Synthesis and self-assembly of PMMA-b-(u)PE-b-PMMA copolymers: study the aggregate morphology in toluene vapor

Well-defined poly(methyl methacrylate)-b-polyethylene-b-poly(methyl methacrylate) triblock copolymers with saturated and unsaturated PE as the central block (PMMA-b-(u)PE-b-PMMA) were synthesized by combining acyclic diene metathesis (ADMET) with thiol-ene click chemistry and atom transfer radical polymerization (ATRP). The mass ratios of (u)PE/PMMA in the copolymers are 1:1 and 1:2 respectively, while the molecular weight of the (u)PE block remained constant (22 k). The characterization, thermal properties and crystallization of copolymers were determined by 1H/13C NMR, IR, TGA, DSC and XRD. As a result, the PMMA blocks can form stereocomplex crystal, which was affected by copolymer composition as well as the crystallization of PE middle block. Under solvent vapor annealing (SVA) conditions, amorphous or weak crystallization block copolymers assembled into worm-like network aggregates, while the aggregates evolution to fibrous or banded and fabric-like network covering particles morphology driving by PE nuclear crystallization and PMMA shell crystallization respectively.