Raphael Barbey

Polymer Brushes via Surface-Initiated Controlled Radical Polymerization: Synthesis, Characterization, Properties, and Applications

Keywords: Fragmentation Chain-Transfer ; Self-Assembled Monolayers ; Walled Carbon Nanotubes ; Well-Defined Polymer ; Nitroxide-Mediated Polymerization ; Block-Copolymer Brushes ; Poly(Methyl Methacrylate) Brushes ; Transfer Raft Polymerization ; Quartz-Crystal Microbalance ; Poly(Acrylic Acid) Brushes Reference EPFL-REVIEW-148464doi:10.1021/cr900045aView record in Web of Science Record created on 2010-04-23, modified on 2017-05-10

Room Temperature, Aqueous Post-Polymerization Modification of Glycidyl Methacrylate-Containing Polymer Brushes Prepared via Surface-Initiated Atom Transfer Radical Polymerization

This manuscript reports on the post-polymerization modification of poly(glycidyl methacrylate) (PGMA) and PGMA-co-poly(2-(diethylamino)ethyl methacrylate) (PGMA(x)-co-PDEAEMA(y)) (co)polymer brushes prepared via surface-initiated atom transfer radical polymerization (SI-ATRP). The aim of this study was to evaluate the ability of tertiary amine groups incorporated in the polymer brush to accelerate the ring-opening of the epoxide groups by primary amines and to facilitate the aqueous, room temperature post-polymerization modification of the brushes. Using Fourier transform infrared (FTIR) spectroscopy to monitor the ring-opening reaction of the epoxide groups, it was found that the incorporation of 2-(diethylamino)ethyl methacrylate (DEAEMA) groups in the PGMA brushes significantly accelerated the rate of the post-polymerization modification reaction with several model amines. The rate enhancement was dependent on the fraction of DEAEMA units incorporated in the copolymer brush. For example, whereas 24 h was necessary to obtain a conversion of approximately 40% for PGMA brushes immersed in a 1 M propylamine solution in water, the same conversion was reached, in identical reaction conditions, after 8 and 2 h with copolymer brushes containing 10 mol % and 25 mol % of DEAEMA along the copolymer chains, respectively. In a final series of proof-of-concept experiments, the feasibility of the glycidyl methacrylate containing brushes to act as substrates for protein immobilization was studied. Using FTIR spectroscopy and quartz crystal microbalance with dissipation (QCM-D) experiments, it could be demonstrated that the incorporation of DEAEMA units not only enhanced the rate of the protein immobilization reaction, but also resulted in higher protein binding capacities as compared to a PGMA homopolymer brush. These features make PGMA(x)-co-PDEAEMA(y) brushes very attractive candidates for the development of protein microarrays, among others.

Ultrafast RAFT polymerization: multiblock copolymers within minutes

The synthesis of multiblock copolymers is often considered to be synthetically challenging and time consuming. In this contribution, the development of a remarkably efficient and versatile procedure to access multiblock copolymers via reversible addition–fragmentation chain transfer (RAFT) polymerization is reported. The robustness and versatility of the RAFT process are demonstrated in this report by preparing multiblock copolymers using uncommon experimental conditions. The synthesis of each block was performed in the presence of air and only required 3 minutes to reach near full monomer conversion. This approach removes the necessity to deoxygenate the solution and allows access to complex copolymer structures in very short time periods. For example, this process allowed the preparation of a heptablock homopolymer with a well-defined architecture in just 21 minutes. We also discuss the limitations inherent to this approach. This strategy is shown to be particularly efficient when blocks with low degrees of polymerization (DP 50), the procedure is typically limited to the preparation of di- or triblock copolymers.

Nonfouling Polypeptide Brushes via Surface-initiated Polymerization of Nε-oligo(ethylene glycol)succinate-L-lysine N-carboxyanhydride

This contribution describes the preparation of nonfouling polypeptide brushes via surface-initiated ring-opening polymerization of oligo(ethylene glycol) modified L-lysine N-carboxyanhydrides. Circular dichroism experiments indicated that these surface-anchored polypeptide chains assume an α-helical conformation, which does not change between pH 4 and 9. Furthermore, nonspecific adsorption of fluorescent labeled bovine serum albumin and fibrinogen on glass slides modified with these brushes was greatly reduced compared to unmodified glass substrates.

Protein Microarrays Based on Polymer Brushes Prepared via Surface-Initiated Atom Transfer Radical Polymerization

Polymer brushes represent an interesting platform for the development of high-capacity protein binding surfaces. Whereas the protein binding properties of polymer brushes have been investigated before, this manuscript evaluates the feasibility of poly(glycidyl methacrylate) (PGMA) and PGMA-co-poly(2-(diethylamino)ethyl methacrylate) (PGMA-co-PDEAEMA) (co)polymer brushes grown via surface-initiated atom transfer radical polymerization (SI-ATRP) as protein reactive substrates in a commercially available microarray system using tantalum-pentoxide-coated optical waveguide-based chips. The performance of the polymer-brush-based protein microarray chips is assessed using commercially available dodecylphosphate (DDP)-modified chips as the benchmark. In contrast to the 2D planar, DDP-coated chips, the polymer-brush-covered chips represent a 3D sampling volume. This was reflected in the results of protein immobilization studies, which indicated that the polymer-brush-based coatings had a higher protein binding capacity as compared to the reference substrates. The protein binding capacity of the polymer-brush-based coatings was found to increase with increasing brush thickness and could also be enhanced by copolymerization of 2-(diethylamino)ethyl methacrylate (DEAEMA), which catalyzes epoxide ring-opening of the glycidyl methacrylate (GMA) units. The performance of the polymer-brush-based microarray chips was evaluated in two proof-of-concept microarray experiments, which involved the detection of biotin-streptavidin binding as well as a model TNFα reverse assay. These experiments revealed that the use of polymer-brush-modified microarray chips resulted not only in the highest absolute fluorescence readouts, reflecting the 3D nature and enhanced sampling volume provided by the brush coating, but also in significantly enhanced signal-to-noise ratios. These characteristics make the proposed polymer brushes an attractive alternative to commercially available, 2D microarray surface coatings.

Diagnostic and Sensory Polymer Brushes

Polymer brushes are thin coatings in which individual polymer chains are tethered by one of their chain ends to a substrate (Fig. 1).[1] Amongst the various strategies that are available for the synthesis of polymer brushes, surface-initiated atom transfer radical polymerization (SI-ATRP) represents an attractive strategy to prepare dense polymer brushes with precise control over thickness, composition and architecture.

CHAPTER 7:Dendritic Polymers from Thiol–Yne Reactions

We review the use of thiol–yne reaction for the design of branched structures, dendrimers and hyperbranched polymers. In addition to its typical ‘click’ chemistry attributes, the advantages of this reaction include the ability to generate almost perfect branching patterns, the possibility to introduce many more functionalities at each generational step and its tolerance towards chemical functionality, allowing the introduction of a wide range of functional groups into the structures.