differential scanning calorimetry(DSC) shows that the PVP chain of the macrocyclic molecular brushes significantly affect rearrangement of PCL crystals. The value of critical micellar concentration for the block copolymers circular brushes increases with the increase in the chain length of the PVP segment. The resulted block copolymer circular brushes form spherical micelles in water as revealed by TEM and light scattering.6. Provide a practical and direct method to synthesize POSS-NH2 by heck reaction. Amino-MOSS can be used as the nanometer hardener for thermosetting resins and shows great potential in modifying nanocomposites. The nanocomposites displayed the higher storage modulus both of glassy state and rubber statein light of dynamic mechanical analysis(DMA).glass trasition temperatures(Tg’s) were increaseded with the increasing amino-MOSS. Moreover, the amino-MOSS as the nanometer hardener to solidify epoxy-MOSS to prepare functional coating rich in silicon.