The nitrile oxide-alkene curing system has attracted
attention
in the solid propellant field due to its byproduct-free, catalyst-free
ligation and room temperature curing. For the propellant field, the
design and synthesis of alkenyl-terminated adhesives are extremely
important, where controllable distribution and quantity of alkene
groups improve the integrity of the cross-linked network of the cured
elastomers. Compared with traditional adhesives for propellants such
as poly(ethylene glycol) (PEG) and polybutadiene (PB), poly(propylene
glycol) (PPG) is both highly flexible and polar due to the presence
of ether linkages and methyl groups. In this study, PPGs of different
number-average molecular weights were used as raw materials and further
modified by esterification and carbamate reactions to successfully
obtain two types of alkenyl-terminated polymers, 1-PPG and 2-PPG.
Based on the nitrile oxide-alkene click cycloaddition reaction, elastomers
were then obtained at room temperature. Strikingly, due to the interaction
of rigid and highly flexible structures, all of the elastomers exhibited
excellent low-temperature mechanical properties (at −40 °C),
particularly in terms of elongation at break (up to a maximum of 1126%).
This research introduced different kinds of alkenyl-terminated adhesives
in the propellant field, providing options for formulation design
and promoting further application of the nitrile oxide-alkene curing
system.