Complex single-chain polymer topologies locked by positionable twin disulfide cyclic bridges.

Oligomers containing the peptide sequence cysteine-any-cysteine (CXC) were attached, at specific locations, to a linear chain of polystyrene. The polymer-bound peptide motifs were then oxidized under dilute conditions to afford a complex bio-hybrid bi-cyclic topology via intramolecular twin disulfide bridge formation.

Sequence-controlled polymerization using dendritic macromonomers: precise chain-positioning of bulky functional clusters.

A simple strategy to insert functional dendrons at precise positions along a linear polymer backbone is reported. Sequence controlled copolymerization of styrene and polyester dendrons containing a maleimide unit at their focal points was utilized to yield such polymers.

Controlled growth of protein resistant PHEMA brushes via S-RAFT polymerization.

The reversible addition-fragmentation chain transfer polymerization of 2-hydroxyethyl methacrylate (HEMA) from surfaces (S-RAFT) using an R-group-attached chain transfer agent (CTA) is presented. The approach was exploited for the efficient preparation of well-defined PHEMA brushes of up to 50 nm thickness in a controlled fashion without using any cytotoxic catalyst. The chemical composition, morphology and wettability of the samples were assessed by X-ray photoelectron spectroscopy, atomic force microscopy and water contact angle measurements, while the growth kinetics were studied by monitoring the dry thickness via spectroscopic ellipsometry. The mechanism and kinetics of the RAFT polymerization on the surface - in the presence of a sacrificial CTA and of solvent mixtures with different polarities - were investigated. A marked effect of the concentration of the sacrificial CTA on the kinetics was observed. Importantly - and for the first time - the living PHEMA brushes were exploited as macroRAFT agents for chain extension, and thicknesses up to 70 nm were achieved. The prepared PHEMA brushes were challenged with protein solutions demonstrating their resistance to fouling.

Precision polyelectrolytes.

Charged macromolecules with controlled microstructures were prepared. Well-defined non-ionic precursors were first synthesized by sequence-controlled radical polymerization of tert-butyl 4-vinyl benzoate with various N-substituted maleimides. Afterwards, these macromolecules were hydrolyzed into polyanions.

Controlled positioning of activated ester moieties on well-defined linear polymer chains.

The successful sequence-controlled installation of an activated ester using a newly designed monomer pentafluorophenyl 4-maleimidobenzoate is demonstrated. Pentafluorophenyl 4-maleimidobenzoate is kinetically installed at different stages of a nitroxide-mediated polymerization, namely, near the α-chain end and in the middle of a PS chain. In addition, successful installation of apolar and polar functional groups is achieved via post-polymerization functionalization, which demonstrated the versatility of the synthesis of a universal precursor for locally functionalized polymers.