Facile synthesis of gemini surface-active ATRP initiator and its use in soap-free AGET ATRP mini-emulsion polymerisation

A novel cationic gemini surfactant has been readily synthesised in 70 % total yield. The functional gemini surfactant can act both as an emulsifier and an atom transfer radical polymerisation (ATRP) initiator in mini-emulsion polymerisation of methyl methacrylate (MMA), in which no other emulsifier was required. 1-(Dimethylamino)dodecane (N,N-dimethyldodecylamine, DMDA) was found to be a good ligand in the activator generated by electron transfer (AGET) ATRP reaction. Kinetic studies indicated that the polymerisation featured controlled/living radical polymerisation.     

Syntheses of cardanol-based cationic surfactants and their use in emulsion polymerisation

Six quaternary ammonium salts were designed and synthesised with moderate to high yields in three steps, based on cardanol, a low-cost and abundant renewable resource. The new ammonium salts can act as reactive surfactants due to their having both a hydrophilic ammonium group and a hydrophobic unsaturated alkyl chain. The gemini surfactants with a linker of a linear saturated aliphatic hydrocarbon chain exhibited a relatively low CMC value (≤ 0.2 mmol L^?1) and surface tension (≤ 27 mN m^?1), signifying that this kind of amphiphile exhibited good surface active properties. The photo-active gemini surfactant with critical micelle concentration (CMC) of 0.05 mmol L^?1 was used successfully as the sole emulsifier in the emulsion polymerisation of methyl methacrylate (MMA). In addition, a benzyl bromide-containing surfactant can act as both an atom transfer radical polymerisation (ATRP) initiator and an emulsifier in an activator generated by the electron transfer atom transfer radical polymerisation (AGET ATRP) of MMA in emulsion. The value of the number-average molecular mass of the resulting cardanol-end poly(methyl methacrylate) (PMMA) is M_n,GPC = 45.1 kDa, with polydispersity of 1.39.     

Use of a simple surface-active initiator in controlled/living free-radical miniemulsion polymerization under AGET and ARGET ATRP conditions

This communication describes the first example of the efficient use of a simple amphiphilic molecule as both a surfactant and an initiator in the miniemulsion polymerization of methyl methacrylate under AGET and ARGET ATRP conditions.     

A New Protocol for Ash Wood Modification: Synthesis of Hydrophobic and Antibacterial Brushes from the Wood Surface

The article presents the modification of ash wood via surface initiated activators regenerated by electron transfer atom transfer radical polymerization mediated by elemental silver (Ag⁰ SI-ARGET ATRP) at a diminished catalyst concentration. Ash wood is functionalized with poly(methyl methacrylate) (PMMA) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) to yield wood grafted with PMMA-b-PDMAEMA-Br copolymers with hydrophobic and antibacterial properties. Fourier transform infrared (FT-IR) spectroscopy confirmed the covalent incorporation of functional ATRP initiation sites and polymer chains into the wood structure. The polymerization kinetics was followed by the analysis of the polymer grown in solution from the sacrificial initiator by proton nuclear magnetic resonance (¹H NMR) and gel permeation chromatography (GPC). The polymer layer covalently attached to the wood surface was observed by scanning electron microscopy (SEM). The hydrophobic properties of hybrid materials were confirmed by water contact angle measurements. Water and sodium chloride salt aqueous solution uptake tests confirmed a significant improvement in resistance to the absorption of wood samples after modification with polymers. Antibacterial tests revealed that wood-QPDMAEMA-Br, as well as wood-PMMA-b-QPDMAEMA-Br, exhibited higher antibacterial activity against Gram-positive bacteria (Staphylococcus aureus) in comparison with Gram-negative bacteria (Escherichia coli). The paper presents an economic concept with ecological aspects of improving wood properties, which gives great opportunities to use the proposed approach in the production of functional hybrid materials for industry and high quality sports equipment, and in furniture production.     

Atom Transfer Radical Polymerization of Methyl Methacrylate Using Telechelic Tribromo Terminated Polyurethane Macroinitiator

Novel telechelic tribromo terminated polyurethane (Br₃-PU-Br₃) was used as a macroinitiator in atom transfer radical polymerization (ATRP) of methyl methacrylate using CuBr as a catalyst and NN,N',N”,N”-pentamethyldiethylenetriamine (PMDETA) as a ligand. During the course of polymerization, poly(methyl methacrylate)-b-polyurethane-b-poly(methyl methacrylate) (PMMA-b-PU-b-PMMA) tri-block copolymers were formed. The resulting tri-block copolymers were characterized by gel permeation chromatography (GPC) and ¹H nuclear magnetic resonance (NMR) spectroscopy. Molecular weight of the tri-block copolymers increases with increasing conversion. This result shows Br₃-PU-Br₃/CuBr/PMDETA initiating system polymerized methyl methacrylate through ATRP mechanism. NMR spectroscopy results revealed that apart from bromine atom transfer from Br₃-PU-Br₃ to PMDETA-CuBr complex, bromine atom transfer from the initially formed tri-block copolymer to PMDETA-CuBr complex also takes place, and, as a result, double bond terminated copolymer formed. Mole ratio of polyurethane and poly(methyl methacrylate) present in the PMMA-b-PU-b-PMMA tri-block copolymers was calculated using ¹H-NMR spectroscopy and it was found to be comparable with the mole ratio calculated through GPC results. Differential scanning calorimetric results confirmed the presence of two different phases in the tri-block copolymers.     

Synthesis of H‐shaped complex macromolecular structures by combination of atom transfer radical polymerization,photoinduced radical coupling,ring‐opening polymerization,and iniferter processes

Three controlled/living polymerization processes, namely atom transfer radical polymerization (ATRP), ring‐opening polymerization (ROP) and iniferter polymerization, and photoinduced radical coupling reaction were combined for the preparation of ABCBD‐type H‐shaped complex copolymer. First, α‐benzophenone functional polystyrene (BP‐PS) and poly(methyl methacrylate) (BP‐PMMA) were prepared independently by ATRP. The resulting polymers were irradiated to form ketyl radicals by hydrogen abstraction of the excited benzophenone moieties present at each chain end. Coupling of these radicals resulted in the formation of polystyrene‐b‐poly(methyl methacrylate) (PS‐b‐PMMA) with benzpinacole structure at the junction point possessing both hydroxyl and iniferter functionalities. ROP of ε‐caprolactone (CL) by using PS‐b‐PMMA as bifunctional initiator, in the presence of stannous octoate yielded the corresponding tetrablock copolymer, PCL‐PS‐PMMA‐PCL. Finally, the polymerization of tert‐butyl acrylate (tBA) via iniferter process gave the targeted H‐shaped block copolymer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4601–4607     

Synthesis of poly(methyl methacrylate)-<Emphasis Type="Italic">block</Emphasis>-poly(tetrahydrofuran) by photo-living radical polymerization using a 2,2,6,6-tetramethylpiperidine-1-oxyl macromediator

The synthesis of a poly(methyl methacrylate)-block-poly(tetrahydrofuran) (PMMA-b-PTHF) diblock copolymer was attained by the photo-living radical polymerization of methyl methacrylate using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) supported on the chain end of poly(tetrahydrofuran) (PTHF) as the macromediator. The polymerization was performed at room temperature by 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) as an initiator in the presence of bis(alkylphenyl)iodonium hexafluorophosphate as a photo-acid generator to produce the diblock copolymer consisting of poly(methyl methacrylate) (PMMA) and PTHF blocks connected through the TEMPO. The polymerization was confirmed to proceed in accordance with a living mechanism based on linear correlations for three different plots of the first order time-conversion, the molecular weight of the copolymer versus the monomer conversion, and the molecular weight versus the reciprocal of the initial concentration of the initiator. The molecular weight distribution of the block copolymer was dependent on the molecular weight of the macromediator based on the miscibility of PMMA and PTHF.     

Synthesis and micelle formation of triblock copolymers of poly(methyl methacrylate)-b-poly(ethylene oxide)-b-poly(methyl methacrylate) in aqueous solution

Amphiphilic triblock copolymers of poly(methyl methacrylate)-b-poly(ethylene oxide)-b-poly(methyl methacrylate) (PMMA-b-PEO-b-PMMA) with well-defined structure were synthesized via atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) initiated by the PEO macroinitiator. The macroinitiator and triblock copolymer with different PMMA and/or PEO block lengths were characterized with ¹H and ¹³C NMR and gel permeation chromatography (GPC). The micelle formed by these triblock copolymers in aqueous solutions was detected by fluorescence excitation and emission spectra of pyrene probe. The critical micelle concentration (CMC) ranged from 0.0019 to 0.016 mg/mL and increased with increasing PMMA block length, while the PEO block length had less effect on the CMC. The partition constant K_v for pyrene in the micelle and in aqueous solution was about 10⁵. The triblock copolymer appeared to form the micelles with hydrophobic PMMA core and hydrophilic PEO loop chain corona. The hydrodynamic radius R_h,app of the micelle measured with dynamic light scattering (DLS) ranged from 17.3 to 24.0 nm and increased with increasing PEO block length to form thicker corona. The spherical shape of the micelle of the triblock copolymers was observed with an atomic force microscope (AFM). Increasing hydrophobic PMMA block length effectively promoted the micelle formation in aqueous solutions, but the micelles were stable even only with short PMMA blocks.     

Novel organotin-containing diblock copolymer with tunable nanostructures: Synthesis, self-assembly and morphological change

Interesting self-assembly behavior and morphological change of a novel organotin-containing diblock copolymer were firstly reported. The organotin-containing diblock copolymer, poly(methyl methacrylate)-block-poly(acetoxydibutyltin methacrylate) (PMMA-b-PADBTMA), was prepared via RAFT polymerization of ADBTMA with PMMA as the macroCTA and AIBN as the initiator in toluene. Both the FT-IR and TG analysis revealed an incorporation of both co-monomers in the resulted polymer backbone. The ratio of two segments was determined indirectly by TG analysis, gravimetric method and derivative process. All results from the different methods were well matched. And it was found that the morphology of the diblock copolymer could be changed easily from vesicles to nano-particle or cross-linked nano-composite under the ultrasonication or additional Ph₂SnCl₂, respectively. All the morphologies were analyzed by SEM, TEM and DLS. The self-assembly and the morphological change attributed to the strong coordination action between tin atoms and the carbonyl groups among PADBTMA segments.     

Ligated anionic block copolymerization of methyl methacrylate with n-butyl acrylate and n-nonyl acrylate as promoted by lithium 2-(2-methoxyethoxy) ethoxide/diphenylmethyllithium

Poly(methyl methacrylate-b-n-butyl acrylate) (PMMA-b-Pn-BuA) and poly(methyl methacrylate-b-n-nonyl acrylate) (PMMA-b-Pn-NonA) diblock copolymers have been successfully synthesized by the sequential anionic polymerization of methyl methacrylate (MMA) and the n-alkyl acrylate (n-BuA or n-NonA), in a 90/10 toluene/tetrahydrofuran (THF) mixture at −78°C. When diphenylmethyllithium (DPMLi) ligated with lithium 2-(2-methoxyethoxy) ethoxide (LiOEEM) is used as the initiator, the polymerization of each block appears to be living. Molecular weight and composition of block copolymers can be predicted from the monomer over initator molar ratio and the molecular weight distribution is narrow. Size exclusion chromatography (SEC) supports that no homo-PMMA contaminates the final copolymer. Although the reverse polymerization sequence Pn-NonA-b-PMMA always results in some contamination by homo-Pn-NonA, it has no really significant effect on the final product characteristics. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1543–1548, 1997     

Experimental Design and Statistical Analysis of AGET ATRP of MMA in Emulsion Polymer Reactor

This study investigates atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) using activators generated by electron transfer (AGET) as the initiation technique in an emulsion well‐mixed 2L stirred tank reactor. The performance of the AGET ATRP of MMA is analyzed for five key independent variables, namely temperature, catalyst complex (CuBr2/dNbpy), initiator (EBiB), reducing agent (ascorbic acid), and surfactant (Brij 98). The reaction is carried out based on a two‐step polymerization procedure. A resolution 5 fractional factorial design technique is employed to assess the influence of the five independent variables on the monomer conversion, polymer average molecular weights, and polydispersity index (PDI). An input–output model is constructed from the data of 21 designed experimental tests. A statistical analysis of the results shows that the temperature is the most influential variable for the three output process responses. The initiator strongly affects the poly(methyl methacrylate) (PMMA) molecular weights. It is the least important key variable affecting MMA conversion and PDI, and the surfactant is the least one affecting PMMA Mn. On assessing the independent interactions effect, the interactions of temperature‐surfactant on conversion, and temperature‐initiator for PMMA M_n are considered. Process simulation in 3D mapping has demonstrated that model predictions agree well with experimental data.     

原子转移自由基细乳液聚合*

本文从正向、反向、同时正向/反向、电子转移活化剂等不同原子转移自由基聚合（ATRP）细乳液引发体系的角度,综述了近年来国内外关于ATRP细乳液聚合的研究进展。在细乳液体系中进行正向ATRP,聚合可控性不理想,反向ATRP相对适合于细乳液体系,其缺点是表面活性剂用量较大。同时正向/反向引发体系的ATRP中催化剂用量大为减少,并且聚合具有良好的可控性;电子转移活化剂（AGET）ATRP是通过电子转移反应来还原过渡金属的氧化态,克服了同时正向/反向ATRP中需要引入自由基引发剂的缺点。     

Specific thermoresponsiveness of PMMA-block-PDMAEMA to selected ions and other factors in aqueous solution

Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) is a functional polymer that presents positive charges at low and neutral pHs. Copolymers bearing PDMAEMA blocks usually show a thermal behavior in water marked by a lower critical solution temperature (LCST). This behavior suggests them as interesting “smart” materials for several applications such as water decontamination and many others. In the present work, the LCST of a poly(methyl methacrylate)-block-poly(2-(dimethylamino)ethyl methacrylate) (PMMA-b-PDMAEMA) synthesized by RAFT was measured in several conditions in aqueous solution. It was demonstrated that ionic strength modulates the LCST and this effect depends on the nature of the anion. For instance, weakly hydrated anions such as perchlorate make the LCST lower as the ionic strength gets higher, on the other hand, strongly hydrated ions such as sulfate have not shown a marked effect on LCST. Those results were understood as a consequence of the specific binding of each anion onto the positive-charged PDMAEMA chains, changing the interactions between the chains and water molecules, as well as affecting their pK _a and the ionic interactions. Also, as expected, the LCST is very dependent on pH. The overall results point to the opportunity of modulating very precisely the thermal behavior of PMMA-b-PDMAEMA systems by usual solution conditions such as the type of the anion present.     

Miniemulsion polymerization of styrene with a block copolymer surfactant

A series of miniemulsion systems based on styrene/azobisisobutyronitrile in the presence of poly(methyl methacrylate‐b‐2‐(dimethylamino)ethyl methacrylate) as a surfactant and hexadecane (HD) as a cosurfactant were developed. For comparison, a series of pseudoconventional emulsions also were carried out with the same procedure used for the aforementioned series but without the cosurfactant (HD). Both the droplet size and shelf life were also measured. Experimental results indicate that it is possible to slow the effect of Ostwald ripening and thereby produce a stable miniemulsion with the block copolymer as the surfactant and HD as the cosurfactant. In addition, the extent to which varying the surfactant concentration and copolymer composition could affect both the polymer particle size during the polymerization and the polymerization rate was examined. Variation in the polymer particle sizes during polymerization indicates that droplet and aqueous (micellar or both homogeneous) nucleation occurs in the miniemulsion polymerization. With the same concentration of the surfactant used in the miniemulsion polymerization, the polymerization rates of systems with M₁₂B₃₆ are faster than those of systems with M₁₂B₁₂. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1818–1827, 2000     

Effects of poly(methyl methacrylate)-block-poly(vinyl acetate) copolymer on the spinodal decomposition of corresponding homopolymer blends

Effects of adding a small amount of poly(methyl methacrylate)-block-poly(vinyl acetate) (PMMA-b-PVAc) to poly(methyl methacrylate)/poly(vinyl acetate) (PMMA/PVAc) blends with a lower critical solution temperature (LCST) phase diagram on the kinetics of late-stage spinodal decomposition (SD) were investigated by time-resolved light scattering at 160°C. It is found that the coarsening process of the structure was slowed down or accelerated upon addition of PMMA-b-PVAc depending on the composition of the block copolymer and the blend. The effect of the block copolymer on the domain size were interpreted as compatibilizing and incompatibilizing effects of the block copolymer on PMMA/PVAc blends based on the evaluation of changes in the stability limits of PMMA/PVAc with the addition of block copolymer using random phase approximation (RPA).     

Synthesis of block and star copolymers by photoinduced radical coupling process

The general design for the synthesis of AB diblock, and A₂B and AB₂ star copolymers based on the statistical coupling of poly(styrene) (PSt) and poly (methyl methacrylate) (PMMA) macromolecules containing photoreactive benzophenone is presented. For this purpose, mono- and bifunctional initiators for Atom Transfer Radical Polymerization (ATRP) bearing benzophenone group were synthesized and characterized. End- and mid-chain benzophenone functional PSt and PMMA with low molecular weights were obtained by ATRP using these initiators in the presence of CuBr/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) catalytic complex. Poly(styrene-block-methyl methacrylate) (PSt-b-PMMA) copolymers were prepared by photolysis of the solutions containing end functional PSt and PMMA in THF at λ = 350 nm for 60 min in the presence of a hydrogen donor such as N-methyldiethanolamine (NMDEA). The proposed mechanism assumes hydrogen abstraction of photoexcited benzophenone moiety by NMDEA. Ketyl radicals resulting from abstraction reaction undergo radical-radical coupling to form benzpinacol structure at the core. Formation of A₂B and AB₂ type star copolymers upon irradiation of solutions containing appropriate combinations of end- and mid-chain functional polymers was also demonstrated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2938–2947, 2009     

Synthesis of ABABA pentablock copolymers via copper mediated living radical polymerisation

In this work, the syntheses of poly(butyl methacrylate-b-methyl methacrylate-b-butyl methacrylate) triblock copolymer and poly(methyl methacrylate-b-butyl methacrylate-b-methyl methacrylate-b-butyl methacrylate-b-methyl methacrylate) pentablock copolymers using copper mediated living radical polymerisation are reported. Living radical polymerisations were performed using the system Cu^IBr/N-(n-propyl)-2-pyridylmethanimine as catalyst in conjunction with a difunctional initiator, the 1,4-(2^′-bromo-2^′-methylpropionoto)benzene (1). The syntheses of poly(MMA), poly(BMA-b-MMA-b-BMA) and poly(MMA-b-BMA-b-MMA-b-BMA-b-MMA) are described in detail using ¹H NMR spectroscopy and size exclusion chromatography. The living behaviour and the blocking efficiency of these polymerisations were investigated in each case. Difunctional initiator, 1, based on hydroquinone was synthesised and fully characterised and subsequently used to give difunctional poly(methyl methacrylate) macroinitiators with molecular weights up to 54,000 g mol⁻¹ and polydispersity between 1.07 and 1.32; molecular weights were close to the theoretical values. The difunctional macroinitiators were used to reinitiate butyl methacrylate to give triblock copolymers of M_n between 17,500 and 45,700 g mol⁻¹. Polydispersities remained narrow below 25,000 g mol⁻¹ but broadened at higher masses. The difunctional triblock macroinitiators were subsequently used to reinitiate methyl methacrylate to give ABABA pentablock copolymers with M_n up to 37,000 g mol⁻¹ with polydispersity=1.13. Under certain conditions radical-radical reaction led to a broadening of polydispersity index.     

Synthesis of poly(2‐hydroxyethyl methacrylate) in protic media through atom transfer radical polymerization using activators generated by electron transfer

Atom transfer radical polymerization (ATRP) using activators generated by electron transfer (AGET) was investigated for the controlled polymerization of 2‐hydroxyethyl methacrylate (HEMA) in a protic solvent, a 3/2 (v/v) mixture of methyl ethyl ketone and methanol. The AGET process enabled ATRP to be started with an air‐stable Cu(II) complex that was reduced in situ by tin(II) 2‐ethylhexanoate. The reaction temperature, Cu catalysts with different ligands, and variation of the initial concentration ratio of HEMA to the initiator were examined for the synthesis of well‐controlled poly(2‐hydroxyethyl methacrylate) and a poly(methyl methacrylate)‐b‐poly(2‐hydroxyethyl methacrylate) block copolymer. The level of control in AGET ATRP was similar to that in normal ATRP in protic solvents, and this resulted in a linear increase in the molecular weight with the conversion and a narrow molecular weight distribution (weight‐average molecular weight/number‐average molecular weight < 1.3). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3787–3796, 2006     

Synthesis of miktoarm star (block) polymers based on a heterofunctional initiator via combination of ROP, ATRP and functional group transformation

Versatile miktoarm three-arm star polymers, (polystyrene)(polyε-caprolactone)₂ ((PS)(PCL)₂), (PS-b-poly(n-butyl acrylate))(PCL-b-PS-b-poly(n-butyl acrylate))₂ ((PS-b-PnBA)(PCL-b-PS-b-PnBA)₂) and (PtBA-b-PS)(PCL-b-PtBA-b-PS)₂ were synthesized via combination of atom-transfer radical polymerization (ATRP), functional group transformation technique and ring opening polymerization (ROP) using 1,1-dihydroxymethyl-1-(2-bromoisobutyryloxy)methyl ethane (DHB) as a heterofunctional initiator. In the synthesis of (PS)(PCL)₂ by combination of ROP of ε-caprolactone (ε-CL) and ATRP, the implementation sequence, ROP followed by ATRP, was proved to be effective to get a well-defined miktoarm star polymer than the reverse one. The two miktoarm star block polymers, (PS-b-PnBA)(PCL-b-PS-b-PnBA)₂ and (PtBA-b-PS)(PCL-b-PtBA-b-PS)₂, were prepared by one ROP step, one group transformation and ATRP steps using the same initiator. All the polymers have defined structures and their molecular weights are adjustable with good controllability.     

Synthesis of phosphonate-functionalized polystyrene and poly(methyl methacrylate) particles and their kinetic behavior in miniemulsion polymerization

Phosphonate-functionalized polymer nanoparticles were synthesized by free-radical copolymerization of vinylphosphonic acid (VPA) with styrene or methyl methacrylate (MMA) using the miniemulsion technique. The influence of different parameters such as monomer and surfactant type, amount of vinylphosphonic acid on the average particle size, and size distribution was studied using dynamic light scattering and transmission electron microscopy. Depending on the amount and type of the surfactant used (ionic or non-ionic), phosphonate-functionalized particles in a size range from 102 to 312 nm can be obtained. The density of the phosphonate groups on the particle surface was higher in the case of using MMA as a basis monomer than polystyrene. The kinetic behavior of VPA copolymerization with styrene or MMA using a hydrophobic initiator was investigated by reaction calorimetry. Different kinetic curves were observed for miniemulsion (co)polymerization of styrene- and MMA-based nanoparticles indicating different nucleation mechanisms.