Diffusion Control of Homogeneous Crystallization in Nanoconfined Domains of Block Copolymers

Abstract

Confined crystallization in a poly(oxyethylene)‐b‐poly(oxybutylene)/poly(oxybutylene) blend (E₁₁₅B₁₀₃/B₂₈, φ_E = 0.14) with bcc morphology and in a polystyrene‐b‐poly (oxyethylene)‐b‐polystyrene (S‐E‐S) triblock copolymer (S₄₀E₁₃₆S₄₀, φ_E = 0.407) with lamellar morphology was studied using differential scanning calorimetry (DSC). Two types of confined crystallization with different characteristic Avrami exponents were identified in both systems. At higher crystallization temperature (T _c), the Avrami exponent is 1.0 and the overall crystallization rate is controlled by the homogeneous nucleation rate. At lower T _c, the Avrami exponent is 0.5, which is attributed to diffusion‐controlled confined crystallization. This shows that diffusion has a great influence on the overall crystallization rate when chain mobility is reduced, which can be caused either by lower T _c or by constrained microstructure.