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

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

In this review, we describe the recent advances in supramolecular helical assemblies formed from chiral and achiral small molecules, oligomers (foldamers), and helical and nonhelical polymers from the viewpoints of their formations with unique chiral phenomena, such as amplification of chirality during the dynamic helically assembled processes, properties, and specific functionalities, some of which have not been observed in or achieved by biological systems. In addition, a brief historical overview of the helical assemblies of small molecules and remarkable progress in the synthesis of single-stranded and multistranded helical foldamers and polymers, their properties, structures, and functions, mainly since 2009, will also be described.

Supramolecular Helical Systems: Helical Assemblies of Small Molecules, Foldamers, and Polymers with Chiral Amplification and Their Functions

Side chains in conjugated polymers have been primarily utilized as solubilizing groups. However, these side chains have roles that are far beyond. We advocate using side chain engineering to tune a polymer’s physical properties, including absorption, emission, energy level, molecular packing, and charge transport. To date, numerous flexible substituents suitable for constructing side chains have been reported. In this Perspective article, we advocate that the side chain engineering approach can advance better designs for next-generation conjugated polymers.

Side Chain Engineering in Solution-Processable Conjugated Polymers

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ev...

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

Two types (imine and boronate) of covalent organic frameworks (COFs) having a porphyrin unit have been synthesized. The two highly crystalline porphyrin COFs (COF-366 and COF-66) display excellent chemical and thermal stability and are permanently porous. Two-dimensional extended layered structures of the two COFs demonstrate very high charge carrier mobility values (8.1 cm2 V−1 s−1).

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Covalent Organic Frameworks with High Charge Carrier Mobility

We report on the solution-state assembly of all-conjugated polythiophene diblock copolymers containing nonpolar (hexyl) and polar (triethylene glycol) side chains. The polar substituents provide a large contrast in solubility, enabling formation of stably suspended crystalline fibrils even under very poor solvent conditions for the poly(3-hexylthiophene) block. For appropriate block ratios, complexation of the triethylene glycol side chains with added potassium ions drives the formation of helical nanowires that further bundle into superhelical structures.

Hierarchical Helical Assembly of Conjugated Poly(3-hexylthiophene)-block-poly(3-triethylene glycol thiophene) Diblock Copolymers

http://absimage.aps.org/image/MAR11/MWS_MAR11-2010-005155.pdf

Hierarchical Helical-Assembly of Conjugated Poly(3-hexylthiophene)- b-poly(3-triethylene glycol-thiophene) Diblock Copolymers

Polyphenylenes (PPs) represent a class of conjugated polymers that have been used in applications ranging from organic electronic devices, sensors, polymer film additives to manipulate their mechanical properties, and even fluorescent tags or nanocarriers in biological media.1−3 The versatility of PPs stem from innovative synthetic strategies that have evolved throughout the years to provide avenues that precisely tune their architecture and function for specific purposes. This Review will cover the state of the art research on various PPs related to the relationship between their structure and resulting properties.

Dimensional Evolution of Polyphenylenes: Expanding in All Directions

The synthesis of diblock copolymer brushes, including poly(styrene) (PSty)-b-PSty, PSty-b-poly(acrylic acid), PSty-b-poly(N-isopropylacrylamide), and poly(methyl acrylate)-b-poly(N,N-(dimethylamino)ethyl acrylate), was achieved utilizing a combination of surface-mediated atom transfer radical polymerization (ATRP) and reversible addition−fragmentation chain transfer (RAFT) polymerization techniques. Conversion of bromine end groups of homopolymer brushes formed by ATRP via a modified atom transfer addition reaction to a RAFT agent and diblock extension via RAFT polymerization allowed the direct formation of well-defined stimuli-responsive diblock copolymer brushes. The addition of sacrificial initiator and/or chain transfer agent permitted formation of well-defined diblock copolymer brushes and free polymer chains in solution. The free polymer chains were isolated and used to estimate the molecular weights and polydispersity index of chains attached to the surface. Ellipsometry, contact angle measurements...

Synthesis of Surface-Initiated Stimuli-Responsive Diblock Copolymer Brushes Utilizing a Combination of ATRP and RAFT Polymerization Techniques

A series of poly(3-hexyl thiophene) (P3HT)-based diblock copolymers were prepared and examined in solution for their assembly into fibrils, and post-assembly cross-linking into robust nanowire structures. P3HT-b-poly(3-methanol thiophene) (P3MT), and P3HT-b-poly(3-aminopropyloxymethyl thiophene) (P3AmT) diblock copolymers were synthesized using Grignard metathesis (GRIM) polymerization. Fibrils formed from solution assembly of these copolymers are thus decorated with hydroxyl and amine functionality, and cross-linking is achieved by reaction of diisocyanates with the hydroxyl and amine groups. A variety of cross-linked structures, characterized by transmission electron microscopy (TEM), were produced by this method, including dense fibrillar sheets, fibril bundles, or predominately individual fibrils, depending on the chosen reaction conditions. In solution, the cross-linked fibrils maintained their characteristic vibronic structure in solvents that would normally disrupt (dissolve) the structures.

Brenton A. G. Hammer

Papers

Hierarchical Helical Assembly of Conjugated Poly(3-hexylthiophene)-block-poly(3-triethylene glycol thiophene) Diblock Copolymers

Hierarchical Helical-Assembly of Conjugated Poly(3-hexylthiophene)- b-poly(3-triethylene glycol-thiophene) Diblock Copolymers

Dimensional Evolution of Polyphenylenes: Expanding in All Directions

Synthesis of Surface-Initiated Stimuli-Responsive Diblock Copolymer Brushes Utilizing a Combination of ATRP and RAFT Polymerization Techniques

Cross-Linked Conjugated Polymer Fibrils: Robust Nanowires from Functional Polythiophene Diblock Copolymers