The Role of\na Diluent in Deformation-Induced Bonding\nof Glassy Polymer Bidisperse Blends

Bonding between polymers below the glass transition temperature\nthrough dilatational-plasticity has recently been introduced. In the\ndeformation-induced bonding (DIB) mechanism, molecular-scale dilatation\n(or densification) with enhanced chain mobility enables polymer chain\nsegments to interdiffuse and form entanglements at the interface,\nfacilitating rapid bonding below the glass transition temperature\n(<i>T</i><sub>g</sub>). Here, we are addressing the role\nof a diluent in bidisperse blends which further amplifies the molecular\nmobility, interchain interactions, and the overall free volume, while\nsimultaneously diluting the overall number of entanglements in the\nsystem as the number of host polymer chains is reduced. These simulations\nreveal that moderate addition (ϕ ≤ 20%) of a low molecular\nweight diluent drastically enhances the number of host polymer chain\nends during deformation at the interfacial region compared to a pure\nglass sample (ϕ = 0%), which improves the possibility of opposite\nside entanglement formation. At higher diluent concentrations, the\nmobility further increases, yet the system suffers a greater loss\nof number of host polymer chains; optimization is found in a balance\nof these effects. The maximum strength of bonded samples with respect\nto bulk <i>G</i><sub>I</sub>,<sub>max</sub>/<i>G</i><sub>b</sub> is thus correlated with the diluent concentration (ϕ).\nFurthermore, the optimization of material and process conditions for\nDIB has yielded a notable advancement for the conditions tested here:\nachieving a higher bonding strength in a short-time frame, approximately\none-third of the bulk, all while remaining below <i>T</i><sub>g</sub>.