Addition-fragmentation Chain Transfer Radical Polymerization Research Articles

Single-Micelle-Templated Synthesis of Hollow Barium Carbonate Nanoparticle for Drug Delivery

A laboratory-synthesized triblock copolymer poly(ethylene oxide-b-acrylic acid-b-styrene) (PEG-PAA-PS) was used as a template to synthesize hollow BaCO3 nanoparticles (BC-NPs). The triblock copolymer was synthesized using reversible addition-fragmentation chain transfer radical polymerization. The triblock copolymer has a molecular weight of 1.88 × 104 g/mol. Transmission electron microscopy measurements confirm the formation of spherical micelles with a PEG corona, PAA shell, and PS core in an aqueous solution. Furthermore, the dynamic light scattering experiment revealed the electrostatic interaction of Ba2+ ions with an anionic poly(acrylic acid) block of the micelles. The controlled precipitation of BaCO3 around spherical polymeric micelles followed by calcination allows for the synthesis of hollow BC-NPs with cavity diameters of 15 nm and a shell thickness of 5 nm. The encapsulation and release of methotrexate from hollow BC-NPs at pH 7.4 was studied. The cell viability experiments indicate the possibility of BC-NPs maintaining biocompatibility for a prolonged time.

A Thermo-Responsive Polymer Micelle with a Liquid Crystalline Core.

An amphiphilic diblock copolymer (PChM-PNIPAM), composed of poly(cholesteryl 6-methacryloyloxy hexanoate) (PChM) and poly(N-isopropyl acrylamide) (PNIPAM) blocks, was prepared via reversible addition-fragmentation chain transfer radical polymerization. The PChM and PNIPAM blocks exhibited liquid crystalline behavior and a lower critical solution temperature (LCST), respectively. PChM-PNIPAM formed water-soluble polymer micelles in water below the LCST because of hydrophobic interactions of the PChM blocks. The PChM and PNIPAM blocks formed the core and hydrophilic shell of the micelles, respectively. With increasing temperature, the molecular motion of the pendant cholesteryl groups increased, and a liquid crystalline phase transition occurred from an amorphous state in the core. With further increases in temperature, the PNIPAM block in the shell exhibited the LCST and dehydrated. Hydrophobic interactions of the PNIPAM shells resulted in inter-micellar aggregation above the LCST.

Sulfur-Free Radical RAFT Polymerization of Methacrylates in Homogeneous Solution: Design of exo-Olefin Chain-Transfer Agents (R-CH2 C(=CH2 )Z).

In this work, the development of exo-olefin compounds (R-CH2 C(=CH2 )Z) as chain-transfer agents for the sulfur-free reversible addition-fragmentation chain transfer (RAFT) radical polymerization of methacrylates in homogeneous solution is described. A series of exo-olefin compounds with a methyl methacrylate (MMA) dimer structure as the R group and a substituted α-methylstyrene unit as the -CH2 C(=CH2 )Z (Z: Ph-Y) group were synthesized and used for the radical polymerization of MMA in toluene and PhC(CF3 )2 OH. These compounds underwent transfer of the CH2 C(=CH2 )Z group via addition-fragmentation of the propagating methacryloyl radical. More electron-donating (Y) substituents, such as methoxy and dimethylamino groups, produced polymers with narrower molecular weight distributions. A continuous monomer addition method further improved molecular weight control and enabled the synthesis of colorless, sulfur-free, multiblock copolymers of methacrylates in homogeneous solutions.

Formation of Water-Soluble Complexes from Fullerene with Biocompatible Block Copolymers Bearing Pendant Glucose and Phosphorylcholine.

Double-hydrophilic diblock copolymers, PMPC100-block-PGEMAn (M100Gn), were synthesized via reversible addition-fragmentation chain transfer radical polymerization using glycosyloxyethyl methacrylate and 2-(methacryloyloxy)ethyl phosphorylcholine. The degree of polymerization (DP) of the poly(2-(methacryloyloxy) ethylphosphorylcholine) (PMPC) block was 100, whereas the DPs (n) of the poly(glycosyloxyethyl methacrylate) PGEMA block were 18, 48, and 90. Water-soluble complexes of C70/M100Gn and fullerene (C70) were prepared by grinding M100Gn and C70 powders in a mortar and adding phosphate-buffered saline (PBS) solution. PMPC can form a water-soluble complex with hydrophobic C70 using the same method. Therefore, the C70/M100Gn complexes have a core-shell micelle-like particle structure possessing a C70/PMPC core and PGEMA shells. The maximum amounts of solubilization of C70 in PBS solutions using 2 g/L each of M100G18, M100G48, and M100G90 were 0.518, 0.358, and 0.257 g/L, respectively. The hydrodynamic radius (Rh) of C70/M100Gn in PBS solutions was 55-75 nm. Spherical aggregates with a similar size to the Rh were observed by transmission electron microscopy. When the C70/M100Gn PBS solutions were irradiated with visible light, singlet oxygen was generated from C70 in the core. It is expected that the C70/M100Gn complexes can be applied to photosensitizers for photodynamic therapy treatments.

Preparation and applications of the polymeric micelle by polymerization-induced self-assembly (PISA)

Polymerization induced self-assembly (PISA) has a high solid content, simple operating steps, and can generally achieve high conversion to monomers in a short time, which has been widely used in the preparation and adjusting to morphologies of polymer micelles self-assembly. In this article, the preparation and applications of the polymeric micelle synthesized by PISA were reviewed. The particle morphology can be adjusted by a variety of active polymerizations with different initiation mechanisms in the preparation of polymer micelles. Among them, free radical active polymerization is more practical. The reversible addition-fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP) were highlighted. Additionally, different shapes such as spheres, worms, and vesicles can be obtained by RAFT in the preparation of nano-objects fields. Researchers construct the phase diagram to get the pure phase for applications. As one form produced by PISA, polymeric micelles are usually artificial nanoreactors for a series of organic and inorganic catalysis and can be used as drug delivery and target agents. Due to the increase in the ultimate tensile strength, RAFT is an optimal technique to produce thermoplastic elastomers.

Synthesis and Characterization of Temperature-Responsive N-Cyanomethylacrylamide-Containing Diblock Copolymer Assemblies in Water.

We have previously demonstrated that poly(N-cyanomethylacrylamide) (PCMAm) exhibits a typical upper-critical solution temperature (UCST)-type transition, as long as the molar mass of the polymer is limited, which was made possible through the use of reversible addition-fragmentation chain transfer (RAFT) radical polymerization. In this research article, we use for the first time N-cyanomethylacrylamide (CMAm) in a typical aqueous dispersion polymerization conducted in the presence of poly(N,N-dimethylacrylamide) (PDMAm) macroRAFT agents. After assessing that well-defined PDMAm-b-PCMAm diblock copolymers were formed through this aqueous synthesis pathway, we characterized in depth the colloidal stability, morphology and temperature-responsiveness of the dispersions, notably using cryo-transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and turbidimetry. The combined analyses revealed that stable nanometric spheres, worms and vesicles could be prepared when the PDMAm block was sufficiently long. Concerning the thermoresponsiveness, only diblocks with a PCMAm block of a low degree of polymerization (DPn,PCMAm < 100) exhibited a UCST-type dissolution upon heating at low concentration. In contrast, for higher DPn,PCMAm, the diblock copolymer nano-objects did not disassemble. At sufficiently high temperatures, they rather exhibited a temperature-induced secondary aggregation of primary particles. In summary, we demonstrated that various morphologies of nano-objects could be obtained via a typical polymerization-induced self-assembly (PISA) process using PCMAm as the hydrophobic block. We believe that the development of this aqueous synthesis pathway of novel PCMAm-based thermoresponsive polymers will pave the way towards various applications, notably as thermoresponsive coatings and in the biomedical field.

PH-Responsive Association Behavior of Biocompatible Random Copolymers Containing Pendent Phosphorylcholine and Fatty Acid.

Well-defined pH-responsive biocompatible random copolymers composed of 2-(methacryloyloxy)ethyl phosphorylcholine and varying quantities of sodium 11-(acrylamido)undecanoate (AaU) (fAaU = 0-58 mol %) were synthesized via reversible addition-fragmentation chain transfer radical polymerization. The pH-responsive association and dissociation behavior of the random copolymers was studied via turbidity, 1H nuclear magnetic resonance relaxation time, dynamic light scattering, static light scattering (SLS), and fluorescence measurements. At basic pH levels, the random copolymers dissolved in water in a unimer state because the AaU units behaved in a hydrophilic manner as a result of the ionization of the pendent fatty acids. The random copolymers with fAaU < 52 mol % associated intramolecularly within a single polymer chain to form unimer micelles at pH 3 because of the protonation of the pendent fatty acids. On the other hand, the random copolymer with fAaU ≥ 52 mol % formed intermolecular aggregates composed of four polymer chains at pH 3, as established by the SLS measurements. The random copolymers displayed the ability to solubilize hydrophobic guest molecules, such as N-phenyl-1-naphthylamine, into the hydrophobic microdomain formed by the pendent dehydrated fatty acids at acidic pHs. At pH 4, 1-pyrememethanol is captured by the random copolymer with fAaU = 52 mol %, and it is released from the random copolymer above pH 9. Furthermore, the mucoadhesive properties of the random copolymer with fAaU = 9 mol % were studied using a surface plasmon resonance technique. The copolymer was adsorbed onto mucin at pH 3; however, the adsorption decreased at pH 7.4.

RAFT synthesis of thioether-based, AB diblock copolymer nanocarriers for reactive oxygen species–triggered release

A well-defined AB diblock copolymer of 2-vinyl-4,4-dimethylazlactone (VDA) and N,N-dimethylacrylamide (DMA) was generated by reversible addition-fragmentation chain transfer (RAFT) radical polymerization. The VDA-DMA diblock copolymer was reacted with 2-(methylthio)ethylamine (MTEA) and 3-(methylthio)propylamine (MTPA) to yield two novel thioether functional diblock copolymers whose structure was confirmed using 1H NMR and FTIR spectroscopy. Both diblock copolymers formed micelles (20–30 nm) in aqueous media as confirmed by dynamic light scattering (DLS) and transmission electron microscopy. The self-assembled micelles were loaded with Nile Red, a model hydrophobic drug to study their ROS-triggered release mechanism. On addition of hydrogen peroxide (H2O2), the most common ROS species, the hydrophobic thioether core of these micelles oxidized, and both diblock copolymers became more hydrophilic. This triggered their disassembly and subsequent cargo release as characterized by UV–visible spectroscopy. The Nile Red loaded micelles demonstrated similar in-vitro ROS-mediated release when exposed to endogenous oxidants in a model inflammation environment simulated by the presence of activated macrophages. The responsive nanomaterials developed in this article have promising potential as drug carriers in applications where ROS-triggered delivery of cargo is required such as in inflammatory conditions.

Synthesis of end group-functionalized PGMA-peptide brush platforms for specific cell attachment by interface-mediated dissociative electron transfer reversible addition-fragmentation chain transfer radical (DET-RAFT) polymerization

Polymer brush synthesis is a powerful approach to fabricate functional bio-interfaces. To enhance the control over brush synthesis and end groups, we have synthesized poly(glycidyl methacrylate) PGMA brushes with carboxylic acid end functional groups by interface-mediated dissociative electron transfer reversible addition-fragmentation chain transfer radical (DET-RAFT) polymerization on titanium surfaces. This method does not require the use of metals and occurs under mild conditions. The brushes obtained were analyzed comprehensively in order to understand how to control cell attachment behavior. The PGMA brushes synthesized by DET-RAFT polymerization were characterized by X-ray photoelectron spectroscopy (XPS), grazing angle Fourier transform infrared (GA-FTIR) spectroscopy, water contact angle measurements and variable angle spectroscopic ellipsometry. The terminal carboxylic acid functional groups were covalently conjugated with arginine-glycine-aspartic acid (RGD) and arginine-alanine-aspartic acid (RAD, negative control) peptides in one step. RGD selective attachment of NIH 3T3 fibroblasts was observed exclusively on PGMA-RGD brushes. Thus, a new versatile strategy has been validated to obtain functional biointerfaces for selective cell attachment in the absence of any metallic catalyst.

Free- and reversible deactivation radical (co)polymerization of isobutylene in water under environmentally benign conditions

The synthesis of a linear polyisobutylene is achieved for the first time by free radical polymerization. The reaction was performed in environmentally friendly conditions, i.e., in an aqueous medium using cyclodextrin solubilizer, around room temperature. This mild and straightforward radical polymerization resulted in a predominantly linear polymer with low dispersity. Isobutylene was also copolymerized with acrylamide via this cyclodextrin assisted aqueous free-radical polymerization, leading to new poly(isobutylene-co-acrylamide) amphiphilic copolymers. The feed composition of copolymerization had a huge effect on the composition and, therefore, the resulting copolymer's solubility. Reversible addition-fragmentation chain transfer radical polymerization (RAFT) of isobutylene was also carried out using a PEG-based symmetrical macro chain transfer agent. Poly(PEG-b-isobutylene-b-PEG) block-copolymer was formed in this one-pot reaction. This novel polymerization method for isobutylene opens new, environmentally benign routes to produce novel copolymers for various applications.

Synthesis of Graphene Oxide-Polystyrene Graft Polymer Based on Reversible Addition Fragmentation Chain Transfer and Its Effect on Properties, Crystallization, and Rheological Behavior of Poly (Lactic Acid)

Graphene oxide-polystyrene graft polymer (SGO-PS) was prepared by reversible addition-fragmentation chain transfer radical polymerization method. Orthogonal experiments indicated that the optimum synthesis reaction conditions for SGO-PS were as follows: the millimole ratio of chain transfer agent to initiator was 0.15 : 0.3, and the amount of styrene was 8 mL at 80°C for 12 hours. The products were characterized by Fourier transform infrared spectroscopy and thermal weightlessness analysis, and the highest grafting rate of SGO-PS was 62.46%. Then, PLA/SGO-PS nanocomposites were prepared using SGO-PS as fillers by melt intercalation method, and its crystallinity, mechanical properties, and thermal stability were significantly improved. Compared with pure PLA, the crystallinity of PLA/SGO-PS (0.3 wt%) nanocomposites was increased by 5 times. Multiple melting behavior tests showed that the introduction of SGO-PS caused the PLA molecular chain to be discharged into the unit cell in time, and the melting temperature shifted to a higher temperature, which ultimately made the grain structure of PLA composites more complete and stable than pure PLA. The rheological performance test showed that the uniform dispersion of SGO-PS in the PLA matrix inhibited the free movement of the PLA molecular chain and caused higher flow resistance, resulting in an increase in the complex viscosity, storage modulus, and loss modulus of PLA/SGO-PS.

Weak bases, an efficient accelerator for the RAFT of isoprene

The use of weak bases as accelerators for reversible addition-fragmentation chain transfer radical polymerization (RAFT) of isoprene is demonstrated. Adding weak bases to RAFT polymerization, the conversion of isoprene could be greatly improved and reach about 50%. The effects of weak base on the polymerization were investigated. The living and controlled character of the RAFT polymerization of isoprene was confirmed by the linear increase in molecular weight with monomer conversion, the narrow molecular weight distribution and synthesis of polyisoprene-block-polystyrene (PIP-b-PS) block copolymer. The results of 1HNMR spectroscopy show that the structure of polyisoprene (PIP) with weak bases as accelerators was the same to the structure of PIP without any accelerator. The data presented here prove that weak bases are an efficient accelerator to inhibit Diels-Alder reaction of isoprene in the RAFT polymerization.

S-nitrosothiol-terminated poly(vinyl alcohol): Nitric oxide release and skin blood flow response

Polymeric biomaterials capable of delivering nitric oxide (NO) topically can be used to enhance skin blood flow (SkBF) and accelerate wound healing. Herein, we used reversible addition-fragmentation chain transfer radical (RAFT) polymerization to synthesize the first poly(vinyl alcohol) (PVA) functionalized with terminal NO-releasing S-nitrosothiol (RSNO) groups for topical NO delivery. This strategy was based on the synthesis of a precursor amino-terminated PVA (PVA-NH2), which was next functionalized with iminothiolane yielding 4-imino-4-amino-PVA-butane-1-thiol (PVA-SH), and finally S-nitrosated yielding S-nitroso 4-imino-4-amino-PVA-butane-1-thiol (PVA-SNO). Real-time chemiluminescence NO detection showed that blended films of pure PVA with PVA-SNO with mass ratios 30:70, 50:50 and 70:30 release NO with initial rates ranging from 1 to 12 nmol g−1 min−1, and lead to a 2 to 10-fold dose-response increase in the SkBF, after topical application on the ventral forearm of volunteers. These results show that PVA-SNO is a potential platform for topical NO delivery in biomedical applications.

Expanding the versatility of poly(dimethylsiloxane) through polymeric modification: an effective approach for improving triboelectric energy harvesting performance

In this work, metal-to-dielectric contact-separation type triboelectric nanogenerators (TENG) are realized using polydimethylsiloxane (PDMS) and steel to harvest energy from daily motions with frequencies of around 1 Hz. A novel polymer modified PDMS has been used as the active material of the TENG device to extend the triboelectric properties of the traditional PDMS. For this purpose, PDMS is functionalized with polystyrene (PS) and poly(pentafluorostyrene) (PPFS) using batch-fabrication compatible methods. Two-step functionalization is employed, first, with the integration of chain transfer polymerization agents into the PDMS matrix and then with the growth of polymers on PDMS using reversible addition-fragmentation chain transfer radical polymerization. Power generation of PDMS in TENG is improved by 16 times with PS and by 48 times with PPFS modification. Steel is used as the counter electrode due to its promising mechanical material properties in forming springs and actuators in microsystems.

Design of hydrophilic photocleavage o-nitrobenzyl acrylate-modified nanogels with outstanding biocompatibility prepared by RAFT polymerization for drug carrier

Three kinds of hydrophilic photocleavage o-nitrobenzyl acrylate-modified nanogels with different particle size and narrow particle size distribution (1.8–0.24) were designed and synthesized by reversible addition-fragmentation chain transfer radical (RAFT) polymerization based on methoxy polyethylene glycol methacrylate (MPEGMA) and UV-light responsive crosslinker 5-(acryloyloxy)-2-nitrobenzyl acrylate (ONB) prepared with acryloyl chloride and 2-hydroxy-5-nitrobenzyl alcohol. The influences of particle size and distribution of the nanogel on its loading, encapsulation and photo-responsive release properties were investigated via the measurements of the final drug loading, the encapsulation efficiency and final cumulative release of coumarin 102 in the nanogel. The final drug loading, the encapsulation efficiency and the final cumulative release of coumarin 102 in the nanogel NG-ONB-300 with narrow particle size distribution were nearly twice more than those in the nanogel NG-ONB-300AIBN with wide particle size distribution (0.33) at the same concentration of coumarin 102 and reached 8.31%, 39.5% and 67%, respectively. With the increase of the particle size of the nanogel, the drug loading and encapsulation efficiency of the nanogel were decreased. Significantly, the in vitro cytotoxicity of the nanogel was also evaluated against HeLa cervical cancer cells by the MTT cell viability assay and its cell viability at different concentrations was greater than 91%, demonstrating that the photocleavage nanogel has an excellent biocompatibility and great potential in drug delivery fields.

Multistimuli-Responsive Emulsifiers Based on Two-Way Amphiphilic Diblock Polymers.

Diblock copolymers of poly(tert-butyl methacrylate) (PtBuMA) and poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) of four different block lengths were prepared by sequential two-step reversible addition–fragmentation chain transfer radical polymerization, followed by hydrolysis of the PtBuMA blocks to obtain poly(methacrylic acid)-b-PDMAEMA (PMAA-b-PDMAEMA). The effect of the PDMAEMA block length on the multistimuli-responsive amphiphilic features of both types of diblock copolymers was investigated as CO2-switchable emulsifiers for emulsification/demulsification of n-octane (an oil) in water in response to CO2/N2 bubbling. The amphiphilicity of PtBuMA-b-PDMAEMA was switched on, and the amphiphilicity of PMAA-b-PDMAEMA was switched off by CO2 bubbling at pH 12 and 25 °C to achieve emulsification/demulsification. A longer PDMAEMA block length in PMAA-b-PDMAEMA conferred more sensitive CO2-responsive amphiphilicity but reduced the extent of recovery of emulsification ability on N2 bubbling. This newly developed diblock copolymer system could potentially serve as a “multifunctional surfactant” for CO2-switchable emulsification/demulsification of oil-in-water and water-in-oil mixtures.

Controlled Synthesis of Methacrylic Acid-Methyl Acrylate Copolymers and Their Properties at Various Interfaces

Conditions were found for controlled reversible addition-fragmentation chain-transfer radical polymerization to obtain narrow-dispersity gradient methacrylic acid-methyl acrylate copolymer (Mn = 1.59 × 104). A copolymer of similar composition and molecular mass (Mn = 1.81 × 104) 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.

Investigation of electrophoretic deposition behavior of fluorinated poly(methacrylate)s: A new paradigm of electrophoretic non-ionic polymers

We demonstrate electrophoresis of non-ionic poly(methacrylate)s containing pendant fluoroalkanes for developing a new polymeric system of enhanced electrophoretic deposition (EPD) by making use of the high electronegativity of fluorinated fragments. Three kinds of fluorinated poly(methacrylaes)s with various fluorine content and molecular weights are synthesized via reversible addition-fragmentation chain transfer (RAFT) radical polymerization. These polymers are characterized in the assembled dispersion particle states in the mixture solvents of tetrahydrofuran and several kinds of alcohols, and investigated for their EPD coating capability onto several kinds of metal plates. In addition, the coatings of fluorinated-polymers prepared via EPD are characterized by performing contact angle measurements. The results reveal exciting electrophoretic behavior of the simple fluorinated poly(methacrylate)s, and we propose the probable EPD mechanism based on our findings. This will lead to expansion of availability of non-ionic polymers with the instinctive EPD function, which gives insights into a new manipulation technique of functional coating.

Highly selective and sensitive ratiometric fluorescent polymer dots for detecting hypochlorite in 100% aqueous media

Hypochlorite (ClO-), as a momentous reactive oxygen species (ROS), is highly desirable due to it associated with a number of human diseases. Therefore, the development of simple and convenient water-soluble ratiometric fluorescent probes is of great significance. In this work, water-soluble ratiometric fluorescent polymer dots (FPDs) for detecting ClO- were prepared via incorporation of reversible addition-fragmentation chain transfer radical polymerization (RAFT), grafting technique and coprecipitation strategy. Upon the addition of ClO-, due to the intramolecular heavy atom effect (HAE) by chlorine (Cl), the fluorescence of fluorescein units in FPDs was significantly quenched, while another reference fluorophore (P2) in FPDs keeps constant. Furthermore, the FPDs exhibited excellent sensitivity (detection limit: 2.2 nM) and selectivity, good water-solubility. In addition, FPDs was successfully utilized to detect ClO- in tap water and drink water. It implies that the nanoprobes have the great potential applications in biological sensing and imaging.

Thermo-Responsive Behavior of Amphoteric Diblock Copolymers Bearing Sulfonate and Quaternary Amino Pendant Groups.

Amphoteric diblock copolymers (S82A n) composed of poly(2-acrylamido-2-methylpropanesulfonic acid sodium salt) (PAMPS) with poly(3-(acrylamido)propyl trimethylammonium chloride) (PAPTAC) blocks were synthesized via reversible addition-fragmentation chain transfer (RAFT) radical polymerization. Three S82A n were prepared with a fixed degree of polymerization (DP) for the PAMPS block (= 82) and different DP values for the PAPTAC blocks ( n = 37, 83, and 183). The solubility of S82A n was studied at different sodium chloride (NaCl) concentrations. S82A83 precipitated in pure water due to attractive electrostatic interactions with interpolymer chains. Conversely, S82A37 and S82A183 dissolved in pure water. In pure water S82A37 dissolved as a unimer state due to electrostatic repulsion of excess anionic charges in the polymer chain. The long anionic PAMPS block segment in S82A37 covered the short cationic PAPTAC block segment within a single polymer chain. In pure water S82A183 dispersed as polyion complex micelles due to electrostatic repulsion of the cationic PAPTAC shells. The oppositely charged PAMPS and PAPTAC blocks in S82A183 formed a core, while the excess PAPTAC block formed shells. S82A n showed lower critical solution temperature (LCST)-type thermo-responsive behavior at certain NaCl concentrations, and the LCST increased with the NaCl concentration. The mechanism of LCST behavior involves hydrogen bonding interactions between the pendant amide groups and water molecules.