Reversible addition-fragmentation chain transfer (RAFT) polymerization, a relatively new method of controlled/living radical polymerization, has attracted scientists’ attention over the last decades due to its simplicity, effectiveness, and high potential for creating complex macromolecular architecture. This article dwells on the issues of pH-switchable dithiocarbamate RAFT agents containing a pyridyl moiety, which can undergo acid-base interactions and modulate the reactivity of the thiocarbonyl group in situ. This capability is essential when aiming to control the polymerization of both more-activated monomers (MAMs) and less-activated monomers (LAMs) using a single compound. This type of RAFT agents has demonstrated excellent control over molecular weight and distribution during the polymerization of monomers of different activity and the ability to synthesize poly(MAM)-block-poly(LAM) copolymers under controlled conditions. In this paper, we report the synthesis of two new N-aryl-N-pyridyl dithiocarbamates and demonstrate how altering the agent’s form (acidic or neutral) and concentration affects the kinetics of the homopolymerization of styrene, vinyl acetate, methyl acrylate, and methyl methacrylate and molecular weight characteristics of obtained polymer. We also report synthesis of polystyrene-block-polyvinyl acetate using synthesized agent.

A series of Ti-containing photocatalysts based on poly(titanium oxide)-containing organic–inorganic copolymers were synthesized and evaluated in photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. The photocatalysts exhibited higher activity and superior control over polymerization compared with conventional TiO 2 . Their performance was investigated in the room-temperature PET-RAFT polymerization of methyl methacrylate. A linear dependence of ln([M] 0 /[M]) on irradiation time was observed, indicating a well-controlled polymerization process with excellent temporal regulation under external light irradiation. The synthesized photocatalysts retained their activity over several polymerization cycles without a significant loss of efficiency. The obtained polymers exhibited relatively narrow molecular weight distributions and preserved terminal chain-transfer functionality, enabling their use as macro-chain transfer agents (macro-CTAs). Furthermore, the developed photocatalysts enabled PET-RAFT polymerization of methyl methacrylate under both blue and green visible-light irradiation. Under green-light irradiation, well-defined poly(methyl methacrylate) with a dispersity of Đ = 1.31 was obtained.

The development of materials based on chitosan and polyesters that possess thermoplastic, biocompatible, and biodegradable properties is a perspective for additive technologies in biomedicine. Research on obtaining such compositions is constrained because the polysaccharide content does not exceed 5 wt.%, which cannot ensure effective tissue regeneration. Herein, we propose a method for obtaining thermoplastic block copolymers based on chitosan and poly(ε-caprolactone) by ultrasonic irradiation of a homogeneous solution of a homopolymer mixture in dimethyl sulfoxide as a common solvent, achieving a yield of 99%. The distinctive feature of the method is the interaction between the components at the molecular level and provides obtaining copolymers at any component ratio. SEM images revealed a homogeneous structure without structural defects in both solvent-cast films and extruded filaments. The block copolymers were characterized by high mechanical property tensile strength of up to 60–70 MPa and elasticity of up to 35% for films and 25–40 MPa and elasticity of up to 50% for filaments. Cell adhesion of composition investigated on fibroblast cells (hTERT BJ-5TA) is at the level of chitosan and demonstrated the absence of cytotoxicity.

Biodegradable starch-based composite material with bactericidal properties was obtained in this work. The material is promising as environmentally safe food packaging. Native potato starch was modified by graft polymerization of vinyl acetate. The synthesis was carried out in the presence of ammonium persulfate in the alkaline medium under a temperature change mode from 70 to 80 °C. The grafting efficiency was 82

A series of methacrylic acid co(polymers) were obtained using various reversible chain transfer agents. The molecular weight characteristics of the synthesized (co)polymers were determined using gel permeation chromatography. In vitro studies showed the absence of cytotoxicity of the obtained compounds against immune cells (peritoneal macrophages) and the absence of an effect on the functional activity of the cells.

Features of the synthesis of n -butyl acrylate copolymers with acrylic acid in 1,4-dioxane by free radical reversible addition-fragmentation chain transfer (RAFT) polymerization mediated by symmetric trithiocarbonates are considered. It is shown that the living mechanism of polymerization is realized in the studied systems. The chemical nature of the RAFT agent dictates different chain microstructures (random block or random) of the copolymers. The effect of chain microstructure on the properties of the copolymers containing about 90 mol % of acrylic acid units is studied by differential scanning calorimetry, contact angle measurements, turbidimetry, potentiometric titration, and dynamic light scattering. It is demonstrated that all the copolymers in the solid phase have similar properties: a single glass transition temperature close to the glass transition temperature of polyacid and a good water wettability. In dilute aqueous solutions, the properties of the copolymers are different: at the inherent pH, random copolymer macromolecules form large associates, while random block copolymers are dispersed into individual coils or micelles. All the copolymers are weaker polyacids compared with PAA; the random block copolymers are characterized by the compaction of macromolecules at small degrees of ionization. Our studies provide evidence that reversible addition-fragmentation chain transfer polymerization is an efficient tool for the targeted insertion of nonpolar units into a polyelectrolyte chain and it can be used for the fine-tuning of its properties.

The regularities of the controlled synthesis of amphiphilic copolymers of styrene and acrylic acid mediated by dithiobenzoate and trithiocarbonates as reversible addition fragmentation chain transfer agents in a 1,4-dioxane solution are considered. The influence of the general composition and chain microstructure on the dispersion stability and hydrodynamic sizes of polymer particles of copolymers containing from 40 to 90 mol % of acrylic acid units is studied. It is shown that in dilute aqueous media random copolymers are dispersed to individual compacted coils owing to the intrachain hydrophobic association of styrene units. The addition of two poly(acrylic acid) blocks to such a copolymer improves its dispersibility in water, and the attachment of two polystyrene blocks makes it insoluble in water because of the interchain association of polystyrene units. The synthesized copolymers possess surface activity, and when applied to a hydrophilic glass surface, they moderately hydrophobize it. In general, this synthetic approach opens up broad prospects for obtaining a wide range of new polymer macromolecules with different properties from one pair of traditional monomers.

Conditions were found for controlled reversible addition-fragmentation chain-transfer radical polymerization to obtain narrow-dispersity gradient methacrylic acid-methyl acrylate copolymer ( M n = 1.59 × 10 4 ). A copolymer of similar composition and molecular mass ( M n = 1.81 × 10 4 ) with random distribution of units was obtained by radical copolymerization in the presence of dodecyl mercaptan. The behavior of the gradient and random copolymers, each containing ∼14 mol % methacrylic acid units, was studied in solutions, Langmuir monolayers, and Langmuir-Blodgett films. Several ranges of the existence of associates and micelles, preserved upon transfer in a Langmuir-Blodgett film, were revealed for the narrow-dispersity copolymer at the water-air interface depending on pH of the subphase. Associates in the form of ribbon structures and molecular ensembles of nanometric size (network structure with loop-like fragments) are observed in the AFM images of Langmuir-Blodgett films of the gradient and random copolymers, respectively.

Copolymerization of 2,2,3,3,4,4,5,5-octafluoropentyl acrylate (OFPA) and acrylic acid (AA), OFPA and tert-butyl acrylate (t-BA) in presence ofdibenzylcarbonotrithioate (BTC) and polymeric RAFT-agents was studied, reactivity ratios were calculated. It was shown that type of RAFT-agent can influence on chain microstructure of obtained polymers. Aggregation behavior of obtained amphiphilic copolymers with different microstructures at the air/water interface was characterized by the Langmuir monolayer technique. The effect of the microstructureand subphase pH on the isotherm curves were shown.

Physicomechanical and surface properties of films of copolymers of methacrylic acid with methyl acrylate, which have close compositions and molecular masses ( M n ≈ 5.7 × 10 4 ) and various chain structures (gradient copolymer and statistical copolymer), were studied. The thermodynamic characteristics of the copolymers were determined; two glass-transition points (29.6 and 141.0°C) were found for the gradient copolymer, and one glass-transition point of 40.1°C, for the copolymer with a statistical distribution of units along the chain. It was found that more mechanically strong films with tensile stress of 2.8 MPa are characteristic of the gradient copolymer. The wetting method was used to determine by using the Hood–Kaelble–Dann–Fowkes approach the surface Gibbs energies of the films and their polar and dispersion components. Atomic-force microscopy was used to find heterogeneities (0.1–0.3 μm) on the surface of a film of a statistical copolymer, whereas the film of a gradient polymer has a homogeneous structure.

The tuning of the relative monomer reactivities of styrene and acrylic acid in a solution of N,N-dimethylformamide by using polymeric RAFT agents.

The microstructure of polystyrene, poly(methyl acrylate), and poly(tert-butyl acrylate) obtained in the presence of tri-n-butylboron in combination with naphthoquinone-1,4 and 2,3-dimethylbenzoquinone is studied. The stereoregularity of polymers formed under these conditions may be described in the framework of the first-order Markov chain model. The use of p-quinones in combination with tri-n-butylboron favors an increase in the content of isotactic triads in the polymers. The causes of the observed deviations are discussed.

Copolymerization of methyl methacrylate (MMA) and n-butyl acrylate (n-BA) in the presence of the tributylborane–p-quinone system has been investigated. Reactivity ratios of the monomers differ from the values known for conventional radical polymerization. The copolymerization proceeds in a controlled manner according to the reversible inhibition mechanism. The nature of p-quinone and the composition of the monomer mixture affect the realization of this mechanism. The microstructure of the copolymers obtained in the presence of borane and p-quinones depends on the nature of the latter.