Preparation, Structure And Properties Of Macrocyclic Oligomeric Silsesquioxanes-containing Polymers

Macrocyclic oligomeric silsesquioxanes (MOSS) are a novel class of silsesquioxanes with unique stereo cyclic structures. They have silsesquioxane frameworks and their inorganic properties are similar to POSS (polyhedral oligomeric silsesquioxanes) molecules. MOSSs have different numbers of Si-O repeat unit, and their functionalizations are very rich. Compared to the preparation of POSS, the preparation of MOSS is more convenient, short-term, high-yield and its need for dryness of solvents and environment is low. In the past, there are some literatures concerning the preparation of MOSS; however, there are few reports on functionalization and application of MOSS. In this contribution, a series of MOSS were prepared, functionalized, and then employed to prepare inorganic/polymer composites.1. Two self-polymerizable MOSS molecules were prepared via metal directed self-assembly and silylation with hydrodimethylchlorosilane. The hydrosilylative polymerizations were carried out with Karstedt catalyst and afford porous polysilsesquioxane material. It is suggested that the size of MOSS significantly influence the porosity.2. 12-membered MOSS containing reactive Si-H groups was modified with allyl 2-bromoisobutyrates and allyl 2-chloroisopropyrates via hydrosilylation reaction to generate two types of ATRP initiators. The former one was employed in ATRP polymerization of tert-butyl acrylates under CuBr/PMDETA catalyst and the obtained MOSS-PtBA hybrid brushes were hydrolyzed to amphiphilic MOSS-poly(acrylic aicd) brushes in formic acid. The MOSS-PAA brushes can assemble into a series of flower-like nanostructures and have different pH responsibilities. The latter one was employed in ATRP polymerization of N-isopropylacrylamide under CuCl/Me6Tren catalyst and generated amphiphilic 12-arm PNIPAM cyclic brushes. The self-assembly and temperature responsibility was investigated using dynamic laser scattering analysis. It is revealed that the self-assembly and temperature responsibility depend on the molecular weight significantly. The presence of MOSS restricts the reverse of conformation of PNIPAM chains.3. MOSS molecule containing six vinyl groups were prepared and carried out thiol-ene reaction with 2-mercaptoethanol to generate initiator with six primary hydroxyl groups. The initiator was used in polymerization ofε-caprolactone with Sn(Oct)2 catalyst to generate six-arm poly(ε-caprolactone). The brushes with different molecular weight were threaded intoα-cyclodextrins to generate supramolecular complexes. NMR results indicated that when the arm length decreased, the mole ratio of CL: CD would increase. It is judged that the topology and bulk MOSS cause difficulty on supramolecular complexation of CDs with PCL segments near the MOSS core. In the same way, MOSS molecule containing twelve vinyl groups was prepared and carried out thiol-ene reaction with 2-mercaptoethanol to generate initiator with twelve primary hydroxyl groups. The initiator was used in polymerization ofε-caprolactone with Sn(Oct)2 catalyst to afford 12-arm poly(ε-caprolactone). The brushes with different molecular weight were threaded intoα- orγ-cyclodextrins to generate supramolecular complexes. NMR results indicated that when the arm length decreased, the mole ratio of CL: CD would increase. It is judged that the topology and bulk MOSS cause difficulty on supramolecular complexation of CDs with PCL segments near the MOSS core.4. MOSS molecules containing twelve hydroxyl or carboxyl groups were prepared via thiol-ene reaction with 2-mercaptoethanol or 3-mercaptopropylic acid, respectively. The miscibility and the special interaction between these two MOSSs and PEO were investigated. It is suggested that the miscibility significantly depends on the special interaction, and only if enough strong special interaction presents, it will be able to prepare organic-inorganic nanocomposites via physical mixing. 5. A series of MOSS molecules containing epoxy groups were synthesized by hydrosilylation reaction with allyl glycidyl ether and introduced into epoxy thermosets and polybenzoxazine thermosets, respectively. The viscoelastic behaviors were studied by dynamic mechanic analysis experiments, and the thermal stabilities were investigated by thermogravimetric analysis.