Preparation And Properties Of Novel Main-chain Benzoxazine Containing PDMS/POSS Via Click Reaction

Polybenzoxazine, as a new high performance thermosetting resin, has more attractive properties than traditional resins, such as excellent thermal and flame-retardant property, zero-shrinkage upon curing, high Tg and curing without any catalyzer. However, the shortcomings of their brittle nature, high cure temperature, need of improvement on thermal property and their miscibility in composites limit the applications of polybenzoxazines. Property enhancement on polybenzoxazines by synthesis of new high-molecular-weight main-chain benzoxazine precursors and modification further has become the hotspot recently. Due to the stable cage skeleton and good reactivity, cooperating with Polyhedral Oligomeric Silsesquioxane (POSS) can improve the thermal properties and resistance to oxidation of polybenzoxazines efficiently. But simple precursor such as PBA-POSS is hard to be formed films, while polysiloxanes especially polydimethylsiloxane (PDMS) can enhance toughness of polybenzoxazines resins due to its flexible and good thermal properties. Modifying polybenzoxazines with PDMS and POSS have a great potential to improve their combination property.In this thesis, a series of novel main-chain benzoxazine precursors containing PDMS/POSS were synthesized via the efficient Click reaction. Toward this end, we firstly synthesized 1,3-bis(azdiopropyl)polydimethylsiloxane (PDMS-N3) and 3, 13-bis(azdiopropyl)octaphenyl double-decker silsequioxane (DDSQ-N3) through azide reaction. The diacetylene bisbenzoxazine (DABB) macromonomer was then used to copolymerize with different contents of PDMS-N3 and DDSQ-N3 to get a series of high-molecular-weight precursors successfully via the copper-catalyzed azide-alkyne cycloaddition. DSC and FTIR were used to study the curing behavior of precursors. Good flexible and thermal properties were presented and can be controlled by the content of PDMS and POSS. The sample of polyBZ-PDMS has so fine toughness that can be blend to 180° with no broken. The T5%、TiO% of polyBZ-POSS in inactive gas were 437℃ and 523℃, which are more than 100℃ than traditional benzoxazine resin, and char yield at 1000℃ can reach to nearly 80%, respectively. All polymers had good antioxidant power under oxygen conditions.