Non‐Shrinking Networked Materials from the Cross‐Linking Copolymerization of Spiroorthocarbonate with Bifunctional Oxetane

Abstract

Summary: The cationic ring‐opening copolymerization behavior of SOC1 with BOXT and the properties of the obtained cross‐linked copolymers are described. SOC1 and BOXT are cationically copolymerized under various feed ratios to obtain the corresponding cross‐linked copolymers in 73–96% yields. The volume change during copolymerization could be controlled by the addition of SOC1 to obtain non‐shrinking or volume‐expanding copolymers. The glass transition temperatures (Tg) of the copolymers also decrease linearly with the feed ratio of SOC1, which suggests that the introduction of the flexible poly(SOC1) segment into the rigid BOXT cross‐linked segment relieves the internal stress in the resins that severely degrade their mechanical properties.

Photoinitiated Cationic Polymerization: Reactivity and Mechanistic Aspects

“…A similar mechanism was proposed for the thermal cross-linking of TOSU with another bifunctional oxatane monomer BOXT [125]. The results reveal that these monomers were polymerized in a sequential manner, that is, first TOSU is polymerized and propagating ends initiates the polymerization of BADGE (Scheme 11.37).…”

“…Several attempts have been made to design systems that undergo little or no volume changes upon polymerization since many important technologies, including dental materials, composites without strain stress, stereolithography, and many imaging applications do not tolerate volume shrinkage during polymerization [123][124][125][126].…”

“…Cross-linking of another expanding monomer, 1,5,7,11-tetraoxaspiro [5.5] undecane (TOSU), with bisphenol A diglycidyl ether (BADGE) and with bifunctional oxetane (BOXT) was investigated by Holder [124] and Endo [125], respectively (Chart 11.14). The resulted networks are nonshrinking cross-linked materials.…”

“…Incorporation of difunctional monomers such as BADGE [124] and BOXT [125] with TOSU provides cross-linking as well as solutions to problems associated with volume shrinkage, lack of rigidity and solvent resistance. Although the obtained homopolymers are expanded, they do not have resistance over the adverse effect of some solvents and are not rigid enough for intended applications particularly in dentistry.…”

Synthesis of the fluorene spiroorthocarbonate and the evaluation of its antishrinking activity in the cationic photopolymerization of an epoxy resin

“…Bailey and collaborators pioneered the studies on the usage of SOCs as expanding monomers [4][5][6]. Since then, numerous reports on the synthesis of new SOCs have appeared [7][8][9][10][11], and employed as shrinkage reduction additives in dioxirane polymerization by using boron trifluoride as catalyst and elevated temperature [12] as well as in cationic photopolymerization of an aromatic dioxirane [13]. Also, previous studies from our group have demonstrated the effectiveness of epoxy and oxetane functionalized SOC [14,15] as low shrinkable agents in cationic UV curing of epoxy and oxetane photocurable formulations.…”