Design of biointerfaces composed of soft materials using controlled radical polymerization

Soft interface materials have an immense potential for the improvement of biointerfaces, which are the interface of biological and artificially designed materials. Controlling the chemical and physical structures of the...

PREPARATION OF CHITOSAN GRAFT COPOLYMERS AND STUDY OF THEIR WATER-SWELLING PROPERTIES

In this work, graft copolymers of chitosan with trimethylmethacryloxyethylammonium methyl sulfate were synthesized by the method of controlled radical polymerization, and it was found that replacing the dimethylformamide aprotic solvent with water increases the degree of grafting. With the aim of the possible use of chitosan copolymers as a functional component for regulating the water-swelling properties of elastomers, the kinetics of swelling of the samples was investigated. An increase in the degree of swelling of the copolymers in comparison with the initial chitosan was revealed, and the influence of the molecular weight and the conditions of their synthesis was established.

Symmetric RAFT-agent for synthesizing multiblock copolymers with different activated monomers

With a bifunctional symmetric RAFT agent well-defined polymer structures can be achieved. This paper shows the possibility to synthesize block copolymer systems consisting out of different activated monomers. With the novel bifunctional symmetric RAFT agent water-born polymer systems with a block structure (B-b-A-b-B) can be polymerized. The symmetric RAFT agent is designed to polymerize both more activated monomers (A) and less activated monomers (B). Due to the ability of a controlled radical polymerization of different activated monomers the dispersity of the resulting polymers is broader compared to common RAFT polymerizations. In regard to industrial applications like emulsifiers, stabilizers or viscosity modifiers the broader molecular weight distribution has no impact. Overall, this paper shows the possibility towards new functional polymers with unique properties.

Reversing RAFT Polymerization: Near-Quantitative Monomer Generation via a Catalyst-Free Depolymerization Approach

The ability to reverse controlled radical polymerization and regenerate the monomer would be highly beneficial for both fundamental research and applications, yet has remained very challenging to achieve. Herein, we report a near-quantitative (up to 92%) and catalyst-free depolymerization of various linear, bulky, crosslinked, and functional polymethacrylates made by reversible addition-fragmentation chain-transfer (RAFT) polymerization. Key to our approach is to exploit the high end-group fidelity of RAFT polymers to generate chain-end radicals via thermal homolytic cleavage of carbon-sulfur bond of the RAFT end-group at 120 °C. These radicals trigger a rapid unzipping of both conventional (e.g. poly(methyl methacrylate)) and bulky polymers (e.g. poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA)). Importantly, the depolymerization product can be utilized to either reconstruct the linear polymer or create an entirely new insoluble gel that can also be subjected to depolymerization. This work expands the potential of polymers made by CRP, pushes the boundaries of depolymerization, offers intriguing mechanistic aspects, and enables new applications.

Connecting Gas-Phase Computational Chemistry to Condensed Phase Kinetic Modeling: The State-of-the-Art

In recent decades, quantum chemical calculations (QCC) have increased in accuracy, not only providing the ranking of chemical reactivities and energy barriers (e.g., for optimal selectivities) but also delivering more reliable equilibrium and (intrinsic/chemical) rate coefficients. This increased reliability of kinetic parameters is relevant to support the predictive character of kinetic modeling studies that are addressing actual concentration changes during chemical processes, taking into account competitive reactions and mixing heterogeneities. In the present contribution, guidelines are formulated on how to bridge the fields of computational chemistry and chemical kinetics. It is explained how condensed phase systems can be described based on conventional gas phase computational chemistry calculations. Case studies are included on polymerization kinetics, considering free and controlled radical polymerization, ionic polymerization, and polymer degradation. It is also illustrated how QCC can be directly linked to material properties.