A Silicon-Containing Polytriazole Resin with Long Storage Time

Cyclo addition reactions have been employed in polymer synthesis since the mid-1960s, these reactions can be used for linear, hyper branched and dendritic architectures that feature special heterocyclic or strained multicyclic units within the polymer backbone. Cyclo addition reactions are very efficient, highly selective and allow even stereo selectivity. Polymers obtained via cycloaddition chemistries have found use in several advanced applications such as liquid crystal displays, semiconductors, electrolyte membranes, and high-temperature performance polymers.[1,2]

 Micheal discovered 1,3-dipolar cycloaddition of phenyl azide and dimethyl acelene dicarboxylate in 1893. As one of a classical cycloaddition reactions, this reaction formed a mixture of 1,4-and 1,5-disubstitued1,2,3-triazole.[3] Since then, the 1,3-dipolar cycloaddition between alkyne and azide groups has become an important rule to synthesize 1,2,3-triazole products and their derivatives.[4,5] In 1960s, the Johson groups synthesized a series of linear polytriazoles (PTAs) from selfpolymerizations of monomers containing both azide and alkyne groups. The obtained PTAs were thermally stable but hardly processable polymers due to the rigid molecular chains, [6,7] thus the PTAs did not cause enough attentions for scientists.

 Until 2002, the Sharpless and Meldal groups independently discovered the copper-catalyzed azide-alkyne cycloaddition (CuAAC reaction), which effectively formed 1,4-disubstitued 1,2,3-triazole.[8,9] CuAAC reaction has remarkable features such as high yield, mild reaction conditions, functional tolerance and simple product isolation. These appealing features enable CuAAC reaction to be a powerful synthetic tool and applied in diverse areas. In particular, it gains popularity in materials science. [10-16]

 Our laboratory has engaged in developing a series of novel polytriazole resins with good processing property and thermal stability by 1,3-dipolar cycloaddition of azide with alkyne groups since 2002. These resins can be cured at 80℃ without Cu (I).[17-21] After that, a series of novel polytriazoleimides (PTAIs) containing 1,2,3-triazole has been reported by thermal or chemical imidization methods. These PTAIs have good mechanical properties and chemical stabilities, and are expected to be used as resins for advanced composites.[22,23]Although these resins have good properties, the storage time of these resins is short due to high reaction activity of terminal alkynes and azide, which limits their applications. Therefore, in order to meet higher requirement of performances, such as higher glass transition temperatures (Tg) and longer storage time, a siliconcontaining polytriazole resin with good processing propertyis prepared and characterized.