Showing papers on "Methyl acrylate published in 2008"

Ultrafast SET-LRP of methyl acrylate at 25 °C in alcohols

Abstract: Alcohols are known to promote the disproportionation of Cu(I)X species into nascent Cu(0) and Cu(II)X. Therefore, alcohols are expected to be excellent solvents that facilitate the single-electron transfer mediated living radical polymerization (SET-LRP) mediated by nascent Cu(0) species. This publication demonstrates the ultrafast SET-LRP of methyl acrylate initiated with bis(2-bromopropionyloxy)ethane and catalyzed by Cu(0)/Me6-TREN in methanol, ethanol, 1-propanol, and tert-butanol and in their mixture with water at 25 °C. The structural analysis of the resulting polymers by a combination of 1H NMR and MALDI-TOF MS demonstrates the synthesis of perfectly bifunctional α,ω-dibromo poly(methyl acrylate)s by SET-LRP in alcohols. Moreover, this work provides an expansion of the list of solvents available for SET-LRP. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2745–2754, 2008

Effect of Symmetry of Molecular Weight Distribution in Block Copolymers on Formation of ``Metastable'' Morphologies

Abstract: Polystyrene-b-poly(methyl acrylate) (PS−PMA) copolymers were synthesized using activators regenerated by electron transfer (ARGET) for atom transfer radical polymerization (ATRP). Polydispersity of the PMA block was varied by adjusting the amount of copper catalyst in ARGET ATRP, and the resulting molecular weight distributions were found to be approximately symmetric. At a composition of 35 vol % of PMA, the formation of a hexagonally perforated lamellar (HPL) morphology was observed for a polydisperse PS−PMA copolymer for short- and long-term solvent-casting conditions. No order−order transitions were observed at elevated temperatures or after prolonged thermal annealing. The observed stabilization of the HPL morphology—that is considered to be metastable in narrow-disperse diblock copolymers as well as diblock copolymers with selective block polydispersity given by a Schulz−Zimm distribution—suggests that the skewness of the distribution of block molecular weights is an important parameter for the stru...

Helix self-assembly through the coiling of cylindrical micelles.

Abstract: Both single and double helical superstructures have been created through solution self-assembly of cylindrical micelles for the first time. Helical micelles were formed from the co-assembly of poly(acrylic acid)-block-poly(methyl acrylate)-block-polystyrene (PAA-b-PMA-b-PS) triblock copolymers with different multiamines. The helix pitch could be adjusted by adjusting the amount and type of multiamine added. The helical structure exhibits unprecedented regularity for a nanostructure self-assembled from solution indicating the presence of strong, synergistic forces underlying the helix formation.

Synthesis of Star Polymers by A New “Core-First” Method: Sequential Polymerization of Cross-Linker and Monomer

Abstract: Star polymers containing a highly cross-linked core and many arms were synthesized by sequential polymerization of cross-linker and monomer. This novel method, termed as “star from in situ generated core”, belongs to the category of “core-first” method and presents an alternative strategy for star synthesis when compared to the traditional “arm-first” method, in which monomer is polymerized first before cross-linker. To illustrate this new concept for the synthesis of star polymers by using controlled radical polymerization techniques, atom transfer radical polymerization was applied for homopolymerization of ethylene glycol diacrylate (EGDA) to generate a multifunctional cross-linked core (nanogel). At high cross-linker conversion, monovinyl monomers were added into the system and polymerized from the polyEGDA nanogel macroinitiator (MI) to form the star arms. By use of different acrylate monomers, including methyl acrylate, n-butyl acrylate, and tert-butyl acrylate, star polymers with different arm chem...

A rationalization of the solvent effect on the Diels–Alder reaction in ionic liquids using multiparameter linear solvation energy relationships

Abstract: The Diels–Alder reaction between cyclopentadiene and three dienophiles (acrolein, methyl acrylate and acrylonitrile) having different hydrogen bond acceptor abilities has been carried out in several ionic liquids and molecular solvents in order to obtain information about the factors affecting reactivity and selectivity. The solvent effects on these reactions are examined using multiparameter linear solvation energy relationships. The collected data provide evidence that the solvent effects are a function of both the solvent and the solute. For a solvent effect to be seen, the solute must have a complimentary character; selectivities and rates are determined by the solvent hydrogen bond donation ability (α) in the reactions of acrolein and methyl acrylate, but not of acrylonitrile.

Polymerization of methyl acrylate mediated by copper(0)/Me6‐TREN in hydrophobic media enhanced by phenols; Single electron transfer‐living radical polymerization

Abstract: Phenol has been used as an additive to enhance the rate of SET-LRP in toluene at ambient temperature. A direct relationship between reaction time and amount of phenol added has been found with the optimum amount being similar to 20 equiv. of phenol with respect to initiator. Polymerization of methyl acrylate (MA) has been carried out in the presence of varying amounts of phenol and the rate of polymerization depends on the concentration of phenol relative to initiator. With a 20-fold excess 93% conversion is observed after 218 min (PDI = 1.06, M-n = 11,500 g mol(-1)) when compared with 80% conversion with a 5-fold excess (PDI = 1.21, M-n = 5310 g mol(-1)). When nonsterically hindered phenols are employed in a 20 molar excess with respect to the initiator the polymerizations have good linear first-order kinetics and give polymers with PDI between 1.06 and 1.16. When a highly hindered phenol is employed there is a significant induction period prior to polymerization taking place which is similar to when using no phenol. Less hindered phenols accelerated the polymerization when compared with polymerizations with no added phenol. Increasing steric hindrance at the -OH prevents this coordination which indicates that the role of phenol is different with either copper(0) or copper(I). Aliphatic and aromatic esters and amides were used successfully as initiators giving polymers with M-n close to that predicted at similar to 10,000 g mol(-1) and PDI typically less than 1.10. An induction period is observed in most cases which can be removed by a pre-equilibrium step before the addition of monomer. This results in excellent first-order kinetics being observed in the polymerization of MA in toluene solution (50 vol %). Here Cu(0) (powder)/Me-6-TREN with 20 equiv. of phenol and all of the reactants, except the monomer, were added to the reaction flask and stirred for 45 min at 25 degrees C. The structure of the polymer is shown by MALDI TOF MS to contain bromide chain ends derived from the alkyl bromide initiator. The retention of this end group is consistent with living radical polymerization. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym. Chem 46: 7376-7385, 2008

Synthesis of Surface-Initiated Stimuli-Responsive Diblock Copolymer Brushes Utilizing a Combination of ATRP and RAFT Polymerization Techniques

Abstract: The synthesis of diblock copolymer brushes, including poly(styrene) (PSty)-b-PSty, PSty-b-poly(acrylic acid), PSty-b-poly(N-isopropylacrylamide), and poly(methyl acrylate)-b-poly(N,N-(dimethylamino)ethyl acrylate), was achieved utilizing a combination of surface-mediated atom transfer radical polymerization (ATRP) and reversible addition−fragmentation chain transfer (RAFT) polymerization techniques. Conversion of bromine end groups of homopolymer brushes formed by ATRP via a modified atom transfer addition reaction to a RAFT agent and diblock extension via RAFT polymerization allowed the direct formation of well-defined stimuli-responsive diblock copolymer brushes. The addition of sacrificial initiator and/or chain transfer agent permitted formation of well-defined diblock copolymer brushes and free polymer chains in solution. The free polymer chains were isolated and used to estimate the molecular weights and polydispersity index of chains attached to the surface. Ellipsometry, contact angle measurements...

Functionally terminated poly(methyl acrylate) by SET‐LRP initiated with CHBr3 and CHI3

Abstract: The single-electron transfer living radical polymerization (SET-LRP) of methyl acrylate initiated with bromoform (CHBr 3 ) and iodoform (CHI 3 ) and catalyzed by Cu(0)/Me 6 -TREN in DMSO at 25 °C provides a reliable method to prepare poly (methyl acrylate) (PMA) with active chain ends and controlled structure that can undergo subsequent functionalization to provide strategies for the synthesis of different block copolymers and other complex architectures. A detailed kinetic and structural analysis was used to assess the scope and the limitations of CHBr 3 and CHI 3 as initiators under SET-LRP conditions.

SET‐LRP of acrylates in the presence of radical inhibitors

Abstract: The Cu(0)/Me6-TREN-catalyzed single-electron transfer mediated living radical polymerization (SET-LRP) of methyl acrylate in the presence of the classic 4-methoxyphenol free radical inhibitor was investigated. Kinetic experiments, combined with 1H NMR, and MALDI-TOF MS analysis of the resulting polyacrylates demonstrated that SET-LRP is a robust synthetic method that does not require the purification of the monomers to remove the radical inhibitor. It is anticipated that these results will contribute to the expansion of technological and fundamental applications of SET-LRP since it allows the synthesis of polymers with a structural perfection that previously was not accessible by any other method, starting from unpurified monomers, solvents, initiators, and ligands. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3174–3181, 2008

Patterning on nonplanar substrates: flexible honeycomb films from a range of self-assembling star copolymers.

Abstract: The effect of glass transition temperature, Tg, on the self-assembly of “honeycomb” microstructures on nonplanar substrates was probed by the synthesis of a library of core cross-linked star polymers with different arm compositions. Star polymers based on poly(dimethyl siloxane), poly(ethyl acrylate), poly(methyl acrylate), poly(tert-butyl acrylate), and poly(methyl methacrylate) were synthesized by the “arm first” strategy using atom-transfer radical polymerization. Reaction conditions were optimized, and a series of high molecular weight star polymers were prepared in high yield. The glass transition temperature of the star polymers ranged from −123 to 100 °C which allowed the suitability for the formation of porous honeycomb-like films via the “breath figure” technique on nonplanar surfaces to be investigated. All star compositions successfully formed ordered films on flat surfaces. However, only star polymer compositions with a Tg below 48 °C could form homogeneous honeycomb coatings on the surface of...

Effect of Cross-Linker Reactivity on Experimental Gel Points during ATRcP of Monomer and Cross-Linker

Abstract: A systematic study of the effect of cross-linker reactivity on experimental gel points was conducted using the atom transfer radical copolymerization (ATRcP) of methyl acrylate (MA) with different types and amounts of divinyl cross-linkers, including ethylene glycol diacrylate (EGDA), ethylene glycol dimethacrylate (EGDMA), and an asymmetric cross-linker EGAMA containing one acrylate group and one methacrylate group. The variations of experimental gel points based on the monomer conversions were determined and compared with each other. Compared to the equivalent reactivity of the acrylate groups in MA and EGDA, the methacrylate groups from EGDMA had higher reactivity and led to faster incorporation of cross-linker unit into polymers and quicker generation of branching points (acceleration effect). However, the branched polymers containing the gradient distribution of pendant vinyl groups and branching points resembled a starlike structure, in which the pendant vinyl groups, located in the more densely cro...

Alkyl chloride initiators for SET‐LRP of methyl acrylate

Abstract: Single-electron transfer living radical polymerization (SET-LRP) proceeds by an outer-sphere single-electron transfer mechanism that induces a heterolytic bond cleavage of the initiating and propagating R-X (where X = Cl, Br, and I) species. Therefore, unlike the homolytic bond cleavage mechanism claimed for ATRP, SET-LRP is expected to show a small dependence of the nature of the halide group on the apparent rate constant of activation. This means the R-X with X = Cl, Br, and I must all be efficient initiators for SET-LRP and no chain transfer must be observed in the case of initiators with X = Br and I. Here, we report the SET-LRP of methyl acrylate initiated with the alkyl chlorides methyl-2-chloropropionate (MCP) and chloroform (CHCl3) and catalyzed by Cu(0)/Me6-TREN/CuCl2 in DMSO at 25 °C. A combination of kinetic and structural analysis was used to elucidate the MCP and CHCl3 initiating behavior under SET-LRP conditions, and to demonstrate the very small dependence of the SET-LRP apparent rate constant of propagation on X while providing polymers with well defined architecture. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4917–4926, 2008

Structure–Reactivity Correlation in “Click” Chemistry: Substituent Effect on Azide Reactivity

Abstract: An investigation was conducted into substituent effects on azide reactivity during CU I -catalyzed click reactions by reacting a variety of model azides with propargyl alcohol in DMF-d 7 using CuBr as catalyst, and monitoring conversions via 1 H NMR. The model azides utilized for this investigation were selected due to structural similarity with the end groups of polymers typically employed in azide-alkyne cycloadditions including polystyrene, poly(methyl acrylate), poly(methyl methacrylate), and polyacrylonitrile. Reactivities of alkyl azides depend on both the electronic properties of the substituent and steric congestion around the end group. The fastest reactions were observed for azides with electron-withdrawing substituents and less sterically congested end groups.

Ab initio study of acrylate polymerization reactions: methyl methacrylate and methyl acrylate propagation.

Abstract: The kinetic parameters of the free radical propagation of methyl methacrylate and methyl acrylate have been calculated using quantum chemistry and transition state theory. Multiple density functional theory (DFT) methods were used to calculate the activation energy, and it was found that MPWB1K/6-31G(d,p) yields results that are in very good agreement with experimental data. To obtain values of the kinetic parameters that were in the best agreement with experimental data, low frequencies were treated using a one-dimensional internal rotor model. Chain length effects were also explored by examining addition reactions of monomeric, dimeric, and trimeric radicals to monomer for both methyl methacrylate and methyl acrylate. The results show that the values for the addition of the trimeric radical to monomer are closest to experimental data. The kinetic parameters that were calculated using a continuum description of the monomer as a solvent were not significantly different from the vacuum results.

Acyclic Triene Metathesis Polymerization with Chain-Stoppers : Molecular Weight Control in the Synthesis of Branched Polymers

Abstract: The synthesis of branched macromolecules from renewable resources via olefin metathesis is described. We observed that it is possible to control the molecular weight during the acyclic triene metathesis (ATMET) of a triglyceride by the application of methyl acrylate as a chain stopper for this straightforward one step one pot polymerization. The resulting branched materials were characterized by GPC, NMR as well as ESI-MS and the combination of these techniques provided valuable insights into the polymer structure as well as occurring side reactions during this olefin metathesis polymerization reaction.

Anti-fouling ultrafiltration membrane prepared from polysulfone-graft-methyl acrylate copolymers by UV-induced grafting method

Abstract: Membrane fouling is one of the most important challenges faced in membrane ultrafiltration operations. The copolymers of polysulfone-graft-methyl acrylate were synthesized by homogeneous photo-initiated graft copolymerization. The variables affecting the degree of grafting, such as the time of UV (Ultraviolet-visible) irradiation and the concentrations of the methyl acrylate and photoinitiator, were investigated. The graft copolymer membranes were prepared by the phase inversion method. The chemical and morphological changes were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), scanning electron microscopy, and water contact angles measurements. Results revealed that methyl acrylate groups were present on the membranes and the graft degree of methyl acrylate had remarkable effect on the performance of membranes. Pure water contact angle on the membrane surface decreases with the increase of methyl acrylate graft degree, which indicated that the hydrophilicity of graft copolymer membranes was improved. The permeation fluxes of pure water and bovine serum albumin solution were measured to evaluate the antifouling property of graft copolymer membranes, the results of which have shown an enhancement of antifouling property for graft copolymer membranes.

Living Radical Polymerization of Acrylates Mediated by 1,3-Bis(2-pyridylimino)isoindolatocobalt(II) Complexes: Monitoring the Chain Growth at the Metal

Abstract: A new type of mediator for cobalt(II)-mediated radical polymerization is reported which is based on 1,3-bis(2-pyridylimino)isoindolate (bpi) as ancillary ligand. The modular synthesis of the bis(pyridylimino)isoindoles (bpiH) employed in this work is based on the condensation of 2-aminopyridines with phthalodinitriles. Reaction of the bpiH protio-ligands with a twofold excess of cobalt(II) acetate or cobalt(II) acetylacetonate in methanol gave [Co(bpi)(OAc)], which crystallize as coordination polymers, and a series of [Co(acac)(bpi)(MeOH)], which are mononuclear octahedral complexes. Upon heating the [Co(acac)(bpi)(MeOH)] compounds to 100 degrees C under high vacuum, the coordinated methanol was removed to give the five-coordinate complexes [Co(acac)(bpi)]. The polymerization of methyl acrylate at 60 degrees C was investigated by using one molar equivalent of the relatively short-lived radical source 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) as initiator (monomer/catalyst/V-70: 600:1:1). The low solubility of the acetato complexes inhibits their significant activity as mediators in this reaction, whereas the acetylacetonate complexes control the radical polymerization of methyl acrylate more effectively. The radical polymerizations of the hexacoordinate complexes did not show a linear increase in number-average molecular weight (M(n)) with conversion; however, the polydispersities were relatively low (PDI=1.12-1.40). By using the pentacoordinate complexes [Co(acac)(bpi)] as mediators, a linear increase in M(n) values with conversion, which were very close to the theoretical values for living systems, and very low polydispersities (PDI<1.13) were obtained. This was also achieved in the block copolymerization of methyl acrylate and n-butyl acrylate. The intermediates with the growing acrylate polymer radical ((.)PA) were identified by liquid injection field desorption/ionization mass spectrometry as following the general formula [Co(acac)(4-methoxy-bpi)-(MA)(n)-R] (MA: methyl acrylate; R: C(CH(3))(CH(2)C(CH(3))(2)OCH(3))CN), a notion also confirmed by NMR end-group analysis.

ATRP−RCM Synthesis of Cyclic Diblock Copolymers

Abstract: A versatile synthetic means for cyclic diblock copolymers has been developed by the combination of atom transfer radical polymerization (ATRP) and ring-closing metathesis (RCM) techniques. Thus, first, an A−B type allyl-telechelic diblock copolymer comprised of two different acrylate ester segments, i.e., poly(methyl acrylate)-b-poly(n-butyl acrylate), poly(MA)-b-poly(BA), was prepared via the ATRP of MA, followed by the addition of the second monomer, BA, with allyl bromide as an initiator and with allyltributylstannane as an end-capping reagent, respectively. Alternatively, an A−B−A type allyl-telechelic triblock copolymer comprised of poly(BA) and poly(ethylene oxide), poly(EO), segments was prepared via the ATRP of BA using a poly(EO) macroinitiator having 2-bromoisobutyryl end groups, followed by the end-capping reaction with allyltributylstannane. The subsequent RCM of the allyl-telechelic block copolymers under dilution in the presence of Grubbs catalyst could afford the corresponding A−B type cycl...

Differentiation of postnatal neural stem cells into glia and functional neurons on laminin-coated polymeric substrates.

Abstract: A series of polymeric biomaterials, including poly(methyl acrylate), chitosan, poly(ethyl acrylate) (PEA), poly(hydroxyethyl acrylate) (PHEA), and a series of random copolymers containing ethyl acrylate, hydroxyethyl acrylate, and methyl acrylate were tested in vitro as culture substrates and compared for their effect on the differentiation of neural stem cells (NSCs) obtained from the subventricular zone of postnatal rats Immunocytochemical assay for specific markers and scanning electron microscopy techniques were employed to determine the adhesion of the cultured NSCs to the different biomaterials and the respective neuronal differentiation The functional properties and the membrane excitability of differentiated NSCs were investigated using a patch-clamp The results show that the substrate's surface chemistry influences cell attachment and neuronal differentiation, probably through its influence on adsorbed laminin, and that copolymers based on PEA and PHEA in a narrow composition window are suitable substrates to promote cell attachment and differentiation of adult NSCs into functional neurons and glia

Synthesis of poly(methyl acrylate) loops grafted onto silica nanoparticles via reversible addition‐fragmentation chain transfer polymerization

Abstract: Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to produce poly(methyl acrylate) (pMA) loops grafted onto silica nanoparticles using doubly anchored bifunctional RAFT agents 1,4-bis(3′-trimethoxysilylpropyltrithiocarbonylmethyl)benzene (Z-group approach) and 1,6-bis(o,p-2′-trimethoxysilylethylbenzyltrithiocarbonyl)hexane (R-group approach) as mediators. In both cases, molecular weights of the resulting surface-confined polymer loops increased with monomer conversion, whereas the grafting density was significantly higher in the case of the R-group supported RAFT polymerization due to mechanistic differences of the RAFT process at the surface. This result was evident from thermogravimetric analysis and supported by scanning electron microscopy. Polymer loops with molecular weights up to 53,000 g mol−1 were accessible with polydispersities of about 2.0 without and 1.5 with the addition of free RAFT agent. UV signals of the detached pMA loops measured via size exclusion chromatography were shifted to higher molecular weights compared with the corresponding RI signals, indicating branching reactions caused by the close proximity of growing radicals and polymer at the surface of the silica nanoparticles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7656–7666, 2008

Synthesis of ABCD 4‐miktoarm star polymers by combination of RAFT, ROP, and “Click Chemistry”

Abstract: The ABCD 4-miktoarm star polymers based on polystyrene (PS), poly(e-caprolactone) (PCL), poly(methyl acrylate) (PMA), and poly(ethylene oxide) (PEO) were synthesized and characterized successfully. Using the mechanism transformation strategy, PS with three different functional groups (i.e., hydroxyl, alkyne, and trithiocarbonate), PS-HEPPA-SC(S)SC12H25, was synthesized by the reaction of the trithiocarbonate-terminated PS with 2-hydroxyethyl-3-(4-(prop-2-ynyloxy)phenyl) acrylate (HEPPA) in tetrahydrofuran (THF) solution. Subsequently, the ring-opening polymerization (ROP) of e-caprolactone (CL) was carried out in the presence of stannous(II) 2-ethylhexanoate and PS-HEPPA-SC(S)SC12H25, and then the PS-HEPPA(PCL)-SC(S)SC12H25 obtained was used in reversible addition-fragmentation chain transfer (RAFT) polymerization of methyl acrylate (MA) to produce the ABC 3-miktoarm star polymer, S(PS)(PCL)(PMA) carrying an alkyne group. The ABCD 4-miktoarm star polymer, S(PS)(PCL)(PMA)(PEO) was successfully prepared by click reaction of the alkyne group on the HEPPA unit with azide-terminated PEO (PEO-N3). The target polymer and intermediates were characterized by NMR, FTIR, GPC, and DSC. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6641–6653, 2008

Scrub and stain-resistant coating

Abstract: A waterborne coating composition is provided, comprising a vinyl copolymer with an optimized level of phosphorus-containing functional groups in conjunction with at least 20% by weight of the copolymer, of ethyl acrylate, methyl acrylate or combinations thereof and one or more opacifying colorants, preferably titanium dioxide.