To achieve high-performance thermosets, three diallyl-containing main-chain type benzoxazine polymers, (MCBP) were prepared from Mannich condensation of 2,2'-diallyl bisphenol A, paraformaldehyde, and three diamines: 4,4'-diaminodiphenylmethane (DDM), 4,4'-oxydianiline (ODA), and 2,2'-bis(4-(4-aminophenoxy)phenyl)propane (BAPP), respectively. These MCBPs can be cured and general a phenolic hydroxyl type benzoxazine thermosets even though no free ortho and free para positions to the oxygen of oxazine in their structures. After thermally curing, the resulting thermosets display much higher T-g than the thermosets of 2,2'-diallyl bisphenol A/aniline-based, 2-allyl phenol/DDM-based, and 2-allylphenol/ODA-based benzoxazine, demonstrating the advantage of MCBP on thermal properties over monomer type benzoxazines. The refractive index of the thermosets is higher than 1.689 at 589 nm, which is relatively high compared with other polymers. These results demonstrate the advantage of diallyl-containing MCBPs on thermal properties and refractive index over allyl-containing monomer type benzoxazines. (C) 2018 Elsevier Ltd. All rights reserved.