Reversible Addition Fragmentation Research Articles

Visible light-induced photo-radical ring-opening copolymerization of thionolactone and acrylates

Radical ring-opening (co)polymerization (RROP) provides an accessible method for synthesizing main chain degradable vinyl polymers. Although the applications of reversible deactivation radical polymerization (RDRP) into RROP have been reported, the use of photo-mediated RDRP methods has received less attention than the thermal process. Here, photo-RROP of the thionolactone dibenzo [c,e]-oxepine-5(7H)-thione (DOT) and methyl acrylate (MA) was studied using photo-iniferter (PI) reversible addition-fragmentation (chain) transfer (RAFT) polymerization at ambient temperature without external radical initiators or photocatalysts. Despite the occurrence of some side reactions including desulfurization-oxygenation and O–S isomerization of DOT promoted by photoexcited thiocarbonyl groups, polymers with thioester linkages in the backbone were prepared, which degraded in the presence of amines and bleach.

Ternary nanocomposite of RAFT‐polymerized DMAEMA‐functionalized graphene oxide, manganese dioxide and polyaniline as active electrode material for supercapacitor

AbstractGraphene and its derivatives are promising energy storage devices due to their high specific surface area, chemical and thermal durability and high charge transfer power. Still, their stacking and aggregate behavior can limit their practical application. To address this issue, reversible addition–fragmentation chain‐transfer (RAFT) polymerization as controlled radical polymerization was applied to functionalize the surface of graphene oxide with poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) via the ‘grafting from’ method. This strategy enhances the distance between graphene sheets by occupying physical volume while improving effective charge transfer through tertiary amine groups participating in the doping process. X‐ray diffraction was used to determine interlayer spacing after polymer grafting, which increased from 0.28 to 1.71 nm after polymer grafting. The hybridization of materials with diverse properties was used to enhance charge transfer capability for supercapacitor applications. PDMAEMA‐functionalized graphene oxide, nano‐manganese dioxide and polyaniline were combined to create a successful nanocomposite as electrode active material. The morphological structure and chemical composition of the synthesized nanocomposite were analyzed, and its electrochemical performance was evaluated using cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The nanocomposite exhibited a maximum specific capacitance, energy density and power density of 364.72 F g−1 (at a scan rate of 50 mV s−1), 239.08 Wh kg−1 and 678.34 W kg−1, respectively. The final nanocomposite's energy storage capacity significantly increased compared to the individual components due to hybridization's synergistic impact, reducing charge transfer resistance. © 2024 Society of Industrial Chemistry.

Photo‐ and pH‐Responsive Hybrid Colloidal Particles

AbstractMaterials that respond to environmental changes in a predictable manner are called “smart”. Here, smart dual‐responsive hybrid colloidal particles were prepared using the interface‐mediated reversible addition–fragmentation chain‐transfer (RAFT) polymerization method. The structure and morphology of the prepared poly(methacrylated‐spiropyran) (p(MMASP)) colloids were characterized by FTIR, 1H‐NMR and GPC spectroscopies, and SEM. The molecular weight and polydispersity were determined as 7877 g mol−1 and 1.16, respectively. Heterocyclic ring cleavage of the spiropyran (SP) pendant group enables the pH‐ and light‐responsive behavior with a reversible conversion between the hydrophobic and hydrophilic states. The isomerization from SP to merocyanine (MC) form proceeds in 7 min, while the reverse action takes 9 min. The pronounced photochromic effect and high fatigue resistance make these colloids suitable for smart applications.

Activity Improvement and Thermal Stability Enhancement of D-Aminoacylase Using Protein-Polymer Conjugates

In this study, the synthesis of new polymer-protein conjugates using a grafting-from strategy was performed by employing photo-induced electron transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. D-aminoacylase is an industrially significant enzyme for the preparation of chiral amino acids and it is coupled with reversible addition-fragmentation (RAFT) chain transfer agent (CTA) using activated ester chemistry. The effects of polymeric side chain compositions on the activity of D-aminoacylase were studied with two different polymeric side chain lengths. For this reason, two monomers, a hydrophilic N-(2-aminoethyl acrylamide) and a hydrophobic and N- (iso-butoxymethyl) acrylamide were used, respectively. It was found that modification by grafting from strategy increased the thermal stability of D-aminoacylase enzyme. Additionally, the hydrophobic monomer conjugate has been reported to increase the activity of the enzyme more than the hydrophilic monomer.

Modification of CNF‐Networks by the Addition of Small Amounts of Well‐Defined Rigid Cationic Nanolatexes

AbstractCellulose nanofibril (CNF)‐networks are modified by the addition of small amounts (below 10 wt%) of well‐defined cationic nanolatexes synthesized through reversible addition–fragmentation chain‐transfer‐mediated polymerization‐induced self‐assembly (PISA). Minute amounts of nanolatex inclusions lead to increased tensile and shear moduli, indicating that nanolatexes can act as bridging‐points between CNFs. At higher nanolatex content, this stiffening effect is lost, likely due to interactions between nanolatexes leading to plasticization. The influence of nanolatex content and size on interparticle distance is discussed and is used as a tool to understand the effects observed in macroscopic properties. Upon annealing, the stiffening effect is lost due to the softening of the nanolatexes, indicating that the core–shell morphology is a prerequisite for this effect. These systems form a versatile platform to develop fundamental insights into complex condensed colloidal systems, to ultimately aid in the development of new sustainable material concepts.

RAFT Polymerization of 2,2,3,3-Tetrafluoropropyl Methacrylate in the Presence of Lewis Acids

The influence of various tacticity regulators on the reversible addition-fragmentation (RAFT) polymerization of 2,2,3,3-tetrafluoropropyl methacrylate in the presence of 2-cyano-2-propyldodecyltritiocarbonate as an chain transfer agent was investigated. Among Lewis acids considered, the polymerization of TFPMA in dioxane with ZnBr2 turned out to be the most effective from the point of view of tacticity; the polymer with the highest isotacticity is formed. The addition of hexafluoroisopropanol leads to an increase in the heterotacticity and a decrease in the isotacticity of the polymer chain.

Poly(acrylated epoxidized soybean oil)‐modified carbon nanotubes and their application in epoxidized soybean oil‐based thermoset composites

AbstractPoly(acrylated epoxidized soybean oil) (PAESO) has been grafted on the surface of multiwalled carbon nanotubes (MWCNTs) by reversible addition–fragmentation chain‐transfer reaction (RAFT). MWCNTs–PAESO as reinforcement has been successfully applied to prepare epoxidized soybean oil/maleopimaric‐based thermosetting composites with good dispersion through probe ultrasonic treatment in ethyl acetate. Micromorphology analyses on composites by transmission electron microscopy and scanning electron microscopy show that MWCNTs–PAESO has better dispersion stability in both ethyl acetate and epoxy matrix and better interface bonding effect with cured matrix, resulting in more uniformly and separately dispersed behavior than hydroxylated multiwalled carbon nanotubes. Correspondingly, by the method of molecular dynamics simulation, it is verified that the nonbond energy and van der Waals force of CNTs–PAESO in solvent can be relatively reduced, and that CNTs–PAESO possesses higher binding energy with matrix compared with CNTsOH. Therefore, MWCNTs–PAESO and PAESO have synergistic enhancement on the mechanical properties of composites demonstrated by rheology testing and dynamic mechanical analysis. The appropriate amount of MWCNTs–PAESO loading at 0.15 wt% can increase the glass transition temperature (Tg) of thermoset from 83.8 to 96.3°C, resulting in the improvement of both mechanical and thermal properties. These results show that surface‐grafting MWCNTs with homologous polymer can effectively increase the interfacial compatibility between matrix and MWCNTs, thereby improving the thermal and mechanical properties of composites.

Polymerization‐induced self‐assembly of amino‐acid‐based nano‐objects by reversible addition–fragmentation chain‐transfer dispersion polymerization

AbstractA series of amino‐acid‐based amphiphilic diblock copolymer nano‐objects having different morphologies were developed by reversible addition–fragmentation chain‐transfer (RAFT) dispersion polymerization of styrene (St) in methanol. This was mediated by six different hydrophilic poly(N‐acryloyl amino acid) macro‐chain transfer agents (CTAs), including three carboxylic‐acid‐containing ones, poly(N‐acryloyl‐l‐proline) (PAProOH), poly(N‐acryloyl‐4‐trans‐hydroxy‐l‐proline) (PAHypOH), and poly(N‐acryloyl‐l‐threonine) (PAThrOH) prepared by RAFT polymerization, and their methyl ester forms, PAProOMe, PAHypOMe, and PAThrOMe. The effects of polymerization conditions on RAFT dispersion polymerization of St using a dithiocarbamate‐terminated PAProOH was investigated. A systematic study of the effects of monomer conversion and concentration afforded the formation of various morphologies (i.e., spheres, worms, and vesicles). The effects of hydrogen‐bonding and ionic interactions of the macro‐CTAs on the assembled structures of the nano‐objects were evaluated using six different macro‐CTAs. Transforming the products from methanol to water via dialysis produced amino‐acid‐based block copolymer nano‐objects, exhibiting pH‐responsive morphological change, in aqueous solution.

Polymeric Nonlinear Absorption Chromophore Array from Controlled Radical Polymerization and “Click” Chemistry

A polyacrylate with pendant nonlinear absorption (NLA) chromophores was prepared via the reversible addition–fragmentation (RAFT)–click synthetic strategy. The polyacrylate backbone of the NLA poly...

Synthesis of Biohybrid Particles by Modification of Chitosan Beads via RAFT Polymerization in Dispersed Media

AbstractSpherical macroscopic particles (beads) made from chitosan (CTS), a polysaccharide derived from the valorization of food waste, are converted into a biohybrid material by grafting poly(4‐vinylpyridine) (P4VP) using a “grafting from” approach via reversible addition–fragmentation chain‐transfer (RAFT) polymerization. Varying the time of reaction, and therefore the conversion, allows to readily tune the composition (CTS vs synthetic polymer content) and consequently the bead properties. P4VP has specific affinity for certain compounds. Thus, the biohybrid particles are promising candidates for applications related to (waste) water treatment, sensors, or biomedical fields. In this study, the potential use of CTS‐g‐P4VP particle beads for the removal of an emerging contaminant of concern (bisphenol A) from water is demonstrated. It is shown that removal efficiency is enhanced from 25% to 70% by the grafting of P4VP on CTS.

Bio‐based vinylphenol family: Synthesis via decarboxylation of naturally occurring cinnamic acids and living radical polymerization for functionalized polystyrenes

ABSTRACTA series of bio‐based vinylphenols or hydroxystyrenes is prepared by simple decarboxylation of various naturally occurring cinnamic acids such as o‐, m‐, and p‐coumaric; caffeic; ferulic; and sinapinic acids, which possess hydroxy groups and other substituents at different positions on the aromatic ring. After protection of the phenolic moieties with trialkylsilyl groups, reversible addition–fragmentation chain‐transfer polymerization is accomplished with cumyl dithiobenzoate to afford various bio‐based hydroxyl‐protected polystyrenes with controlled molecular weights and narrow molecular weight distributions. Subsequent deprotection of the silyl groups under mild conditions results in a series of well‐defined functionalized polystyrenes possessing different numbers (mono‐, di‐, tri‐) of hydroxy groups at different positions (o, m, p). The obtained functionalized polystyrenes show unique thermal properties depending on the substituents, and those with phenol and catechol groups serve as reducing agents for silver ions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 91–100

Multiple morphologies of a poly(methyl methacrylate)‐block‐poly(N,N‐dimethyl aminoethyl methacrylate) copolymer with pH‐responsiveness and thermoresponsiveness

ABSTRACTWe successfully prepared a series of pH‐responsive and thermoresponsive poly(methyl methacrylate) (PMMA)‐block‐poly(N,N‐dimethyl aminoethyl methacrylate (PDMAEMA) copolymers via reversible addition–fragmentation chain‐transfer polymerization with PMMA as a macro chain‐transfer agent. Control over the chain length of PDMAEMA allowed the morphological transformation of PMMA‐b‐PDMAEMA. The critical water content and critical micelle concentration also depended on the length of the PDMAEMA block. UV–visible and fluorescence spectrum analyses indicated that the PMMA‐b‐PDMAEMA copolymer exhibited a lower critical solution temperature type phase transition in water. The particle size of PMMA‐b‐PDMAEMA was dominated by the pH value, as evidenced by dynamic light scattering and transmission electron microscopy. In addition, the PMMA‐b‐PDMAEMA copolymers exhibited good reversible thermoresponsive behavior between 33 and 38°C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47972.

Facile Synthesis of an Eight-Armed Star-Shaped Polymer via Coordination-Driven Self-Assembly of a Four-Armed Cavitand.

The polystyrene chains were installed at the lower rim of a resorcinarene-based cavitand via reversible addition-fragmentation (RAFT) polymerization to form a four-armed star-shaped polymer. A star-shaped polystyrene-functionalized supramolecular capsule was prepared through the coordination-driven self-assembly of the four-armed start-shaped polymer with silver ions. The eight-armed start-shaped supramolecular capsule encapsulated 4,4'-diacetoxybiphenyl as did a cavitand-based self-assembled capsule. A DOSY measurement indicated that the eight-armed star-shaped polymer was twice as large as the four-armed star-shaped polymer. The solution behaviors of these compounds resulted in a difference in their zero-shear viscosities.

Thermally amendable tailor‐made acrylate copolymers via RAFT polymerization and ultrafast alder‐ene “click” chemistry

ABSTRACTThis investigation reports the preparation of thermally amendable copolymers of 2‐hydroxyethylmethacrylate (HEMA) with methyl methacrylate (MMA) and butyl methacrylate (BMA) via reversible addition fragmentation chain‐transfer (RAFT) polymerization followed by Alder‐ene reaction. The chemical compositions and molecular weights of the copolymers were determined via 1H NMR and gel‐permeation chromatography (GPC) analyses. The hydroxyl groups of PHEMA in the copolymer were modified to incorporate indole functional group, which was further modified via an ultrafast Alder‐ene reaction using a bifunctional 1,2,4‐triazoline‐3,5‐dione (TAD) derivative. The thermoreversible character of the resultant crosslinked network was studied via differential scanning calorimetry (DSC) and FT‐IR analyses. Different microscopic analyses were performed to study the self‐healing property and self‐healing efficiency of the crosslinked network. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2310–2318

Synthesis of PMMA-b-PEG-b- PMMA by controlled Polymerization Using Macro-RAFT Agents

In this work controlled radical polymerization (CRP) of methyl methacrylate was carried out in thepresence of the Poly(ethylene glycol)(PEG) xanthate reversible addition fragmentation (RAFT) chain transferagent designated as (CTA1) and (CTA2). Firstly, PEGs having different molecular weights (400 and 600 g/mol)were reacted KOH and CS2 and the terminated 4-chloro benzoyl chloride to obtain PEG-xathates. RAFT agentpossessing PEG chain was used in the RAFT polymerization of MMA to yield PMMA-b-PEG-b-PMMA tri-blockcopolymers which can be used in various potential applications. With the gravimetric follow of the reaction, thecontrol mechanism works well and the molecular weight has grown linearly. The structures of the synthesizedmacro RAFT agents and polymers were characterized by 1H-NMR, 13C-NMR and FT-IR spectroscopic methods.

Photochemical "In-Air" Combinatorial Discovery of Antimicrobial Co-polymers.

There is an urgent need to identify new, non‐traditional antimicrobials. The discovery of new polymeric antimicrobials is limited by current low‐throughput synthetic tools, which means that limited chemical space has been explored. Herein, we employ photochemical “in‐air” reversible addition–fragmentation chain‐transfer (RAFT) polymerization with microwell plates, using liquid‐handling robots to assemble large libraries of cationic polymers, without the need for degassing or purification steps, facilitating transfer to screening. Several lead polymers were identified including a co‐polymer with propylene glycol side chains with significantly enhanced antimicrobial activity and increased therapeutic window. Mechanistic studies showed that this polymer was bacteriostatic, and surprisingly did not lyse the cell membranes, implying an alternative mode of action. This versatile method using simple robotics will help to develop new biomaterials with emergent properties.

Heteroatom‐Doped Carbon Dots (CDs) as a Class of Metal‐Free Photocatalysts for PET‐RAFT Polymerization under Visible Light and Sunlight

AbstractA key challenge of photoregulated living radical polymerization is developing efficient and robust photocatalysts. Now carbon dots (CDs) have been exploited for the first time as metal‐free photocatalysts for visible‐light‐regulated reversible addition–fragmentation chain‐transfer (RAFT) polymerization. Screening of diverse heteroatom‐doped CDs suggested that the P‐ and S‐doped CDs were effective photocatalysts for RAFT polymerization under mild visible light following a photoinduced electron transfer (PET) involved oxidative quenching mechanism. PET‐RAFT polymerization of various monomers with temporal control, narrow dispersity (Đ≈1.04), and chain‐end fidelity was achieved. Besides, it was demonstrated that the CD‐catalyzed PET‐RAFT polymerization was effectively performed under natural solar irradiation.

Highly efficient adsorbent for organic dyes based on a temperature‐ and pH‐responsive multiblock polymer

ABSTRACTThe self‐assembly behavior of amphiphilic block copolymers in selective solutions has many applications in environmentally responsive polymer materials. In this article, we report on a new amphiphilic, temperature and pH dual‐responsive poly[2‐dimethylaminoethyl methacrylate‐co‐(methyl methacrylate)]‐b‐poly[poly(ethylene glycol) methacrylate] [P(DMAEMA‐co‐MMA)‐b‐PPEGMA], which was synthesized via reversible addition–fragmentation chain‐transfer polymerization. The structure, self‐assembly behaviors, and process of organic dye adsorption were characterized by 1H‐NMR, ultraviolet–visible absorbance spectroscopy, and DLS measurements. P(DMAEMA‐co‐MMA)‐b‐PPEGMA was proven to be an outstanding adsorbent with excellent reversibility. Methyl red was released from the micelles as the pH value of the solution was adjusted to 4, and it could also be encapsulated again when the pH value was adjusted to 7.4 because of the sensitive pH‐responsive ability. It is promising that the triblock polymer had a positive effect on dye adsorption for environmental protection. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46626.

Polymers Diffusivity Encoded by Stimuli‐Induced Phase Transition: Theory and Application to Poly(N‐Isopropylacrylamide) with Hydrophilic and Hydrophobic End Groups

AbstractThe self‐diffusion of various nano‐objects investigated by high‐resolution nuclear magnetic resonance diffusometry proves to be an efficient method for the characterization of dynamics, aggregation kinetic, and matrix morphology. This study investigates how the two‐state model and Boltzmann function approach can be used for the evaluation of the thermodynamic parameters of temperature‐induced phase transition encoded in polymer diffusivity. The characteristics of the phase transition given by the transition temperature, change of entropy, and width of transition are obtained for poly(N‐isopropylacrylamide) (PNIPAm) linear polymers with hydrophilic and hydrophobic end‐group functionalization. The effect of end groups upon the polymer diffusivity is investigated as a function of molecular weight (M n), from which fractal dimensions and hydrodynamic drag coefficients are obtained. The PNIPAm diffusivity is affected strongly by the end groups, and it is reflected in the hydrodynamic radius dependence upon molecular weight that obeys different power‐law relations. In this study, the synthesis of α‐ω‐heterotelechelic PNIPAm of different molecular weights with a thiol end group and a hydrophilic NIPAm‐like as well as a hydrophobic benzyl end group are described by reversible addition–fragmentation chain‐transfer polymerization.

Vesicular and micellar self‐assembly of stimuli‐responsive poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) amphiphilic diblock copolymers

ABSTRACTDually responsive amphiphilic diblock copolymers consisting of hydrophilic poly(N‐isopropyl acrylamide) [poly(NIPAAm)] and hydrophobic poly(9‐anthracene methyl methacrylate) were synthesized by reversible addition fragmentation chain‐transfer (RAFT) polymerization with 3‐(benzyl sulfanyl thiocarbonyl sulfanyl) propionic acid as a chain‐transfer agent. In the first step, the poly(NIPAAm) chain was grown to make a macro‐RAFT agent, and in the second step, the chain was extended by hydrophobic 9‐anthryl methyl methacrylate to yield amphiphilic poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) block copolymers. The formation of copolymers with three different hydrophobic block lengths and a fixed hydrophilic block was confirmed from their molecular weights. The self‐assembly of these copolymers was studied through the determination of the lower critical solution temperature and critical micelle concentration of the copolymers in aqueous solution. The self‐assembled block copolymers displayed vesicular morphology in the case of the small hydrophobic chain, but the morphology gradually turned into a micellar type when the hydrophobic chain length was increased. The variations in the length and chemical composition of the blocks allowed the tuning of the block copolymer responsiveness toward both the pH and temperature. The resulting self‐assembled structures underwent thermally induced and pH‐induced morphological transitions from vesicles to micelles and vice versa in aqueous solution. These dually responsive amphiphilic diblock copolymers have potential applications in the encapsulation of both hydrophobic and hydrophilic drug molecules, as evidenced from the dye encapsulation studies. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46474.