Synthesis and crystallization-driven solution self-assembly of PE-b-PMMA: controlling Micellar morphology through crystallization temperature and molar mass

Three polyethylene-block-poly(methyl methacrylate) (PE196-b-PMMA62, PE325-b-PMMA91 and PE607-b-PMMA208) crystalline-coil copolymers with very similar block mass ratios (r = MPE/MPMMA = 1) but different molar masses were synthesized by a tri-step reaction procedure. The molecular weight, the molecular structure and the thermal properties of PEn-OH and PEn-b-PMMAm were characterized by gel permeation chromatography (GPC), thermogravimetric analysis (TGA), proton nuclear magnetic resonance (1H NMR), fourier transform infrared spectroscopies (FTIR), and differential scanning calorimetry (DSC), respectively. The self-assembly behaviors of PEn-b-PMMAm in toluene at different crystallization temperatures were investigated by dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experiment results shown that crystallization temperatures and different molar masses exerted remarkable influence on the morphology of the resulting micelles. When the temperature of solvents were 90 °C (T > Tc), PEn-b-PMMAm could self-assemble into three different initial micelles, that is unimer, spherical micelles and large compound micelles. With the decrease of temperature (T < Tc), fibrous, spiral wound fibrous and fusiform aggregates were formed from three initial micelles respectively. In addition, the molar masses of copolymers could influence the stability as well as the disaggregation temperature of the large compound micelles.