Living anionic polymerization of lauryl methacrylate and synthesis of block copolymers with methyl methacrylate

Anionic polymerization of lauryl methacrylate (LMA) with 1,1‐diphenylhexyl lithium in tetrahydrofuran (THF) at ?40 °C resulted in a multimodal and broad molecular weight distribution (MWD) with poor initiator efficiency. In the presence of additives such as dilithium salt of triethylene glycol (G₃Li₂), LiCl, and LiClO₄, the polymerization resulted in polymers with a narrow MWD (≤ 1.10). Diblock copolymers of methyl methacrylate (MMA) and LMA were synthesized by anionic polymerization using DPHLi as initiator in THF at ?40 °C with the sequential addition of monomers. The molecular weight distribution of the polymers was narrow and without homopolymer contamination when LMA was added to living PMMA chain ends. Diblock copolymers with broad/bimodal MWD were obtained with a reverse‐sequence monomer addition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 875–882, 2004     

Libraries of methacrylic acid and oligo(ethylene glycol) methacrylate copolymers with LCST behavior

Homopolymers of methacrylic acid (MAA), monoethyleneglycol methyl ether methacrylate (MEOMA), diethyleneglycol methyl ether methacrylate (MEO₂MA), oligo(ethyleneglycol) methyl ether methacrylate (OEGMA₄₇₅ and OEGMA₁₁₀₀) and oligo(ethyleneglycol) ethyl ether methacrylate (OEGEMA₂₄₆) were synthesized with various chain lengths via reversible addition fragmentation chain transfer (RAFT) polymerization. The homopolymers of MAA, MEOMA and OEGMA₁₁₀₀ did not show any cloud point (CP) in the range of 0–100 °C, whereas at a pH value of 7, the CPs were found to be 20.6, 93.7, and 20.0 °C for p(MEO₂MA), p(OEGMA₄₇₅) and p(OEGEMA₂₄₆), respectively, with an initial monomer to initiator ratio of 50. Furthermore, statistical copolymer libraries of MAA with OEGMA₄₇₅ and OEGMA₁₁₀₀ were prepared. The cloud points of the random copolymers of MAA and OEGMA₄₇₅ were found to be in the range of 20–90 °C; surprisingly, even though the homopolymers of MAA and OEGMA₁₁₀₀ did not exhibit any LCST behavior, the copolymers of these monomers at certain molar ratios (up to 40% OEGMA₁₁₀₀) revealed a double responsive behavior for both temperature and pH. Finally, the cloud points were found to be in the range of 22–98 °C, measured at pH values of 2, 4, and 7, while no cloud point was detected at pH 10. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7138–7147, 2008     

Copolymers of 2-hydroxyethyl methacrylate and alkyl methacrylates. I. Synthesis and characterization

Copolymerization of 2-hydroxyethyl methacrylate (HEMA) with ethyl methacrylate (EMA) and n-butyl methacrylate (BMA) was carried out in bulk at 70°C ± 1°C using 0.2% benzoyl peroxide as initiator in nitrogen atmosphere. Number average molecular weight (M _n) of the copolymers was determined by dynamic osmometry. Intrinsic viscosity [η] of HEMA-BMA copolymers was evaluated at 35°C in dimethyl formamide. These copolymers were also characterized by infrared spectroscopy and density measurements. Cohesive energy densities (CED) of these polymers were determined by observing their swelling behavior in different solvents. It was found that a decrease in alkyl methacrylate content resulted in an increase in the CED values of the copolymers.     

Preparation of novel alkaline pH‐responsive copolymers for the formation of recyclable aqueous two‐phase systems and their application in the extraction of lincomycin

Aqueous two‐phase systems have potential industrial application in bioseparation and biocatalysis engineering; however, their practical application is limited primarily because the copolymers involved in the formation of aqueous two‐phase systems cannot be recovered. In this study, two novel alkaline pH‐responsive copolymers were synthesized and examined for the extraction of lincomycin. The two copolymers could form a novel alkaline aqueous two‐phase systems when their concentrations were both 6% w/w and the pH was 8.4(±0.1)–8.7(±0.1). One copolymer was synthesized using acrylic acid, 2‐(dimethylamino)ethyl methacrylate, and butyl methacrylate as monomers. Moreover, 98.8% of the copolymer could be recovered by adjusting the solution pH to its isoelectric point (pH 6.29). The other copolymer was synthesized using the monomers methacrylic acid, 2‐(dimethylamino)ethyl methacrylate, and methyl methacrylate. In this case, 96.7% of the copolymer could be recovered by adjusting the solution pH to 7.19. The optimal partition coefficient of lincomycin was 0.17 at 30°C in the presence of 10 mM KBr and 5.5 at 40°C in the presence of 80 mM Ti(SO₄)₂ using the novel alkaline aqueous two‐phase systems.     

Molecular and crystalline structure of pyrocatechol and hydroquinone dimethacrylates and their reactivity in melts

X-ray diffraction analysis of pyrocatechol and hydroquinone dimethacrylates (T _m = 18 and 86–88°C, respectively) shows that the oligomer molecules within crystals are packed in stacks where the methacrylate fragments of neighboring molecules are parallel to each other. The minimum distances between the centers of double bonds of adjacent methacrylate fragments in crystals of pyrocatechol and hydroquinone dimethacrylates are 4.621(3) and 4.269(4) Å. The curves showing the reduced rate of photopolymerization of oligomer melts versus conversion (9,10-phenanthrenequinone used as the initiator) display a maximum at conversions of 1.5–3.0%. The limiting conversion in photopolymerization of molten pyrocatechol dimethacrylate at 25 and 40°C is 20%; for hydroquinone dimethacrylate at 95°C, it is approximately 10%. As the temperature rises from 25 to 40°C, the maximum reduced rate of photopolymerization of pyrocatechol dimethacrylate increases by a factor of 1.4.     

Synthesis,characterization, microstructure determination,thermal studies of poly (N-vinyl pyrrolidone-maleic anhydride-methyl methacrylate)

Synthesis of Poly (N-vinyl pyrrolidone-maleic anhydride-methyl methacrylate) terpolymer using azobisisobutyronitrile in 1,4-dioxan is described. The polymers with different composition were synthesized and characterized using FTIR, ¹HNMR, ¹³NMR, TGA and DSC techniques. The monomer-monomer interactions were studied using Finemann-Ross and Kelen-Tudos methods by calculating the reactivity ratio. The reactivity ratio r₁ and r₂ with respect to methyl methacrylate and N-vinylpyrrolidone-maleic anhydride complexomer are found to be 6.05 and 0.06 respectively. The study showed methyl methacrylate have higher reactivity than N-vinyl-2-pyrrolidone-maleic anhydride complex, i.e., the terpolymer contained methyl methacrylate in higher ratio. The thermal stability of poly (N-vinyl pyrrolidone-maleic anhydride-methyl methacrylate) was 165°C and the glass transition temperature was found to increase from 153°C to 182°C as MMA concentration increase. The studies indicate the activity of the polymer to inhibit bacterial growth is very poor.     

Polymerization of methyl methacrylate by Ziegler-Natta type catalyst systems: Fe(acac)3-AlEt2Br and Fe(acac)3-ZnEt2

The polymerization of methyl methacrylate was carried out with the following Ziegler-Natta type initiating systems: Fe(AcAc)₃-AlEt₂Br, Fe(AcAc)₃-ZnEt₂ (acac = acetyl acetonate). Both the catalyst systems are active under homogeneous conditions in benzene at 40°C for methyl methacrylate polymerization. The polymerization kinetics suggests that the average rate of polymerization was first order with respect to [monomer] for both the catalyst systems, and the overall activation energies were found to be 14.0 and 12.8 kcal mol ^?1.     

Synthesis of bio-based poly(methacrylates) using SG1-containing amphiphilic macroinitiators by nitroxide mediated miniemulsion polymerization

SG1-based amphiphilic macroinitiators were synthesized from oligoethylene glycol methyl ether methacrylate and 10 mol% acrylonitrile or styrene (as the controlling comonomer) to conduct the nitroxide mediated polymerization of bio-based methacrylic monomers (isobornyl methacrylate (IBOMA) and C13 alkyl methacrylate (C13MA)) in miniemulsion. The effect of the addition of surfactant (DOWFAX 8390), co-stabilizer (n-hexadecane) and different reaction temperatures (80, 90 and 100°C) on polymerization kinetics was studied. We found that the NMP of IBOMA/C13MA using amphiphilic macroalkoxyamines were most effective during miniemulsion polymerization (linear trend of M_n versus conversion and high latex stability) in presence of 2 wt% surfactant and 0.8 wt% co-stabilizer (relative to monomer) at 90°C. The effect of surfactant, co-stabilizer and temperature on particle size during the polymerization was studied and suggested a decrease in initial particle size with the addition of surfactant and co-stabilizer. Finally, the thermal properties of IBOMA/C13MA polymers, prepared by amphiphilic macroinitiators, were examined thoroughly, indicating a T_g in the range of −44°C < T_g < 109°C.     

Polar anchoring strengths of nematic liquid crystal on high-density polymer brush surfaces

ABSTRACT

Herein, the polar anchoring energy coefficient (A_θ) of nematic liquid crystal (NLC) was examined for high-density polymer brushes via capacitance measurements. The A_θ is 10^?4 J m^?2 for the brushes of poly(methyl methacrylate), poly(ethyl methacrylate) and poly(styrene). The value decreases to 10^?5 J m^?2 for poly(n-butyl methacrylate) and poly(hexyl methacrylate) with lower glass transition temperatures. However, each polymer brush displays a constant A_θ value over a temperature range of ?15°C to 90°C, which is hardly affected by the graft density and brush thickness. At 25°C, A_θ is 10 times greater than the corresponding azimuthal anchoring energy coefficient (A_φ); therefore, NLCs on polymer brushes can be preferentially aligned along the in-plane component of the applied field.     

Aqueous polymerization of methyl methacrylate catalyzed by corundum and characterization of the obtained polymers

The aqueous polymerization of methyl methacrylate (MMA) was studied using sodium bi-sulfite as initiator in the absence and presence of corundum (Al₂O₃). It was found that corundum has a catalytic effect on the polymerization reaction. The polymers obtained in the presence of corundum were found to have a wider molecular weight distribution than in its absence; this was deduced by thin-layer chromatographic analysis in a binary mixture (benzene: methanol 1:1.5 by volume) at 25°C. The apparent energy of activation was calculated between 40 and 50°C, and was found to be 4.50 × 10⁴ and 1.70 × 10⁴ J/mol in the absence and presence of 0.5 g corundum (type 600 grit)/105 mL of the reaction mixture, respectively.     

High pressure phase behavior and modeling of CO2–propyl acrylate and CO2–propyl methacrylate systems

High pressure phase behavior are obtained for CO₂–propyl acrylate system at 40, 60, 80, 100 and 120 °C and pressure up to 161 bar and for CO₂–propyl methacrylate systems at 40, 60, 80, 100 and 120 °C and pressure up to 166 bar. The solubility of propyl acrylate and propyl methacrylate for the CO₂–propyl acrylate and CO₂–propyl methacrylate systems increases as the temperature increases at constant pressure. The CO₂–propyl acrylate and CO₂–propyl methacrylate systems have continuous critical mixture curves that exhibit maximums in pressure at temperatures between the critical temperatures of CO₂ and propyl acrylate or propyl methacrylate. The CO₂–propyl acrylate and CO₂–propyl methacrylate systems exhibit type-I phase behavior with a continuous mixture critical curve.The experimental results for CO₂–propyl acrylate and CO₂–propyl methacrylate systems are modeled using both the statistical associating fluid theory (SAFT) and Peng–Robinson equations of state. A good fit of the data are obtained with SAFT using two adjustable parameters for CO₂–propyl acrylate and CO₂–propyl methacrylate systems and Peng–Robinson equation using one and two adjustable parameter for CO₂–propyl acrylate and CO₂–propyl methacrylate system.     

ESR spectra of poly(methacrylic acid) and poly(methyl methacrylate): Reinterpretation of the 9-line spectrum

The temperature dependence of the ESR spectra of poly(methacrylic acid) and poly-(methyl methacrylate) γ-irradiated at room temperature was studied between ?196°C and +25°C. The conventional 9-line spectrum was observed throughout this range with no significant spectral change, in contrast to the propagating radical ··· CH₂? °C(CH₃)COOR found in methacrylic acid monomer or barium methacrylate dihydrate irradiated at ?196°C. In addition, the irradiation of methacrylic acid monomer with a low dose at 0°C gave the same 13-line spectrum as that of the propagating radical obtained by the irradiation at ?196°C, while prolonged irradiation at 0°C gave the same conventional 9-line spectrum as that of poly(methacrylic acid) or poly(methyl methacrylate). The conventional 9-line spectrum has a much weaker 4-line component than that of the propagating radical. The difference comes from the surrounding matrix, and the conventional 9-line spectrum is well interpreted by introducing the concept of the distribution of the conformational angle in the irregular polymer matrix. From simulation of the ESR spectrum, it was found that the intensity of the 4-line component is very sensitive to the distribution, and that the observed 9-line spectrum is well reproduced assuming a Gaussian distribution (half-height width of 5–6°) around the most probable conformation which is nearly the same as that of the propagating radical, where the conformational angles of the two C? H_β bonds to the half-filled p-orbital are 55° and 65°.     

Polymerization of Methyl Methacrylate in the Presence of Imidazole Derivatives. Kinetics and Polymer Structure

The kinetics of the polymerization of methyl methacrylate (MMA) in the presence of imidazole (Im), 2-methylimidazole (2MIm), or benz-imidazole (BIm) in tetrahydrofuran (THF) at 15–40°C was investigated by dilatometry. The rate of polymerization, R_p , was expressed by R_p = k[Im] [MMA]², where k = 3.0 × 10^?6 L²/(mol² s) in THF at 30°C. The overall activation energy, E_a , was 6.9 kcal/mol for the Im system and 7.3 kcal/mol for the 2MIm system. The relation between logR_p and 1 T was not linear for the BIm system. The polymers obtained were soluble in acetone, chloroform, benzene, and THF. The melting points of the polymers were in the range of 258–280°C. The ¹H-NMR spectra indicated that the polymers were made up of about 58–72% of syndiotactic structure. The polymerization mechanism is discussed on the basis of these results.     

An unusual reaction polymerization in nitric acid medium

We are investigating an unusual reaction that occurs when methyl methacrylate (MMA) is kept in contact with concentrated nitric acid¹ (65% HNO₃, sp. gr. 1.41). Polymer of high molecular weight is formed, showing about one unit of methacrylic acid (MAA) per unit of MMA, when equilibrium is reached. The reaction depends on the temperature, the molar ratio MMA:HNO₃, and the reaction time. Although we also found polymer at temperatures in the range 50–70°C,² in this paper we only report the results when the temperature was kept between 25 and 40°C. Methacrylic acid (MAA) was found to homopolymerize under those mild conditions; its behavior was investigated. Although we also observed that polymer is formed with sulfuric acid (96%) and that acrylic acid polymerizes with both nitric and sulfuric acid at 20–30°C, we are limiting this article to the observed polymerizing action of nitric acid on methyl methacrylate and on methacrylic acid. Work proceeds on this matter in this laboratory.     

Semi‐micro reversed‐phase liquid chromatography for the separation of alkyl benzenes and proteins exploiting methacrylate‐ and polystyrene‐based monolithic columns

Monolithic columns were synthesized inside 1.02 mm internal diameter fused‐silica lined stainless‐steel tubing. Styrene and butyl, hexyl, lauryl, and glycidyl methacrylates were the functional monomers. Ethylene glycol dimethacrylate and divinylbenzene were the crosslinkers. The glycidyl methacrylate polymer was modified with gold nanoparticles and dodecanethiol (C₁₂). The separation of alkylbenzenes was investigated by isocratic elution in 60:40 v/v acetonitrile/water. The columns based on polystyrene‐co‐divinylbenzene and poly(glycidyl methacrylate)‐co‐ethylene glycol dimethacrylate modified with dodecanethiol did not provide any separation of alkyl benzenes. The poly(hexyl methacrylate)‐co‐ethylene glycol dimethacrylate and poly(lauryl methacrylate)‐co‐ethylene glycol dimethacrylate columns separated the alkyl benzenes with plate heights between 30 and 60 μm (50 μL min^?1 and 60°C). Similar efficiency was achieved in the poly(butyl methacrylate)‐co‐ethylene glycol dimethacrylate column, but only at 10 μL min^?1 (0.22 mm s^?1). Backpressures varied from 0.38 MPa in the hexyl methacrylate to 13.4 MPa in lauryl methacrylate columns (50 μL min^?1 and 60°C). Separation of proteins was achieved in all columns with different efficiencies. At 100 μL min^?1 and 60°C, the lauryl methacrylate columns provided the best separation, but their low permeability prevented high flow rates. Flow rates up to 500 μL min^?1 were possible in the styrene, butyl and hexyl methacrylate columns.     

Redox initiator systems for emulsion polymerization of acrylates

The performance of different redox initiator couples to initiate the emulsion polymerization of butyl acrylate at low temperature (40–50 °C) was investigated in both batch and seeded semibatch polymerizations. Polymerizations were carried out mimicking industrial conditions, that is, technical grade monomer and no N₂ purging was used during the polymerizations. The redox systems used contained as oxidants persulfates or hydroperoxides and as reducing agents ascorbic acid, formaldehyde sulfoxilate (SFS), tetramethyl ethylene diamine (TMEDA), Bruggolit 6 and 7 (FF6 and FF7), and sodium metabisulfites. Batch experiments showed that for systems using persulfates, the ammonium persulfate (APS)/TMEDA system provided the lower induction period and higher conversion, whereas for the systems with hydroperoxide oxidants, tert‐butyl hydroperoxide (TBHP)/FF7, TBHP/SFS, and H₂O₂/FF7 were the best alternatives. When these selected systems were used in seeded semibatch experiments of BA with allyl methacrylate, it was found that to obtain similar kinetics and microstructure (gel content and crosslinking density) than in case of using a thermal initiator at 80 °C, the polymerization could be run at 40 °C if the reactor was purged with N₂. Alternatively, in absence of N₂ polymerization, temperature should be increased to 50 °C and initiator concentration increased. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2917–2927, 2009     

Homo‐ and Copolymerization of Phenacyl Methacrylate via the Atom Transfer Radical Polymerization Method

The homo‐ and copolymers via atom transfer radical (co)polymerization (ATRP) of phenacyl methacrylate (PAMA) with methyl methacrylate (MMA) and t‐butyl methacrylate (t‐BMA) was performed in bulk at 90°C in the presence of ethyl 2‐bromoacetate, cuprous(I)bromide (CuBr), and 2,2′‐bipyridine. The polymerization of PAMA was carried out at 70, 80, and 100°C. Also, free‐radical polymerization of PAMA was carried out at 60°C. Characterization using FT‐IR and ¹³C‐NMR techniques confirmed the formation of a five‐membered lactone ring through ATRP. The in situ addition of methylmethacrylate to a macroinitiator of poly(phenacyl methacrylate) [Mn=2800, Mw/Mn=1.16] afforded an AB‐type block copolymer [Mn=13600, Mw/Mn=1.46]. When PAMA units increased in the living copolymer system, the Mn values and the polydispersities were decreased (1.1<Mw/Mn<1.79). The monomer reactivity ratios were computed using Kelen‐Tüdös (K‐T), Fineman‐Ross (F‐R) and Tidwell‐Mortimer (T‐M) methods and were found to be r₁= 1.17; r₂= 0.76; r₁=1.16; r₂=0.75 and r₁=1.18; r₂=0.76, respectively (r₁=is monomer reactivity ratio of PAMA). The initial decomposition temperatures of the resulting copolymers were measured by TGA. Blends of poly(PAMA) and poly(MMA) obtained via the ATRP method have been characterized by differential thermal and thermogravimetric analyses.     

Slow ester side‐group flips in glassy poly(alkyl methacrylate)s characterized by centerband‐only detection of exchange nuclear magnetic resonance

Slow side‐group dynamics in a series of five poly(alkyl methacrylate)s with various side‐group sizes [poly(methacrylic acid) (PMAA), poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), poly(isobutyl methacrylate) (PiBMA), and poly(cyclohexyl methacrylate), with ? H, ? CH₃, ? CH₂CH₃, ? CH₂CH(CH₃)₂, and ? cyclohexyl alkyl substituents (CODEX), respectively] were studied quantitatively by centerband‐only detection of exchange nuclear magnetic resonance (NMR). Flips and small‐angle motions of the ester groups associated with the β relaxation were observed distinctly in the CODEX NMR data, and the fraction of slowly flipping groups was measured with a precision of 3%. In PMMA, 34% of the side groups flipped on a 1‐s timescale, whereas the fraction was 31% in PEMA at 25 °C. Even the large isobutylether and cyclohexylester side groups flipped in the glassy state, although the flipping fraction was reduced to 22 and about 10%, respectively. In PMAA, no slow side‐group flips were detected on the 1‐s timescale. A striking difference in the temperature dependence of the flipping fraction in PMMA versus PEMA and PiBMA was observed. In PMMA, the flipping fraction was temperature‐independent between 25 and 80 °C, whereas in PEMA, it increased continuously from 31 to 60% between 25 and 60 °C. A similar doubling was also observed in PiBMA. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2444–2453, 2001     

Study of molecular deformation mechanisms in the glassy state. I. Temperature effect on stress-birefringence and strain-birefringence responses of poly(methyl methacrylate)

In order to gain better understanding of the molecular deformation processes occurring in poly-(methyl methacrylate), a series of studies was carried out in uniaxial tension on the simultaneous stress and birefringence response in both constant-strain-rate and stress relaxation experiments. The former covered the temperature range ?120 to 75°C and the latter 0 to 90°C. Three deformation mechanisms, i.e., (i) change in intermolecular distance, (ii) distortion of the conformation of the COOCH₃ group from its thermal equilibrium state, and (iii) orientation of main-chain segments, are invoked to interpret the experimental results. It is concluded that, in the temperature range from ?120 to 75°C and possibly at higher temperatures as well, the polymer chains deform in the small-strain region by an orientation of those chain segments having lower potential-energy barriers to conformational changes and straining those chain segments having higher potential-energy barriers. Subsequent chain orientation of the already strained segments occur in the higher strain regions. Changes in intermolecular distances occur over the entire temperature range from ?120 to 90°C, but their magnitude decreases gradually as the temperature increases from ?40 to 40°C and then decreases sharply for temperatures above 40°C. Strain-induced distortion of the conformation of the COOCH₃ group may involve only rotation of the OCH₃ group around the C? O bond rather than rotation of the entire ester group itself.     

Thermally latent synthesis of networked polymers from multifunctional hemiacetal ester and diepoxide catalyzed by Schiff‐base‐zinc chloride complex

Thermally latent reaction of a copolymer ( P1 ) bearing hemiacetal ester and n‐butyl methacrylate moieties and glycidyl phenyl ether ( 2 ) was catalyzed by bis(p‐methoxybenzylidene)‐1,2‐diiminoethane/zinc chloride complex (ZnCl₂/ 3 ) at 30–150 °C for 6 h. No reaction of P1 and 2 took place below 70 °C, and it smoothly proceeded above 120 °C. The latencies and activities mean that ZnCl₂/ 3 meets both the high latencies at ambient conditions and the high activities at desired temperatures. Thermal crosslinking reaction employing multifunctional derivatives was carried out using ZnCl₂/ 3 at 140 °C for 6 h to afford a networked polymer in high yields. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3682–3689, 2008