Halogen-bond Mediated 3D Confined Assembly Of AB Or ABC Block Copolymer And Homopolymer Blends

Halogen bonds are important noncovalent interactions for constructing functional materials with tunable morphology via self-assembly.Compared with hydrogen bonds,halogen bonds cover a wider energy range(5-180 k J/mol)and thus show distinct advantage in molecular recognition.Unlike hydrogen bonds,halogen bonds are stable in polar solvents.Therefore,halogen bonds are fairly advantageous for self-assembled supramolecular systems.Halogen-bond mediated supramolecular systems have become a research hotspot in the fields of synthetic chemistry and nanoscience.However,only preliminary studies have been reported so far to discuss halogen-bond mediated confined assembly in emulsion droplets.In this work,we observed block copolymer nanoparticles with complex morphology via halogen-bond driven confined assembly of block copolymer in emulsion droplet,and revealed the law of order-to-order transitions of internal morphology.Details are described as follows:(1)Polystyrene-b-poly(4-vinyl pyridine)(PS_51k-b-P4VP_18k)AB diblock copolymer was designed as halogen acceptor;poly(3-(2,3,5,6-tetrafluoro-4-iodophenoxy)propyl acrylate(PTFIPA_32k)was used as halogen donor via reversible addition-fragmentation chain transfer(RAFT),with iodine(I)at the side group of the PTFIPA_32k homopolymer,which can interact with nitrogen(N)at the P4VP segment of PS_51k-b-P4VP_18k to form a halogen bonding donor-acceptor pair(I....N).I....N bond mediated self-assembly was utilized to enable PS_51k-b-P4VP_18kand PTFIPA_32k to form nanoparticles with diverse internal morphological features(e.g.,spherical,cylindrical,vermiform,lamellar,inverse cylindrical)in three-dimensional(3D)confined spaces by tuning PTFIPA_32k content and the type of surfactant.Additionally,mesoporous microspheres and other disassembled particles were obtained by selective swelling/deswelling of the P4VP segments in the nanospheres.Halogen bonds may pertinently change the chemical constitution of an assembly unit and effectively alter the shape,structure,and surface composition of microspheres.(2)Polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide)(PS_75k-b-P2VP_21k-b-PEO_16.5k)triblock copolymer was selected as halogen acceptor to form donor-acceptor pairs with the halogen donor PTFIPA_32k.Due to the complex chemical structure,triblock copolymers could self-assemble into microparticles with more diversified morphological features,such as spiral,cyclic,and giant segmental vermiform.I....N bond mediated self-assembly supports PS_75k-b-P2VP_21k-b-PEO_16.5k and PTFIPA_32k in forming spherical,layered?annular cavities in3D confined spaces by tuning PTFIPA_32k content.The type of surfactant denotes a convenient and highly efficient approach to create tailored polymer microspheres with delicate designs of cavity structures that can be used as drug and catalyst carriers and templates for hybrid materials.