Low molecular weight interconnection monomers including polyepichlorohydrin, poly(propylene oxide), poly(ethylene glycol adipate), and poly(butylene adipate) were synthesized to evaluate the effects of the molecular structure of interconnection monomers on the bonding efficiency of borate ester bonding agents (BEBA) applied in four-component hydroxy-terminated polybutadiene (HTPB) propellants. The monomers were characterized by IR spectroscopy, elemental analysis, and gel permeation chromatography. A series of new borate ester bonding agents were synthesized using the as-synthesized interconnection monomers as well as poly(ethylene glycol) and applied in the preparation of four-component HTPB propellants. The application results showed that BEBA-4 prepared from poly(butylene adipate) could significantly improve the mechanical properties of the four-component HTPB propellant, reduce the slurry viscosity leading to improvement of processing properties and aging resistant performance, while no significant effect on the burning characteristics of the propellant was observed.