<p>A diepoxide monomer bearing two rigid adamantane-like moieties obtained from orthoester derivatives of <i>myo</i>-inositol is synthesized from a naturally occurring <i>myo</i>-inositol. The diepoxide undergoes polyaddition reactions with diamines and trithiols, along with imidazole-initiated anionic ring-opening polymerization to afford the corresponding network polymers. Network polymers bearing the ortho-ester moieties derived from the diepoxide exhibit much higher glass transition temperatures (<i>T</i>_g) than those obtained from bisphenol A diglycidyl ether, indicating that the introduction of rigid adamantane-like ortho-ester moieties into the polymers effectively suppresses the polymer chains mobility, thereby improving their thermal stability. This approach is expected to find applications in the development of high-performance polymer materials from renewable feedstocks.</p> Graphical Abstract <p></p> <p>A diepoxide monomer bearing two rigid adamantane-like moieties was synthesized from naturally occurring myo-inositol. The polyaddition of diamines and dithiols to the diepoxide, as well as the imidazole-initiated anionic ring-opening polymerization of the diepoxide, yielded the corresponding network polymers, which exhibited significantly higher glass transition temperatures than those obtained from bisphenol A diglycidyl ether. Thus, incorporating rigid diepoxide structures is an effective strategy for developing high-performance polymer materials from renewable feedstocks.</p>