Conventional free-radical and RAFT copolymerization of poly(ethylene oxide) containing macromonomers (original) (raw)
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Designed Monomers and Polymers, 2004
Polymerization of bifunctional α,ω-methacryloyloxypoly(ethylene oxide) (PEO) macromonomers was performed in water (or in organic solvents) via free radical or Atom Transfer Radical Polymerization (ATRP). Rapid cross-linking was observed when the reaction was conducted at 60 • C via classical free radical polymerization with potassium peroxodisulfate as initiator. ATRP also yielded hydrogels, but the system was much more complex. In both cases, the characteristics of the resulting hydrogels (amount of extractable material, equilibrium swelling degree and uniaxial compression modulus) were studied. They depend on several parameters (precursor molar mass, macromonomer concentration, polymerization time and nature of the initiating system). The hydrogels obtained by ATRP are characterized by higher amounts of extractable materials and exhibit rather poor mechanical properties. Regardless of the polymerization process (free radical or ATRP), far better results were obtained when the reaction was conducted in water. In fact, in aqueous media, the hydrophobic end-standing polymerizable methacrylic units of the macromonomers self-organize, after which gel formation takes place much more rapidly.
Polymer, 2007
Poly(methyl methacrylate-b-ethylene oxide-b-methyl methacrylate) (PMMAePEOePMMA) triblock copolymers were synthesized using atom transfer radical polymerization (ATRP) and halogen exchange ATRP. PEO-based macroinitiators with molecular weight from M n ¼ 2000 to 35,800 g/mol were used to initiate the polymerization of MMA to obtain copolymers with molecular weight up to M n ¼ 82,000 g/mol and polydispersity index (PDI) less than 1.2. The macroinitiators and copolymers were characterized by gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy. The melting temperature and glass transition temperature of the copolymers were measured by differential scanning calorimetry (DSC). Crystallinities of the PEO blocks were determined from the WAXS patterns of both homopolymers and block copolymers, which revealed the fragmentation of PEO blocks due to the folding of the PMMA chains. Interestingly, the fragmentation was less pronounced when cast on surfaces compared to that in bulk, as measured by GISAXS. Solvent casting was used to control the morphology of the copolymers, permitting the formation of various states including amorphous, induced micellar with a PMMA core and flower-like PEO arms, and a cross-linked gel. Atomic force microscopy (AFM) was used to visualize the different copolymer morphologies, showing micellar and amorphous states.
Journal of Polymer Science Part A: Polymer Chemistry, 2005
A surface-active p-vinyl benzyloxy-hydroxy-poly(ethylene oxide) macromonomer containing 22 pendant structural units of ethylene oxide (St-PEO 22) was synthesized with an initiation method. Because of its solubility in a large variety of solvents, the free-radical copolymerization with electron-acceptor N-phenylmaleimide (NPMI) was performed at 60°C in benzene and tetrahydrofuran (THF) as isotropic media and in a water-THF mixture or water as a heterogeneous medium. Oil-soluble 2,2Ј-azobisisobutyronitrile and water-soluble 4,4Ј-azobis(4-cyanovaleric acid) were used as the initiators at fixed concentrations. Two different St-PEO 22 /NPMI comonomer ratios (1/1 and 3/7) at a fixed total comonomer concentration in the polymerization system were used. The structures, compositions, and microstructure peculiarities of the obtained alternating, amphiphilic, comblike copolymers were determined by NMR analysis. For the copolymers synthesized in hydrophilic media, differential scanning calorimetry showed, near the endothermic peak attributed to the melting of the poly-(ethylene oxide) side chains, the presence of a second peak due to the partially ordered phase that could exist between the crystalline state and the isotropic melt. Also, the thermal stability of the obtained copolymers was studied with thermogravimetric analysis.
Journal of Polymer Science Part A: Polymer Chemistry, 2008
The synthesis of well-defined poly(methyl methacrylate)-block-poly(ethylene oxide) (PMMA-b-PEO) dibock copolymer through anionic polymerization using monohydroxy telechelic PMMA as macroinitiator is described. Living anionic polymerization of methyl methacrylate was performed using initiators derived from the adduct of diphenylethylene and a suitable alkyllithium, either of which contains a hydroxyl group protected with tert-butyldimethylsilyl moiety in tetrahydrofuran (THF) at À78 8C in the presence of LiClO 4. The synthesized telechelic PMMAs had good control of molecular weight with narrow molecular weight distribution (MWD). The 1 H NMR and MALDI-TOF MS analysis confirmed quantitative functionalization of chain-ends. Block copolymerization of ethylene oxide was carried out using the terminal hydroxyl group of PMMA as initiator in the presence of potassium counter ion in THF at 35 8C. The PMMA-b-PEO diblock copolymers had moderate control of molecular weight with narrow MWD. The 1 H NMR results confirm the absence of transesterification reaction of propagating PEO anions onto the ester pendants of PMMA. The micellation behavior of PMMA-b-PEO diblock copolymer was examined in water using 1 H NMR and dynamic light scattering. V
European Polymer Journal, 1995
The graft copolymers (polystyrene-graft-polyoxyethylene) (PSt-graft-PEO) were prepared by the radical dispersion copolymerization of methacryloyl (MA)-terminated PEO macromonomer and styrene. By means of size-exclusion chromatography, liquid chromatography at the critical adsorption point, and light scattering, the molecular weight parameters and the solution properties of PSt-graft-PEO were investigated. The apparent average molecular weight and the molecular weight distribution (MWD) of graft copolymers were found to decrease with increasing molecular weight of PEO-MA macromonomer. This decreased molecular weight was attributed to the chain transfer to PEO unit and increased contribution of the solution polymerization. The broad MWD varied with the ratio of the polymerization in the continuous phase and the polymer particles. The number of PEO grafts per PSt backbone decreased with increasing molecular weight of the PSt-graft-PEO copolymer, which was attributed to the intramolecular association of PEO segments. The intrinsic viscosity or the coil size of graft copolymer molecules varied with temperature as a result of the dehydration of PEO segments.
Journal of Applied Polymer …, 2009
Atom transfer radical bulk copolymerization of styrene (St) and methyl acrylate (MA) initiated with trichloromethyl-terminated poly(vinyl acetate) macroinitiator was performed in the presence of CuCl/PMDETA as a catalyst system at 90 C. Linear dependence of ln[M] 0 /[M] versus time data along with narrow polydispersity of molecular weight distribution revealed that all the homoand copolymerization reactions proceed according to the controlled/living characteristic. To obtain more reliable monomer reactivity ratios, the cumulative average copolymer composition at moderate to high conversion was determined by 1 H-NMR spectroscopy. Reactivity ratios of St and MA were calculated by the extended Kelen-Tudos (KT) and Mao-Huglin (MH) methods to be r St ¼ 1.018 AE 0.060, r MA ¼ 0.177 AE 0.025 and r St ¼ 1.016 AE 0.053, r MA ¼ 0.179 AE 0.023, respectively, which are in a good agreement with those reported for the conventional free-radical copolymerization of St and MA. Good agreement between the theoretical and experimental composition drifts in the comonomer mixture and copolymer as a function of the overall monomer conversion were observed, indicating that the reactivity ratios calculated by copolymer composition at the moderate to high conversion are accurate. Instantaneous copolymer composition curve and number-average sequence length of comonomers in the copolymer indicated that the copolymerization system tends to produce a random copolymer. However, MA-centered triad distribution results indicate that the spontaneous gradient copolymers can also be obtained when the mole fraction of MA in the initial comonomer mixture is high enough.
Macromolecular Research, 2014
Alternative copolymers of acrylic acid (AA) and oligo(ethylene glycol) methyl ether methacryate (475 g/ mol (OEGMA 475)) macromer, having various amounts of two monomers, were synthesized using aqueous solution free radical copolymerization at 50°C with ammonium persulfate (APS) as an initiator. The structures of the copolymers were confirmed by nuclear magnetic resonance (NMR) spectroscopy. In fact, samples with different molar ratios of two monomers in deionized water were prepared and subsequently copolymerization reaction was performed to low conversion levels (below 10%). Monomer reactivity ratios of OEGMA 475 , AA pair were estimated using the Finemann-Ross (FR), inverted Finemann-Ross (IFR), Kelen-Tüdös (KT), extended Kelen-Tüdös (EKT), Mayo-Lewis (ML) and Yezrelieve-Brokhina-Roskin (YBR) graphical methods. The value ranged from 0.908 to 0.963 for r OEGMA and from 0.208 to 0.243 for r AA depending on conversion percentage and calculation methods of monomer reactivity ratios. In all the cases, r OEGMA ×r AA <1 and r OEGMA >r AA indicate that the resulting copolymer has a tendency toward alternation with an azeotropic point in M OEGMA =0.905. Structural parameters of the copolymers were obtained by calculating the dyad monomer sequence fractions and the mean sequence length.
Atom-Transfer Radical Polymerization of a Reactive Monomer: 3-(Trimethoxysilyl)propyl Methacrylate
Macromolecules, 2004
Atom-transfer radical polymerizations (ATRPs) of a reactive monomer, 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), mediated by CuBr/N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PM-DETA) in anisole have been studied using ethyl 2-bromoisobutyrate (2-EBiB) and poly(ethylene oxide) methyl ether 2-bromoisobutyrate (PEO-Br) as initiators. In general, the polymerizations of TMSPMA exhibited first-order kinetics, and molecular weights increased linearly with monomer conversion. Molecular weight distributions remained low throughout the polymerizations (M w/Mn ) 1.20-1.40). The overall rate of polymerization with PEO-Br as the initiator was enhanced compared to that with 2-EBiB as the initiator. A series of reactive diblock copolymers, poly(ethylene oxide)-b-poly[3-(trimethoxysilyl)propyl methacrylate] (PEO-b-PTMSPMA), were thus synthesized. By random copolymerization with methyl methacrylate (MMA), PEO-b-P(TMSPMA-r-MMA) copolymer was prepared at the same time. Organic/inorganic hybrid nanospheres were produced by the self-assembly of PEO-b-P(TMSPMA-r-MMA) in a selective solvent and further gelation of the trimethoxylsilyl groups within each individual sphere. Preparation of organic/inorganic nanocomposites was also explored preliminarily on the basis of the solgel process of PEO-b-PTMSPMA diblock copolymers and the tetraethyl orthosilicate.
Dispersion copolymerization of poly(oxyethylene) macromonomers and styrene
Journal of Polymer Science Part A: Polymer Chemistry, 1997
The kinetics of dispersion copolymerization of methacryloyl-terminated poly(oxyethylene) (PEO-MA) and p-vinylbenzyl-terminated (PEO-St) polyoxyethylene macromonomers and styrene (St), initiated by a water-and/or oil-soluble initiator, was investigated using conventional gravimetric and NMR methods at 60ЊC. The batch copolymerizations in the water/ethanol continuous phase were conducted to high conversion. The rate of polymerization was described by the curve with a maximum at very low conversion. The initial rate of polymerization and the number-average molecular weight were found to decrease with increasing [PEO-MA], and the decrease was more pronounced in the range of a high macromonomer concentration. The rate per particle (at ca. 20% conversion) was found to be proportional to the 01.55th, the particle size to the 00.92nd, and the number of particles (at final conversion) to the 3.2nd power of [PEO-MA], respectively. At the beginning of polymerization the continuous phase is the main reaction locus. As the polymerization advances, the reaction locus is shifted from the continuous phase to the polymer particles. The transform of the reaction loci from the continuous phase to the polymer particles increases the rate of polymerization and the polymer molecular weights. The increase of the weight ratio PEO-MA/St favors the formation of monodisperse polymer particles, the colloidal stability of dispersion, and the formation of a larger number of polymer particles. ᭧ 1997