The characteristic of expansion monomer is no volume shrinkage during the polymerization process

even to produce volume expansion. This special performance has broad application prospects. Currently spiro compounds that can be used as expansion monomer mainly include spiro orthocarbonate (SOC)

spiro orthoester (SOE) and bicyclic orthoester (BOE). Spiro orthoester (SOE) is discovered the first class of compounds capable of swelling polymerization. This article demonstrated the discovery

synthetic methods and polymerization reaction of spiro orthoesters

and reviewed their applications

then proposed their future developments.