  Bonding between polymers below the glass transition temperature through
molecular-scale dilatation (or densification)-based interdiffusion of
macromolecules has recently been introduced. In this mechanism, short timeframe
plastic deformation enables polymer chains to interdiffuse and form
entanglements at the interface, facilitating rapid bonding below the glass
transition temperature ($T_g$). Here, we are addressing the role of a lower
molecular weight diluent in bonding polymer interfaces of bidisperse blends
through deformation-induced bonding (DIB) at temperatures well below both the
surface and bulk glass transition temperatures, $T_g^s$ and $T_g^b$,
respectively, by using molecular simulations. These simulations reveal that
addition of the diluent ($\phi\le$20\%) drastically enhances the number of
chain-ends at the interfacial region compared to a pure glass sample
($\phi=0\%$) during deformation below $T_g^s$, which improves the possibility
of opposite side entanglement formation. The changes in stress-strain response
of debonded samples correlate with the normalized entanglement density.
Likewise, the maximum interfacial fracture energy $G_{I,max}$ of debonded
samples is correlated with the diluent concentration ($\phi$), below $T_g^s$.
Furthermore, the optimization of material and process conditions for DIB has
yielded a notable advancement for the conditions tested here: achieving a
higher bonding strength, approximately one-third of the bulk, all while
remaining below $T_g$.
