Huysecom An-Sofie, Glorieux Christ, Thoen Jan, Thielemans Wim, Fustin Charles-André, Moldenaers Paula, Cardinaels Ruth
Soft Matter, Rheology and Technology, Department of Chemical Engineering, KU Leuven, Celestijnenlaan 200J, 3001 Leuven, Belgium.
Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium.
J Colloid Interface Sci. 2023 Jul;641:521-538. doi: 10.1016/j.jcis.2023.03.013. Epub 2023 Mar 7.
The micellization of block copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) is driven by the dehydration of PPO at elevated temperatures. At low concentrations, a viscous solution of isolated micelles is obtained, whereas at higher concentrations, crowding of micelles results in an elastic gel. Alternating PEO-PPO multiblock copolymers are expected to exhibit different phase behavior, with altered phase boundaries and thermodynamics, as compared to PEO-PPO-PEO triblock copolymers (Pluronics®) with equal hydrophobicity, thereby proving the pivotal role of copolymer architecture and molecular weight.
Multiple characterization techniques were used to map the phase behavior as a function of temperature and concentration of PEO-PPO multiblock copolymers (ExpertGel®) in aqueous solution. These techniques include shear rheology, differential and adiabatic scanning calorimetry, isothermal titration calorimetry and light transmittance. The micellar size and topology were studied by dynamic light scattering.
Multiblocks have lower transition temperatures and higher thermodynamic driving forces for micellization as compared to triblocks due to the presence of more than one PPO block per chain. With increasing concentration, the multiblock copolymers in solution gradually evolve into a viscoelastic network formed by soluble bridges in between micellar nodes, whereas hairy triblock micelles jam into liquid crystalline phases resembling an elastic colloidal crystal.
聚环氧乙烷（PEO）和聚环氧丙烷（PPO）的嵌段共聚物在高温下的胶束化是由PPO的脱水驱动的。在低浓度下，可获得孤立胶束的粘性溶液，而在较高浓度下，胶束的聚集会导致弹性凝胶。与具有相同疏水性的PEO-PPO-PEO三嵌段共聚物（普朗尼克）相比，交替的PEO-PPO多嵌段共聚物预计会表现出不同的相行为，相界和热力学会发生变化，从而证明共聚物结构和分子量的关键作用。
使用多种表征技术来绘制PEO-PPO多嵌段共聚物（ExpertGel®）在水溶液中的相行为随温度和浓度的变化情况。这些技术包括剪切流变学、差示扫描量热法和绝热扫描量热法、等温滴定量热法和透光率。通过动态光散射研究胶束大小和拓扑结构。
由于每条链上存在多个PPO嵌段，与三嵌段共聚物相比，多嵌段共聚物具有更低的转变温度和更高的胶束化热力学驱动力。随着浓度的增加，溶液中的多嵌段共聚物逐渐演变成由胶束节点之间的可溶性桥形成的粘弹性网络，而多毛的三嵌段胶束则会挤入类似弹性胶体晶体的液晶相。
