We propose a model for MgCl 2 -supported Ziegler−Natta catalysts, which is capable to reconcile the discrepancies emerging in the last 20 years, in which attempts have been made to rationalize experimental data by molecular models. We show that step defects on the thermodynamically more stable (104) facet of MgCl 2 can lead to sites for strong TiCl 4 adsorption. The corresponding Ti-active site is stereoeselective, and its stereoselectivity can be enhanced by coordination of Al-alkyls or Lewis bases in the close proximity. The surface energy of the step defected (104) MgCl 2 facet is clearly lower than that of the well accepted (110) facet.

The micelles of a poly(ε-caprolactone)-b-poly(ethylene oxide) block copolymer (PCL 59 -b-PEO 113 ) in different mixed solvents were held at 53 °C for 5 min, and seed solutions with different micellar morphologies and amounts of micellar semicrystalline seeds were prepared. The crystallinity of these seed micelles was identified by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). It is found that mostly amorphous spherical micelles are formed by heating micellar solutions in H 2 O/THF (5/1 v/v) and H 2 O/dioxane (5/1 v/v) mixed solvents, a mixture of amorphous spherical micelles and short semicrystalline cylindrical micelles is yielded in H 2 O/DMF (5/1 v/v), whereas mostly short semicrystalline cylindrical micelles are obtained in H 2 O/DMSO (5/1 v/v) mixed solvent. The seed solutions were placed at 4 °C for micellar growth. Transmission electron microscope (TEM) shows that micellar growth driven by epitaxial crystallization of core-forming PCL chains takes place and the length of grown cylindrical micelles increases with time. Two growth modes are observed. One is the growth of unimers (or amorphous spherical micelles) on the active ends of semicrystalline cylindrical micelles in micellar solution in H 2 O/DMF (5/1 v/v) at the initial growth period. The other is the growth by end-to-end coupling of cylindrical micelles in H 2 O/DMSO (5/1 v/v). The kinetics of micellar growth is strongly dependent on the growth mechanism. The growth of the cylindrical micelles in the H 2 O/DMF (5/1 v/v) solution is much faster than that in the H 2 O/DMSO (5/1 v/v) solution. On long time scale, micellar growth by end-to-end coupling of semicrystalline cylindrical micelles occurs with slow rate in both H 2 O/DMF (5/1 v/v) and H 2 O/DMSO (5/1 v/v) solutions, and the growth rate in H 2 O/DMF (5/1 v/v) solution is even slower than that in H 2 O/DMSO (5/1 v/v).

The effect of crystallization temperature on the micellar morphology of PCL‐b‐PEO block copolymers in water has been studied. It is found that the micellar morphology of PCLnPEO44 and PCLnPEO113 changes with crystallization temperature in different ways because of two competitive factors: perfection of the PCL crystals in the core and deformation of the soluble PEO block. For PCLnPEO44, perfection of the PCL crystals dominates the micellar morphology and lamellar micelles are formed at a higher crystallization temperature. For PCLnPEO113 the micellar morphology is mainly determined by the tethering density and spherical micelles or cylindrical micelles with a larger length/diameter ratio are formed at a higher crystallization temperature because of the larger tethering density.

Two hydrogen (H)-bond donors, phenol and l-threonine, were added into the aqueous solutions containing crystalline micelles of a poly­(ε-caprolactone)-b-poly­(ethylene oxide) (PCL-b-PEO) block copolymer, respectively. Dynamic light scattering (DLS) characterization showed that the micellar size became smaller after addition of phenol. Transmission electron microscopy (TEM) results revealed that the long crystalline cylindrical micelles formed in the neat aqueous solution were fragmented into short cylinders and even quasi-spherical micelles, as the phenol concentration increased. By contrast, the spherical PCL-b-PEO crystalline micelles could be transformed into short cylinders and then long cylinders after addition of l-threonine. Reversible morphological transformation was realized for the PCL-b-PEO crystalline micelles by adding these two H-bond donors alternately. It is confirmed that both phenol and l-threonine could form H-bonds with PEO. We proposed that, the micellar corona was swollen by phenol, leading to fragmentation of the micellar core, whereas the PEO blocks in the micellar corona was dynamically cross-linked by l-threonine beacuse of its multiple H-bond-donation groups, resulting in a smaller reduced tethering density.