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The Reversible Addition Fragmentation chain Transfer (RAFT) polymerizations of acrylic acid were performed in 1,4-Dioxane solution using three different chain transfer agent (CTA), and 4,4′-azobis(4-cyanopentanoic acid) (ACPA) as initiator. The molar ratios of monomer, CTA and initiator were kept similar for each experiment and all polymerization exhibited high conversion (>90%) at 8 h. Well-defined polyacrylic acids (PAAs) were obtained. Their molecular weights increased linearly with monomer conversion and the dispersity of the molecular weight distribution extended between 1.1 and 1.3. Nuclear magnetic resonance (NMR) spectroscopic studies showed that the PAA prepared are actually random copolymers of AA and the dimer of AA (H2C=CHCO2CH2CH2CO2H), which forms spontaneously from AA, even at room temperature. PAA samples were methylated by addition of trimethylsilyldiazomethane (TMSCHN2 a methylating agent) using a mixture of water/tetrahydrofuran (THF) or methanol/THF. Samples were submitted to different analyses before and after the methylation process in the order to examine the effect of the methylating agent. PAA were characterized by size exclusion chromatography (SEC) in aqueous phase and also in organic phase following methylation. Methylation is accompanied by variable amounts of chain cleavage in the case of PAA prepared using a symmetrical, trithiocarbonate RAFT chain transfer agent. Less extensive cleavage is seen on treatment of poly(methyl acrylate) (PMA), prepared from the trithiocarbonate RAFT reagent with TMSCHN2. Fourier transform infrared (FT-IR), UV-Vis, 1D and 2D NMR spectroscopic studies confirmed that TMSCHN2 reacts with the thiocarbonyl group, though all of the products of this reaction could not be identified. End group analysis using Ellman's reagent demonstrates that some of the polymer chains have a thiol end group, as does a thiol-ene reaction using 9-vinylcarbazole.

Well-defined poly(methyl acrylate) (PMA) and poly(n-butyl acrylate) (PBA) are prepared via photochemically induced atom transfer radical polymerization (photoATRP) using ppm amounts of CuBr2/tris[2-(dimethylamino)ethyl]amine (Me6TREN) catalyst complex without degassing of the polymerization mixture. The effect of light intensity and partial replacement of the excess of expensive Me6TREN ligand with cheaper tertiary amines on kinetics of the polymerization was investigated in various solvents. The addition of triethylamine to photoATRP system resulted in both significant shortening the induction period and increasing the polymerization rate. High livingness of the oxygen tolerant photoATRP system containing triethylamine was proved by chain-extension polymerizations resulting in formation of PMA-b-PBA copolymer. The presented photoATRP system can have tremendous importance from an industrial point of view since the well-defined polyacrylates can be prepared almost without any induction period and in short polymerization time without necessity of both air removal and using the excess of expensive ligand.

Exerting high shear force and adding compatilizer are two different methods used for regulating the size of dispersed phase of polymer blends. Nevertheless, the comparison of the effect of the high shear force and adding compatilizer on the phase morphologyies and properties is less studied, not to mention the synergistic effect. In this work, the incompatible PP/PLA binary blends with large polarity differences were prepared using high-shear processing, compared with the effect of adding ethylene-(methyl acrylate)-(glycidyl methacrylate) (EMA-GMA) as reactive compatibilizer for PP/PLA blends. It was found that adding compatilizer under relative low shear force was more efficient on improving the interface, showing blurred boundaries, compared with the reduction of the dispersed phase size under high shear force without compatilizer. As a result, the blends with the compatilizer presented a higher elongation at break; yet the yield strength of the binary blends prepared under high shear force was higher than that of the ternary blends. Furthermore, the synergistic effect of adding compatibilizer and high shear force was limited, which could be attributed to the fact that the degree of reactive compatibilization had already reached saturation under the rotation speed of 100 rpm due to the high efficiency of EMA-GMA.

Microsuspension conventional radical polymerization (ms CRP) of methyl acrylate (MA), which is more hydrophilic monomer than methyl methacrylate (MMA), was carried out at different benzoyl peroxide (BPO) concentrations (0.8–8.0 wt% relative to MA), gave not similar micrometer-size poly(MA) (PMA) particles as MA droplets but submicrometer-size ones. That is, emulsion polymerization proceeded in the ms CRP systems. When microsuspension iodine transfer polymerization (ms ITP) with CHI3 as chain transfer agent was carried out at 8.0 wt% BPO (relative to MA), at which micrometer-size poly(MMA) particles were successfully synthesized without submicrometer-size byproduct particles in a previous particle, only submicrometer-size PMA particles were formed, too. However, the percentage of the byproduct particles obviously decreased with a decrease in the BPO concentration, resulting in zero practically at 0.8 wt% BPO, where number-average molecular weight of the micrometer-size PMA particles was nearly equal to theoretical one and polydispersity was comparatively narrow (Mw/Mn = 1.43). Such experimental results were presumed based on the kinetic simulation study. Above results support the validity of the “radical exit depression (RED) effect” proposed and indicate a decisive effectiveness of ms ITP to improve a long-standing problem of ms CRP of “hydrophilic” monomer.

The dilute solution properties of a sample of high molecular weight rosin substituted hydrogenated polynorbornene (hPDNB) homopolymer, prepared via ROMP and post-polymerization modified by backbone hydrogenation, was investigated by the online measurement of intrinsic viscosity, refractive index, two-angle light scattering and size exclusion chromatography (SEC) in tetrahydrofuran (THF) at 35 °C. The weight average molecular weight ( M ‾ w), intrinsic viscosity ([η]), radii of gyration ( R ‾ G) and hydrodynamic ( R ‾ H) radii, and concentration of the polymer fractions were obtained from corresponding traces of the chromatograms. From these data, the double logarithmic plots of M ‾ w versus [η], M ‾ w versus R ‾ G and R ‾ H, and [ η ] M ‾ w − ½ versus M ‾ w ½ scaled the dimensions of the polymer chains to molar mass. The results, surprisingly, indicated that the rosin-substituted polynorbornene is flexible like poly(methyl acrylate). To confirm the results, the data were analyzed by the worm-like touched-bead model which predicated the polymer to be more rigid than poly(methyl acrylate) but less rigid than hindered poly(di-alkyl phenyl acrylate) and poly(di-tert-butyl fumarate).

A series of well-defined ABC2, AB2C3, (ABC2)4, and (ABC2)6 type miktoarm star branched polymers consisting of poly(methyl methacrylate) (PMMA), poly(methyl acrylate) (PMA), and poly(L-lactide) (PLLA) were obtained by the combination of organocatalyzed group transfer polymerization (GTP) and ring-opening polymerization (ROP) using bi and trialdehydic aromatic compounds, 4-(diethoxymethyl)benzaldehyde and benzene-1,3,5-tricarbaldehyde respectively, as the chain end coupling agents. The entire synthetic route includes three main steps. The first one is an arm-first route in which the Mukaiyama aldol-type end coupling reaction between a living PMMA obtained through the t-Bu-P4-catalyzed GTP of MMA and an excess amount of a coupling agent was implemented to afford the aromatic aldehyde-bearing PMMA macroterminator. The second one is still an arm-first route in which a further aldol-type end coupling reaction between the aldehyde group left in the aforementioned PMMA macroterminator and a living PMA obtained by the dimethylphenylsilane-mediated B(C6F5)3-catalyzed GTP of MA to produce the multihydroxyl functionalized PMMA and PMA based copolymers, which were later used as the macroinitiators. Therefore, the third one is the ROP of L-lactide (LLA) using the above macroinitiators to give the final star branched polymers in a core-first way. Interestingly, the PMA and PMMA arms could be readily cleaved from the end-coupling bonds using fluoride anion. The resulting star branched polymers were well characterized by SEC, 1H NMR, MALLS, and TGA measurements.

In this study, specific acyclic nitroxide and corresponding alkoxyamine compounds containing thiophenyl group and intramolecular hydrogen bonding were designed (i.e., 2-(oxyl(2-methyl-1-(thiophen-2-yl)propyl)amino)-2-methylpropan-1-ol (HOT2NO•) and 2-methyl-2-((2-methyl-1-(thiophen-2-yl)propyl)(1-phenylethoxy)amino)propan-1-ol (HOT2NOPhEt)). The type of acyclic structures could render nitroxide-mediated polymerizations (NMPs) of acrylates at mild reaction temperatures that can effectively suppress side reactions of (macro)radicals. To enhance the reactivity of the initiator, one of our design to introduce a thiophenyl group is to increase hindrance/polarity feature. Another introduction of intramolecular hydrogen bonding (IHB) is to decrease the bond dissociation energy (BDE) of the “NO–C″ linkage of the initiator. Accordingly, both azo- and alkoxyamine-initiated NMPs were examined. The azo-initiated NMPs (i.e., using HOT2NO•/AIBN) of n-butyl acrylate (BA) and methyl acrylate (MA) showed uncontrolled radical polymerization fashions, presumably due to insufficient reactivation/deactivation from HOT2NO• during polymerization. The alkoxyamine-initiated NMPs of BA with proper amounts of deactivator (i.e., BA/HOT2NOPhEt/HOT2NO•) revealed controlled/living radical polymerization fashions at 120 and 100 °C and afforded Ph-PBA-ON macroinitiator (Mn,max = ca. 38 k and PDI

Fluorescence imaging, especially specific organelle imaging, has become a significant technology to comprehending cell transplantation, migration, division, fusion, and lysis. In this paper, we designed and synthesized a water soluble and fluorescent polymer named as Poly(AA-TPA-d), which was pH-responsive by the fluorescence channel due to the presence of poly acrylic acid as the polymer backbone. The research results demonstrated that Poly(AA-TPA-d) exhibits novel aggregation-induced-emission (AIE) property. Additionally, due to the hydrogen bond formation and C=O···π interactions between methyl acrylate groups, Poly(AA-TPA-d) was of excellent hydrogel formation ability. Moreover, Poly(AA-TPA-d) displayed good bio-compatibility with the living MPC5 cells and highly specific cytoplasm-targeting ability by MTT assay and cell staining experiment respectively.

This paper describes the feasibility of achieving melt-processable polyacrylonitrile copolymer precursors for producing high strength carbon fibers. High molecular weight poly(acrylonitrile- ran -methyl acrylate) (PAN-MA) copolymers with high acrylonitrile content were mixed were various binary melting point modifiers with one component being water to produce systems that formed stable melts at temperatures below the temperature corresponding to the onset of PAN-MA crosslinking. The structure of the copolymer was 96.5 ± 0.13 mol% AN and 4.40 ± 0.13 mol % MA by 1 H NMR with an M w = 238 kDa and polydispersity of 1.9 determined by size exclusion chromatography. A reduction in the T m of the copolymer of 200 °C was established for one of the copolymer/melting point modifier systems, which corresponds to the greatest reduction in a PAN-based copolymer melting temperature yet reported. From isothermal DSC and pressurized capillary rheometry experiments it was found that the stability of the resulting melts shows a strong temperature dependence, but does not show a strong dependence on shear-rate. Copolymer mixtures consisting of H 2 O and acetonitrile or adiponitrile were found to be suitable for melt-extrusion at 170 °C with viscosities ranging from 1800 to 2000 Pa*s and stabilities of the melts ≥1 h.

Highly homogeneous block and random amphiphilic conetworks (APCNs) of sodium acrylate (NaA) and methyl acrylate (MA) with the same composition (NaA/MA ∼ 2/1) were synthesized via end-linking reaction between tetra-arm copolymers of tert-butyl acrylate and MA by copper-catalyzed azide-alkyne cycloaddition followed by the removal of the protecting tert-butyl group and neutralization. Measurement of the degrees of swelling in saline (Qs) and in pure water (Qpw) showed that the ratio of Qs to Qpw for the random APCNs was similar to that for homopolymer networks of NaA, whereas it was significantly smaller for the block APCNs. The result indicated that hydrophobic interaction between PMA blocks was induced by added salt. Taking advantage of the salt-responsive property of the block APCNs, their ability to capture and release a hydrophobic compound was investigated by confocal laser scanning microscopy using fluorescein as a probe molecule.

This work reports a novel design strategy for a strong polyacrylonitrile (PAN) fiber using an electrochemical wet-spinning process. First, a spinning dope was prepared using PAN copolymer containing methyl acrylate. This was spun using a conventional wet-spinning setup, but with a special nozzle spinneret whereby an electric potential could be applied. In situ electrochemical oxidation of methyl acrylate was then induced within the nozzle, resulting in electrochemical demethylation of the PAN copolymer. The subsequently endowed hydrophilic and hygroscopic properties of the PAN fibers improved the chain mobility of the PAN molecules and reduced void formation during wet-spinning. Investigation of the quantitative relationships between the degree of electrochemical demethylation and the mechanical properties of the PAN fibers clarified the in situ plasticization effect of absorbed water induced by the electrochemical demethylation. The Young's modulus and tensile strength of the PAN fibers were improved by 23.4% and 23.5%, respectively, and the breaking strain was increased by 28.1%. These results demonstrate the innovativeness of our new electrochemical wet-spinning process.

Synthesis, characterization, electrochemical studies and ATRA activity of copper complexes with N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) ligand in the presence of ascorbic acid as a reducing agent were reported. [CuII(TPEN′)Br][Br] (TPEN′ denotes tetracoordinated ligand) catalyst showed a very low activity in ATRA of CBr4 to 1-octene, methyl methacrylate, methyl acrylate and styrene in methanol, which is a typical solvent used for ATRA reactions employing ascorbic acid. On the contrary, the yields and stereoselectivity towards monoadduct formation were dramatically increased in slightly polar but aprotic acetone. Based on molecular structures of isolated [CuII(TPEN)][BPh4] and [CuII(TPEN′)Br][Br] complexes, as well as UV–Vis and cyclic voltammetry studies, an equilibrium was proposed involving inactive [CuII(TPEN)]2+ and ATRP active [CuII(TPEN′)Br]+ cations The halidophilicity of the bromide-based deactivating complex ([CuII(TPEN′)Br][Br]) decreased approximately 750 times upon changing the solvent from acetone (KBr = 3000 ± 230) to methanol (KBr = 4.1 ± 0.1), explaining poor catalytic activity in methanol. In acetone, [CuII(TPEN′)Br][Br] complex was nearly as active in ATRA reactions employing ascorbic acid as previously reported [CuII(TPMA)Br][Br].

Herein, synthesis and characterization of a series of bulky aryl substituted iminopyridyl ligands and the corresponding palladium and nickel complexes are described in detail. The as-synthesized palladium complexes show moderate activity in the ethylene polymerization and generate highly-branched oligoethylene or polyethylene with low molecular-weights. Meanwhile, the prepared palladium complexes perform a high degree of comonomer incorporation in ethylene/methyl acrylate (MA) or ethylene/acrylic acid (AA) copolymerizations. Exclusively, Pd3 catalyst exhibits a high comonomer incorporation and provides copolymers with an appreciable molecular weight for ethylene/MA (8.4 MA%, 12937 g mol−1) and ethylene/AA (8.9 AA%, 12552 g mol−1). The corresponding nickel complexes are all highly active in ethylene polymerization and produce branched oligoethylene and/or polyethylene with low to moderate molecular weights. Intriguingly, the orientation of aryl substituents plays a decisive role in the molecular weight of the attained polymer or copolymer under the performed reaction conditions.

Site-specific cobaltocenium-labeled polymers are synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization using cobaltocenium-labeled chain transfer agents. These chain transfer agents show counterion-dependent solubility. Based on the chemical structure of the chain transfer agents, single cobaltocenium moieties are dictated to be in predetermined locations at either the center or terminals of the polymer chains. Polymerization of hydrophobic monomers (methyl methacrylate, methyl acrylate and styrene) and hydrophilic monomers (2-(dimethylamino)ethyl methacrylate and methacrylic acid) is demonstrated to follow a controlled manner based on kinetic studies. Cobaltocenium-labeled polymers with molecular weights greater than 100,000 Da can be prepared by using a difunctional chain transfer agent. Photophysical properties, electrochemical properties, thermal properties and morphology of the cobaltocenium-labeled polymers are also investigated.

Dibrominated poly(methyl acrylate) (BrPMABr) was prepared by atom transfer radical polymerization (ATRP), and this unpurified reaction mixture was used directly in a radical trap-assisted atom transfer radical coupling (RTA-ATRC) reaction to achieve cyclic PMA by intramolecular chain-end coupling. When the polymerization-to-cyclization crossover was performed as a one pot-two step sequence simply by the addition of the radical trap 2-methyl-2-nitrosopropane (MNP) and increased amounts of ligand-catalyst complex, cyclic PMA could be formed in yields up to 65% by adjusting the total volume and reactant ratios during the intramolecular RTA-ATRC, based on gel permeation chromatography (GPC) analysis. In analogous intramolecular ATRC trials lacking the radical trap, cyclization was not successful and instead chain extension by continuation of ATRP was observed. When the ATRP reaction mixture containing the BrPMABr precursor was added drop-wise into a redox active solution containing MNP, yields of cyclic polymer were increased up to 85%. The effect of the ligand was studied, with the highest amounts of cyclic product obtained in intramolecular RTA-ATRC reactions using tris[2-(dimethylamino)ethyl]amine (Me 6 TREN) as the ligand. Cyclic diblock copolymers were also prepared by this method, using telechelic poly(methyl acrylate- block -styrene- block -methyl acrylate) (PMA-b-PS-b-PMA) linear precursors prepared by sequential ATRP reactions.

Electrospun polyacrylonitrile (PAN) copolymer nanofibers (particularly those after the post-spinning stretching process) are expected to be an innovative type of precursors for making continuous carbon nanofibers with superior mechanical properties. In this study, three types of unidirectionally aligned PAN-based nanofibers including homo-PAN, binary-PAN (a PAN copolymer with itaconic acid units), and ternary-PAN (a PAN copolymer with itaconic acid and methyl acrylate units) were prepared by the electrospinning technique; thereafter, the nanofibers (in the form of bundles) were stretched into 3 times of their original lengths in hot water at 97 °C. The effects of chemical composition and post-spinning stretching process on morphological, structural, and thermo-chemical properties of these precursor nanofibers were investigated. The results indicated that, the stretched electrospun binary-PAN nanofibers possessed the most desired thermo-chemical properties, macromolecular regularity, crystal and macromolecule orientations, and dimensional stability; and thus they are suitable for the development of high-performance carbon nanofibers.

In this paper, synthesis of very high molecular weight (VHMW) polyacrylonitrile-co-methyl acrylate (PAN-co-MA) polymers with weight average molecular weights of at least 1.7 million g/mole were repeatedly achieved on a laboratory scale using emulsion polymerization. The development of a hybrid dry-jet gel solution spinning technique for the VHMW PAN-co-MA enabled continuous spinning of 100 filament count tows, 100s of meters in length. Single filaments were analyzed and tested for tensile performance. Experimentally, the hybrid spinning method coupled with VHMW polymers produced precursor fibers with excellent tensile properties, averaging 954 MPa in strength and 15.9 GPa in elastic modulus (N ¼ 296), with small filament diameters (5 mm). Results indicate a strong correlation between decreasing filament diameter, facilitated by high molecular weight polymer, and exponentially increasing tensile properties, using a hybrid dry-jet gel spinning process.

A novel synthetic procedure is reported for the preparation of block copolymers by means of successive 1,3-benzoxazine-thiol and Husigen type azide-alkyne coupling methodologies in one-pot and sequential synthesis. The applied 1,3-benzoxazine-thiol process based on catalytic opening of the lateral benzoxazine rings by thiols is proposed as a new thiol-X chemistry. Azide functional poly(methyl acrylate) (PMA-N3), poly(ethylene glycol) (PEG-N3) and thiol functional polystyrene (PS-SH) were prepared. The obtained PMA-N3 or PEG-N3, PS-SH and propargyl benzoxazine as a click-linker were reacted in sequential or one-pot two step manner to yield desired PS-b-PMA and PS-b-PEG block copolymer. The described thiol-benzoxazine chemistry offers a facile and efficient route to exploring the many possibilities in macromolecular synthesis.

This paper investigates the influence of the “C” segment distribution on phase behavior in a series of ABC terpolymers comprised of poly(hydroxyethyl acrylate) (H, “A” block), poly(octyl acrylate) (O, “B” block), and poly(methyl acrylate) (M, “C” block). We show, using five distinct chain architectures including two triblock terpolymer sequences and three disparate diblock terpolymer sequences, that the manipulation of the “C” segment distribution through statistical copolymerization is a simple tool that polymer chemists may use to tune the stable morphology at constant chemical composition. Using Reversible Addition-Fragmentation chain Transfer (RAFT) techniques, five polymer architectures, HOM (poly(hydroxyethylacrylate-b-octylacrylate-b-methylacrylate)), HO/M (poly(hydroxyethylacrylate-b-octylacrylate-stat-methylacrylate)), H/MO/M, HMO, and H/MO, were synthesized at four chemical compositions with increasing M content and fixed H:O ratio. The self-assembly of the 20 polymers was probed with synchrotron small-angle x-ray scattering (SAXS) and dynamic shear rheology. Up to an M volume fraction of fM = 0.31, architecture H/MO/M was microphase-separated, indicating that M can be distributed into both H and O domains without overly compatibilizing the system. Three distinct morphologies were observed for the architecture HO/M over a narrow composition range, centered around f O M ∗ = 0.50. The results reported here are useful to those seeking to partially decouple the formulation of a block copolymer from its morphology.

The reversible addition-fragmentation chain transfer (RAFT) copolymerization of vinylidene chloride (VDC) with methyl acrylate (MeA) was studied in the presence of poly(ethylene oxide)-based macromolecular RAFT (macroRAFT) agents of the trithiocarbonate type (PEO-TTC) in solution and in aqueous emulsion. Firstly the formation of PEO- b -P(VDC- co -MeA) diblock copolymers was performed in toluene solution at 30 °C and a good control over the polymerization with high chain-end functionality was shown. A first aqueous emulsion copolymerization of VDC with MeA was performed using one of the amphiphilic PEO- b -P(VDC- co -MeA) diblock copolymers as macromolecular stabilizer. Then, in a series of experiments the PEO-TTC macroRAFT agents were directly tested as both chain transfer agents and stabilizing agents in similar conditions (aqueous batch emulsion copolymerization of VDC with MeA at 70 °C). The influence of the nature and concentration of the initiating system and the presence or not of a buffer were studied. We demonstrated that in simple conditions, nanometric latex particles composed of amphiphilic PEO- b -P(VDC- co -MeA) diblock copolymers formed by polymerization-induced self-assembly (PISA). It can thus be concluded that PEO-TTC macroRAFT agents are valuable non-ionic macromolecular stabilizers in the emulsion copolymerization of VDC and MeA and allow the formation of core–shell diblock copolymer particles in the absence of free surfactant. However, when rather high molar masses of the hydrophobic PVDC-based block were targeted, the determined molar masses deviated from the theoretical values.

Crosslinkable ruthenium complex dye, Ru(2,2′-bipyridine-4,4′-bicarboxylic acid)(4,4′-bis((4-vinyl benzyloxy)methyl)-2,2′-bipyridine)(NCS) 2 (denoted as Ru-S dye), was synthesized and characterized using 1 H-NMR, 13 C-NMR, Fourier transform infrared (FTIR) and UV/vis spectroscopies.The power conversion efficiency of dye-sentitized solar cell (DSSC) using Ru-S and liquid electrolyte containing lithium iodide (LiI) reached 7.53% under standard global AM 1.5 full sunlight, which is partly attributed to Li + being coordinated by Ru-S as verified by ATR-FTIR spectroscopy. As Ru-S was further crosslinked with glycerol propoxylate triacrylate (GPTA), not only 89% of dye retained on TiO 2 mesoporous surface after rinsed by 0.1 N NaOH aqueous solution, the power efficiency was also increased to 7.88%. As poly(methyl acrylate) was used to gel the electrolyte system, the power efficiency of DSSC with Ru-S dye was 6.96% but increased to 7.57% after crosslinking with GPTA. Notably, both DSSCs showed a good long-term stability after one month storage.

Optimised matrix-assisted laser desorption/ionisation (MALDI) and electrospray ionisation (ESI) mass spectrometry (MS) methodologies were systematically compared in terms of their relative abilities to identify distinct chemical species present in samples associated with a polymer mechanistic study. In order to perform the investigation, formation processes involved in atom transfer radical polymerisation (ATRP) mediated methyl acrylate (MA) star polymerisations were studied. In addition to the 4-armed ATRP initiator employed in the polymerisations, initiator side-products were found to generate oligomeric chains. At a relatively high monomer to polymer conversion, terminal Br loss was observed in these oligomers; this Br loss was hypothesised to occur via degradative transfer reactions involving the radicals (CH3)2 _ COH, _ CH3 and _ CH2COCH3, which were derived from the acetone used as a solvent in the polymerisations, as well as hydrogen radicals donated by the ligand N,N 0

Nitroxide-mediated crosslinking radical copolymerizations of styrene and divinylbenzene have been carried out in aqueous miniemulsion with Dowfax 8390 as surfactant at 125 °C employing TEMPO-based macroinitiators of various hydrophilicities (random copolymers comprising styrene and methyl acrylate). The pendant conversion (i.e. the degree of crosslinking) increased with increasing macroinitiator hydrophilicity and with decreasing particle size. It is proposed that a concentration gradient is generated within the particle such that the macroinitiator concentration tends to be higher near the oil–water interface than in the particle interior. The macroinitiators are surface active and are thus preferentially adsorbed at/located near the oil–water interface. This in turn leads to an increase in the ratio [pendant unsaturation]/[monomer] in the vicinity of propagating radicals, which are generated from the macroinitiators, and thus an increase in pendant conversion. This effect is enhanced by an increase in macroinitiator hydrophilicity and a decrease in particle size. The present approach offers novel means of controlling network formation in dispersed systems.

Particle formation and growth in the monomer-starved emulsifier-free emulsion polymerisation of monomers with different water solubility including methyl acrylate (MA), methyl methacrylate (MMA), and vinyl acetate (VA) were studied. The rate of formation of precursor particles, via homogenous nucleation, is proportional to the monomer concentration in the water phase. One may think that the maximum number of particles will be obtained when the water phase is saturated with the monomer. The number of PMA particles showed a maximum when the water phase was starved with the monomer. The number of PVA particles did not show any sensitivity to the monomer concentration in the water phase. More unexpectedly the final number of PMMA particles showed a minimum when the water phase was just saturated with the monomer. The minimum in the final number of PMMA particles was correlated with the enhanced rate of particle growth due to the gel effect. Under monomer-starved conditions, the number of particles produced was in the order of water solubility of the monomers; MA > VA > MMA. A reverse order was produced under monomer-saturated conditions as particle coagulation became progressively more important for some of the monomers.

Seeded suspension polymerization can be applied to obtain core–shell particles with particle diameters larger than 1000 μm, which finds application in the rigid foam industry, for instance. However, depending on the operation conditions, the formation of secondary particles decreases drastically the efficiency of monomer incorporation in the seed particles. In the present work, the mechanism of secondary particles formation during seeded suspension polymerization was investigated using monomers (styrene, methyl acrylate and methyl methacrylate) and initiators (benzoyl peroxide and lauroyl peroxide) with different water solubilities and, in the case of the initiators, also different decomposition rates. Results showed that there was no seed polymer in the composition of the secondary particles but only pure polymer from the monomer feed, meaning that they were not formed by erosive breakage of the swelled seeds. The fraction of secondary particles increased when monomers with higher water solubility and initiators with decreasing water solubility were used. These results were consistent with the formation of secondary particles by homogeneous nucleation and monomer droplet nucleation.

It is known that the preferential solvation and conformation of a polymer in a solvent mixture are functions of the polymer's molecular weight and the solvent qualities. This paper demonstrates that these relationships can be exploited to delay the onset of macrogelation for branched poly(methyl methacrylate/ethylene glycol dimethacrylate) (p(MMA/EGDMA)) polymers and star-like poly(methyl acrylate/ethylene glycol dimethacrylate) (p(MA/EGDMA)) polymers synthesised via conventional free-radical polymerisation (CFRP) in a binary solvent mixture (consisting of a good solvent and a precipitant for the polymer). The gelation limits of the MMA/EGDMA and MA/EGDMA polymerisations in a methyl ethyl ketone (MEK)/heptane binary solvent mixture can be extended to regions of higher monomer concentration with increases in polymer yield between 13 and 50 ± 5 w/w% for the p(MMA/EGDMA) system and between 8 and 19 ± 6 w/w% for the p(MA/EGDMA) system across the gelation boundary. Thus, a facile method of increasing the concentration of batch reaction mixtures by the simple addition of small amounts of precipitant into the reaction solutions is presented. Furthermore, the gelation limits of both polymerisation systems in the binary solvent mixtures were further extended with increases in polymer yield between 11 and 17 ± 4%w/w for the p(MMA/ODA/EGDMA) system and between 8 and 20 ± 5%w/w for the p(MA/VS/EGDMA) system by the respective incorporation of octadecyl acrylate (ODA) and vinyl stearate (VS) surfmers into the polymers, demonstrating the application of steric hinderance to shield the propagating polymers from excessive cross-linking reactions.

Well-defined statistical, gradient and block copolymers consisting of isobornyl acrylate (IBA) and n-butyl acrylate (nBA) were synthesized via atom transfer radical polymerization (ATRP). To investigate structure–property correlation, copolymers were prepared with systematically varied molecular weights and compositions. Thermomechanical properties of synthesized materials were analyzed via differential scanning calorimetry (DSC), dynamic mechanical analyses (DMA) and small-angle X-ray scattering (SAXS). Glass transition temperature (Tg) of the resulting statistical poly(isobornyl acrylate-co-n-butyl acrylate) (P(IBA-co-nBA)) copolymers was tuned by changing the monomer feed. This way, it was possible to generate materials which can mimic thermal behavior of several homopolymers, such as poly(t-butyl acrylate) (PtBA), poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA) and poly(n-propyl acrylate) (PPA). Although statistical copolymers had the same thermal properties as their homopolymer equivalents, DMA measurements revealed that they are much softer materials. While statistical copolymers showed a single Tg, block copolymers showed two Tgs and DSC thermogram for the gradient copolymer indicated a single, but very broad, glass transition. The mechanical properties of block and gradient copolymers were compared to the statistical copolymers with the same IBA/nBA composition.

A novel benzodithioate compound with a pyrene structure in the R group, pyrenylmethyl benzodithioate (PMB) was synthesized. Using PMB as the chain transfer agent (CTA), the RAFT polymerizations of styrene with AIBN as an initiator were carried out in different reaction conditions. The results indicated that PMB was an effective CTA for the RAFT polymerizations of styrene with the “living”/controlled characteristics. The structures of the obtained polymers were characterized by 1 H NMR. The results showed that majority of the polymer chains contained the pyrene moiety in the chain end. The enhanced fluorescence property in CHCl 3 solution was observed. The chain-extension experiments of the obtained polystyrene (PS) with the monomers of styrene and methyl acrylate were successfully carried out.

We studied the relationship between segmental dynamics of matrix polymers and tracer diffusion of low mass compounds by the use of forced Rayleigh scattering and dielectric spectroscopy. Specifically poly(methyl acrylate), poly(ethyl acrylate) and poly( n -butyl acrylate) were used as the polymer matrices and six azobenzene derivatives with various substituents as the diffusant. The temperature dependence of the tracer diffusion coefficient D was measured on methylyellow (MY)/polyacrylate blends at the MY concentration of 1 wt%. The results indicate that the temperature dependence of D is weaker than the dielectric loss maximum frequencies f m for the α processes of the matrices. The effect of volume of the dye molecules on D was also investigated at 305 K. Comparison of the tracer diffusion coefficients among various dye/polymer systems indicates that log D in the same matrix decreases linearly with the molar volume of the dyes.

International audience; Iodo-terminated polystyrene and poly(methyl acrylate) (PMA-I) were synthesized by reverse iodine transfer polymerization. The resulting polymers were coupled by atom transfer radical coupling using Cu(I)/linear amino-ligand catalysts in the presence of reducing Cu(0). The efficiency of the coupling reaction is discussed as a function of various factors, namely, the Cu(0) particle sizes, the number of nitrogen present in the ligand structure, the type of halogen associated with Cu(I) (CuX, X = I, Br, Cl), the nature of the polymer and the nature of the chain ends. In particular, a quantitative coupling (100%) was obtained with a CuBr/HMTETA system in the presence of nanosized Cu(0) for PMA-I, thus opening for the first time a facile route to telechelic and multiblock poly(acrylate)-based structures.

Free radical copolymerization reaction of vinyl acetate (VA) and methyl acrylate (MA) in solution of benzene- d 6 using benzoyl peroxide (BPO) as the initiator was studied with on-line 1 H NMR kinetic experiments at 60 °C. It was observed that composition drifts in the comonomer mixture with reaction progress is significant. Hence, the monomer reactivity ratios of VA/MA system could be calculated by the data collected only from one sample via on-line following the comonomer mixture and copolymer compositions at different reaction time intervals up to medium overall monomer conversions. The results were in good agreement with the literature data reported for this system. The good fitting between theoretical and experimental changes in the comonomer mixture compositions as a function of reaction progress was observed, indicating the accuracy of the monomer reactivity ratios calculated by the new procedure presented here.

An investigation on the copolymerization of allyl glycidyl ether (AGE), an epoxy-functional monomer, with methyl acrylate (MA) was performed in the presence of benzyl 1H-imidazole-1-carbodithioate (BICDT) under 60 Co γ-ray irradiation. The polymerizations revealed good characteristics of RAFT process. The content of AGE incorporation into the copolymer increased with higher monomer conversion and higher molar fraction of the AGE in the monomer feed. However, the polymerization could slow down when the fraction of AGE increased in the monomer feed, which might be attributed to the low activity of AGE. Taking advantage of RAFT process, functional block copolymer poly(AGE/MA)- block -poly(styrene) was prepared in the presence of poly(styrene) macroRAFT agent, and the copolymer was characterized by 1 H NMR spectra and GPC.

Thermal polymerization of methyl (meth)acrylate (MMA) was carried out using 2-cyanoprop-2-yl-1-dithionaphthalate (CPDN) and cumyl dithionaphthalenoate (CDN) as chain transfer agents. The kinetic study showed the existence of induction period and rate retardation, especially in the CDN mediated systems. The molecular weights of the polymers increased linearly with the monomer conversion, and the molecular weight distributions ( M w / M n s) of the polymers were relatively narrow up to high conversions. The maximum number-average molecular weights ( M n s) reached to 351 900 g/mol ( M w / M n = 1.47) and 442 400 g/mol ( M w / M n = 1.29) in the systems mediated by CPDN and CDN, respectively. Chain-extension reactions were also successfully carried out to obtain higher molecular weight PMMA and PMMA- block -polystyrene (PMMA- b -PSt) copolymer with controlled structure and narrow M w / M n . Thermal polymerization of methyl acrylate (MA) in the presence of CPDN, or benzyl (2-phenyl)-1-imidazolecarbodithioate (BPIC) also demonstrated “living”/controlled features with the experimented maximum molecular weight 312 500 g/mol ( M w / M n = 1.57). The possible initiation mechanism of the thermal polymerization was discussed.

A novel well-defined amphiphilic graft copolymer of poly(ethylene oxide) as main chain and poly(methyl acrylate) as graft chains is successfully prepared by combination of anionic copolymerization with atom transfer radical polymerization (ATRP). The glycidol is protected by ethyl vinyl ether first, then obtained 2,3-epoxypropyl-1-ethoxyethyl ether (EPEE) is copolymerized with EO by initiation of mixture of diphenylmethyl potassium and triethylene glycol to give the well-defined poly(EO-co-EPEE), the latter is deprotected in the acidic conditions, then the recovered copolymer [(poly(EO-co-Gly)] with multi-pending hydroxyls is esterified with 2-bromoisobutyryl bromide to produce the ATRP macroinitiator with multi-pending activated bromides [poly(EO-co-Gly)(ATRP)] to initiate the polymerization of methyl acrylate (MA). The object products and intermediates are characterized by NMR, MALDI-TOF-MS, FT-IR, and SEC in detail. In solution polymerization, the molecular weight distribution of the graft copolymers is rather narrow (Mw/Mn < 1.2), and the linear dependence of Ln [M0]/[M] on time demonstrates that the MA polymerization is well controlled. 2006 Elsevier Ltd. All rights reserved.