Reversible Addition-fragmentation Chain Transfer Agent Research Articles

Versatile morphology transition of nano-assemblies via ultrasonics/microwave assisted aqueous polymerization-induced self-assembly based on host–guest interaction

Nano-assemblies have wide applications in biomedicine, functional coatings, Pickering emulsifiers, hydrogels, and so forth. The preparation of assemblies mainly utilizes the polymerization-induced self-assembly (PISA) method, which can produce high-concentration nanoscale assemblies in one step. However, the initiation processes of most reported PISA are limited to thermal initiation. Here, we reported two green and efficient methods for synthesizing nano-assemblies with various morphologies using ultrasound (20 kHz)/ microwave (500 W) assisted aqueous-phase RAFT-PISA in 3 h and 1 h. Cyclodextrin (CD) and styrene (St) nucleating monomer were complexed in a 1:1 ratio. Then, using Poly (ethylene glycol) methyl ether as the macromolecular reversible addition-fragmentation chain transfer (RAFT) agent (PEG-CTA) to control the CD/St complexes, the conversion rate of St monomer was respectively 27 %–60 %, 20 %–30 % within 3 h and 1 h under ultrasonics/microwave assisted PISA. Results showed that the morphologies of the assemblies are not only related to the length of PS block, but also to the assistance types and the remaining monomer concentration. The results showed that only PEG45-b-PS90 and PEG45-b-PS241 assemblies prepared by ultrasonics assisted PISA form evolved lamellaes and vesicles (100 nm), which break through the limitation of kinetic freezing. But the ultrasonic reaction on morphology of assemblies is not all favourable. For one thing, it can promote the movement of particles; for another, it makes reverse morphology transformation and sphere is preferred morphology. Therefore, the main reason of morphology evolution is the remaining monomer concentration of PEG45-b-PS90 and PEG45-b-PS241 assemblies reaches to 55 %–65 %, which promoting the segment movement. The results showed that the morphology of the assemblies prepared by microwave assisted PISA changed from spherical micelles to short rods, and finally to vesicles (120–140 nm) as the length of hydrophobic PS block increases. The kinetic freezing problem was solved in microwave-assisted PISA due to the action of microwaves and more remaining monomer concentration. Both them can boost particles movement.

RAFT mediated dispersion copolymerization of glycidyl methacrylate and octadecyl methacrylate

Micrometer sized copolymeric particles of glycidyl methacrylate and octadecyl methacrylate (poly(GMA-co-OMA) were prepared by reversible addition fragmentation chain transfer (RAFT) mediated dispersion copolymerization technique using polyvinyl pyrrolidone (PVP) as steric stabilizer and 2-cyano-2-propyl benzodithioate (CPB) as RAFT agent in ethanol. Different reaction parameters on the characteristics of poly(GMA-co-OMA) particles and their effects were investigated thoroughly in the presence of RAFT agent. Formation of poly(GMA-co-OMA) particle sizes, its stability and morphology depends on the concentration of RAFT agent, stabilizer as well as the monomer ratio. Spherical poly(GMA-co-OMA) particles of size ranges1-13 μm were obtained after optimization of the ratio between GMA and OMA. In the presence of RAFT, with the increased amount of hydrophobic monomer OMA, instabilities of the particles are observed while particle sizes found to be decreased with the increased amount of GMA in the reaction mixture. Prepared poly(GMA-co-OMA) particles were characterized by different analytical techniques such as NMR, IR, GPC, TGA etc. while Field Emission Scanning Electron Microscope (FE-SEM) was applied to study the poly(GMA-co-OMA) particle sizes and its morphology.

Surface Modification of Cellulose Nanocrystal Films via RAFT Polymerization for Adsorption of PFAS

Cellulose nanocrystals (CNCs) are bio-based materials able to be functionalized following different approaches, which expands their range of applications. One such approach is surface-initiated polymerization, which involves the attachment of an initiator to the CNC’s surface to initiate the growth of the polymer. This work reports the modification of CNCs using the described approach. First, a CNC-based film was prepared, on which an initiator (RAFT agent) was grafted, and then (trimethylaminoethyl methacrylate, a positively charged monomer, was polymerized using reversible addition–fragmentation chain-transfer (RAFT) polymerization. The CNC film was successfully modified and fully characterized. Different degrees of polymerization were targeted to emphasize the effect of the positively charged polymer and their chain length on the adsorption efficiency. The results showed that by increasing the chain length of the grafted polymer, up to 80% of both pollutants could be removed, with a faster adsorption of PFOS as compared to PFOA.

Preparation of diblock copolymer nano-assemblies by ultrasonics assisted ethanol-phase polymerization-induced self-assembly

Assemblies are widely used in biomedicine, batteries, functional coatings, Pickering emulsifiers, hydrogels, and luminescent materials. Polymerization-induced self-assembly (PISA) is a method for efficiently preparing particles, mainly initiated thermally. However, thermally initiated PISA usually requires a significant amount of time and energy. Here, we demonstrate the preparation of nano-assemblies with controllable morphologies and size using ultrasound (20 kHz) assisted ethanol-phase RAFT-PISA in three hours. Using poly (N, N-dimethylaminoethyl methacrylate) as the macromolecular reversible addition-fragmentation chain transfer agent (PDMA-CTA) to control the nucleating monomer benzyl methacrylate (BzMA), we obtained nano-assemblies with different morphologies. With the length of hydrophobic PBzMA block growth, the morphologies of the assemblies at 15 wt% solid content changed from spheres to vesicles, and finally to lamellae; the morphologies of the assemblies at 30 wt% changed from spheres micelles to short worms, then vesicles, and finally to large compound vesicles. With the same targeted degree of polymerization, nano-assemblies having a 30 wt% solid content display a more evolved morphology. The input of ultrasonic energy makes the system have higher surface free energy, results the mass fraction interval of solventphilic blocks (fhydrophilic) corresponding to the formation of spherical micelles is expanded from fhydrophilic > 45 % to fhydrophilic > 31 % under ultrasound and the fhydrophilic required to form worms, vesicles, and large composite vesicles decreases in turn. It is worth noting that the fhydrophilic interval of worms prepared by ultrasonics assisted PISA gets larger. Overall, the highly green, externally-regulatable and fast method of ultrasonics assisted PISA can be extended to vastly different diblock copolymers, for a wide range of applications.

Controlled Polymerization of N‐Vinyl Imidazole, N‐Vinyl Pyrrolidone, and N‐Vinyl Carbazole with Dithiocarbamates toward High Molar Mass Polymers

AbstractAchieving control over the polymerization of less activated monomers like N‐vinyl carbazole (NVC), N‐vinyl pyrrolidone (NVP), and N‐vinyl imidazole (NVIm) to produce high molar mass polymers poses a significant challenge. To accomplish this, eight different dithiocarbamate‐based reversible addition–fragmentation chain transfer (RAFT) agents are synthesized and employed to polymerize NVIm, NVC, and NVP in order to understand and establish a suitable agent for their controlled polymerization to achieve high molar mass polymers. Chain end presence of these RAFT‐derived polymers is established through 1H NMR studies. Further, these active chain ends are used for chain extension reactions to prepare block copolymers. Synthesized RAFT agents 04, 05, 06, and 08 that are bearing primary leaving groups (methyl 2‐acetate, ethyl 2‐acetate, tert‐butyl 2‐acetate, and cyanomethane) display moderate to good control over the polymerization of NVIm and NVC. Among these, RAFT agent‐08 with cyanomethane leaving group produces poly(NVIm) and poly(NVC) with the highest molar masses of 44 670 Da (1.52) and 53 620 Da (1.4), respectively. Interestingly, RAFT agents bearing both secondary and primary leaving groups show good control over the NVP polymerization. Notably, RAFT agent‐02 with ethyl‐2‐propionate leaving group yields poly(NVP) with the highest molar mass of 89 450 Da and dispersity of 1.43.

Synthesis and Characterization of All-Acrylic Tetrablock Copolymer Nanoparticles: Waterborne Thermoplastic Elastomers via One-Pot RAFT Aqueous Emulsion Polymerization.

Reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerization is used to prepare well-defined ABCB tetrablock copolymer nanoparticles via sequential monomer addition at 30 °C. The A block comprises water-soluble poly(2-(N-acryloyloxy)ethyl pyrrolidone) (PNAEP), while the B and C blocks comprise poly(t-butyl acrylate) (PtBA) and poly(n-butyl acrylate) (PnBA), respectively. High conversions are achieved at each stage, and the final sterically stabilized spherical nanoparticles can be obtained at 20% w/w solids at pH 3 and at up to 40% w/w solids at pH 7. A relatively long PnBA block is targeted to ensure that the final tetrablock copolymer nanoparticles form highly transparent films on drying such aqueous dispersions at ambient temperature. The kinetics of polymerization and particle growth are studied using 1H nuclear magnetic resonance spectroscopy, dynamic light scattering, and transmission electron microscopy, while gel permeation chromatography analysis confirmed a high blocking efficiency for each stage of the polymerization. Differential scanning calorimetry and small-angle X-ray scattering studies confirm microphase separation between the hard PtBA and soft PnBA blocks, and preliminary mechanical property measurements indicate that such tetrablock copolymer films exhibit promising thermoplastic elastomeric behavior. Finally, it is emphasized that targeting an overall degree of polymerization of more than 1000 for such tetrablock copolymers mitigates the cost, color, and malodor conferred by the RAFT agent.

ABC or ACB triblock copolymers? Changing the RAFT group position in diblock copolymer macro-RAFT agents leads to different PISA behaviors in RAFT dispersion polymerization

ACB and ABC triblock copolymer nanoparticles were prepared by reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization using diblock copolymer macromolecular RAFT (macro-RAFT) agents with different RAFT group positions.

Shape matters: Effect of amphiphilic polymer topology on antibacterial activity and hemocompatibility

Understanding the intricate relationship between polymer architecture and biological activity is critical for advancing the development of antibacterial polymers. In this study, we systematically investigated the antibacterial properties and hemocompatibility of 27 different synthetic polymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. The antibacterial activities of these polymers were probed against two gram-negative bacteria, namely Pseudomonas aeruginosa PAO1 and Escherichia coli K12. Furthermore, the antibacterial efficacy and hemocompatibility of synthetic polymers were correlated with their polymer topology, encompassing linear (LPs), hyperbranched (HPs), and star polymers (SPs), characterized by varying hydrophobic compositions (20 %, 25 %, and 30 %). HPs were prepared using two types of crosslinking monomer (acrylate vs. acrylamide). The [crosslinker]:[RAFT agent] ratio in the synthesis of HPs greatly affect their hemocompatibility, while the type of crosslinker had a negligible impact. HPs showed a remarkable 2- to 4-fold enhancement in hemocompatibility compared to LPs at the same hydrophobic ratio. Interestingly, SPs with a low hydrophobic ratio, did not display toxicity towards red blood cells, while maintaining similar potent antibacterial activities as LPs and HPs. Overall, SPs exhibited superior bioactivity compared to HPs and LPs (SPs > HPs > LPs), demonstrating that the manipulation of polymer topology offers a promising avenue for enhancing the performance of synthetic antibacterial polymers.

Photo-RDRP for everyone: Smartphone light-induced oxygen-tolerant reversible deactivation radical polymerization

Oxygen-tolerant reversible deactivation radical polymerization (RDRP) was carried out utilizing a smartphone flashlight. Well-controlled poly(oligo(ethylene oxide) monomethyl ether methacrylate) (POEOMA500) with relatively low dispersity (Đ = 1.16–1.35) was obtained employing dual catalysis atom transfer radical polymerization (ATRP) with CuBr2/tris(2-pyridylmethyl)amine (TPMA) and three different organic photocatalytic dyes (i.e. eosin Y (EY), fluorescein (FL), and riboflavin (RF)). The smartphone flashlight was also used for carrying out oxygen-tolerant photoinduced electron/energy transfer (PET) reversible addition–fragmentation chain transfer (RAFT) polymerization with EY and dithioesters RAFT agents , and photoiniferter (PI) RAFT polymerization with trithiocarbonate RAFT agent. The formation of crosslinked gels and facile measurement of gel points via recording the gelation process by in-built smartphone camera was also demonstrated.

Visible Light Photoiniferter Polymerization for Dispersity Control in High Molecular Weight Polymers

AbstractThe synthesis of polymers with high molecular weights, controlled sequence, and tunable dispersities remains a challenge. A simple and effective visible‐light controlled photoiniferter reversible addition‐fragmentation chain transfer (RAFT) polymerization is reported here to realize this goal. Key to this strategy is the use of switchable RAFT agents (SRAs) to tune polymerization activities coupled with the inherent highly living nature of photoiniferter RAFT polymerization. The polymerization activities of SRAs were in situ adjusted by the addition of acid. In addition to a switchable chain‐transfer coefficient, photolysis and polymerization kinetic studies revealed that neutral and protonated SRAs showed different photolysis and polymerization rates, which is unique to photoiniferter RAFT polymerization in terms of dispersity control. This strategy features no catalyst, no exogenous radical source, temporal regulation by visible light, and tunable dispersities in the unprecedented high molecular weight regime (up to 500 kg mol−1). Pentablock copolymers with three different dispersity combinations were also synthesized, highlighting that the highly living nature was maintained even for blocks with large dispersities. Tg was lowered for high‐dispersity polymers of similar MWs due to the existence of more low‐MW polymers. This strategy holds great potential for the synthesis of advanced materials with controlled molecular weight, dispersity and sequence.

Visible Light Photoiniferter Polymerization for Dispersity Control in High Molecular Weight Polymers.

The synthesis of polymers with high molecular weights, controlled sequence, and tunable dispersities remains a challenge. A simple and effective visible-light controlled photoiniferter reversible addition-fragmentation chain transfer (RAFT) polymerization is reported here to realize this goal. Key to this strategy is the use of switchable RAFT agents (SRAs) to tune polymerization activities coupled with the inherent highly living nature of photoiniferter RAFT polymerization. The polymerization activities of SRAs were in situ adjusted by the addition of acid. In addition to a switchable chain-transfer coefficient, photolysis and polymerization kinetic studies revealed that neutral and protonated SRAs showed different photolysis and polymerization rates, which is unique to photoiniferter RAFT polymerization in terms of dispersity control. This strategy features no catalyst, no exogenous radical source, temporal regulation by visible light, and tunable dispersities in the unprecedented high molecular weight regime (up to 500 kg mol-1 ). Pentablock copolymers with three different dispersity combinations were also synthesized, highlighting that the highly living nature was maintained even for blocks with large dispersities. Tg was lowered for high-dispersity polymers of similar MWs due to the existence of more low-MW polymers. This strategy holds great potential for the synthesis of advanced materials with controlled molecular weight, dispersity and sequence.

Unique Polymer-Stabilized Liquid Crystal Structure Prepared by Addition of a Reversible Addition-Fragmentation Chain Transfer Agent.

Polymer-stabilized liquid crystals (PSLCs) are important electrically switchable materials due to their superior electro-optical properties. Nevertheless, it remains a formidable challenge to balance PSLCs' instant electro-optical performance and long-term durability due to their relatively low polymer content and the related sensitivity to external force. Herein, we demonstrate the possibility of regulating the polymer network structure in PSLCs via reversible addition-fragmentation chain transfer (RAFT) polymerization reactions of acrylate monomers with a chain transfer agent (CTA). By controlling the concentration of CTA and conditions of photopolymerization, the kinetics of the polymerization reaction can be modified. Compared to conventional free-radical (FR) polymerization, the reduced chain growth rate leads to sufficient chain relaxation, reorientation of liquid crystal (LC) directors, and alleviation of shrinkage stresses in the RAFT polymerization process. This in turn produces an ordered polymer network structure in the vertical direction and a uniform distribution in the horizontal plane. As a result, the PSLC network presents increased elasticity with a lower hysteresis effect and greatly improved durability. Our research offers insightful guidance for the fine-tuning of polymer network structures to prepare advanced LC/polymer composite structures with outstanding performances.

Tailoring highly stable anion exchange membranes with graft molecular structure ordering using reversible addition-fragmentation chain transfer polymerization for alkaline fuel cells

The radiation-induced grafting is used to prepare a variety of anion-exchange membranes (AEM) based on poly(ethylene-co-tetrafluoroethylene) (ETFE) utilizing a reversible addition-fragmentation chain transfer (RAFT) agent. The copolymerization process is controlled by the RAFT agent, resulting in AEMs with a restricted molecular weight dispersion. As a result, RAFT-AEMs exhibit decreased water uptake and reduced swelling. A significant improvement in thermal and mechanical characteristics is evidenced, while the conductivity remains practically unaltered. Anion-exchange membrane fuel cell (AEMFC) tests revealed that conventional RIG-AEMs and RAFT-AEMs with low RAFT content (5 wt%) have comparable beginning-of-life performances (∼0.95 W cm−2). However, for higher RAFT contents, the performance trends to decrease indicating an imbalance in water management. Furthermore, short-term stability tests suggest that RAFT-AEMs are able to operate highly stable, with a conductivity rate loss of 0.05% h−1, which represents an improvement of 160% in comparison to conventional RIG-AEM. AFM analysis demonstrated that structural ordering molecular and morphology tailor the fundamental properties of ETFE-based AEMs, combining enhanced performance and stability for alkaline fuel cell applications.

Azobenzene-Containing Liquid Crystalline Twisted Ribbons via Polymerization-Induced Hierarchical Self-Assembly.

Polymerization-induced self-assembly incorporating liquid crystallization, as a polymerization-induced hierarchical self-assembly (PIHSA) method to produce polymeric particles with anisotropic morphologies facilely and efficiently, has drawn wide attention recently. However, the means of regulating the morphologies of liquid crystalline (LC) polymer assemblies still need to be explored. Herein, a route is presented to fabricate the twisted ribbons via PIHSA containing azobenzene based on poor reversible addition-fragmentation chain transfer (RAFT) control, called poorly controlled PIHSA. Cyano-4-(dodecylsulfanylthiocarbonyl)sulfanyl pentanoic acid-2-(2-pyridyldithio) ethyl ester is used as the RAFT agent with poor controllability, and the morphological evolution from ribbons to twisted ribbons can be observed in the corresponding PIHSA system. The formation mechanism of the twisted ribbons is studied systematically and the broad molecular weight distribution is considered to be the decisive factor. Moreover, the supramolecular chirality induced by symmetry breaking is also related to the twist of the ribbons. This study enriches the methods of controlling the morphologies of LC polymer particles and is helpful for further clarifying the mechanism of PIHSA.

Ultrasound-responsive copolymeric micelles prepared by RAFT polymerization using a difunctional spiropyran-based RAFT agent: Investigation of mechanochromism kinetics, responsivities, and enhanced spiropyran mechanoactivation within micelles

An in-depth investigation of the ultrasonic response of mechanophores containing weak covalent bonds within nanosized aggregates is vital for ultrasound imaging, drug delivery, and sensors. In this work, well-defined amphiphilic block SP-[poly(methyl methacrylate-b-N-isopropylacrylamide)]2SP-[p(MMA-b-NIPAM)]2 (P1) and amphiphilic random, SP-[poly(methyl methacrylate-r-N-isopropylacrylamide)]2SP-[p(MMA-r-NIPAM)]2 (P2) copolymers with SP mechanophore embedded at midpoint polymer chain are prepared by RAFT (reversible addition-fragmentation chain transfer) polymerization using a pre-synthesized novel functional bi (trithiocarbonate) and spiropyran (SP)-based RAFT reagent. Both P1 and P2 copolymers self-assemble in spherical micelles in AcCN/water mixed solvents, and several assemblies with different water contents are fabricated. The structural differentiation between block P1 and random P2 dominates the inverse influence of water content on the aggregate sizes of micelles. Under ultrasound irradiation, the SP mechanophore is activated within both micelles, and the amount of activated SP mechanophore increases progressively with prolonged sonication time. For P1, the mechanochemical reaction (mechanochromism) kinetics in an aggregated state and a single chain state are different, while that of P2 micelles and liner are similar, inferred to be associated with the structure difference between both micelles. The mechanoactivation of SP mechanophore within micelles in AcCN/water mixed solvents is higher than in dissolved state due to the micellization of P1 and P2, entangling the hydrophobic PMMA segments and partially swelling in the micellar core. Moreover, an increase in the medium's dielectric constant around the core's SP is also observed, promoting the SP mechanoactivation. This approach may provide a new strategy for preparing novel mechanophore-centered amphiphilic copolymers with colorful structures and high hydrophilicity. These can self-aggregate into nanoparticles in aqueous or mixed solutions, exhibiting effective effects of ultrasonic responsiveness. We expect this work to push forward the in-depth studies on the ultrasonic responsive mechanism of assembly and help open new research avenues into the mechanochemical reactions within nanosized aggregates.

A Strategy for Controlling the Polymerizations of Thiyl Radical Propagation by RAFT Agents.

The ability to extend the polymerizations of thiyl radical propagation to be regulated by existing controlled methods would be highly desirable, yet remained very challenging to achieve because the thiyl radicals still cannot be reversibly controlled by these methods. In this article, we reported a novel strategy that could enable the radical ring-opening polymerization of macrocyclic allylic sulfides, wherein propagating specie is thiyl radical, to be controlled by reversible addition-fragmentation chain transfer (RAFT) agents. The key to the success of this strategy is the propagating thiyl radical can undergo desulfurization with isocyanide and generate a stabilized alkyl radical for reversible control. Systematic optimization of the reaction conditions allowed good control over the polymerization, leading to the formation of polymers with well-defined architectures, exemplified by the radical block copolymerization of macrocyclic allylic sulfides and vinyl monomers and the incorporation of sequence-defined segments into the polymer backbone. This work represents a significant step toward directly enabling the polymerizations of heteroatom-centered radical propagation to be regulated by existing reversible-deactivation radical polymerization techniques.

A Strategy for Controlling the Polymerizations of Thiyl Radical Propagation by RAFT Agents

AbstractThe ability to extend the polymerizations of thiyl radical propagation to be regulated by existing controlled methods would be highly desirable, yet remained very challenging to achieve because the thiyl radicals still cannot be reversibly controlled by these methods. In this article, we reported a novel strategy that could enable the radical ring‐opening polymerization of macrocyclic allylic sulfides, wherein propagating specie is thiyl radical, to be controlled by reversible addition–fragmentation chain transfer (RAFT) agents. The key to the success of this strategy is the propagating thiyl radical can undergo desulfurization with isocyanide and generate a stabilized alkyl radical for reversible control. Systematic optimization of the reaction conditions allowed good control over the polymerization, leading to the formation of polymers with well‐defined architectures, exemplified by the radical block copolymerization of macrocyclic allylic sulfides and vinyl monomers and the incorporation of sequence‐defined segments into the polymer backbone. This work represents a significant step toward directly enabling the polymerizations of heteroatom‐centered radical propagation to be regulated by existing reversible‐deactivation radical polymerization techniques.

Surface grafted gold nanorods (GNRDs) using thermosensitive copolymers with various transition temperatures: Nanomaterials with potential application for photothermal therapy

A series of diblock copolymers containing a biocompatible polyethylene glycol (PEG) block and a thermoresponsive poly(N-vinyl caprolactam) (PNVCL) based block, were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The cloud point temperature (Tcp) in water of the diblocks was adjusted from 35 to 42 °C by adding N-vinyl pyrrolidone (NVP) units in the thermoresponsive block. The terminal trithiocarbonate group evolving from the RAFT agent used in the synthesis, was modified to thiol to stabilize gold nanorods (GNRDs) via a “grafting-to” approach. Stability of the PEG-b-P(NVCL-co-NVP)@GNRDs nanomaterials was monitored during 8 days; where the localized surface plasmon resonance (LSPR) absorption band did not shifted or showed any broadening. Aqueous dispersed samples were irradiated with near-infrared laser light for 10 min, observing a temperature increase from 25 to 50 °C depending on the laser optical power (between 100 and 500 mW); while no precipitation was observed. For temperatures above the cloud point temperature of the copolymers (Tcp), the formation of aggregates in sizes around 200 nm was observed without precipitation. This study demonstrates that the stabilization of gold nanorods by grafting with the title thermoresponsive block copolymers, and the observed temperature-dependent block-copolymer@GNRD aggregation, has potential uses in drug-delivery applications for photothermal therapy.

Synthesis of bio‐based modified amphoteric acrylate epoxy emulsion surface sizing agent via RAFT polymerization

AbstractThe synthesis of bio‐based modified amphoteric epoxy modified acrylate sizing emulsion based on reversible addition fragmentation chain transfer (RAFT) polymerization and its application in paper sizing were studied. A macromolecular chain transfer agent for RAFT polymerization was synthesized by the esterification of epoxy resin E‐51 with RAFT agent to eliminate the active groups on RAFT agent. Amphoteric polymer emulsifiers with good emulsification and dispersion effects in acidic and alkaline media were successfully prepared by RAFT polymerization. After neutralization, other monomers were polymerized to access cationic sizing emulsion (acid neutralization) and anionic sizing emulsion (alkali neutralization). The effects of bio‐based monomer content, hydrophilic monomer dimethylaminoethyl methacrylate (DM) content and degree of quaternization on the properties of sizing emulsion and sizing paper were further explored. In addition to the particle size and polymer dispersion index (PDI) of latex particles in different experimental groups, the water resistance, folding resistance, bursting strength, tensile strength and surface roughness of sized paper were analyzed and evaluated. Based on these results, a better sizing emulsion formulation was established. It was confirmed that the addition of bio‐based monomers can improve the sizing performance of paper.

Synthesis and Characterization of Charge-Stabilized Poly(4-hydroxybutyl acrylate) Latex by RAFT Aqueous Dispersion Polymerization: A New Precursor for Reverse Sequence Polymerization-Induced Self-Assembly.

The reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 4-hydroxybutyl acrylate (HBA) is conducted using a water-soluble RAFT agent bearing a carboxylic acid group. This confers charge stabilization when such syntheses are conducted at pH 8, which leads to the formation of polydisperse anionic PHBA latex particles of approximately 200 nm diameter. The weakly hydrophobic nature of the PHBA chains confers stimulus-responsive behavior on such latexes, which are characterized by transmission electron microscopy, dynamic light scattering, aqueous electrophoresis, and 1H NMR spectroscopy. Addition of a suitable water-miscible hydrophilic monomer such as 2-(N-(acryloyloxy)ethyl pyrrolidone) (NAEP) leads to in situ molecular dissolution of the PHBA latex, with subsequent RAFT polymerization leading to the formation of sterically stabilized PHBA-PNAEP diblock copolymer nanoparticles of approximately 57 nm diameter. Such formulations constitute a new approach to reverse sequence polymerization-induced self-assembly, whereby the hydrophobic block is prepared first in aqueous media.