The oligomerization of mono-functional benzoxazines is demonstrated with intermolecular cyclization via a Mannich bridge structure as the primary reaction pathway.

Two series of benzoxazine/epoxy copolymers are prepared from polyetheramine-type benzoxazines and diglycidyl ether of bisphenol A (DGEBA) in various weight ratios. Each copolymer appears a single glass-transition temperature (T g ), and the T g shows a systematic increase with increasing DGEBA content for both copolymer systems, but copolymers with low DGEBA content show respectively lower T g s than the corresponding pristine polybenzoxazines. Compared to the corresponding pristine polybenzoxazines, the effect of DGEBA content on the variation in T g of the copolymers depends on the substituent structure of benzoxazines. The two series of copolymers exhibit one-way dual shape memory effect based on T g , and the shape memory effect is affected by both the substituent structure of benzoxazines and the content of DGEBA. Under motion constraints in tensile deformation mode, copolymers with low DGEBA content exhibit high shape recovery ratios (91.0-96.1%) over the corresponding polybenzoxazines (84.5%), whereas copolymers with high DGEBA content show relatively low shape recovery ratios (75.0-84.7%).

Two series of poly(benzoxazine‐ether‐urethane)s (PBEUs) are prepared through thermally activated ring‐opening polymerization (ROP) of bi‐functional benzoxazines containing ether‐urethane moieties. The bi‐functional benzoxazines are synthesized through coupling reaction of hydroxyl‐containing mono‐functional monomers based on phenol, o‐allylphenol, o‐cresol, p‐cresol, diglycolamine, and paraformaldehyde with 1,6‐hexamethylene diisocyanate (HDI) and 2,4‐toluene diisocyanate (TDI), respectively. The ROP temperature of each HDI‐based benzoxazine is higher than that of the counterpart based on TDI, and they are in descending order ortho‐, para‐, and unsubstituted phenol for both series. Due to the difference in structure symmetry between the two series monomers, the variation of polymerization rate with temperature of each TDI‐based benzoxazine is different from that of the counterpart based on HDI. The ortho‐ and para‐substituted‐phenol‐based PBEUs show lower glass transition temperatures than that of the phenol‐based counterpart. In the vicinity of the glass transition temperature, the HDI‐based PBEUs exhibit thermally induced one‐way dual‐shape memory effect.

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