Qiangbing Wei

A versatile macro-initiator with dual functional anchoring groups for surface-initiated atom transfer radical polymerization on various substrates

A versatile macro-initiator with dual functional anchoring groups for surface-initiated atom transfer radical polymerization (SI-ATRP) on various substrates is reported. Conventional free radical copolymerization was performed with N-(3,4-dihydroxyphenyl) ethyl methacrylamide (a dopamine anchor-containing monomer), 4-(1-pyrenyl) butyl methacrylate (a pyrene anchor-containing monomer), and 2-(2-bromoisobutyryloxy) ethyl methacrylate (an ATRP-initiating monomer) to produce a random copolymer. Dopamine anchors on the copolymer could assemble on the macroscopic planar substrates (e.g., Si, Ti, Au, Cu, stainless steel, Al2O3, PI, PTFE, PDMS, textile, and wood) and pyrene anchors on the carbon-based nanoscaled materials (e.g., two-dimensional graphene oxide and one-dimensional carbon nanotubes). The successful preparation of polymer brushes through SI-ATRP in a water and methanol system from various substrates was characterized via ATR-IR, AFM, XPS, TGA, and TEM, which confirmed the versatility of the macro-initiator. More importantly, a synergistic anchoring effect between catechol and pyrene groups was discovered, leading to high quantities of grafted polymers from the graphene oxide substrates. Microcontact printing of the macro-initiator was also demonstrated in the formation of patterned surfaces on the Ti substrate.

Noncovalent Microcontact Printing for Grafting Patterned Polymer Brushes on Graphene Films

This article describes a simple and universal approach to prepare patterned polymer brushes on graphene-based substrate surfaces by microcontact printing (μCP) of initiator molecules and subsequent surface initiated atom transfer radical polymerization (SI-ATRP) method. Four different initiators are designed and have strong adhesion with graphene-based substrates through noncovalent interaction. Optical and fluorescence microscopy, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the successful polymerization of vinyl monomers on substrate surfaces. To demonstrate the broad applicability of this strategy, polymer brushes with different functionalities including cationic and anionic polyelectrolyte, thermally and pH responsive polymers, as well as polymer patterns on different graphene-based surfaces are fabricated. Binary polymer brushes can also be easily prepared by further initiating the initiator backfilled in the bare areas.

Stratified polymer brushes from microcontact printing of polydopamine initiator on polymer brush surfaces.

Stratified polymer brushes are fabricated using microcontact printing (μCP) of initiator integrated polydopamine (PDOPBr) on polymer brush surfaces and the following surface initiated atom transfer radical polymerization (SI-ATRP). It is found that the surface energy, chemically active groups, and the antifouling ability of the polymer brushes affect transfer efficiency and adhesive stability of the polydopamine film. The stickiness of the PDOPBr pattern on polymer brush surfaces is stable enough to perform continuous μCP and SI-ATRP to prepare stratified polymer brushes with a 3D topography, which have broad applications in cell and protein patterning, biosensors, and hybrid surfaces.

Mussel-Inspired Thermoresponsive Polypeptide–Pluronic Copolymers for Versatile Surgical Adhesives and Hemostasis

Inspired by marine mussel adhesive proteins, polymers with catechol side groups have been extensively explored in industrial and academic research. Here, Pluronic L-31 alcoholate ions were used as the initiator to prepare a series of polypeptide-Pluronic-polypeptide triblock copolymers via ring-opening polymerization of l-DOPA-N-carboxyanhydride (DOPA-NCA), l-arginine-NCA (Arg-NCA), l-cysteine-NCA (Cys-NCA), and ε-N-acryloyl lysine-NCA (Ac-Lys-NCA). These copolymers demonstrated good biodegradability, biocompatibility, and thermoresponsive properties. Adhesion tests using porcine skin and bone as adherends demonstrated lap-shear adhesion strengths up to 106 kPa and tensile adhesion strengths up to 675 kPa. The antibleeding activity and tissue adhesive ability were evaluated using a rat model. These polypeptide-Pluronic copolymer glues showed superior hemostatic properties and superior effects in wound healing and osteotomy gaps. Complete healing of skin incisions and remodeling of osteotomy gaps were observed in all rats after 14 and 60 days, respectively. These copolymers have potential uses as tissue adhesives, antibleeding, and tissue engineering materials.

In situ formation of gold nanoparticles on magnetic halloysite nanotubes via polydopamine chemistry for highly effective and recyclable catalysis

In this study, we present a simple and green approach to fabricate a magnetic halloysite nanotube (MHNT) supported Au nanoparticle (NP) composite (MHNTs–PDA–Au) with a polydopamine functional coating for highly effective and recyclable catalysis. The fabrication of MHNTs–PDA–Au involves decoration of Fe3O4 NPs on HNTs via a one-step co-precipitation method, deposition of a polydopamine layer on the MHNTs and subsequent in situ reduction of Au NPs via polydopamine chemistry. All the processes are simple and eco-friendly without use of additional toxic reagents and complicated treatment. The obtained MHNTs–PDA–Au composite exhibits excellent and versatile catalytic activity toward the reduction of various nitrobenzene derivatives and methylene blue dye when only trace amounts of Au catalyst are used. In addition, the catalytic system can be easily recycled for several cycles based on its good magnetic properties. The synergistic combination of MHNTs, polydopamine coating and metal NPs offers a versatile platform for design of natural HNT based composite materials and will expand the applications of HNTs in heterogeneous catalysis, water purification and green chemistry.

The synthesis and tissue adhesiveness of temperature-sensitive hyperbranched poly(amino acid)s with functional side groups

The incorporation of L-3,4-dihydroxyphenylalanine (L-DOPA) residues in mussel-like biomimetic copolymers has drawn great attention due to their adhesive properties. In this work, a series of temperature-sensitive and hyperbranched poly(amino acid)s containing different functional side groups (catechol, guanidyl, mercapto and double bond) were designed and synthesized by the ring-opening polymerization of N-carboxy-α-amino acid anhydride (NCA), using a temperature-sensitive and multi-hydroxyl end pluronic L-31 as the initiator in this process. The tissue adhesive properties of these copolymers were evaluated by tensile strength tests on wet pork skin. We found that the topological structure, side groups of copolymers, adhesive temperature and cure time had influence on the wet adhesive strength, especially side groups. While only L-DOPA was incorporated into copolymeric chains, the wet adhesive strength was about 106 kPa. With guanidyl, mercapto and double bonds incorporated into copolymeric chains, an obvious increase in the wet adhesive strength was observed. Additionally, the wet adhesive strength improved by about 20 kPa at body temperature (37 °C) as compared to that at room temperature (25 °C). Meanwhile, we found that it has good biocompatibility and degradability through its cytotoxicity and degradation tests.