Synthesis and Characterization of Novel Nano Six-arms of (polylactide-dipentaerythritol)-block-N-hydroxyethyl Acrylamide and N,N-dimethylamino Ethyl Methacrylate Biocopolymers by Atom Transfer Radical Polymerization (original) (raw)
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European Polymer Journal, 2003
Homopolymerization of methyl acrylate (MA) and methyl methacrylate (MMA) by atom transfer radical polymerization (ATRP) were carried out at 90°C using methyl-2-bromopropionate (MBP) as initiator, copper halide (CuX, X ¼ Cl, Br) as catalyst, 2,2 0-bipyridine (bpy) or N,N,N 0 ,N 0 ,N 00-pentamethyldiethylenetriamine (PMDETA) as ligand in 1-butanol (less polar and containing OH) and acetonitrile (more polar) solvents. It was found that with CuCl/bpy catalyst ATRP of MA and MMA in 1-butanol proceeded faster than that in acetonitrile. The rate of ATRP of MA and MMA in acetonitrile and 1-butanol was comparable when CuCl/PMDETA used as catalyst system. The numberaverage molecular weights ðM n Þ increased with conversion and polydispersities were low ðM w =M n < 1:5Þ. The ATRP of MA and MMA with vinyl acetate telomer having trichloromethyl end group (PVAc-CCl 3) were also used to synthesize new block copolymers. The structures and molecular weight of synthesized PVAc-b-PMA and PVAc-b-PMMA were characterized by 1 H NMR, FTIR spectroscopy and gel permeation chromatography (GPC) and shown that the block copolymers were novel.
Journal of Polymer Science Part A: Polymer Chemistry, 2005
The atom transfer radical polymerization of octadecyl acrylate (ODA) has been investigated and optimized to produce polymers with predetermined molecular weights and narrow polydispersities (Ͻ1.2). The poor solubility of the catalytic system formed with conventional ligands such as the N-(n-propyl)-2-pyridylmethanimine and 2,2Ј-bipyridine with Cu(I)Br in nonpolar reaction conditions gave poor control over molecular weight characteristics in ODA polymerizations. The use of N-(n-octyl)-2pyridylmethanimine in combination with Cu(I)Br yielded a more soluble catalyst that improved control over the polymerization. The products from the polymerizations were further improved when an initiator, octadecyl 2-bromo-2-methyl-propanoate, similar in structure to the monomer, was used. Together, these modifications produced polymerizations that showed true controlled character as well as products with predetermined molecular weights and narrow polydispersities. Diblock copolymers of PODA were prepared with methyl methacrylate (MMA) and olig(oethylene glycol) methyl ether methacrylate (OEGMA). The PODA-block-POEGMA copolymers are the first examples of all comblike amphiphilic block copolymers. One of PODA-block-POEGMA copolymer samples has been shown to self-assemble as micelles in a dilute aqueous solution.
European Polymer Journal, 2003
The synthesis of tert-butyl acrylate by atom transfer radical polymerization (ATRP) is reported. This polymer was prepared using FeCl 2 AE 4H 2 O(PPh 3 ) 2 catalyst system in conjunction with methyl 2-bromopropionate as initiator, in bulk and in solution using acetone as a solvent. The addition of solvent was necessary in order to decrease the polymerization rate and to afford low polydispersity polymers. The number-average molecular weights of the resulting polymers increased in direct proportion to the monomer conversion, and the polydispersities (M w =M n ) were as low as 1.2. In addition, the preparation of an AB diblock copolymer of poly (n-butyl methacrylate)-block-poly (tert-butyl acrylate) by ATRP is reported. The resulting polymers and copolymers were characterized by means of size exclusion chromatography and 1 H-NMR Spectroscopy.
Macromolecules, 2012
Atomic transfer radical polymerization (ATRP) of acrylamide has been accomplished in aqueous media at room temperature. By using methyl 2-chloropropionate (MeClPr) as the initiator and tris[2-(dimethylamino)ethyl]amine (Me 6 TREN)/copper halogenide (CuX) as the catalyst system, different linear polyacrylamides with apparent molecular weights up to >150 000 g/mol were synthesized with dispersities as low as 1.39. The molecular weights agreed well with the theoretical ones at relatively low-medium monomer/initiator ratios (<700:1). Initial chain extension experiments (isolated macroinitiator) resulted in a polymer with bimodal distribution. However, in situ chain extension experiments, carried out by addition of a second fresh batch of monomer to the reaction mixture, confirmed the living nature of the polymerization. By adding a fresh batch of monomer to a linear macroinitiator (M n = 22 780 g/mol, PDI = 1.42) in solution, an increase in the molecular weight up to 30 220 g/mol (PDI = 1.64) was observed. In addition, linear polyacrylamides were used as macroinitiators for the synthesis of block copolymers polyacrylamide-b-poly(N-isopropylacrylamide).
Journal of Polymer Science Part A: Polymer Chemistry, 2008
Living-radical polymerization of acrylates were performed under emulsion atom transfer radical polymerization (ATRP) conditions using latexes prepared by a nanoprecipitation technique previously employed and optimized for the polymerization of styrene. A macroinitiator of poly(n-butyl acrylate) prepared under bulk ATRP was dissolved in acetone and precipitated in an aqueous solution of Brij 98 to preform latex particles, which were then swollen with monomer and heated. Various monomers (i.e. n-butyl acrylate, styrene, and tert-butyl acrylate) were used to swell the particles to prepare homo-and block copolymers from the poly(n-butyl acrylate) macroinitiator. Under these conditions latexes with a relatively good colloidal stability were obtained. Furthermore, amphiphilic block copolymers were prepared by hydrolysis of the tertbutyl groups and the resulting block copolymers were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The bulk morphologies of the polystyrene-b-poly(n-butyl acrylate) and poly(n-butyl acrylate)-b-poly(acrylic acid) copolymers were investigated by atomic force microscopy (AFM) and small angle X-ray scattering (SAXS).
Polymer, 2004
Atom transfer radical polymerization of lauryl methacrylate (LMA) was carried out in the presence of various ligands using ethyl-2bromoisobutyrate as initiator and CuBr as catalyst in toluene at 95 8C. The ligands used were 2,2 0-bipyridyl,4,4 0-dimethyl-2,2 0-bipyridyl, N,N,N 0 ,N 0 ,N 00-pentamethyldiethylenetriamine (PMDETA) and N-(n-propyl)-2-pyridylmethanimine (PPMI). Controlled polymerization was observed with PMDETA and PPMI ligands and poly(LMA)s with narrow molecular weight distribution (MWD) ðM w =M n # 1:2Þ were obtained. The first-order time-conversion plot showed the presence of termination in the presence of PMDETA. A linear first-order timeconversion plot with a small induction period (,10 min) was observed in the presence of PPMI ligand. Di-block copolymers of LMA and methylmethacrylate with controlled molecular weight and narrow MWDs were synthesized via sequential monomer addition.
Journal of Polymer Science Part A: Polymer Chemistry, 2005
The syntheses of triblock copolymers by the atom transfer radical polymerization of tert-butyl and iso-butyl acrylates as inner blocks with cyclohexyl methacrylate as outer blocks are reported. The living behavior and blocking efficiency of these polymerizations were investigated in each case. The use of difunctional macroinitiators led to ABA triblock copolymers with narrow polydispersities and controlled number-average molecular weights. These copolymers were prepared from bromo-terminated macroinitiators of poly(tert-butyl acrylate) and poly(iso-butyl acrylate), with copper chloride/N,N,N 0 ,N@,N@-pentamethyldiethylenetriamine as the catalytic system, at 40 8C in 50% (v/v) toluene solutions. The block copolymers were characterized with size exclusion chromatography and 1 H NMR spectroscopy. Differential scanning calorimetry measurements were performed to reveal the phase segregation. The glass transition of the inner block was not clearly detected, with the exception of the copolymer synthesized with the longest poly(iso-butyl acrylate) macroinitiator length.
Polymer, 2005
Amphiphilic di-and tri-block copolymers of poly(methyl methacrylate) (PMMA) and poly(2-dimethylamino)ethyl methacrylate (PDMAEMA) have been synthesized by atom transfer radical polymerization (ATRP) at ambient temperature (35 8C) in the environment-friendly solvent, aqueous ethanol (water 16 vol%) using CuCl/o-phenanthroline as the catalyst. The PDMAEMA blocks are contaminated with ethyl methacrylate (EMA) residues to the extent of 1-2 mol% of DMAEMA depending on the length of the PDMAEMA block. The EMA forms through the autocatalyzed ethanolysis of the DMAEMA monomer and undergoes random copolymerization with the latter. The rate of ethanolysis is unexpectedly greater in the aqueous ethanol than in neat ethanol, which has been attributed to the higher polarity of the former than of the latter. In contrast to the ethanolysis no hydrolysis of DMAEMA in the aqueous ethanol medium could be detected for 133 h. The block copolymers form micelles in water. Their solubility and CMC in neutral water have been studied. Dynamic light scattering (DLS) studies reveal that for a fixed degree of polymerization (DP) of the PMMA block the hydrodynamic diameter of the micelles in methanolic water (water 95 vol%) increases at a faster rate with the DP of the PDMAEMA block when it is much greater than that of the PMMA block compared to when it is less than or close to that of the latter. q
European Polymer Journal, 2008
Amphiphilic block copolymers of methyl methacrylate (MMA) and sodium styrene sulfonate (SSNa) were successfully synthesized via direct atom transfer radical polymerization (ATRP) of SSNa. First, poly(sodium styrene sulfonate) (PSSNa) or poly(methyl methacrylate) (PMMA) macroinitiators were prepared using proper ATRP systems for each case. In some cases, functional initiators, which allow further reactions, were used. The macroinitiators were characterized and further used to synthesize PSSNa/PMMA block copolymers, by using proper solvent combinations, such as N,N-dimethylformamide/water or methanol/water at appropriate volume ratios, in order to ensure solubility of the synthesized amphiphilic copolymers. The molecular weight of the copolymers was determined by gel permeation chromatography, using water as eluent. By using a combination of analytical techniques like 1 H NMR, FTIR and thermogravimetry, the chemical structure and the actual copolymer composition were determined. Since, the block copolymers were soluble in water, forming hydrophilic/hydrophobic domains in aqueous solution, their micellization behavior was further studied by pyrene fluorescence probing.
Journal of Applied Polymer Science, 2013
This study investigates the use of homogeneous reverse atom transfer radical polymerization for the synthesis of polystyrene (PS) initiated by conventional radical peroxide with copper bromide in the lower oxidation state and a 2,2 0-bypyridine complex as the catalyst. In a second stage, an amphiphilic block copolymer containing methyl methacrylate (MMA) was synthesized via normal atom transfer radical polymerization in two steps, followed by partial hydrolysis of the methyl ester linkage of the MMA block under acidic conditions. The block copolymer PS 699-b-P(MMA 232 /MAA 58) obtained had a narrow molecular weight dispersity (Ð < 1.3). The structure of the precursor, PS-b-PMMA, and resultant polymer, was characterized and verified by FTIR and 1 H-NMR spectroscopy as well as size exclusion chromatography. The self-aggregation of PS 699-b-P(MMA 232 /MAA 58) in organic solvents was monitored by UV spectroscopy, whereas the morphology and size of the formed microaggregates were investigated by transmission electron microscopy and dynamic light scattering. The results indicate that this copolymer formed regular spherical reverse micelles with a core-shell structure. The atomic force micrographs of PS 699-b-P(MMA 232 /MAA 58) showed a rough surface morphology owing to microphase separation of the block copolymer. In addition, thermal characterization was performed by differential scanning calorimetry and thermogravimetric analysis. The glass transition temperature of PS 699-b-P(MMA 232 /MAA 58) decreased significantly (65 C), when compared to PS and PMMA, suggesting that an enhanced movement of the polymer chains resulted by the segregation of the hydrolyzed P(MMA 232 /MAA 58) block. V