Ordering Kinetics of the BCC Morphology in Diblock Copolymer Solutions over a Wide Temperature Range

Abstract

The morphology and order-to-disorder transition (ODT) of solutions of a low molecular weight poly(styrene-b-ethylene-alt-propylene) in squalane were studied by four different methods: DSC, modulated DSC, rheology, and small-angle X-ray scattering (SAXS). The ordering from disordered micelles to the BCC morphology was traced by both rheological and SAXS measurements. The ordering mechanism was found to follow the "nucleation and growth" pathway under both shallow and deep temperature quenches. The ordering process resembles the crystallization of semicrystalline polymers. The ordering half-time (t 0.5) showed a clear minimum at an intermediate temperature. At temperatures far below the ODT temperature (TODT) but well above the glass transition temperatures of the solvent and the corona block of the micelles, t0.5 increased with concentration. The temperature dependence of the ordering process was analyzed using the Fredrickson-Binder theory. Following a shallow quench (TODT -T < 15 °C), t0.5 was found to vary with the quenching depth as ln t0.5 ∝ (TODT -T) -2 . Following a deep quench (TODT -T > 50 °C), the ordering time followed a simple Arrhenius relationship, and the activation energy showed negligible dependence on concentration.

Dynamics of a Supercooled Disordered Sphere-Forming Diblock Copolymer as Determined by X-ray Photon Correlation and Dynamic Mechanical Spectroscopies

“…An induction period precedes nucleation and growth of a polycrystalline BCC state. As shown in other studies of block polymer melts and solutions, 7,25,27 G′ measured at low frequency increases monotonically and eventually reaches a plateau at long times as randomly oriented grains of the BCC structure develop throughout the sample. From the measurements shown in Figure S2, we constructed a time−temperature transformation (TTT) diagram where the fractional conversion to the ordered state X(t) = [G′(t) − G′(200 s)]/[G′(t → ∞) − G′(200 s)] is shown in Figure 1B as a function of time t for X(t) = 25%, 50%, and 75%.…”

Shear‐induced structuring kinetics in thermoplastic segmented polyurethanes monitored by rheological tools

“…Nevertheless, in both cases, the global trend of the plot of the solidification characteristic times versus the temperature should lie on a U‐shaped curve (or a bell‐shaped curve in terms of solidification velocity). Indeed, for relatively high temperatures, the phase separation mechanism kinetics for block copolymers (melts or solutions) is mainly governed by the so‐called quenching depth, which is evaluated by the difference between the temperature of the order–disorder transition ( T ODT ) and the actual temperature 60–62. For the crystallization mechanism, still in the high temperature range, the kinetics is also governed by a temperature difference, namely the supercooling, which is the difference between the melting temperature of the infinite crystal ( T ) and the actual temperature 63.…”

“…Nevertheless, this trend should not follow an Arrhenius law. Conversely, in the lower temperature range, both mechanisms (phase separation and crystallization) are governed by the diffusion of molecules and therefore can follow an Arrhenius law 62. Obviously, in that case, the solidification time increases when the temperature decreases.…”

Kinetics of Block Copolymer Phase Segregation during Sub-millisecond Transient Thermal Annealing

“…Previous kinetic studies − have followed the ODT in pure polymer systems for shallow quench depths on the order of ∼10 °C. Other studies have examined the ODT − or the order–order transition (OOT) − kinetics in solvent/polymer systems at comparable quench depths while inducing the phase transformation by controlling temperature − or changing the solvent volume fraction . Direct measurements of the segregation process, however, are difficult at quench depths beyond ∼10 °C − due to the fast kinetics, and little work has been reported in this deeply metastable regime.…”