In diblock copolymer systems with blocks of similar melting temperature, such as poly(ethylene oxide)-block-poly(ε-caprolactone), the block crystallization mechanism can be manipulated by altering the isothermal crystallization temperature or relative block length. Two crystallization mechanisms exist: coincident, where both blocks nucleate and crystallize nearly simultaneously, and sequential, where the crystallization of the second block cannot crystallize under the same conditions as the first. DSC and TD-FTIR experiments were conducted using PEO-b-PCL samples to better understand the boundary between these block crystallization mechanisms. In each case, the sample was held at an isothermal crystallization temperature (Tc). Upon finishing the isothermal crystallization period, the sample was cooled to observe a coincident or sequential block crystallization mechanism. In symmetric and near symmetric block length systems (wf ≈ 0.50), coincident crystallization was observed at all Tcs. In asymmetric systems (0.50 &gt; wf &gt; 0.65), the block crystallization mechanism may be manipulated to be sequential or coincident depending on the Tc. In largely asymmetric systems (wF &gt; 0.65), a sequential block crystallization mechanism was always observed.

Block crystallization mechanisms of PEO-b-PCL as a function of weight fraction and isothermal crystallization temperature

255th National Meeting (2018)

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