Isotactic polystyrene-block-poly(ethylene glycol) (iPS-b-PEG) was synthesized via a thiol–ene click coupling reaction of vinyl-terminated isotactic polystyrene (iPS–) with thiol-terminated poly(ethylene glycol) (PEG-SH). iPS– was prepared by the extremely highly isospecific polymerization of styrene with 1,4-dithiabutandiyl-2,2′-bis(6-tertbutyl-4-methylphenoxy) titanium dichloride and methylaluminoxane (MAO) in the presence of 1,7-octadiene as a chain transfer agent. PEG-SH was synthesized by the direct esterification of hydroxyl-terminated PEG (PEG-OH) with 3-mercaptopropionic acid using HfCl4·2THF as a catalyst. The behavior and micelle morphology of the crystallization-driven self-assembly of iPS-b-PEG in N,N-dimethylformamide (DMF) were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results revealed that the crystallinity of the iPS blocks in the micelle cores was increased with increasing the storage time of the micelle solution at room temperature, and the increase of crystallinity led to the transition from spherical to petal-like micelles. With time these petal-like micelles could self-associate into flower-like aggregates. Moreover, when the newly prepared micelle DMF solution of iPS-b-PEG was dialyzed against deionized water, bowl-like micelles were formed due to the diffusion of DMF from the iPS cores into the aqueous phase.
Rapid and highly efficient side-chain functionalization of polypeptides was achieved via combination of ring-opening polymerization of a new clickable monomer of γ-propargyl-L-glutamateN-carboxyanhydride (PLG-NCA) and thiol-yne photochemistry, which provides a convenient and universal route to prepare diverse polypeptide-based biomimetic hybrid materials.
Well-defined polyethylene-block-poly(N-isopropylacrylamide) (PE-b-PNIPAM) and polyethylene-block-poly(N-isopropylacrylamide)-block-poly(2-vinylpyridine) (PE-b-PNIPAM-b-P2VP) were successfully synthesized by a combination of coordination chain transfer polymerization (CCTP) with reversible addition-fragmentation chain transfer (RAFT) polymerization in a "living"/controlled manner. Hydroxyl-terminated polyethylene (PE–OH) was firstly prepared by in situoxidation of polymer produced by CCTP with bis(imino)pyridine iron/MAO/ZnEt2 catalytic system. After an esterification of PE–OH with S-1-dodecyl-S′-(α,α′-dimethyl-α′′-acetate) trithiocarbonate, trithiocarbonate-terminated polyethylene (PE–trithiocarbonate) was obtained in high yield and used as a macromolecular chain transfer agent (macro-CTA) for RAFT polymerizations of NIPAM and 2VP. The results confirm that the tandem polymerization is an effective approach for synthesizing polyolefin-based amphiphiles. The amphiphilic block copolymers in aqueous solution can self-assemble into a nanodisk-like micelle containing a thin crystalline PE lamella domain between layers of the hydrophilic blocks. Dynamic light scattering (DLS) analyses demonstrated the thermo-responsive property of diblock copolymer PE-b-PNIPAM and double thermo- and pH-responsive properties of triblock copolymer PE-b-PNIPAM-b-P2VP.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
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