Block Copolymers Featuring Highly Photostable Photoacids Based on Vinylnaphthol: Synthesis and Self-Assembly

The synthesis of a photoresponsive amphiphilic diblock quarterpolymer containing 5-vinyl-1-naphthol (VN) as a photostable photoacidic comonomer is presented. The preparation is realized via a sequential reversible addition fragmentation chain transfer (RAFT) polymerization starting from a nona(ethylene glycol) methyl ether methacrylate (MEO₉ MA/"O") hydrophilic block, which is then used as a macro-RAFT agent in the terpolymerization of styrene (S), 2-vinylpyridine (2VP), and TBS-protected VN (tVN). The terpolymerization proceeds in a controlled fashion and two diblock quarterpolymers, P(O_m )-b-P(S_x -co-2VP_y -co-VN_z ), with varying functional comonomer compositions are prepared. These diblock quarterpolymers form spherical core-corona micelles in aqueous media according to dynamic light scattering (DLS) and cryogenic transmission electron microscopy (cryo-TEM). Upon irradiation, the photoacids within the micellar core experience a drastic increase in acidity causing a proton transfer from the photoacid to neighboring 2VP units. As a result, the hydrophilic/hydrophobic balance of the entire assembly is shifted, and the encapsulated cargo is released.

Size effects of self-assembled block copolymer spherical micelles and vesicles on cellular uptake in human colon carcinoma cells

Block copolymers, poly(oligo ethylene glycol methyl ether methacrylate)-block-poly(styrene), POEGMEMA-b-PS, with various block lengths were prepared via RAFT polymerization and subsequently self-assembled into various aggregates to investigate their uptake ability into cancer cells.

Star Polymers of Sodium Styrenesulfonate Prepared by One-Pot TEMPO-Controlled SFRP

Star polymers of sodium styrenesulfonate with controlled arm length were prepared in a one-pot polymerization. Sodium styrenesulfonate was first polymerized with controlled molecular weight and narrow polydispersity by stable free radical polymerization. Poly(sodium styrenesulfonate) was terminated with divinyl benzene and star polymers prepared via stable free radical coupling of vinylic terminal groups. Star polymers based on arms of 20 and 32 repeat units possessed ~33 and ~41 arms per star respectively. Formation of star polymers with much longer arms was limited by poor coupling kinetics.

Conducting Material-incorporated Electrorheological Fluids: Core-shell Structured Spheres

Conducting material-based electro-responsive particles have become important as the smart soft matter in electrorheological (ER) fluids. These materials include conducting polymers, such as polyaniline, polypyrrole and poly(3,4-ethylenedioxythiophene), and carbon materials, such as carbon nanotubes and graphene oxide. Core-shell structured ER particles containing these materials as either core or shell species have attracted increasing interest owing to their outstanding advantages of an enhanced ER effect or diverse ER mechanism, lighter particulate density and lower cost. This paper summarizes the recent advances in synthesis methods as well as the critical characteristics of the core-shell structured particles, such as shear stress, yield stress and dielectric properties.

Analysis of Thiol-sensitive Core-cross-linked Polymeric Micelles Carrying Nucleoside Pendant Groups using 'On-line' Methods: Effect of Hydrophobicity on Cross-linking and Degradation

Amphiphilic block copolymers were prepared via reversible–addition fragmentation chain transfer (RAFT) polymerization and their synthesis, cross-linking, and degradation were studied using on-line monitoring. The focus of this work is the systematic alteration of the hydrophobic block using copolymers based on 5′-O-methacryloyluridine (MAU) and styrene at different compositions to determine the effect of the copolymer composition on the properties of the micelle. A poly(poly(ethylene glycol) methyl ether methacrylate) (PEGMA) macroRAFT agent was chain extended with a mixture of styrene and MAU. In both systems, an increasing fraction of styrene was found to reduce the rate of polymerization, but the functionality of the RAFT system was always maintained. The amphiphilic block copolymers were dialyzed against water to generate micelles with sizes between 17 and 25 nm according to dynamic light scattering (DLS). Increasing styrene content lead to smaller micelles (determined by DLS and transmission electron microscopy) and to lower critical micelle concentrations, which was measured using surface tensiometry. The micelles were further stabilized via core-cross-linking using bis(2-methacroyloxyethyl) disulfide as crosslinker. NMR analysis revealed a faster consumption of crosslinker with higher styrene content. These stable cross-linked micelles were investigated regarding their ability to degrade in the presence of dithiothreitol as a model reductant. Increasing the styrene content resulted in a faster degradation of the cross-linked micelles into unimers.

Everything Under the Sun: The 11th Pacific Polymer Conference

The 11th Pacific Polymer Conference brought together experts in all fields of polymer science. In this issue some of the recent advances presented at the meeting are highlighted.