Cationic Thermoresponsive Poly(<i>N</i>‑vinylcaprolactam) Microgels Synthesized by Emulsion Polymerization Using a Reactive Cationic Macro-RAFT Agent

A series of reactive poly­([2-(acryloyloxy)­ethyl]­trimethyl­ammonium chloride) (P­(AETAC)) cationic polymers with varying degrees of polymerization were synthesized by RAFT/MADIX polymerization and investigated as stabilizers for the emulsion polymerization of <i>N</i>-vinylcaprolactam (PVCL) in the presence of a cross-linker. It was demonstrated that the xanthate chain end of the cationic P­(AETAC-X) polymers played a crucial role to produce stable cationic PVCL-based microgels at higher initial solids content (5–10 wt %) than usually reported for the synthesis of PVCL microgels. The thermoresponsive PVCL microgels with cationic shell undergo a reversible volume shrinkage upon heating in the absence of any hysteresis in accordance with the narrow particle size distribution. The values of the volume phase transition temperature ranged between 28 and 30 °C for the microgels synthesized using 4 and 8 wt % of P­(AETAC-X) based on VCL. The presence of a cationic outer shell onto the microgels was evidenced by the positive values of the electrophoretic mobility. The swelling behavior of the thermoresponsive microgel particles can be tuned by playing on two synthesis variables which are the initial solids content and the content of P­(AETAC-X) macro-RAFT stabilizer. Furthermore, the inner structure of the synthesized microgels was probed by transverse relaxation nuclear magnetic resonance (<i>T</i>₂ NMR) and small-angle neutron scattering (SANS) measurements. The fit of <i>T</i>₂ NMR data confirmed a core–shell morphology with different cross-linking density in PVCL microgels. Through the determination of the network mesh size, SANS was suitable to explain the increase of the values of the PVCL microgel swelling ratios by increasing the initial solids content of their synthesis

Improved Solid Electrolyte Conductivity via Macromolecular Self-Assembly: From Linear to Star Comb-like P(S-<i>co</i>-BzMA)‑<i>b</i>‑POEGA Block Copolymers

Star block copolymer electrolytes with a lithium-ion conducting phase are investigated in the present work to assess the influence of this complex architecture compared to that of the linear one, on both, bulk morphology and ionic conductivity. For that purpose, the controlled synthesis of a series of poly(styrene-co-benzyl methacrylate)-b-poly[oligo(ethylene glycol) methyl ether acrylate] [P(S-co-BzMA)-b-POEGA] block copolymers (BCPs) by reversible addition–fragmentation transfer polymerization was performed from either a monofunctional or a tetrafunctional chain transfer agent containing trithiocarbonate groups. We emphasized how a small amount of styrene (6 mol %) drastically improved the control of the RAFT polymerization of benzyl methacrylate mediated by the tetrafunctional chain transfer agent. Transmission electron microscopy and small-angle X-ray scattering demonstrated a clear segregation of the BCPs in the presence of lithium salt. Interestingly, the star BCPs gave rise to highly ordered lamellar structures as compared to that of the linear analogues. Consequently, the reduced lamellae tortuosity of self-assembled star BCPs improved the lithium conductivity by more than 8 times at 30 °C for ∼30 wt % of the POEGA conductive phase

Terpene and Dextran Renewable Resources for the Synthesis of Amphiphilic Biopolymers

The present work shows the synthesis of amphiphilic polymers based on the hydrophilic dextran and the hydrophobic terpenes as renewable resources. The first step concerns the synthesis of functional terpene molecules by thiol–ene addition chemistry involving amino or carboxylic acid thiols and dihydromyrcenol terpene. The terpene-modified polysaccharides were subsequently synthesized by coupling the functional terpenes with dextran. A reductive amination step produced terpene end-modified dextran with 94% of functionalization, while the esterification step produced three terpene-grafted dextrans with a number of terpene units per dextran of 1, 5, and 10. The amphiphilic renewable grafted polymers were tested as emulsifiers for the stabilization of liquid miniemulsion of terpene droplets dispersed in an aqueous phase. The average hydrodynamic diameter of the stable droplets was observed at about 330 nm