Construction\nof Elastomeric Nanobelts in a Glassy\nPolymer Matrix: Toward Supertoughened Nanoalloys with Significantly\nDepressed Yielding Behaviors

Rubber-toughened glassy polymers, researched as a prominent\ntoolkit\nto fabricate high-performance plastics, are usually confronted with\na great loss of tensile strength at the point of apparent yielding.\nExploiting advanced plastic nanoalloys with high toughness and small\nstress difference (Δσ) between yielding and tensile platforms\nat high-strain levels is extremely being pursued yet challenging.\nTaking glassy poly(l-lactide) (PLLA) as an example, here,\na viable and universal approach is discovered to elaborate supertoughened\nnanoalloys with significantly depressed yielding behaviors by virtue\nof elastomeric nanobelts to replace conventional rubber droplets in\na glassy matrix by a simple reactive processing strategy. Stereocomplex\ncrystal (SC)-immobilized EGMA, prepared by cocrystallization of enantiopure\nPDLA-/PLLA pairs respectively pregrafted onto EGMA chains, is used\nto toughen PLLA. Therefore, the structure of the elastomer, from droplets\nand shells to nanobelts in the PLLA matrix, can be achieved. Such\ncontrollable morphology allows for the corresponding nanoalloys with\nsignificantly enhanced notched impact strength (from 5.7 to 60.2\n to 91.3 kJ/m<sup>2</sup>) and shortened Δσ (from 17.5\nto 15.8 to 6.8 MPa). Furthermore, tricontinuous morphology integrates\npenetrative elastomeric nanobelts (EGMA), glassy polymers (PLLA),\nand SC phases, which are achieved by adjusting SC moieties. The authors\ndemonstrate that the resulting nanoalloy integrates superior performance\n(toughness, heat resistance, and crystallization rate) and stress\nleveling-off without fully undergoing real yielding (<i>Δσ</i> = 1.4 MPa), surpassing most elastomer-toughened PLA alloys. The\nmorphology development and underlying origin of the impact/deformation\nmechanism are elucidated. To our knowledge, this is the first time\nthat the validity of such supertoughened glassy polymer alloys with\nsignificantly necking-suppressed deformation has been demonstrated.\nThe versatile strategy can be further extended to arbitrary engineering\nplastics, including PET, PBT, and nylon, providing a paradigm in the\ndevelopment of advanced nanoalloys, which is quite challenging via\nexisting industrial technologies.