Combination Of Atom Transfer Radical Polymerization Research Articles

Preparation and Self-Assembly of pH-Responsive Hyperbranched Polymer Peptide Hybrid Materials.

In recent years, the coupling of structurally and functionally controllable polymers with biologically active peptide materials to obtain polymer-peptide hybrids with excellent properties and biocompatibility has led to important research progress in the field of polymers. In this study, a pH-responsive hyperbranched polymer hPDPA was prepared by combining atom transfer radical polymerization (ATRP) with self-condensation vinyl polymerization (SCVP) using a three-component reaction of Passerini to obtain a monomeric initiator ABMA containing functional groups. The pH-responsive polymer peptide hybrids hPDPA/PArg/HA were obtained by using the molecular recognition of polyarginine (β-CD-PArg) peptide modified with β-cyclodextrin (β-CD) on the hyperbranched polymer, followed by the electrostatic adsorption of hyaluronic acid (HA). The two hybrid materials, h1PDPA/PArg12/HA and h2PDPA/PArg8/HA could self-assemble to form vesicles with narrow dispersion and nanoscale dimensions in phosphate-buffered (PB) at pH = 7.4. The assemblies exhibited low toxicity as drug carriers of β-lapachone (β-lapa), and the synergistic therapy based on ROS and NO generated by β-lapa had significant inhibitory effects on cancer cells.

Preparation of spiro-shaped multicyclic polymer by combination of ATRP, CuAAC and photo-induced coupling

This paper elaborated the preparation of spiro-shaped multicyclic polymer with repeating heterocyclics. Block copolymer PEO-PS-Br was prepared by atom transfer radical polymerization (ATRP) of styrene (St) with a poly(ethylene oxide) telechelic macroinitiator PEO-Cou-Br, in which both ends of PEO chain were capped by coumarin groups in advance. After azidation of terminal bromine, bimolecular cyclization was conducted with a diyne as difunctional linker to provide heterocyclic polymer with coumarin groups at the boundaries between PEO and PS blocks. The heterocyclic polymer was exposed to UV irradiation at 365 nm to afford spiro-shaped multicyclic polymer via dimerization of coumarin. GPC, 1H NMR and FT-IR were used to characterize obtained products. Photocleavage of multicyclic polymer under irradiation of 254 nm was also investigated, and GPC trace suggests the successful cleavage from spiro-shaped structure to monocycles.

Glasses‐shaped triblock copolymer prepared by combination of atom transfer radical polymerization and ring opening polymerization

AbstractA glasses‐shaped triblock copolymer of poly(ε‐caprolactone)‐b‐polystyrene‐b‐poly(ε‐caprolactone) (PCL‐b‐PS‐b‐PCL) is prepared by combining atom transfer radical polymerization (ATRP) and ring opening polymerization (ROP). Polystyrene (PS) star polymers are prepared via ATRP using a tetra‐functional initiator, followed by azidation to yield azide end‐functionalized star polymers. An alkyne‐functionalized coupling agent, 2,2‐bis[(2‐propyn‐1‐yloxy)methyl]‐1‐propanol is employed to produce hydroxy 8‐shaped PS via copper(I)‐catalyzed alkyne‐azide cycloaddition. Herein, hydroxy 8‐shaped PS with high purity is obtained through preparative size exclusion chromatography (Prep SEC) and high‐performance liquid chromatography, followed by the characterizations using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS), size exclusion chromatography (SEC), infrared, and proton nuclear magnetic resonance (1H NMR) spectroscopy. The hydroxy groups of the 8‐shaped PS are utilized as initiators for the ROP of ε‐caprolactone to obtain linear chains attached to the 8‐shaped architecture. After SEC fractionation, the glasses‐shaped triblock copolymer is characterized using 1H NMR and SEC. This unprecedented topology possesses two free chain‐ends and two cycles; thus, both the properties of linear and cyclic polymers may be expected to be observed.

Molecular Brushes with a Polyimide Backbone and Poly(ε-Caprolactone) Side Chains by the Combination of ATRP, ROP, and CuAAC.

An approach to the synthesis of the novel molecular brushes with a polyimide (PI) backbone and poly(ε-caprolactone) (PCL) side chains was developed. To obtain such copolymers, a combination of various synthesis methods was used, including polycondensation, atom transfer radical polymerization (ATRP), ring opening polymerization (ROP), and Cu (I)-catalyzed azide-alkyne Huisgen cycloaddition (CuAAC). ATRP of 2-hydroxyethyl methacrylate (HEMA) on PI macroinitiator followed by ROP of ε-caprolactone (CL) provided a “brush on brush” structure PI-g-(PHEMA-g-PCL). For the synthesis of PI-g-PCL two synthetic routes combining ROP and CuAAC were compared: (1) polymer-analogous transformations of a multicenter PI macroinitiator with an initiating hydroxyl group separated from the main chain by a triazole ring followed by ROP of CL, or (2) a separate synthesis of macromonomers with the desirable functional groups (polyimide with azide groups and PCL with terminal alkyne groups), followed by a click reaction. Results showed that the first approach allows to obtain graft copolymers with a PI backbone and relatively short PCL side chains. While the implementation of the second approach leads to a more significant increase in the molecular weight, but unreacted linear PCL remains in the system. Obtained macroinitiators and copolymers were characterized using 1H NMR and IR spectroscopy, their molecular weight characteristics were determined by SEC with triple detection. TGA and DSC were used to determine their thermal properties. X-ray scattering data showed that the introduction of a polyimide block into the polycaprolactone matrix did not change the degree of crystallinity of PCL.

Synthesis and micellar property of amphiphilic brush-arm star copolymers via living ROMP

Norbornene macromonomers (MMs) with polystyrene (PS) or poly(tert-butyl acrylate) (PtBA) side chains were synthesized by a combination of atom-transfer radical polymerization (ATRP) and click reactions. A series of amphiphilic linear and star-shaped brush block copolymers were obtained through sequential ring opening metathesis polymerization (ROMP) of MMs by the use of the highly active olefin metathesis Blechert's catalyst and tri-functionalized Blechert's catalyst respectively, followed by hydrolysis reaction. These well-defined diblock molecular brushes can undergo further self-assembly to form spherical micelles in solution, which have been characterized using DLS, AF4-MALLS, AFM, TEM and fluorescence spectra. The dynamic diameter increases as the hydrophilic backbone content increases for the vast majority of the linear and star copolymers. Brush-arm star diblock amphiphilic copolymers have smaller hydrodynamic diameter and aggregation number than the corresponding linear analogues. Moreover, the critical micelle concentration (CMC) values of star diblock copolymers show less sensitive to the variety of composition.

Synthesis and self-assembly of brush-shaped block copolymer structure via ATRP and ROP

Well-controlled brush-shaped block copolymers (BBCPs) of high molecular weight with polystyrene (PS) and polylactic (PLA) side chains, (poly (cis-5-norbornene-exo-2,3-dicarboximide-end poly (styrene)))-block-(poly (cis-5-norbornene-exo-2,3-dicarboximide-end poly (lactide))) (PNB- g -PS)- b -(PNB- g -PLA) were synthesized by combining atom transfer radical polymerization (ATRP) and ring opening polymerization (ROP). The synthesis of the (PNB- g -PS)- b -(PNB- g -PLA) was well-controlled with molecular weight and polydispersity index ( M n, GPC = 1310000 g mol - 1 and M w / M n (GPC) = 1.16). The SEM, XRD and DSC reveal that there are two immiscible cis-5-norbornene-exo-2,3-dicarboximide-end poly(styrene) (NB-PS) and cis-5-norbornene-exo-2,3-dicarboximide-end poly(lactide) (NB-PLA) phases in BBCP after self-assembly, which leads to partial crystallization. Moreover, the effect of the self-assembly temperature on morphology and reflectance of (PNB- g -PS)- b -(PNB- g -PLA) has been investigated. These (PNB-g-PS)-b-(PNB-g-PLA) exhibit obvious pearlescent appearance and wide band reflection after heat-treated at different temperatures (120 °C, 130 °C, 140 °C and 150 °C). Besides, with the increase of the self-assembly temperature, the domain spacing of (PNB- g -PS)- b -(PNB- g -PLA) decreases and the reflectance in visible range of (PNB- g -PS)- b -(PNB- g -PLA) increases. However, the self-assembly temperature does not significantly influence the reflection wavelength range of (PNB- g -PS)- b -(PNB- g -PLA). • A brush-shaped block copolymer was synthesized via ATRP and ROP. • The BBCP after self-assembly shows crystallization behavior. • The temperature of self-assembly can tune the domain spacing of BBCP. • The BBCPs exhibit obvious pearlescent appearance and wide band reflection after heat-treated at different temperatures.

Activator Generated Electron Transfer Combined Atom Transfer Radical Polymerization (AGET-ATRP) for Controlled Grafting Location of Glycidyl Methacrylate on Regenerated Cellulose Ultrafiltration Membranes

This investigation indicates the ability to selectively graft glycidyl methacrylate (GMA) only from the external surface of regenerated cellulose (RC) ultrafiltration (UF) membranes using activator generated electron transfer (AGET) atom transfer radical polymerization (ATRP). This controlled polymerization resulted in epoxy functionalized polymer brush ends. Further reaction of the terminal epoxy groups provides a flexible platform to introduce desired functionalities either by electrophilic or nucleophilic epoxy ring opening. Selective grafting from the external membrane surface was achieved by using an appropriate pore filling solvent prior to modification. A high viscosity pore filling solvent that is immiscible with the reactive monomer solution used during surface modification was the most effective in supressing grafting from the internal pore surface. The effects of grafting on membrane performance were evaluated by determining water permeability and protein rejection.

Designing Microparticle-Impregnated Polyelectrolyte Composite: The Combination of ATRP, Fast Azidation, and Click Reaction Using a Single-Catalyst, Single-Pot Strategy.

Polystyrene microparticles were covalently impregnated into the networks of functional polyelectrolyte chains designed via a tandem run of three reactions: (i) synthesis of water-soluble polyelectrolyte, (ii) fast azidation and (iii) a ‘click’ reaction, using the single-catalyst, single-pot strategy at room temperature in mild aqueous media. The model polyelectrolyte sodium polystyrenesulfonate (NaPSS) was synthesized via the well-controlled atom transfer radical polymerization (ATRP) whose halogen living-end was transformed to azide and subsequently coupled with an alkyne carboxylic acid through a ‘click’ reaction using the same ATRP catalyst, throughout. Halogen to azide transformation was fast and followed the radical pathway, which was explained through a plausible mechanism. Finally, the success of microparticle impregnation into the NaPSS network was evaluated through Kaiser assay and imaging. This versatile synthetic procedure, having a reduced number of discrete reaction steps and eliminated intermediate work-ups, has established a fast and simple pathway to design functional polymers required to fabricate stable polymer-particle composites where the particles are impregnated covalently and controllably.

One-Pot Synthesis of Star Copolymers by the Combination of Metal-Free ATRP and ROP Processes.

A completely metal-free strategy is demonstrated for the preparation of star copolymers by combining atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP) for the syntheses of block copolymers. These two different metal-free controlled/living polymerizations are simultaneously realized in one reaction medium in an orthogonal manner. For this purpose, a specific core with functional groups capable of initiating both polymerization types is synthesized. Next, vinyl and lactone monomers are simultaneously polymerized under visible light irradiation using specific catalysts. Spectral and chromatographic evidence demonstrates the success of the strategy as star copolymers are synthesized with controlled molecular weights and narrow distributions.

Facile Synthesis of Helical Rod–Coil Block Polymers by the Combination of ATRP and Pd(II)‐Initiated Isocyanides Polymerizations

AbstractA bifunctional initiator containing propargyl bromoisobutyrate and alkyne‐Pd(II) (PBB‐Pd(II)) is designed and synthesized. The propargyl bromoisobutyrate unit of PBB‐Pd(II) can initiate the atom transfer radical polymerization (ATRP) of vinyl monomers, while the Pd(II) complex can initiate the polymerization of phenyl isocyanides. Both the ATRP and Pd(II)‐mediated isocyanide polymerization are proceeded in living/controlled manner. Thus, combining the two living polymerizations, a series of well‐defined block copolymers bearing rod poly(phenyl isocyanide)s and coil poly(acrylate) segments can be facilely prepared in high yield with tunable composition, controlled molar masses (Mns), and narrow molar mass distributions (Mw/Mns). What is more, benefiting from this synthetic strategy, well‐defined core cross‐linked star polymers are readily synthesized. Optically active block copolymers and star polymers can be facilely obtained by using chiral isocyanide monomers due to the formation of predominated one‐handed helix. The chiral star polymers show excellent enantioselective recognition ability in enantioselective crystallization of racemic compounds.

Amphiphilic Bottlebrush Block Copolymers: Analysis of Aqueous Self-Assembly by Small-Angle Neutron Scattering and Surface Tension Measurements

A systematic series of 16 amphiphilic bottlebrush block copolymers (BCPs) containing polystyrene and poly(N-acryloylmorpholine) (PACMO) side chains were prepared by a combination of atom-transfer radical polymerization (ATRP), photoiniferter polymerization, and ring-opening metathesis polymerization (ROMP). The grafting-through method used to prepare the polymers enabled a high degree of control over backbone and side-chain molar masses for each block. Surface tension measurements on the self-assembled amphiphilic bottlebrush BCPs in water revealed an ultralow critical micelle concentration (cmc), 1–2 orders of magnitude lower than linear BCP analogues on a molar basis, even for micelles with >90% PACMO content. Combined with coarse-grained molecular dynamics simulations, fitting of small-angle neutron scattering traces (SANS) allowed us to evaluate solution conformations for individual bottlebrush BCPs and micellar nanostructures for self-assembled macromolecules. Bottlebrush BCPs showed an increase in a...

Effective Construction of Hyperbranched Multicyclic Polymer by Combination of ATRP, UV-Induced Cyclization, and Self-Accelerating Click Reaction

Multicyclic polystyrene (PS) with hyperbranched structure was constructed in an efficient way. First, a seesaw-type PS was synthesized via atom transfer radical polymerization (ATRP) using a Y-shaped ATRP initiator containing one hydroxyl at center and bromine at each end. After azidation, the anthryl and hydroxyl groups were introduced to the ends of the polymer chain by click reaction with a trifunctional molecule bearing alkynyl, hydroxyl, and anthryl groups (alkynyl-OH-ant). By irradiation with 365 nm UV light in a highly dilute condition, cyclic polymer with three hydroxyl groups (c-PS-(OH)3) can be obtained; then it was converted to a cyclic polymer containing three azides (c-PS-(N3)3) by bromination of the hydroxyl groups and azidation. This “A3” cyclic macromonomer was then used to construct hyperbranched multicyclic polymers via self-accelerating click reaction with sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DBA). The properties of obtained polymer were characterized by NMR, FT-IR, MALDI-TOF MS, a...

Topologically Reversible Transformation of Tricyclic Polymer into Polyring Using Disulfide/Thiol Redox Chemistry

A polyring capable of reversible growth and dissociation is synthesized from a tricyclic polystyrene (PS) prepared by combining atom transfer radical polymerization of a 4-arm star-shaped PS and azide–alkyne click reactions. In the preparation of the tricyclic PS, a coupling agent containing a disulfide linkage is used in the click cyclization reaction. The reduction of the disulfide linkage in the tricyclic PS results in an 8-shaped PS with thiol groups which on oxidation leads to a high molecular weight polyring. The topology transformation between the polymers occurs via reversible redox reaction of disulfide/thiol. The high molecular weight of the polyring is realized due to the formation of flexible S–S linkage between the 8-shaped PSs. Their structures are confirmed by FT-IR, 1H NMR, SEC, and MALDI-TOF MS analyses. In addition, molecular weight control of the polyring according to polymer concentration has been confirmed through SEC analysis.

Characterizations of radicals formed in radical polymerizations and transfer reactions by electron spin resonance spectroscopy

Abstract Electron spin resonance (ESR, aka electron paramagnetic resonance, EPR) investigations have been conducted on radicals formed during radical polymerizations and provide a detailed characterization of the active radical species. Active propagating radicals can be observed during actual radical polymerizations by ESR/EPR. The chain lengths of the observed radicals were estimated by a combination of atom transfer radical polymerization (ATRP) and ESR/EPR. The structures of the chain end radicals were determined by analysis of the ESR/EPR spectra. An increase in the dihedral angles between terminal p-orbital of radical and Cβ–H bonds was observed with increasing chain lengths of methacrylate polymers. Radical transfer reactions were observed during radical polymerization of acrylates. A combination of ATRP and ESR/EPR clarified a 1,5-hydrogen shift mechanism of the radical transfer reactions using model adamantyl acrylate radicals. Penultimate unit effects were also observed. Time-resolved ESR/EPR (TR ESR) spectroscopy clarified the initiation processes of an alternating copolymerization of styrene with maleic anhydride and the copolymerization of styrene with 1,3-butadiene. Several unsolved problems in conventional radical polymerization processes have been clarified using combinations of ATRP with ESR/EPR and TR ESR. Characterization of the radicals in radical polymerizations using various ESR techniques would definitely provide interesting and useful information on conventional radical polymerizations.

A Novel Poly(vinylidene fluoride)-Based 4-Miktoarm Star Terpolymer: Synthesis and Self-Assembly

A well-defined amphiphilic miktoarm polymer incorporating poly(vinylidene fluoride) (PVDF), polystyrene (PS), and poly(ethylene glycol) (PEG) blocks was synthesized via a combination of atom-transfer radical polymerization (ATRP), iodine transfer radical polymerization (ITP), and copper-catalyzed azide-alkyne cycloaddition (CuAAC). Morphology and self-assembly of this star polymer were examined in organic solvents and in water. The aggregates formed in water were found to possess unusual frustrated topology due to immiscibility of PS and PVDF. The polymer was evaluated for transport of small hydrophobic molecules in water.

Preparation of novel polyamine-type chelating resin with hyperbranched structures and its adsorption performance.

This paper explored the method of combining atom transfer radical polymerization (ATRP) technology and hyperbranched polymer principle to prepare the high capacity chelating resin. First, surface-initiated atom transfer radical polymerization (SI-ATRP) method was used to graft glycidyl methacrylate (GMA) on chloromethylated cross-linked styrene-divinylbenzene resin, and then the novel polyamine chelating resin with a kind of hyperbranched structure was prepared through the amination reaction between amino group of (2-aminoethyl) triamine and epoxy group in GMA. This resin had a selective effect on As(V) and Cr(VI) at a relatively low pH and can be used for the disposal of waste water containing As(V) and Cr(VI). It had a relatively strong adsorption effect on Cu(II), Pb(II), Cd(II) and Cr(III) and can be used for the disposal of heavy metal ion waste water. The finding was that, the adsorption capacity of resin on the studied heavy metal ions was higher than that of the chelating resin synthesized by traditional technology and also higher than that of the resin modified by ATRP technology and bifunctional chelator, indicating that the combination of ATRP and hyperbranched polymer concept is an effective method to prepare chelating resin with high capacity.

Contact Active Antimicrobial Coatings Prepared by Polymer Blending.

Herein, contact active antimicrobial films are prepared by simply blending cationic amphiphilic block copolymers with commercial polystyrene (PS). The copolymers are prepared by combining atom transfer radical polymerization and "click chemistry." A variety of copolymers are synthesized, and composed of a PS segment and an antimicrobial block bearing flexible side chain with thiazole and triazole groups, 4-(1-(2-(4-methylthiazol-5-yl)ethyl)-1H-1,2,3-triazol-4-yl) butyl methacrylate (TTBM). The length of the TTBM block is varied as well as the alkylating agent. Different films are prepared from N,N-dimethylformamide solution, containing variable PS-b-PTTBM/PS ratio: from 0 to 100 wt%. Remarkably, the blend films, especially those with 30 and 50 wt% of copolymers, exhibit excellent antimicrobial activities against Gram-positive, Gram-negative bacteria and fungi, even higher than films prepared exclusively from the cationic copolymers. Blends composed of 50 wt% of the copolymers present a more than 99.999% killing efficiency against the studied microorganisms. The better activity found in blends can be due to the higher roughness, which increases the surface area and consequently the contact with the microorganisms. These results demonstrate that the use of blends implies a reduction of the content of antimicrobial agent and also enhances the antimicrobial activity, providing new insights for the better designing of antimicrobial coatings.

Simple, Direct Routes to Polymer Brush Traps and Nanostructures for Studies of Diffusional Transport in Supported Lipid Bilayers.

Patterned poly(oligo ethylene glycol) methyl ether methacrylate (POEGMEMA) brush structures may be formed by using a combination of atom-transfer radical polymerization (ATRP) and UV photopatterning. UV photolysis is used to selectively dechlorinate films of 4-(chloromethyl)phenyltrichlorosilane (CMPTS) adsorbed on silica surfaces, by exposure either through a mask or using a two-beam interferometer. Exposure through a mask yields patterns of carboxylic acid-terminated adsorbates. POEGMEMA may be grown from intact Cl initiators that were masked during exposure. Corrals, traps, and other structures formed in this way enable the patterning of proteins, vesicles, and, following vesicle rupture, supported lipid bilayers (SLBs). Bilayers adsorbed on the carboxylic acid-terminated surfaces formed by C–Cl bond photolysis in CMPTS exhibit high mobility. SLBs do not form on POEGMEMA. Using traps consisting of carboxylic acid-functionalized regions enclosed by POEGMEMA structures, electrophoresis may be observed in lipid bilayers containing a small amount of a fluorescent dye. Segregation of dye at one end of the traps was measured by fluorescence microscopy. The increase in the fluorescence intensity was found to be proportional to the trap length, while the time taken to reach the maximum value was inversely proportional to the trap length, indicating uniform, rapid diffusion in all of the traps. Nanostructured materials were formed using interferometric lithography. Channels were defined by exposure of CMPTS films to maxima in the interferogram, and POEGMEMA walls were formed by ATRP. As for the micrometer-scale patterns, bilayers did not form on the POEGMEMA structures, and high lipid mobilities were measured in the polymer-free regions of the channels.

Synthesis of Poly(arylene vinylene)s with Different End Groups by Combining Acyclic Diene Metathesis Polymerization with Wittig-type Couplings.

A series of end-functionalized poly(9,9'-di-n-octylfluorene vinylene)s (EF-PFVs) with different end groups were obtained by 1) synthesizing EF-PFV with vinyl end groups by acyclic diene metathesis (ADMET) polymerization with a molybdenum catalyst and termination with an aldehyde and 2) subsequent olefin metathesis of the vinyl group with the molybdenum catalyst followed by Wittig-type coupling with another aldehyde. The exclusive formation of EF-PFVs containing a vinyl end group by the ADMET polymerization was confirmed by grafting PEG, and by the synthesis of amphiphilic triblock copolymers by combining atom transfer radical polymerization from the PFV chain end with PEG grafting through a click reaction. Various EF-PFVs with different end groups, such as C6 F5 , pyridyl, ferrocenyl, and terthiophene, have thus been prepared. Their fluorescence spectra (e.g., intensities, emission wavelengths) were influenced by the end groups and the length of the conjugation.

Synthesis of Poly(arylene vinylene)s with Different End Groups by Combining Acyclic Diene Metathesis Polymerization with Wittig‐type Couplings

AbstractA series of end‐functionalized poly(9,9′‐di‐n‐octylfluorene vinylene)s (EF‐PFVs) with different end groups were obtained by 1) synthesizing EF‐PFV with vinyl end groups by acyclic diene metathesis (ADMET) polymerization with a molybdenum catalyst and termination with an aldehyde and 2) subsequent olefin metathesis of the vinyl group with the molybdenum catalyst followed by Wittig‐type coupling with another aldehyde. The exclusive formation of EF‐PFVs containing a vinyl end group by the ADMET polymerization was confirmed by grafting PEG, and by the synthesis of amphiphilic triblock copolymers by combining atom transfer radical polymerization from the PFV chain end with PEG grafting through a click reaction. Various EF‐PFVs with different end groups, such as C6F5, pyridyl, ferrocenyl, and terthiophene, have thus been prepared. Their fluorescence spectra (e.g., intensities, emission wavelengths) were influenced by the end groups and the length of the conjugation.