Synthesis and Thermoreversible Gelation of Coil-Rod Copolymers with a Dendritic Polyethylene Core and Multiple Helical Poly(γ-benzyl-L-glutamate) Arms

Coil-rod copolymers with a dendritic polyethylene (DPE) core and multiple helical poly(gamma-benzyl-L-glutamate) (PBLG) arms (DPE-(PBLG)(n)) were prepared by palladium-catalyzed copolymerization in tandem with ring-opening polymerization (ROP). Macroinitiator (DPE-(NH2)(11)) was firstly prepared by the group transformation of DPE-(OH)(11) generated from palladium-catalyzed copolymerization of ethylene and acrylate comonomer. Coil-helical DPE-(PBLG)(11) copolymers were prepared by ROP of gamma-benzyl-L-glutamate-N-carboxyanhydride (BLG-NCA). These DPE-(PBLG)(11) copolymers could form thermoreversible gels in toluene solvent, and the dendritic topology of the DPE core increased the critical gelation concentrations. The self-assembled nanostructure of gels was fully characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD), and the morphology of the fibrous structure was a twisted flat ribbon through a self-assembled nanoribbon mechanism. The self-assembled fibers formed by DPE-(PBLG(45))(11) are more heterogeneous and ramified than previously observed fibers formed by PBLG homopolymer and block copolymers.