Poly(styrene-co-butyl acrylate)/mesoporous diatomaceous earth mineral nanocomposites by in situ AGET ATRP

Journal of Thermal Analysis and Calorimetry - Mesoporous diatomite platelets were used for in situ copolymerization of styrene and butyl acrylate by activators generated by electron transfer for...     

PMMA/organomodified montmorillonite nanocomposites prepared by in situ bulk polymerization

Kinetics of the in situ bulk polymerization of methyl methacrylate in the presence of organomodified montmorillonite (MMT) was investigated using differential scanning calorimetry (DSC) and gravimetrically. Different amount and types of MMT under the trade names Cloisite were employed. Using DSC, the amount of heat released versus time, under isothermal conditions, was recorded, and eventually, the time evolution of polymerization rate and monomer conversion was calculated. Results on the variation of monomer conversion with reaction time were in good agreement to corresponding from the gravimetric measurements. The nanocomposites prepared were characterized with WAXD, TEM and FTIR, and their glass transition temperature, T _g, was measured with DSC. Depending on the added amount of nano-MMT, either exfoliated or intercalated structures were obtained. An enhancement of the polymerization rate with the presence of the nanoparticles was observed especially in the gel effect region. This was accompanied by a higher T _g and average molecular weight, as measured by GPC, of all nanocomposites compared to neat PMMA.     

PMMA/MMT nanocomposites prepared by one-step in situ intercalative solution polymerization

Poly(methylmetacrylate)/montmorillonite (PMMA)/(MMT) nanocomposites were prepared by one-step in situ intercalative solution polymerization involving simultaneous modification of MMT with quaternary ammonium salts (QAS), polymerization and polymer intercalation. Polymerization proceeded at 70 °C in a mixture of ethanol and water, whereas the nanocomposite was precipitated with only water. Four QAS’s with different alkyl chain lengths, as well as a QAS with an additional acrylic group, were used to study the influence of the type of quaternary ammonium salt on intercalation. The largest extent of intercalation was achieved in nanocomposites with the QAS having one long alkyl (C16) chain. The obtained PMMA/MMT intercalated nanocomposites exhibited a higher glass transition temperature, better thermal stability, and improved solvent resistance than the pure PMMA.     

Preparation of Al(OH)3/PMMA nanocomposites by emulsion polymerization

Al(OH)₃/PMMA nanocomposites were prepared by the emulsion polymerization of methyl methacrylate (MMA) in the presence of surface‐functionalized Al(OH)₃ particles. Nanosized Al(OH)₃ particles were previously functionalized with a silane coupling agent, 3‐(trimethoxysilyl) propyl methacrylate (γ‐MPS), which was confirmed by FT‐IR and XRF analysis. The average size of seed particles was around 70 nm, and the density of the coupling agent on the particles was calculated to be 8.9 µmol m^?2. The emulsion polymerization was attempted at relatively high solid content of 40–46 wt%. The ratio of the seed particles to MMA had a strong influence on the stability of latex as well as the morphology of composites. Nanocomposites where several PMMA nodules were attached on the surface of Al(OH)₃ core were produced with stable latex emulsion when the weight percents of Al(OH)₃ to MMA were below 20. In the case of higher ratio of 30%, however, the latexes became unstable with an aggregation, and the product morphology was in the shape of large composite. Thermogravimetric analysis showed an improved thermal stability of PMMA composites with the incorporation of Al(OH)₃ nanoparticles. Copyright © 2008 John Wiley & Sons, Ltd.     

Polystyrene/mesoporous diatomite composites by in situ simultaneous reverse and normal initiation technique for atom transfer radical polymerization

Mesoporous diatomite platelets were employed to synthesize different polystyrene/diatomite composites by in situ polymerization of styrene via simultaneous reverse and normal techniques of atom transfer radical polymerization. Furrier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning and transmission electron microscopy, gas and size exclusion chromatography were used to examine characteristics of polymer and composite. Addition of 3 wt% pristine mesoporous diatomite leads to increase of conversion from 79 to 93%, while control over molecular weight characteristics become worse.     

PP/PMMA Block Copolymers by Combination of ATRP and Metallocene Catalysis

PP-b-PMMA has been synthesized by a combination of metallocene catalysis and the controlled radical polymerization technique ATRP. Cp₂ZrCl₂/MAO and (Me₄Cp)SiMe₂(N-tert-Bu)TiCl₂/MAO were used for the synthesis of atactic polypropylene. By a series of chemical modifications pp macroinitiators for the ATRP polymerization of MMA were synthesized. The PP-b-PMMA with polydispersities from 1.8–2.8 and an M_n ranging from 8 to 26 kg/mol was characterized by ¹H-NMR,SEC and DSC.     

Study on the PMMA/GO nanocomposites with good thermal stability prepared by in situ Pickering emulsion polymerization

Graphene oxide (GO) is used as a stabilizer in the Pickering emulsion polymerization of methyl methacrylate (MMA) to prepare PMMA/GO nanocomposites. Transmission electron microscope studies of the emulsion polymerization products showed that the average diameter of nanocomposite particles was about 150 nm, the transparent GO flakes covered the surface of the particles, and were well dispersed in polymer matrix. The influence of GO on the thermal stability of PMMA was investigated by thermogravimetry analysis and differential scanning calorimetry. The results showed that the thermal stability and the glass transition temperature (T _g) of PMMA/GO nanocomposites were improved obviously compared with PMMA. The apparent activation energy (E _a) for the degradation process of PMMA/GO nanocomposites was evaluated by Kissinger method, which indicated that their E _a s were much higher than those of PMMA both in nitrogen and air atmosphere.     

Preparation and characterization of polypropylene/mesoporous silica nanocomposites with confined polypropylene

Polypropylene (PP)/Ti-MCM-41 nanocomposites were prepared by isospecific propylene polymerization with Ti-MCM-41/Al(i-C₄H₉)₃ catalyst. The cross polarization/magic angle spinning (CP/MAS) ¹³C NMR spectrum of the composite was similar to that of the conventional isotactic PP, and the decrease in the pore volume of Ti-MCM-41 in the nanocomposites, as measured by N₂ adsorption, was consistent with the value calculated from the weight loss in the thermogravimetric analysis (TGA) curve; both these facts attest to propylene polymerization within the mesopores of Ti-MCM-41. Alkali treatment followed by extraction with o-dichlorobenzene allows us to extract the confined PP out of the Ti-MCM-41 mesopores. Although the PP/Ti-MCM-41 nanocomposites do not exhibit a crystalline melting point, the same PP when extracted from the mesopores showed a clear melting point at 154.7 °C; this indicates that the crystallization of PP confined in mesopores is strongly hindered. For the PP polymerized within the confinement, the molecular weight (M_w) and molecular weight distribution (M_w/M_n) were 84,000 and 4.3, respectively; these values were considerably smaller than those of the PP polymerized concurrently outside the Ti-MCM-41 mesopores (M_w = 200,000–450,000, M_w/M_n = 40–75). Therefore, the confinement also has a marked effect on the molecular weight of the PP. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3324–3332, 2003     

Glass‐transition temperature behavior of alumina/PMMA nanocomposites

Alumina/poly(methyl methacrylate) (PMMA) nanocomposites were synthesized by an in situ free‐radical polymerization process with 38 and 17 nm diameter γ‐alumina nanoparticles. At extremely low filler weight fractions (<1.0 wt % of 38 nm fillers or < 0.5 wt % of 17 nm fillers) the glass‐transition temperature (T_g) of the nanocomposites drops by 25 °C when compared to the neat polymer. Further additions of filler (up to 10 wt %) do not lead to additional T_g reductions. The thermal behavior is shown to vary with particle size, but this dependence can be normalized with respect to a specific surface area. The nanocomposite T_g phenomenon is hypothesized to be because of nonadhering nanoparticles that serve as templates for a porous system with many internal interfaces that break up the percolating structure of dynamically heterogeneous domains recently suggested by Long, D.; and Lequeux, F. Eur Phys J E 2001, 4, 371 to be responsible for the T_g reductions in polymer ultrathin films. The results also point to a far field effect of the nanoparticle surface on the bulk matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4371–4383, 2004     

Preparation and characterization of polypyrrole/magnetite nanocomposites synthesized by in situ chemical oxidative polymerization

This work describes the preparation and characterization of polypyrrole (PPy)/iron oxide nanocomposites fabricated from monodispersed iron oxide nanoparticles in the crystalline form of magnetite (Fe₃O₄) and PPy by in situ chemical oxidative polymerization. Two spherical nanoparticles of magnetite, such as 4 and 8 nm, served as cores were first dispersed in an aqueous solution with anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate to form micelle/magnetite spherical templates that avoid the aggregation of magnetite nanoparticles during the further preparation of nanocomposites. The PPy/magnetite nanocomposites were then synthesized on the surface of the spherical templates. Structural and morphological analysis showed that the fabricated PPy/magnetite nanocomposites are core (magnetite)‐shell (PPy) structures. Morphology of the PPy/magnetite nanocomposites containing monodispersed 4‐nm magnetite nanoparticles shows a remarkable change from spherical to tube‐like structures as the content of nanoparticles increases from 12 to 24 wt %. Conductivities of these PPy/magnetite nanocomposites show significant enhancements when compared with those of PPy without magnetite nanoparticles, in particular the conductivities of 36 wt % PPy/magnetite nanocomposites with 4‐nm magnetite nanoparticles are about six times in magnitude higher than those of PPy without magnetite nanocomposites. These results suggest that the tube‐like structures of 36 wt % PPy/magnetite nanocomposites may be served as conducting network to enhance the conductivity of nanocomposites. The magnetic properties of 24 and 36 wt % PPy/magnetitenanocomposites show ferromagnetic behavior and supermagnetism, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1291–1300, 2008     

Effect of nanoparticles on the thermal stability of PMMA nanocomposites prepared by in situ bulk polymerization

Al₂O₃ and ZnO filled poly(methyl methacrylate) nanocomposites were synthesized by free radical (bulk) polymerization. Efficient dispersion was achieved by predispersing the nanoparticles in propylene glycol methyl ether acetate (PGMEA) followed by ultrasonication of nanoparticles into the PMMA syrup. Thermal analysis confirms chemisorption between PGMEA and metal oxide particles. The addition of nanoparticle affects degradation mechanism and consequently improves thermal stability of PMMA. The reduction of polymer chain mobility and the tendency of nanoparticles to eliminate free radicals are the principal effects responsible for these enhancements.     

Polyethylene/graphite nanocomposites obtained by in situ polymerization

The synthesis of polyethylene/graphite nanocomposites by in situ polymerization was achieved using the catalytic system Cp₂ZrCl₂ (bis(cyclopentadienyl)zirconium(IV) dichloride)/methylaluminoxane (MAO). Graphite with nano dimensions, previously treated with MAO, was added into the reactor as filler at percentages of 1, 2, and 5% (w/w). XRD analysis showed that the chemical and thermal treatments employed preserve the structure of the graphite sheets. The formation of graphite nanosheets and nanocomposites was confirmed by TEM and AFM. TEM micrographics showed that the polyethylene grew between the graphene nanosheets, giving intercalated and exfoliated graphite nanocomposites. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 692–698, 2010     

Preparation of well-defined polystyrene/silica hybrid nanoparticles by ATRP

Immobilization of the atom transfer radical polymerization (ATRP) macroinitiators at the silica nanoparticle surfaces was achieved through surface modification with excess toluene-2,4-diisocynate (TDI), after which the residual isocyanate groups were converted into ATRP macroinitiators. Structurally well-defined polystyrene chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well-defined, densely grafted outer polystyrene by ATRP, which was initiated by the as-synthesized silica-based macroinitiator. FTIR, NMR and gel permeation chro-matography (GPC) were used to characterize the polystyrene/silica hybrid particles.     

ATRP/RAFT联用制备星型多臂共聚物 h-PCMS-g-PMMA-b-PBMA

以4-氯甲基苯乙烯(CMS)为单体,CuCl/2,2′-联吡啶(bpy)为催化体系,通过原子转移自由基聚合反应(ATRP)制得超支化聚4-氯甲基苯乙烯(h-PCMS);再采用黄原酸钾对h-PCMS表面的功能端基进行修饰,制得端基带有大量双硫酯基团的大分子链转移剂（h-PCMS macro-CTA）;通过可逆加成 断裂链转移聚合(RAFT)方法,以h-PCMS macro-CTA依次引发甲基丙烯酸甲酯(MMA)和甲基丙烯酸丁酯(BMA)聚合制备星型多臂聚合物h-PCMS-2300-g-PMMA-5500-b-PBMA-33000,分子量分布为1.6,其结构和性能经¹H NMR, IR, GPC和DSC表征。     

Preparation of mesoporous TiO2/CNT nanocomposites by synthesis of mesoporous titania via EISA and their photocatalytic degradation under visible light irradiation

Stabilized mesoporous TiO₂ was synthesized by evaporation induced self assembly (EISA) method and mechanically incorporated into single-walled carbon nanotubes (SWCNT) with different ratios. The physicochemical properties of the nanocomposites (mesoporous TiO₂/SWCNT) materials were investigated by Brunauer–Emmett–Teller (BET) measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), photoluminescence (PL) and ultraviolet–visible (UV–Vis) spectroscopy measurements. The catalytic activity of mesoporous TiO₂ and nanocomposites were assessed by examining the degradation of rhodamine B as model aqueous solution under visible light. CNTs are facilitating the photocatalytic activity of mesoporous TiO₂ in the degradation of rhodamine B efficiently.     

Preparation and characterization of carbon nanotubes-polymer/CdSe hybrid nanocomposites through combining electrostatic adsorption and ATRP technique

This paper describes a new strategy through noncovalent functionalization of multi-walled carbon nanotubes (MWNTs) by a kind of new copolymer Polyethyleneimine-graft-Polyacrylonitrile for attaching CdSe nanoparticles onto the MWNTs to fabricate Carbon Nanotube/CdSe heterostructures. Polyethyleneimine (PEI), an amino-rich cationic polyelectrolyte, can interact with the MWNTs through electrostatic interaction. Then, CNT/PEI-g-PAN was successfully prepared by in situ atom transfer radical polymerization (ATRP), which did not introduce defects to the structure of CNTs. Thus, CdSe nanoparticles can be covalently coupled to functionalized carbon nanotubes (CNTs) in a uniform and controllable manner. Moreover, this method ensures good dispersion and high stability in any commonly used organic or inorganic solvent. In this manner, our strategy allows the attachment of various colloidal nanoparticles to CNTs, independent of their surface properties, i.e. hydrophilic or hydrophobic. TEM, XRD, EDS and FT-IR are all used to characterize the CNT/CdSe composite materials. In addition, the optical properties are investigated by UV–vis spectrum.     

表面引发原子转移自由基聚合方法合成Fe3O4/PMMA复合纳米微粒

采用表面引发原子转移自由基聚合方法合成了核壳结构的磁性高分子纳米微粒. 作为聚合反应引发剂的3-氯丙酸, 首先与油酸修饰的Fe3O4纳米微粒表面的部分油酸置换, 然后在Fe3O4纳米微粒表面引发甲基丙烯酸甲酯聚合, 合成的纳米复合材料用TEM, FTIR, XRD和DSC表征. 磁性测试结果表明, 所制备的磁性高分子纳米微粒仍具有超顺磁性, 但由于聚合物的存在, 其饱和磁化强度降低.     

Well-defined nanofiberous polystyrene nanocomposites with twofold chains by ATRP

Polystyrene nanocomposites, being a combination of nanoclay-attached and free polystyrene chains were prepared using in situ atom transfer radical polymerization. Subsequently, they were electrospun to form fibers with diameter varying from 450?C700 nm according to scanning electron microscopy data; in addition, the transmission electron microscopy and x-ray diffraction analysis revealed that nanoclay layers were oriented along the nanofiber axis during the electrospinning process. Molecular weight of the extracted free polymer chains from the nanocomposites is higher than the attached chains. However, Anchored chains are characterized by higher polydispersity index in comparison with the free ones. Polydispersity index of polymer chains increases by the addition of nanoclay. Thermogravimetric analysis results shows that increasing clay content leads to a decrease in the quantity of polymer chains attached to the clay surface.     

Preparation and characterization of polymer/silica nanocomposites via double in situ miniemulsion polymerization

Polymer/SiO₂ nanocomposite microspheres were prepared by double in situ miniemulsion polymerization in the presence of methyl methacrylate, butyl acrylate, γ‐methacryloxy(propyl) trimethoxysilane, and tetraethoxysilane (TEOS). By taking full advantage of phase separation between the growing polymer particles and TEOS, inorganic/polymer microspheres were fabricated successfully in a one‐step process with the formation of SiO₂ particles and the polymerization of organic monomers taking place simultaneously. The morphology of nanocomposite microspheres and the microstructure, mechanical properties, thermal properties, and optical properties of the nanocomposite films were characterized and discussed. The results showed that hybrid microspheres had a raspberry‐like structure with silica nanoparticles on the shells of polymer. The silica particles of about 20 nm were highly dispersed within the nanocomposite films without aggregations. The transmittance of nanocomposite film was comparable to that of the copolymer film at around 70–80% from 400 to 800 nm. The mechanical properties and the fire‐retardant behavior of the polymer matrix were improved by the incorporation of silica nanoparticles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3128–3134, 2010     

The disorderly exfoliated LDHs/PMMA nanocomposites synthesized by in situ bulk polymerization: The effects of LDH-U on thermal and mechanical properties

The disorderly exfoliated layered double hydroxides/poly(methyl methacrylate) (LDHs/PMMA) nanocomposites were obtained in a two-stage process by the in situ bulk polymerization of methyl methacrylate (MMA) in the presence of 10-undecenoate intercalated LDH (LDH-U). The dispersed behavior of the LDH-U in the PMMA matrix was identified by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV/visible transmission spectroscopy. All these nanocomposites showed significantly enhancement of glass transition temperature (T_g) and the decomposition temperatures compared to pristine PMMA, as identified in differential scanning calorimetry (DSC) and thermogravimetric (TGA) analysis. The tensile modulus of these nanocomposites was also enhanced by incorporating the LDH-U into the PMMA matrix and increased as the amount of LDH-U increased. According to the analytical method of Ozawa-Flynn, the degradation activation energies of these nanocomposites are higher than that of pristine PMMA.