Synthesis and interfacial properties of a novel inverse demulsifier of nanosized poly[(methyl methacrylate)-co-(ethyl acrylate)-co-(methacrylic acid)-co-(acrylamide)] latex

An acrylic emulsion-type inverse demulsifier (named as PMEMA latex) was prepared by using methyl methacrylate (MMA), ethyl acrylate (EA), methacrylic acid (MAA), and acrylamide (AM) as monomers. The effects of reaction conditions toward the copolymerization results were investigated by evaluating various evaluation parameters, including conversion, molecular weight, and diameter. In addition, the interfacial properties of PMEMA latex were investigated to study its demulsification mechanism about treating the O/W emulsion.     

Synthesis of core/shell structure of glycidyl–functionalized poly(methyl methacrylate) latex nanoparticles via differential microemulsion polymerization

The differential microemulsion polymerization technique was used to synthesize the nanoparticles of glycidyl-functionalized poly(methyl methacrylate) or PMMA via a two-step process, by which the amount of sodium dodecyl sulfate (SDS) surfactant required was 1/217 of the monomer amount by weight and the surfactant/water ratio could be as low as 1/600. These surfactant levels are extremely low in comparison with those used in a conventional microemulsion polymerization system. The glycidyl-functionalized PMMA nanoparticles are composed of nanosized cores of high molecular weight PMMA and nano-thin shells of the random copolymer poly[(methyl methacrylate)-ran-(glycidyl methacrylate)]. The particle sizes were about 50 nm. The ratios of the glycidyl methacrylate in the glycidyl-functionalized PMMA were achieved at about 5–26 wt.%, depending on the reaction conditions. The molecular weight of glycidyl-functionalized PMMA was in the range of about 1 × 10⁶ to 3 × 10⁶ g mol⁻¹. The solid content of glycidyl-functionalized PMMA increased when the amount of added glycidyl methacrylate was increased. The glycidyl-functionalized polymer on the surface of nano-seed PMMA nanoparticles was a random copolymer which was confirmed by ¹H-NMR spectroscopy. The amounts of functionalization were investigated by the titration of the glycidyl functional group. The structure of the glycidyl-functionalized PMMA nanoparticles was investigated by means of TEM. The glycidyl-functionalized PMMA has two regions of T_g which are at around 90 °C and 125 °C, respectively, of which the first one was attributed to the poly[(methyl methacrylate)-ran-(glycidyl methacrylate)] and the second one was due to the PMMA. A core/shell structure of the glycidyl-functionalized PMMA latex nanoparticles was observed.     

Synthesis and characterization of poly[(methylsilylene ethynylenephenyleneethynylene)-co-(dimethylsilylene ethynylenephenyleneethynylene)]s

<正>A series of poly[(methylsilylene ethynylenephenyleneethynylene)-co-(dimethylsilylene ethynylenephenyleneethynylene)]s were synthesized by the incorporation of various ratios of methylsilylene to dimethylsilylene units into the polymer chain backbone.The resultant copolymers were soluble in a variety of common organic solvents at room temperature.The copolymers were characterized by FT-IR,~1H-NMR,GPC,rheological analysis,differential scanning calorimetry(DSC) and thermogravimetric analysis(TGA).The results showed that the copolymers exhibited good processability and cured at low temperatures like 200℃.The curing reactions involved in hydrosilylation of Si—H and alkyne groups and the polymerization of alkynes.Y_(d5)(5%weight loss) of the cured copolymers ranged from 629℃to 686℃,and the decomposition residues of cured copolymers at 1000℃ranged from 88.1%to 90.9%under nitrogen.Thermal stability of the copolymers increased with the introduction of methylsilylene units into polymer chains.The cured copolymers were sintered at 1450℃,and the results of X-ray diffraction analysis showed that β-SiC was formed in the sintered products.     

Synthesis and characterization of poly (n-butyl acrylate)-poly (methyl methacrylate) latex interpenetrating polymer networks by radiation-induced seeded emulsion polymerization

A series of latex interpenetrating polymer networks (LIPNs) were prepared via a two-stage emulsion polymerization of methyl methacrylate (MMA) or mixture of MMA and n-butyl acrylate (n-BA) on crosslinked poly(n-butyl acrylate)(PBA) seed latex using ⁶⁰Co γ-ray radiation. The particles of resultant latex were produced with diameters between 150 and 250 nm. FTIR spectra identified the formation of crosslinked copolymers of PMMA or P(MMA-co-BA). Dynamic light scattering (DLS) showed that with increasing n-BA concentration in second-stage monomers, the particle size of LIPN increased. Transmission electron microscope(TEM) photographs showed that the morphology of resultant acrylate interpenetrating polymer network (IPN) latex varied from the distinct core-shell structure to homogenous particle structure with the increase of n-BA concentration, and the morphology was mainly controlled by the miscibility between crosslinked PBA seed and second-stage copolymers and polarity of P(MMA-co-BA)copolymers. In addition, differential scanning calorimeter (DSC) measurements indicated the existence of reinforced miscibility between PBA seed and P(MMA-co-BA)copolymer in prepared LIPNs.     

Conjugation of bioactive groups to poly(lactic acid) and poly[(lactic acid)-co-(glycolic acid)] films

A novel PLA-based polymer containing reactive pendent ketone or hydroxyl groups was synthesized by the copolymerization of L-lactide with epsilon-caprolactone-based monomers. The polymer was activated with NPC, resulting in an amine-reactive polymer which was then cast into thin polymeric films, either alone or as part of a blend with PLGA, before immersion into a solution of the cell adhesion peptide GRGDS in PBS buffer allowed for conjugation of GRGDS to the film surfaces. Subsequent 3T3 fibroblast cell adhesion studies demonstrated an increase in cellular adhesion and spreading over films cast from unmodified PLGA. Hence the new polymer can be used to obtain covalent linkage of amine-containing molecules to polymer surfaces.     

End-functional poly(methyl methacrylate)s via group transfer polymerization

Hydroxyl-, amine-, and lactone-end-functional poly(methyl methacrylate)s (PMMA) were prepared with controlled molecular weights and M_w/M_n = 1.06–1.19 via group transfer polymerization. This was achieved by the electrophilic termination of silyl ketene acetal ended PMMAs with benzaldehyde, N-trimethylsilyl benzaldimine, and 5,6-dihydro-2H-pyran-2-one, respectively. The number-average degree of functionalization, as determined by NMR/SEC, was in the range of 0.70–0.85. A Lewis acid was used for terminating silyl ketene acetal ended PMMA with N-trimethylsilyl benzaldimine, whereas tetra-n-butyl ammonium bibenzoate was used in the case of benzaldehyde and 5,6-dihydro-2H-pyran-2-one. MALDI-TOF MS analysis of the end-functional polymers indicated the competing formation of cyclic end groups due to a back-biting reaction along with end-functional PMMAs. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2514–2531, 2007     

Synthesis of poly(methyl methacrylate) nanocomposites via emulsion polymerization using a zwitterionic surfactant

The synthesis of nanocomposites via emulsion polymerization was investigated using methyl methacrylate (MMA) monomer, 10 wt % montmorillonite (MMT) clay, and a zwitterionic surfactant octadecyl dimethyl betaine (C18DMB). The particle size of the diluted polymer emulsion was about 550 nm, as determined by light scattering, while the sample without clay had a diameter of about 350 nm. The increase in the droplet size suggests that clay was present in the emulsion droplets. X-ray diffraction indicated no peak in the nanocomposites. Transmission electron microscopy showed that emulsion polymerization of MMA in the presence of C18DMB and MMT formed partially exfoliated nanocomposites. Differential scanning calorimetry showed an increase of 18 degrees C in the glass transition temperature (Tg) of the nanocomposites. A dynamic mechanical thermal analyzer also verified a similar Tg increase, 16 degrees C, for the partially exfoliated nanocomposites over poly(methyl methacrylate) (PMMA). Thermogravimetric analysis indicated a 37 degrees C increase in the decomposition temperature for a 20 wt % loss. A PMMA nanocomposite with 10 wt % C18DMB-MMT was also synthesized via in situ polymerization. This nanocomposite was intercalated and had a Tg 10 degrees lower than the emulsion nanocomposite. The storage modulus of the partially exfoliated emulsion nanocomposite was superior to the intercalated structure at higher temperatures and to the pure polymer. The rubbery plateau modulus was over 30 times higher for the emulsion product versus pure PMMA. The emulsion technique produced nanocomposites of the highest molecular weight with a bimodal distribution. This reinstates that exfoliated structures have enhanced thermal and mechanical properties over intercalated hybrids.     

Synthesis of cross-linked poly(methyl methacrylate) via dispersion polymerization in supercritical carbon dioxide

Cross-linked poly(methyl methacrylate) particles were prepared via dispersion polymerization in supercritical carbon dioxide (scCO₂) using poly(heptadecafluorodecyl methacrylate) (PHDFDMA) and 2,2′-azobisisobutyronitrile as the dispersant and the initiator, respectively. The following chemicals were used as cross-linking agents: ethylene glycol dimethacrylate (EGDMA), 1,4-buthanediol di(meth)acrylate (1,4-BD(M)A), and trimethylolpropane trimethacrylate. PHDFDMA was synthesized by solution polymerization in scCO₂. We investigated the effect of the chemical structure, concentration of the cross-linking agents, reaction pressure, and CO₂ density on the morphology, the polydispersity, and the cross-linking density of polymer particles. The resulting polymer particle was characterized by field emission SEM, differential scanning calorimetry, and thermal gravimetric analysis. The cross-linked PMMA particles is more agglomerate as the cross-linking agent concentration increased and as pressure decreased at constant temperature. Glass-transition temperature (T _g) of the resulting polymer increased as the cross-linking agent increased with temperature and pressure increasing at the same CO₂ density. Decomposition temperature is slightly increased as 1,4-BDA concentration increased. From these results, we can confirm that the thermal stability of the polymer increased as the cross-linking agent and EGDMA is the best cross-linking agent in term of the thermal stability.     

Thermoresponsive copolymers of methacrylic acid and poly(ethylene glycol) methyl ether methacrylate

Copolymers of methacrylic acid (MAA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) were prepared and their cloud points in aqueous solution were studied as a function of comonomer ratio, solution pH, and presence of hydrophobic comonomers. Under acidic conditions, the cloud point falls below 0 °C for copolymers with between 25% to 60% ether content, because of the formation of hydrophobic H‐bonded ether–acid complexes. The cloud point also decreases with solution pH. For equivalent ether to acid ratios, the cloud point decreases with decreasing PEG chain length, because of the presence of a larger number of hydrophobic methyl and methacrylate groups. Similarly, the cloud point decreases upon incorporation of hydrophobic comonomers such as butyl, lauryl, or glycidyl methacrylates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6095–6104, 2005     

Synthesis and characterization of silica/poly (methyl methacrylate) nanocomposite latex particles through emulsion polymerization using a cationic azo initiator

Following a previous work (J. L. Luna-Xavier et al., Colloid Polym. Sci.279, 947 (2001)), silica-poly (methyl methacrylate) (PMMA) nanocomposite latex particles have been synthesized in emulsion polymerization using a cationic initiator, 2,2'-azobis (isobutyramidine) dihydrochloride (AIBA), and a nonionic polyoxyethylenic surfactant (NP30). Silica beads with diameters of 68, 230, and 340 nm, respectively, were used as the seed. Coating of the silica particles with PMMA was taking place in situ during polymerization, resulting in the formation of colloidal nanocomposites with a raspberry-like or a core-shell morphology, depending on the size and nature of the silica beads. The amount of surface polymer was quantified by means of ultracentrifugation and thermogravimetric analysis as extensively described in the first article of the series (see above reference). The influence of some determinant parameters such as the pH of the suspension, the initiator, silica, monomer, or surfactant concentration on the amount of coating polymer and on the efficiency of the coating reaction was investigated in details and discussed in light of the physicochemical properties of the seed mineral. Electrostatic attraction between the positive end groups of the macromolecules and the inorganic surface proved to be the driving force of the polymer assembly on the seed surface at high pH, while polymerization in adsorbed surfactant bilayers (so-called admicellar polymerization) appeared to be the predominant mechanism of coating at lower pH. Optimal conditions have been found to reach high encapsulation efficiencies and to obtain a regular polymer layer around silica.     

Synthesis and electrorheological response of nano-sized laponite stabilized poly(methyl methacrylate) spheres

Poly(methyl methacrylate) (PMMA) nanospheres were fabricated via surfactant-free Pickering emulsion polymerization, in which hydrophilic laponite clay was used to stabilize the emulsions of methyl methacrylate dispersed in distilled water. These synthesized PMMA nanoparticles, of which the surface is compactly wrapped by laponite clay, are observed, as confirmed by scanning electron microscopy and transmission electron microscope images. Fourier-transform infrared spectra and thermogravimetry analysis confirm the chemical composition, thermal property, and mass percent of the laponite located on the surface of PMMA particles. Finally, laponite-wrapped nano-sized PMMA spheres were adopted as an electrorheological material. By using an optical microscope, the chain-like structure was observed when an external electric field was applied. In addition, the ER performance was also examined via a rotational rheometer equipped with a high voltage generator.     

Production of nanoparticles of methyl methacrylate and butyl methacrylate copolymers by microemulsion polymerization in the presence of maleic acid terminated poly(N-acetylethylenimine) macromonomers as cosurfactant

In this study, MMA/BMA copolymer nanoparticles were synthesized in oil-in-water microemulsions that were stabilized by sodium dodecyl sulphate (SDS) and initiated by potassium persulphate KPS. Maleic acid terminated poly(N-acetylethylenimine) (PNAEI) with two different chain lengths was also included in the recipe, as a cosurfactant and a comonomer. FTIR and ¹H-NMR proved incorporation of the macromonomer in the structure. High polymerization yields were achieved upto 98%. The viscosity average molecular weights of the copolymers were in the range of 2.77-5.50 × 10⁵. The glass transition temperatures of these copolymers were between 50.0 and 63.9 °C. The average diameter of nanoparticles were in range of 40-96 nm. It was possible to produce nanoparticles smaller than 100 nm and with narrower size distributions by using much lower concentrations of SDS by including the macromonomers in the microemulsion polymerization recipe.     

多臂聚丙烯酸丁酯-b-聚甲基丙烯酸甲酯嵌段共聚物的合成及性能研究

采用电子转移再生催化剂原子转移自由基聚合(ARGET ATRP)制备了端羟基聚丙烯酸丁酯-b-聚甲基丙烯酸甲酯嵌段共聚物(HO-PBA-b-PMMA),在此基础上,与六亚甲基二异氰酸酯三聚体(N3390)反应,合成了多臂聚丙烯酸丁酯-b-聚甲基丙烯酸甲酯嵌段共聚物.通过凝胶渗透色谱(GPC)、核磁共振仪(1H-NMR)、傅里叶变换红外光谱计(FTIR)对聚合物的结构进行了表征,利用原子力显微镜(AFM)观察了其形貌,采用动态热机械分析仪(DMA)和万能拉伸机研究了聚合物的热性能、力学性能及多臂嵌段共聚物对PMMA的增韧性能.结果表明:成功制备了端羟基聚丙烯酸丁酯-b-聚甲基丙烯酸甲酯,以及多臂聚丙烯酸丁酯-b-聚甲基丙烯酸甲酯嵌段共聚物.在异氰酸酯基/羟基(NCO/OH)摩尔比为1.2/1时,制得的多臂嵌段共聚物相对分子质量最大,Mark-Houwink参数α值最小,表明此时三臂嵌段共聚物最多.多臂嵌段聚合物的拉伸强度和断裂伸长率比线型聚合物均有明显提高,且在NCO/OH摩尔比为1.2/1时达到最大,分别为7.6 MPa和73%.多臂嵌段聚合物具有更高的玻璃化转变温度(Tg).通过原子力显微镜(AFM)表明,多臂聚丙烯酸丁酯-b-聚甲基丙烯酸甲酯嵌段共聚物形成了以聚丙烯酸丁酯链段为核,聚甲基丙烯酸甲酯为壳的核壳结构.具有核壳结构的多臂聚丙烯酸丁酯-b-聚甲基丙烯酸甲酯嵌段共聚物对聚甲基丙烯酸甲酯有明显的增韧作用.     

Dynamics of adsorbed poly(methyl acrylate) and poly(methyl methacrylate) on silica

Deuterium NMR and modulated differential scanning calorimetry (MDSC) were used to probe the behavior of ultrathin adsorbed poly(methyl acrylate) (PMA). The spectra for the bulk methyl-labeled PMA-d₃ were consistent with the motions of the polymer segments being spatially homogeneous. For the polymers adsorbed on silica, multicomponent line shapes were observed. The segmental mobility of the surface polymers increased with increased adsorbed amounts. In contrast to the behavior of the polymers in bulk, the adsorbed lower-molecular-mass PMA-d₃ was less mobile than the adsorbed high-molecular-mass polymer. The presence of a polymer overlayer was sufficient to suppress the enhanced mobility of the more-mobile segments of the adsorbed (inner) polymer. MDSC studies on adsorbed poly(methyl methacrylate) showed that the glass-transition temperature of the thin polymer films increased and broadened compared to the behavior of the polymer in bulk. The presence of a motional gradient with the less-mobile segments near the solid-polymer interface and the more-mobile segments near the polymer-air interface was consistent with the experimental observations.     

Structure and properties of poly(methyl methacrylate) particles prepared by a modified microemulsion polymerization

Nanoscale poly(methyl methacrylate) (PMMA) particles were prepared by modified microemulsion polymerization. Different from particles made by traditional microemulsion polymerization, the particles prepared by modified microemulsion polymerization were multichain systems. PMMA samples, whether prepared by the traditional procedure or the modified procedure, had glass-transition temperatures (T_g's) greater than 120 °C and were rich in syndiotactic content (55–61% rr). After the samples were dissolved in CHCl₃, there were decreases in the T_g values for the polymers prepared by the traditional procedure and those prepared by the modified process. However, a more evident T_g decrease was observed in the former than in the latter; still, for both, T_g was greater than 120 °C. Polarizing optical microscopy and wide-angle X-ray diffraction indicated that some ordered regions formed in the particles prepared by modified microemulsion polymerization. The addition of a chain-transfer agent resulted in a decrease in both the syndiotacticity and T_g through decreasing polymer molecular weight. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 733–741, 2004     

Synthesis of monodisperse poly(methacrylic acid) microspheres by distillation-precipitation polymerization

Monodisperse poly(methacrylic acid) (PMAA) microspheres were prepared by distillation-precipitation polymerization in acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as initiator. The polymeric microspheres were formed simultaneously via a precipitation polymerization manner during the distillation of the solvent out of the reaction system in the absence of any surfactant and crosslinker. Monodisperse PMAA microspheres with spherical shape and smooth surface were synthesized with diameters ranging from 60 to 290 nm below the glass transition temperature of PMAA without any stabilizer. The particle size increased with increasing monomer concentration, which may be resulted from the higher molecular weight for the polymerization. To investigate the growth procedure of PMAA microspheres, the morphology of microspheres over the distillated acetonitrile volume was conducted by monitoring the morphologies with TEM. GPC and FTIR provide key insights into the particle growth mechanism. The PMAA microspheres may be formed by an internal contraction due to the marginal solvency of the continuous phase with the aid of the hydrogen-bonding interaction between the carboxylic acid unit, in which the particles were stabilized by the steric effect of the pendent chains and surface gel as well as the electrostatic repulsion from the carboxylic acid group.