Synthesis and Characterization of 2-(Dimethylamino)ethyl Methacrylate Homopolymers via aqueous RAFT Polymerization and Their Application in Miniemulsion Polymerization

Summary Homopolymers of 2-(dimethylamino)ethyl methacrylate (DMAEMA) have been synthesized directly in aqueous media by reversible addition-fragmentation chain transfer polymerization (RAFT) using 4,4-azobis(4-cyanopentanoic acid) (V501) as a water-soluble azo initiator and 4-cyanopentanoic acid dithiobenzoate (CPADB) as a chain transfer agent. The resulting polymers were controlled in the range of narrow molecular weight distributions, with lower than 1.3. Using the produced dithioester-capped DMAEMA homopolymer as a macro chain transfer agent, miniemulsion RAFT polymerization of methyl methacrylate and styrene were carried out, respectively. ¹H NMR analysis showed that the diblock copolymer PDMAEMA-b-PMMA in the form of stable latices was obtained as expected. This revised version was published online at the end of November 2004. Unfortunately, the received date was incorrect due to a technical problem.     

Synthesis of chemically amplified photoresist polymer containing four (Meth)acrylate monomers via RAFT polymerization and its application for KrF lithography

KrF photoresist polymers (PASTMs) were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. Four (meth)acrylates with lithographic functionalities including styrene (St), 4-acetoxystyrene (AST), 2-methyl-2-adamantyl methacrylate (MAMA), and tert-butyl acrylate(TBA) were used as monomer components and 2-methyl-2-[(dodecylsulfanylthiocarbonyl) sulfanyl]propanoic acid (MDFC) was used as RAFT agent, varying the RAFT content could modulate molecular weight. Fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (¹H NMR) indicated that the synthesis was successful. Gel permeation chromatography (GPC) showed that the molecular weight decreased with the increased content of MDFC, and all the polymers possessed weight-average molecular weight below ten thousand and polydispersity less than 1.32. Thermogravimetric analysis (TGA) characterized the thermal properties, the results implied that initial thermal decomposition temperature reached 200 °C, which could satisfy the lithography process. Differential scanning calorimetry (DSC) showed that the Tg decreases with molecular weight. The RAFT polymerization kinetics plots demonstrated that the polymerization was first-order, the number-average molecular weights of the polymers with relatively low polydispersity index values increased with total monomer conversions indicating that the concentration of growing radicals was constant throughout the polymerization process. The narrow molecular weight distribution and composition uniformity of the polymers prepared by RAFT polymerization could be beneficial for lithography, after alcoholysis, lithography evaluation under KrF lithography showed that this homogeneous polymer photoresist exhibited better space and line (S/L) pattern with resolution of 0.18 μm according to the SEM image.     

SYNTHESIS,CHARACTERIZATION, AND THERMAL STABILITY OF HOMOPOLYMER AND COPOLYMER OF SOME 3-ARYL-2-HYDROXYPROPYL METHACRYLATES

Three new hydroxypropyl methacrylates having three different aryl rings were synthesized by addition of 2,3-epoxypropyl aromatic hydrocarbon to methacrylic acid. The monomers prepared are 3-phenyl-2-hydroxypropyl methacrylate, 3-tolyl-2-hydroxypropyl methacrylate, (THPMA), and 3-naphtyl-2-hydroxypropyl methacrylate. The homopolymers of these monomers and two different copolymers, [poly(THPMA-co-BMA)], were obtained from polymerization at 60°C in 1,4-dioxane solution using AIBN as initiator. All the monomers and the polymers were characterized by FT-IR and ¹H and ¹³C NMR techniques. Solubility parameters of the polymers and average molecular weight of poly(THPMA) were determined. Thermal stabilities of the polymers were given as comparing with each other by using TGA curves. Thermal degradation of poly(THPMA60%-co-BMA40%) was studied in detail.     

Synthesis by RAFT polymerization and properties of anionic cylindrical molecular brushes bearing poly(acrylic acid) side chains

RAFT polymerization of acrylic acid (AA) in the presence of low-molecular chain transfer agent (2-(butylthiocarbonothioylthio) propanoic acid and polyacrylate-based backbone bearing multiple butylthiocarbonothioylthio moieties is reported demonstrating successful synthesis of linear pAA with low polydispersity and anionic cylindrical molecular brushes, respectively. Twofold excess of butylthiocarbonothioylthio moieties attached to polyacrylate-based backbone over the initiator was optimal enabling to synthesize graft copolymers with rather low polydispersity (PDI 1.23–1.36) and reasonably high DP of pAA side chains (up to 25). Anionic cylindrical molecular brushes were characterized by SEC with triple detection, DLS, ¹H NMR spectroscopy, and potentiometric titration. Thermal transitions and thermal stability of the brush polymers bearing pAA side chains were determined by DSC and TGA.     

(S)-2-(ethyl propionate)-(O-ethyl xanthate)- and (S)-2-(Ethyl isobutyrate)-(O-ethyl xanthate)-mediated RAFT polymerization of vinyl acetate

(S)-2-(Ethyl propionate)-(O-ethyl xanthate) (X1) and (S)-2-(Ethyl isobutyrate)-(O-ethyl xanthate) (X2) were used as the reversible addition-fragmentation chain transfer (RAFT) agents for the radical polymerization of vinyl acetate (VAc). The former showed the better chain transfer ability in the polymerization at 60°C. Kinetic study with both RAFT agents showed pseudo-first order kinetics up to around 85% monomer conversion. Molecular weight of the resulting polymer increased linearly with increase in the monomer conversion up to around 85%. The observed molecular weights calculated from ¹H-NMR spectrum [M_n(NMR)] are close to the corresponding theoretical molecular weights [M_n(theor)]. The corresponding polydispersity index (PDI) of the resulting polymers remained almost constant at around 1.2 up to ∼ 65% monomer conversion and then increased gradually with the further increase in the monomer conversion. Chain-end analysis of the resulting polymers by ¹H-NMR showed clearly that polymerization started with the radical forming out of the xanthate mediator. The negligible homo-chain extension and the hetero-chain extension involving synthesis of poly(VAc)-b-poly(NVP) diblock copolymer were occurred. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthetic method of polyethylene-poly(methylmethacrylate) (PE-PMMA) polymer hybrid via reversible addition-fragmentation chain transfer (RAFT) polymerization with functionalized polyethylene

Summary Polyethylene-poly(methylmethacrylate) (PE-PMMA) polymer hybrid was synthesized via RAFT polymerization of MMA with PE chain transfer agent (PE-CTA) for the first time. The structure of PE-CTA produced by sequential functionalization of terminally hydroxylated PE was confirmed by ¹H NMR and FT-IR analyses. The results of GPC after MMA polymerization revealed that the molecular weight (M_w) of the resulting polymers increased compared with the one of the PE-CTA. ¹H NMR analysis of resulting polymers confirmed that the amounts of PMMA segments were in a range of 7.8 and 23 wt %. TEM images indicated the nanometer level microphase-separation morphology between the PE segment and PMMA segment.     

Preparation of nano-TiO2/polyurethane emulsions via in situ RAFT polymerization

Stable nano-TiO₂/polyurethane (PU) emulsions were prepared via in situ reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization of 2-hydroxyethyl acrylate (HEA)-capped PU macromonomer, using azobisisobutyronitrile (AIBN) as a radical initiator and 2-{[(butylsulfanyl)carbonothioyl]sulfanyl} propanoic acid (BCSPA) anchored onto TiO₂ nanoparticles (TiO₂-BCSPA) as a RAFT agent. When the molar ratio of AIBN to TiO₂-BCSPA was changed from 1:3 to 1:10, the polydispersity index (PDI) of polymers in the emulsions decreased from 1.83 to 1.06, due to more effective RAFT polymerization in the emulsions. The TiO₂ nanofillers were well-dispersed throughout the polymer films. The tensile strengths of the nanocomposite films were significantly enhanced due to coordination bonding between the TiO₂ nanofillers and the –COOH end groups of the polymers, as evidenced by the FT-IR spectral data.     

Synthesis and pH-dependent micellization of 2-(diisopropylamino)ethyl methacrylate based amphiphilic diblock copolymers via RAFT polymerization

The polymerization of 2-(diisopropylamino)ethyl methacrylate (DPA) by RAFT mechanism in the presence of 4-cyanopentanoic acid dithiobenzoate in 1,4-dioxane was studied. The DPA homopolymer was employed as a macro chain transfer agent to synthesize pH-sensitive amphiphilic block copolymers using poly(ethylene glycol) methyl ether methacrylate (PEGMA) as the hydrophilic block. ¹H NMR and GPC measurements confirmed the successful synthesis of these copolymers. Potentiometric titrations and fluorescence experiments proved that the copolymers underwent a sharp transition from unimers to micelles at a pH of ∼6.7 in phosphate buffered saline solutions. It was found that the hydrophilic/hydrophobic balance of these block copolymers had no apparent effect on their pH-induced micellization behaviors. The DLS investigation revealed that the micelles have a mean hydrodynamic diameter below 60 nm with a narrow size distribution.     

One‐step synthesis of triarm block copolymers via simultaneous reversible‐addition fragmentation chain transfer and ring‐opening polymerization

One‐step synthesis of star copolymers by reversible addition–fragmentation chain transfer (RAFT) and ring‐opening polymerization (ROP) by using a novel dual initiator is reported. Triarm block copolymers comprising one polystyrene (or polyacrylamide) arm and two poly(β‐butyrolactone) arms were synthesized in one‐step by simultaneous RAFT polymerization of styrene (St) (or acrylamide, designated as AAm) and ROP of β‐butyrolactone (BL) in the presence of a novel trifunctional initiator, 1,2‐propanediol ethyl xanthogenate (RAFT‐ROP agent). This dual initiator was obtained through the reaction of 3‐chloro‐1,2‐propanediol with the potassium salt of ethyl xanthogenate. The principal parameters such as monomer concentration, initiator concentration, and polymerization time that affect the one‐step polymerization reaction were evaluated. The characterization of the products was achieved using Fourier‐transform infrared spectroscopy (FTIR), ¹H‐nuclear magnetic resonance (¹H‐NMR), ¹³C‐nuclear magnetic resonance (¹³C‐NMR), Gas chromatography–mass spectrometry (GC–MS), gel‐permeation chromatography (GPC), thermogravimetric analysis (TGA), and fractional precipitation (γ) techniques. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of water-soluble single-walled carbon nanotubes by RAFT polymerization

Water-soluble single-walled carbon nanotubes (SWNTs) were synthesized by grafting poly(acrylamide) (PAM) from the surface of SWNT via reversible addition-fragmentation chain transfer (RAFT) polymerization. The RAFT agents were covalently attached to the SWNTs by functionalizing SWNTs with in situ generated diazonium compounds. The product was characterized by means of FT-IR, Raman, ¹H NMR, TGA and TEM. The results showed that PAM chains had successfully grafted from SWNT by RAFT polymerization. The amount of PAM grown from SWNT increased with the polymerization time. The acrylamide conversion increased linearly with the polymerization time, indicating the “living” characteristics of the RAFT polymerization. TEM was utilized to image PAM-g-SWNT, showing relatively uniform polymer coatings present on the surface of individual, debundled nanotubes.     

Reversible addition fragmentation chain transfer polymerization of 3-[tris(trimethylsilyloxy) silyl] propyl methacrylate

Reversible addition fragmentation chain transfer (RAFT) bulk polymerizations of 3-[tris(trimethylsilyloxy)silyl] propyl methacrylate (TRIS) have been carried out at 60 °C, employing cumyl dithiobenzoate (CDB) and 2-cyanoprop-2-yl dithiobenzoate (CPDB) as mediating agents at concentrations ranging from 5.0×10⁻³ to 2.0×10⁻² mol l⁻¹. The monomer conversion vs. time evolution was followed via dilatometry and ¹H NMR spectroscopy. The CDB mediated polymerization displays RAFT agent concentration dependent inhibition and rate retardation phenomena, whereas the CPDB mediated polymerization process is less susceptible to rate retardation and inhibition effects. The different behavior of CDB and CPDB in TRIS polymerization is most likely due to the increased stability of the intermediate macroRAFT radicals in the CDB mediated process. The generated RAFT polymers were analyzed via size exclusion chromatography indicating linear macromolecular growth with respect to monomer conversion and low polydispersities (PDI<1.15) up to high monomer to polymer conversion (>90%).     

Synthesis of hybrid TiO2 nanoparticles with well-defined poly(methyl methacrylate) and poly(tert-butyldimethylsilyl methacrylate) via the RAFT process

Surface of titania nanoparticles (TiO₂) was modified by a coupling agent as 3-(trimethoxysilyl)propyl methacrylate (MPS) to form TiO₂-MPS polymerizable particles. Methyl methacrylate (MMA) and tert-butyldimethylsilyl methacrylate (MASi) were radically polymerized through the immobilized vinyl bond on the surface in the presence of the reversible addition-fragmentation chain transfer (RAFT) agent 2-cyanoprop-2-yl dithiobenzoate using 2,2′-azobisisobutylnitrile (AIBN) as an initiator. FTIR spectroscopy confirmed the presence of the coupling molecule and the methacrylate groups on the surface. Thermogravimetric analysis and elemental analysis revealed a surface coverage of the coupling molecule of 2.0 wt%. TGA measurements showed that grafted PMMA and PMASi were accounted for 10% and 4.8% of the particle mass, respectively. ¹H NMR and SEC were used to verify the livingness of the polymerization. Transmission electron microscopy (TEM) was used to study the morphology of the particles before and after the surface grafting.     

Preparation and characterization of novel side-chain azobenzene polymers containing tetrazole group

A novel methacrylate monomer containing azobenzene chromophore and tetrazole moiety, 4′-(2-methacryloxyethyl)methylamino-4-(5-chlorotetrazol-1-yl)azobenzene (MACA), was synthesized and polymerized to form homopolymer (PMACA) via reversible addition-fragmentation chain transfer (RAFT) polymerization using 2-cyanoprop-2-yl dithiobenzoate (CPDB) as the RAFT agent and azobisisobutyronitrile (AIBN) as an initiator in dimethyl formamide (DMF) solution. Meanwhile, block copolymers (PMMA-b-PMACAs) were successfully obtained by RAFT polymerization of MACA using PMMA as the macro-RAFT agent and AIBN as an initiator. Gel permeation chromatography (GPC) characterization indicated that polymers with well-controlled molecular weights and narrow molecular weight distributions (M_w/M_ns < 1.30) were obtained. The structures of these polymers were characterized by ¹H NMR and FT-IR spectra. Thermal and photoisomerization behaviors of the polymers indicated that these polymers were amorphous state with good heat stability and photoisomerization performance. Relationship between the electrochemical behavior of block copolymer (PMMA-b-PMACA) and the photoisomerization of azobenzene was investigated by cyclic voltammetry (CV) in chloroform solution, which showed that the oxidation peak of copolymer shifted from 1.0 V to 0.6 V during azobenzene isomerization from trans to cis form. Furthermore, surface relief gratings (SRGs) formed on the films of PMMA-b-PMACAs were also investigated with illumination of a linearly polarized Kr⁺ laser beam. The diffraction efficiency of the SRGs was 1.22 (PMMA-b-PMACA1), 2.38 (PMMA-b-PMACA2) and 3.02 (PMMA-b-PMACA3), respectively, which increased with the azobenzene contain for the copolymers.     

Synthesis,Characterization, Antimicrobial Activity,and Adhesive Property of Amino Benzyl Group Substituted Acrylic/Methacrylic Polymers and Their Copolymers

The monomers 2-aminobenzylacrylate (2-ABA) and 2-aminobenzyl methacrylate (2-ABMA) were synthesized. The homopolymers and various compositions of copolymers with ethoxylated bisphenol-A-dimethacrylate (EBPADMA) were synthesized using free radical polymerization. The polymers were characterized by FT-IR, ¹H NMR, and ¹³C NMR spectral techniques. The thermal property of the polymers was determined by thermogravimetric analysis and differential scanning calorimeter. The prepared adhesives were tested on leather and metal surfaces using single-lap-joint shear test method. The antimicrobial activity of polymers and copolymers has been studied using Mueller Hinton Broth method.     

A temperature-responsive carbon black nanoparticle prepared by surface-induced reversible addition-fragmentation chain transfer polymerization

A reversible addition-fragmentation chain transfer (RAFT) agent, 2-{[(dodecylsulfanyl)carbonothioyl]sulfanyl}propanoic acid (DSCTSP), was immobilized on the hydroxyl-functionalized carbon black (CB) surface via a direct condensation reaction, producing CB-DSCTSP. Then, RAFT polymerizations were carried out on carbon black surface using the CB-DSCTSP as a chain transfer agent. Poly(N-isopropylacrylamide) (PNIPAAm) chains were grown from the carbon black surface by a surface-induced reversible addition-fragmentation chain transfer (SI-RAFT) polymerization. FT-IR, ¹H NMR, TGA, TEM, and dynamic light scattering were used to characterize the carbon black grafted with poly(N-isopropylacrylamide) (CB-g-PNIPAAm). Dispersion experiment showed that CB-g-PNIPAAm had a good solubility in water. ¹H NMR, AFM and dynamic light scattering measurements showed that CB-g-PNIPAAm behaved a reversible temperature-responsive property in water.     

Electroactive Nanofibers of Poly (2-hydroxyethyl methacrylate-graft-aniline) Copolymers and Their Blends with Polycaprolactone

Copolymers of poly (2-hydroxyethyl methacrylate)-graft-polyaniline (PHEMA-g-PANI) were synthesized by atom-transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate using polyaniline macro-initiators. The macro-initiators were synthesized by the reaction of amine nitrogens of polyaniline with chloroacetyl choloride. The obtained polymers were characterized by FT-IR and ¹H NMR spectroscopies. Uniform nanofibers consisting of blends of PHEMA-g-PANI copolymers and polycaprolactone (PCL) were prepared using an electrospinning technique. SEM was used to investigate the morphology of nanofibers produced from PHEMA-g-PANI copolymers and PCL blends. The cyclic voltammetry measurement of blends confirmed the preparation of electroactive nanofibers.     

A novel approach to graft silicones onto waterborne polyacrylate for synthesizing anti-graffiti coatings by polydimethylsiloxane-functionalized RAFT agent

Linear organoalkoxysilane-based RAFT agent functionalized polydimethylsiloxane (RAFT-PDMS) has been prepared for the first time via co-condensation of a new organoalkoxysilane based RAFT agent (RAFT-Agent), 2-((methyldimethoxysilyl)propyl)carbontrithio-2-methyl-propanoicacidmethylester, with diethoxydimethylsilane (DDS) in an aqueous acidic solution. The RAFT-Agent and RAFT-PDMS was confirmed by FT-IR and ¹H NMR spectroscopy techniques. The obtained RAFT-PDMS was used to prepare the silicone-modified polyacrylate anti-graffiti emulsions via RAFT polymerization with functional monomers. The living character of RAFT polymerization of RAFT-PDMS and the narrow molecular weight distribution of the polymerization product were confirmed by GPC. The transformation of the particle state from a small micelle structure to a spherical core-shell micelle structure during polymerization was verified by TEM and dynamic light scattering analysis. Moreover, DSC and TGA analysis disclosed that increasing the content of RAFT-PDMS can reduce the glass transition temperature and improve the thermal stability of the resin. Finally, the effect of RAFT-PDMS on the surface morphology and properties of coatings were examined by SEM and contact angle. These experimental results suggest that increasing the content of RAFT-PDMS increases the surface porosity of the coating film and thus enhances its hydrophobic properties.     

N-[2-(8-heptadecenyl)-4,5-dihydro-1H-imidazole-1-ethyl]-2-bromoisobutyramide as initiator for atom transfer radical polymerization (ATRP) and surface-initiated ATRP of methyl methacrylate on iron

N-[2-(8-heptadecenyl)-4,5-dihydro-1H-imidazole-1-ethyl]-2-bromoisobutyramide (IEB) was synthesized and characterized by elemental analysis, FT-IR, and ¹H NMR. It had been successfully used as a bidentate initiator for the ATRP of methyl methacrylate with CuBr/2,2′-bipyridine as the catalyst, and N,N-dimethylformamide as the solvent at 70 °C. The kinetics was first order in monomer and the number-average molecular weight of the polymer increased linearly with the monomer conversion, indicating the ‘living’/controlled nature of the polymerization. The polymerization reached high conversions producing polymers with a low molecular weight distribution ( M _w/M _n = 1.319). The obtained poly(methylmethacrylate) (PMMA) functionalized with 2-(8-heptadecenyl)-4,5-dihydro-1H-imidazoleyl and ω-Br as the end groups were characterized by FT-IR spectroscopy. They can be used as macroinitiators for chain extension reaction. Then, PMMA coatings were grafted from iron substrates by surface-initiated ATRP from a surface-bound IEB initiator. The EIS measurements confirmed the successful grafting of the polymer coatings. Greatly improved short-term anticorrosive properties for PMMA-modified electrodes were demonstrated by substantially increased resistance of the film for a period of 24 h as compared to bare iron.     

Synthesis and characterization of AB2-type star polymers via combination of ATRP and click chemistry

Homo/miktoarm star polymers were successfully synthesized via combination of the “arm-first” and “coupling-onto” strategies. Firstly, the multifunctional coupling agent (core), 2, 4, 6-tris(3-ethynylphenyl)-1,3,5-triazine-2,4,6-triamine (TPTTA), was synthesized. Secondly, the linear polystyrene-Cl (PS-Cl) and poly(2-(dimethylamino)ethyl methacrylate)-Br (PDMAEMA-Br) were prepared by atom transfer radical polymerization (ATRP) method. Then, the linear PS-Cl and PDMAEMA-Br chains were modified by a nucleophilic substitution reaction with sodium azide. Finally, homo/miktoarm star polymers PS₃ and PS(PDMAEMA)₂ were designed by click reaction between the core (TPTTA) and the arm precursor (PS-N₃ or PDMAEMA-N₃). The structures of the PS₃, PS(PDMAEMA)₂ and the precursors were all characterized by NMR, FT-IR, UV and GPC analysis. Moreover, the self-assembly behaviors of the miktoarm amphiphilic copolymer PS(PDMAEMA)₂ was also investigated by transmission electron microscopy (TEM).     

Synthesis of Miktoarm Dumbbell-Like Amphiphilic Triblock Copolymer by Combination of Consecutive RAFT Polymerizations and ATRP

Summary  A novel synthetic route, combining three reversible addition-fragmentation chain transfer (RAFT) and one atom transfer radical polymerization (ATRP) processes, for the preparation of a miktoarm dumbbell-like amphiphilic triblock copolymer, poly(poly(ethylene glycol) methyl ether methacrylate)-b-polystyrene-b-(poly(4-vinylbenzyl chloride)-g-polystyrene) (PPEGMA-b-PS-b-(PVBC-g-PS)), was developed using 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as a RAFT agent, and the benzyl chloride group of the VBC units in the PVBC block as active ATRP macroinitiators, respectively. The structures of the obtained (co)polymers were characterized by ¹H NMR spectroscopy. The obtained PPEGMA-b-PS-b-(PVBC-g-PS) amphiphilic triblock graft copolymer could self-assemble into spherical micelles with 100-300 nm diameters in a selective solvent.