Unique Toroidal Morphology from Composition and Sequence Control of Triblock Copolymers

• Published in: Journal of the American Chemical Society 2005-06, Vol.127 (24), p.8592-8593
• Main Authors: Chen, Zhiyun, Cui, Honggang, Hales, Kelly, Li, Zhibin, Qi, Kai, Pochan, Darrin J, Wooley, Karen L
• Format: Article
• Language: English
• Subjects: Acrylic Resins - chemistry; Applied sciences; Drug Delivery Systems; Edetic Acid - analogs & derivatives; Edetic Acid - chemistry; Exact sciences and technology; Hydrophobic and Hydrophilic Interactions; Microscopy, Electron, Transmission; Nanostructures - chemistry; Organic polymers; Physicochemistry of polymers; Polymers - chemistry; Polymethacrylic Acids - chemistry; Polystyrenes - chemistry; Properties and characterization; Structure, morphology and analysis
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja050290p

The mechanism by which the unique toroidal supramolecular assemblies were formed for triblock copolymers of acrylic acid (AA), methyl acrylate (MA), and styrene (S), PAA99-b-PMA73-b-PS66, was probed in this study by investigating the influences of the block copolymer compositions and sequences. Two triblock copolymers, PAA99-b-PMA73-b-PS66 and PAA99-b-PS76-b-PMA62, and two diblock copolymers, PAA99-b-PMA155 and PAA99-b-PS133, were studied under experimental solution-state conditions that involved a range of solvent/nonsolvent (tetrahydrofuran/water) compositions, each in the presence of 2,2‘-(ethylenedioxy)bis(ethylamine). The resulting morphologies were determined by transmission electron microscopy. The failures to afford toroidal supramolecular assemblies from both diblock copolymers having comparable lengths of the total hydrophobic chain segment, either entirely PMA or entirely PS, and from the triblock copolymer having a reversed connection sequence for the hydrophobic (PMA and PS) segments demonstrate the unique self-assembly behaviors of triblock copolymers and the importance of the block copolymer sequence.