Renaud Nicolaÿ

How far can we push polymer architectures

We here report the synthesis and characterization of a complex polymeric architecture based on a block copolymer with a cylindrical brush block and a single-chain polymeric nanoparticle block folded due to strong intramolecular hydrogen-bonds. The self-assembly of these constructs on mica surfaces was studied with atomic force microscopy, corroborating the distinct presence of block copolymer architectures.

The balance between intramolecular hydrogen bonding, polymer solubility and rigidity in single-chain polymeric nanoparticles

A library of copolymers with pendant, protected ureido-pyrimidinone (UPy) groups was prepared applying controlled polymerization techniques. The polymer backbones were based on polyacrylate, polymethacrylate, polystyrene and polynorbornene and differ in stiffness, molecular weight and the linking moiety between the backbone and the UPy group. In all cases, the percentage of protected UPy groups was kept constant. The effect of solvent on the behaviour of the polymers before and after removal of the protecting groups was evaluated in, among others, chloroform and tetrahydrofuran (THF). After deprotection of the UPy protecting group, the UPys dimerize via four-fold H-bonding in THF, inducing a collapse into single-chain polymeric nanoparticles (SCPNs), as evidenced by a combination of 1H-NMR spectroscopy, size-exclusion chromatography and dynamic light scattering. In chloroform, on the other hand, dimerization of the UPy groups is present but interchain interactions occur as well, resulting in less-defined SCPNs. Remarkably, the flexibility of the polymer backbone, the polymer molecular weight and the nature of the linker unit all do not affect SCPN formation. In contrast, the interaction between solvent and the UPy moiety is a critical parameter for SCPN formation. For example, strong intramolecular dimerization of the UPys is observed in THF while interparticle interactions are suppressed. From this investigation we conclude that a wide variety of polymer backbones are suitable for polymer collapse via supramolecular interactions and thus allow for the formation of SCPNs but that the solvent choice is crucial to enhance intramolecular H-bonding and, at the same time, to suppress interparticle interactions.

Standing Arrays of Gold Nanorods End‐Tethered with Polymer Ligands

Nanomaterials with vectoral electromagnetic properties have potential applications in solar cells, plasmonic cavity resonators, light polarizers, and biosensing. Here a new, simple, solution-based method for producing nanomaterials comprising vertically aligned standing arrays of gold nanorods (NRs) end-functionalized with polymer ligands is reported. The method utilizes the side-by-side assembly of the NRs into large 2D superlattices, followed by the precipitation of the lattices on a solid substrate. The critical design rules for the self-assembly of superlattices are demonstrated, and they show the generality of the method by forming standing arrays from the NRs end-tethered with poly(N-vinylcarbazole) or with polystyrene molecules.

Synergistic Interaction Between ATRP and RAFT: Taking the Best of Each World*

This review covers recent developments on the combination of atom transfer radical polymerization (ATRP) and reversible addition–fragmentation chain transfer (RAFT) polymerization to produce well controlled (co)polymers. This review discusses the relative reactivity of the R group in ATRP and RAFT, provides a comparison of dithiocarbamate (DC), trithiocarbonate (TTC), dithioester (DTE), and xanthate versus bromine or chlorine, and an optimization of catalyst/ligand selection. The level of control in iniferter polymerization with DC was greatly improved by the addition of a copper complex. New TTC inifers with bromopropionate and bromoisobutyrate groups have been prepared to conduct, concurrently or sequentially, ATRP from Br-end groups, ATRP from the TTC moiety, and RAFT polymerization from the TTC moiety, depending on the combination of monomer and catalyst employed in the reaction. The use of concurrent ATRP/RAFT (or copper-catalyzed RAFT polymerization or ATRP with dithioester leaving groups), resulted in improved control over the synthesis of homo- and block (co)polymers and allowed preparation of well-defined high-molecular-weight polymers exceeding 1 million. Block copolymers that could not be prepared previously have been synthesized by sequential ATRP and RAFT polymerization using a bromoxanthate inifer. A simple, versatile, and one-step method involving atom-transfer radical addition–fragmentation (ATRAF) for the preparation of various chain transfer agents (including DC, DTE, and xanthate) in high purity is discussed and a one-pot, two-step polymerization starting with a RAFT agent synthesized by ATRAF, followed by polymerization, is demonstrated.