Poly(methyl acrylate-co-methyl methacrylate)/montmorillonite nanocomposites fabricated by soap-free emulsion polymerization

The exfoliated poly(methyl acrylate-co-methyl methacrylate)/montmorillonite (MMT) nanocomposite latex solutions fabricated by soap-free emulsion polymerization were able to cast into a film. The films were transparent and ductile unless more than 5 wt% of MMT was incorporated. With the MMT content higher than 5 wt%, the inflammable residuals of nanocomposites after combustion could preserve their original film profile acting like an inflammable scaffold. Moreover, as 20 wt% MMT was incorporated, the yield strength of the films was increased up to 20 times and Young’s modulus up to 2,000 times. However, the water vapor permeability coefficient of the films was only decreased down to its half value. This unexpected behavior of permeability was associated with the decrease of T _g as the content of MMT was increased, owing to the large difference of the reactivity ratios between methyl acrylate and methyl methacrylate monomers and their differential absorption to the MMT during copolymerization.     

Synthesis of poly(methyl methacrylate)-silica nanocomposites using methacrylate-functionalized silica nanoparticles and RAFT polymerization

Well-defined poly(methyl methacrylate)-silica nanocomposites were produced by “grafting through” using reversible addition-fragmentation chain transfer (RAFT) polymerization. The surface of silica nanoparticle was modified covalently by attaching methacryl group to the surface using 3-methacryloxypropyldimethylchlorosilane. Polymerization of methyl methacrylate (MMA) using the 4-cyano-4-(dodecylsulfanylthiocarbonyl)sulfanyl pentanoic acid RAFT agent, produced the PMMA-SiO₂ nanocomposites. Characterization of these well-defined nanocomposites included FT-IR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), transmission electron microscopy (TEM) and dynamic mechanical analysis. These results show that the T_g values are higher and the mechanical strength of the PMMA-SiO₂ nanocomposites is slightly improved when compared to bulk PMMA. Further, the molecular weight of the PMMA (up to M_n = 100,000) is controlled and the SiO₂ are well dispersed in the PMMA matrix.     

Characterization and Properties of Poly(methyl methacrylate)/Graphene,Poly(methyl methacrylate)/Graphene Oxide and Poly(methyl methacrylate)/p-Phenylenediamine-Graphene Oxide Nanocomposites

In this study, poly(methyl methacrylate)/p-phenylenediamine-graphene oxide, poly(methyl methacrylate)/graphene, and poly(methyl methacrylate)/graphene oxide nanocomposite series were prepared using simple solution blending technique. In poly(methyl methacrylate)/p-phenylenediamine-graphene oxide series, graphene oxide modified with p-phenylenediamine was used to improve its dispersion and interfacial strength with matrix. Morphology study of poly(methyl methacrylate)/p-phenylenediamine-graphene oxide nanocomposite revealed better dispersion of p-phenylenediamine-graphene oxide flakes and gyroid patterning of poly(methyl methacrylate) over the filler surface. Due to nonconducting nature of graphene oxide, there was no significant variation in the thermal or electrical conductivity of these nanocomposites. Thermal conductivity of poly(methyl methacrylate)/p-phenylenediamine-graphene oxide 1.5 was 1.16 W/mK, while the electrical conductivity was found to be 2.3 × 10^?3 S/cm.     

Surface mechanical properties of transparent poly(methyl methacrylate)/zirconia nanocomposites prepared by in situ bulk polymerization

Poly(methyl methacrylate)/zirconia (PMMA/ZrO₂) nanocomposites with ZrO₂ content as high as 15 wt% were prepared by modifying non-aqueous synthesized ZrO₂ nanoparticles with methacryloxypropyltrimethoxysilane (MPS) in tetrahydrofuran, dispersing MPS-functionalized ZrO₂ nanoparticles in MMA and following in situ bulk polymerization with controlled pre-polymerization time. The MPS-functionalized ZrO₂ nanoparticles showed an efficient crosslinking role in the polymerization, leading to a complete gel of PMMA at 5 wt% of ZrO₂ content. Homogeneous dispersion of the ZrO₂ nanoparticles at primary particle size level was observed in all nanocomposites, which results in good clarity of the obtained nanocomposites. Hardness tests (pendulum hardness tests and indentation tests) and anti-scratch tests (abrasion tests and nano scratch tests) were employed to probe the surface mechanical properties of the nanocomposites. The properties of nanocomposites as a function of ZrO₂ content, revealing from various characterization techniques, are not consistent and discussed in detail. At low ZrO₂ content, the mechanical properties are enhanced by the formed crosslinking structure. However, remarkable improvements of hardness and scratch resistance of PMMA were achieved when 15 wt% of ZrO₂ content was embedded.     

Poly(methyl methacrylate)/POSS hybrid networks by type II photoinitiated free radical polymerization

A new strategy for organic–inorganic hybrid networks is presented through in‐situ Type II photoinitiated polymerization of methyl methacrylate with diethanolamino‐functionalized polyhedral oligomeric silsesquioxanes (POSS‐DEA). The diethanolamino groups are simply incorporated onto POSS nanoparticles by nucleophilic ring‐opening reaction of commercially available epoxycyclohexyl POSS and diethanol amine. The photoinitiated polymerization of methyl methacrylate in the presence of benzophenone as photosensitizer and POSS‐DEA as hydrogen donor leads to poly(methyl methacrylate) (PMMA)/POSS hybrid networks under UV light irradiation. The morphology and thermal properties of hybrid networks are investigated by using Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and transmission electron microscopy. The morphology results confirm that POSS cages are homogeneously distributed in PMMA matrix at the molecular levels, whereas the thermal analyses shows that the obtained hybrid networks have higher glass transition temperatures and better thermal stabilities compared to parent PMMA homopolymer. POLYM. COMPOS., 35:1614–1620, 2014. © 2013 Society of Plastics Engineers     

Synthesis and characterization of poly(methyl methacrylate)/montmorillonite nanocomposites by in situ bulk polymerization

Poly(methyl methacrylate)/montmorillonite (MMT) nanocomposites were prepared by in situ bulk polymerization. The results showed that the silicone coupling agent affected the structure and properties of hybrid materials. XRD analysis showed that the dispersion of clay in nanocomposites with silicone‐modified organophilic MMT was more ordered than that in nanocomposites with unmodified organophilic MMT. The glass transition temperature (T_g) of the nanocomposites was 6–15°C higher and the thermal decomposition temperature (T_d) was 100–120°C higher than those of pure PMMA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2256–2260, 2003     

Suspension polymerization of poly(methyl methacrylate)/clay nanocomposites

Polymer/clay nanocomposites (PCNs) of poly(methyl methacrylate) and an organically modified clay, Cloisite 15a, were synthesized in situ with a suspension polymerization technique. The amount of clay present in the PCNs was varied to provide a better understanding of the effect of the clay on the properties of the polymer matrix. However, unexpectedly, we found that the concentration of clay had a dramatic impact on the molecular weight of the polymer matrix, and a relationship between the clay concentration and polymer molecular weight was determined. The PCNs were characterized with size exclusion chromatography (SEC), X‐ray diffraction, transmission electron microscopy, and oscillatory shear rheology. From oscillatory shear rheology, the full master curves for the PCNs were obtained by application of the time–temperature superposition principle. To enable the effect of the clay on the rheology to be quantified, the experimental data was compared to the time‐dependent diffusion model of des Cloizeaux for polydisperse polymer melts, which enabled the polydispersity to be incorporated through the use of the molecular weight distribution obtained via SEC. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(ε-caprolactone)/clay nanocomposites prepared by melt intercalation: mechanical, thermal and rheological properties

(Nano)composites of poly(ε-caprolactone) (PCL) were prepared by melt blending the polymer with natural Na⁺ montmorillonite and montmorillonite modified by hydrogenated tallowalkyl (HTA)-based quaternary ammonium cations, such as dimethyl 2-ethylhexyl HTA ammonium and methyl bis(2-hydroxyethyl) HTA ammonium. Microcomposites or nanocomposites were prepared depending on whether neat or modified montmorillonites was used, as assessed by X-ray diffraction and transmission electron microscopy. Mechanical and thermal properties were studied as a function of the filler content by tensile testing, Izod impact testing, thermogravimetric analysis and differential scanning calorimetry. The rheological behaviour at 80 °C was also analysed in relation to the structure and content of the layered silicate. Effect of exfoliated silicates on the mechanical properties, thermal stability and flame resistance of PCL was considered. Stiffness and thermal stability improved with the filler loading until a content of 5 wt%. Further loading resulted in the levelling off and possibly in a decrease of these properties. A marked charring effect was observed upon exposure to a flame.     

Synthesis and properties of poly(methyl methacrylate)/montmorillonite (PMMA/MMT) nanocomposites

PMMA/MMT nanocomposites were successfully synthesized via in situ intercalative polymerization, and characterized by means of wide‐angle X‐ray diffractometry, transmission electron microscopy, thermal gravimetric analysis, dynamic mechanical analysis and Fourier‐transform infrared analysis. The nanocomposites possess partially exfoliated and partially intercalated structure, in which the silicate layers are exfoliated into nanometre secondary particles with thickness of less than 20 nm and uniformly dispersed in the polymer matrix. In comparison with pure PMMA, the thermal stability, glass transition temperature, and mechanical properties of the polymer are notably improved by the presence of the nanometric silicate layers. It was found that part of the PMMA chains in the nanocomposites are well immobilized inside and/or onto the layered silicates and, therefore, the unique properties of the nanocomposites result from the strong interactions between the nanometric silicate layers and the polymer chains. Copyright © 2003 Society of Chemical Industry     

Different composition poly(methyl methacrylate-co-butyl methacrylate) copolymers through seeded semi-batch emulsion polymerization

In the present work the synthesis and the chemical and thermal characterization of poly(methyl methacrylate-co-butyl methacrylate) copolymer, in three different macromolecular compositions, are reported. The aim of the present work was the identification of a standard method to obtain copolymers with controlled macromolecular composition, molecular weights and particle size distribution, together with the identification of the effect of the macromolecular composition on the material properties. A monomer-starved seeded semi-batch emulsion reaction was carried out and optimized, monitoring the kinetic of the copolymerization through the evaluation of residual monomer amounts. Then, an evaluation of the macromolecular composition was performed by Fourier transform infrared spectroscopy analysis. Molecular weight, molecular weight distribution, latex characteristics and thermal behaviour were also investigated.     

Effect of Clay Type on Structure and Properties of Poly(methyl methacrylate)/Clay Nanocomposites

Summary: PMMA nanocomposites using natural Cloisite 6A and synthetic Lucentite SPN clays were produced via melt blending. The degree of intercalation or exfoliation was measured for both composites using transmission electron microscopy (TEM) and the results were confirmed with small angle X‐ray scattering (SAXS). The smaller dimensions of the synthetic SPN, as well as the complete absence of Fe ion impurities allowed for the production of a composite which was optically clear and completely colorless. TEM and SAXS measurements were performed on samples heated to high temperatures. The data showed that in both cases large ribbons composed of the individual platelets were formed. We postulated that these ribbons formed a barrier against spreading of the flame and hence the smaller clays, which are more mobile, had a higher efficiency.

TEM image of a high degree of exfoliation of synthetic clay SPN in the PMMA matrix.     

Electrospinning of cyclodextrin functionalized poly(methyl methacrylate) (PMMA) nanofibers

Cyclodextrin functionalized PMMA nanofibers (PMMA/CD) were successfully produced by electrospinning technique with the goal to develop functional nanowebs. Bead-free uniform electrospun PMMA/CD nanofibers were obtained from a homogeneous solution of CDs and PMMA in dimethylformamide (DMF) using three different types of CDs, α-CD, β-CD and γ-CD. The electrospinning conditions were optimized in order to form bead-free PMMA/CD nanofibers by varying the concentrations of PMMA and CDs in the solutions. The concentration of CDs was varied from 5% up to 50% w/w, with respect to the PMMA matrix. We find that the presence of the CDs in the PMMA solutions facilitates the electrospinning of bead-free nanofibers from the lower polymer concentrations and this behavior is attributed to the high conductivity and viscosity of the PMMA/CD solutions. The X-ray diffraction (XRD) spectra of PMMA/CD nanowebs did not show any significant diffraction peaks indicating that the CD molecules are homogeneously distributed within the PMMA matrix and does not form any phase separated crystalline aggregates. Furthermore, attenuated total reflection Fourier transform infrared (ATR-FTIR) studies elucidate that some CD molecules are located on the surface of the nanowebs. This suggests that these CD functionalized nanowebs may have the potential to be used as molecular filters and/or nanofilters for waste treatment purposes.     

聚甲基丙烯酸甲酯／纳米SiO2复合粒子的制备与表征

采用甲基丙烯酸-3-甲氧基硅丙酯（MPs）对分散于甲基丙烯酸甲酯（MMA）中的纳米SiO2粒子进行偶联改性，得到了表面改性的纳米SiO2单体分散液，用原位悬浮聚合方法制备了不同SiO2含量的PMMA／纳米SiO2复合粒子。通过红外光谱、透射电镜、差示扫描量热分析和热重分析等方法对制备的纳米复合粒子进行了表征，结果表明，纳米SiO2粒子在PMMA中分散良好；MMA可通过与MPS的共聚而有效地接枝到SiO2粒子表面，当SiO2含量为6．6％（质量分数，下同）、MPS用量为0．06g／gSiO2时，其接枝率可达73．8％；同时，纳米SiO2的引入可提高PMMA的耐热性能，当Si02含量为14.7％时，其玻璃化转变温度和最大热分解速率时的温度分别提高了11．8℃和18．8℃。     

Preparation of monodisperse poly(methyl methacrylate) particles by radiation-induced dispersion polymerization using vinyl terminus polysiloxane macromonomer as a polymerizable stabilizer

Monodisperse poly(methyl methacrylate) particles were prepared directly by radiation-induced dispersion polymerization in hexane-ethanol media using vinyl terminus polysiloxane (PSI) macromonmer as a polymerizable stabilizer at room temperature. This method takes advantage of the specialties of radiation-induction, which may result in the formation of uniform polymer particles. The gel effect is evident from the polymerization kinetics curves. Vinyl terminus PSI macromonomer acted as not only a comonomer, but also as a stabilizer. The characterization of PMMA particles was carried out by the scanning electron microscope (SEM), FT-IR, ¹H-NMR and X-ray photoelectron spectroscope (XPS). XPS results show that the graft PSI macromonomers were anchored on the surface of PMMA particles to provide a steric stabilization to the PMMA particles.     

Efficiency of ligands in atom transfer radical polymerization of lauryl methacrylate and block copolymerization with methyl methacrylate

Atom transfer radical polymerization of lauryl methacrylate (LMA) was carried out in the presence of various ligands using ethyl-2-bromoisobutyrate as initiator and CuBr as catalyst in toluene at 95 °C. The ligands used were 2,2′-bipyridyl,4,4′-dimethyl-2,2′-bipyridyl, N,N,N′,N′,N″-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) (M_w/M_n≤1.2) were obtained. The first-order time-conversion plot showed the presence of termination in the presence of PMDETA. A linear first-order time-conversion 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.     

Preparation of gold nanoparticles on poly(methyl methacrylate) nanospheres with surface-grafted poly(allylamine)

A facile method for in situ anchoring of gold nanoparticles onto the surface of polymer nanospheres was successfully developed in this study. As polymer nanospheres, amphiphilic poly(methyl methacrylate) (PMMA)/poly(allylamine) (PAA) nanospheres were prepared by graft copolymerization of methyl methacrylate from PAA. The gold nanoparticles anchored were spherically symmetric and the average sizes were ∼12 nm for all samples. It was found that surface-grafted PAA effectively anchored and stabilized gold nanoparticles for a long period of time.     

Hot-drawing of poly(methyl methacrylate) and simulation using a glass-rubber constitutive model

The large-deformation three-dimensional glass-rubber constitutive model for isotropic, amorphous, linear polymers near the glass transition, previously proposed, has been extended to include a spectrum of network relaxations. In addition, an experimental programme of uniaxial tension and compression tests was carried out on high molecular weight cast sheets of poly(methyl methacrylate) (PMMA), with varying strain-rate and temperature across the range from 114 to 190 °C, encompassing the thermoforming range of practical importance. The extended model was found to fit successfully the data for PMMA, provided a doublet network relaxation spectrum was employed. The original model, with only a single network relaxation, was found to be grossly inadequate when there was significant network relaxation by entanglement slippage. Parameters of the model for PMMA, obtained by fitting to the new data, were compared with values obtained by other routes.     

Poly(ethylene-oxide)/clay/silica nanocomposites: Morphology and thermomechanical properties

Poly(ethylene-oxide) PEO/clay/silica nanocomposites were prepared via solution intercalation by exploiting phase separation based on the bridging of particles by polymer chains. The intercalated morphology of nanocomposites was confirmed by XRD. Vibrational modes of the ether oxygen of PEO in the hybrids are shifted due to the coordination of the ether oxygen with the sodium cations of clay and the H-bonding interactions of the ether oxygen with the surface silanols of hydrophilic fumed silica. Based on SEM, the overall density of nanoparticle aggregates in the interspherulitic region was observed to be higher compared to that inside spherulites. PEO/clay/silica hybrids show significant property improvements compared to PEO/clay hybrids and pure PEO. The system containing 10 wt.% clay and 5 wt.% silica has substantially higher modulus and much lower crystallinity compared to the 15 wt.% clay system. The physics behind the reinforcement effect and the reduction of crystallinity as a function of fumed silica loading is discussed based on the morphological characterization of the hybrids. Lastly, PEO/clay/silica hybrids display good thermal stability and are much stiffer compared to pure PEO and PEO/clay nanocomposites.     

抗聚结MBS的制备及性能

通过分子结构设计,合成了一系列提高MBS粉末特性的包裹剂,研究了抗聚结新型MBS的制备工艺以及包裹剂化学结构对MBS粉末特性及PVC／MBS共混物力学性能的影响。结果表明,加入包裹剂后,MBS粉末流动性及其堆积密度均有较大提高,而且显著提高PVC／MBS共混物的抗冲强度和抗拉强度。     

Poly(methyl methacrylate)-block-polysulfide-block-poly(methyl methacrylate) copolymers obtained by free-radical polymerization combined with oxidative coupling

Summary Poly(methyl methacrylate)-block-polysulfide-block-poly(methyl methacrylate) copolymers were synthesized for the first time through a new method involving the free radical polymerization of MMA in the presence of a thiocol oligomer as a chain transfer agent, followed by chemical oxidation of the remaining SH end-groups. The chain transfer constant of the SH end-groups of the thiocol was estimated from the rate of consumption of the thiol groups versus the rate of consumption of the monomer (C_T=0.67). The triblock copolymers synthesized were characterized by SEC and ¹H NMR measurements.