Morphology and rheological properties of silica‐filled poly(carbonate)/poly(methyl methacrylate) blends

The effect of silica nanoparticles on the morphology and the rheological properties was investigated in the immiscible polymer blend poly(carbonate)/poly(methyl methacrylate) (PC/PMMA). In the melt state, the linear viscoelastic properties of the nanocomposite showed a reduction effect of the silica nanoparticles on the mobility of one of the polymer which is related to the state of distribution of the silica nanoparticles. Hydrophilic and hydrophobic silica particles were used to study particle migration and their effects on the morphology and it was shown that the distribution of the nanoparticles depends on the balance of interactions between the surface of the particles and the polymer components. The effect on the coarsening kinetics was investigated in both hydrophilic and hydrophobic silica‐filled blends. Compared to the hydrophilic silica, a better compatibilization can be obtained by introducing the hydrophobic silica particles at the PC/PMMA interface as the solid barrier. POLYM. ENG. SCI., 55:1951–1959, 2015. © 2014 Society of Plastics Engineers     

Synthesis and characterization of exfoliated poly(styrene-co-methyl methacrylate)/clay nanocomposites via emulsion polymerization with AMPS

A method was described for synthesis of exfoliated poly(styrene-co-methyl methacrylate)/clay nanocomposites through an emulsion polymerization with reactive surfactant, 2-acrylamido-2-methyl-1-propane sulfonic (AMPS) which made the polymer end-tethered on pristine Na-MMT.AMPS widened the gap between clay layers and facilitates comonomers penetrate into clay. Silicate layers affect the composition of comonomers, for example A0.3M10S10T5 showed the elevated composition of MMA end tethered on silicate when compared to the feed ratio and polar methyl methacrylate (MMA) was considered to have the stronger interaction with clay layers than styrene.The exfoliated structure of extracted nanocomposite was confirmed by XRD and transmission electron microscopy. The onset of thermal decomposition for nanocomposites shifted to a higher temperature than that for neat copolymer. The dynamic moduli of nanocomposites increase with clay content. Dynamic storage modulus and complex viscosity increased as the clay content increased. In low frequency region all prepared nanocomposites exhibited apparent low-frequency plateaus in the linear storage modulus. Complex viscosity showed shear-thinning behavior as the clay content increases.     

纳米TiO2/HPMC-PMMA-PBMA复合粒子的制备及表征

先用非离子型高聚物羟丙基甲基纤维素(HPMC)和阴离子表面活性剂十二烷基硫酸钠(SDS)对纳米TiO2进行表面处理，得到表面吸附有HPMC-SDS的纳米TiO2粒子，然后在其上接枝了甲基丙烯酸甲酯(MMA)和甲基丙稀酸丁酯(BMA)。通过正交实验，得出了吸附和接枝的最佳条件。采用透射电子显微镜(TEM)和红外光谱仪(FTIR)对复合粒子的性质进行了表征，利用热重分析仪对复合粒子的耐热性能进行了研究。     

ZrO2/聚甲基丙烯酸甲酯纳米复合物:制备及其在聚合物阵列中的分散（英文）

ZrO2/PMMA nanocomposite particles are synthesized through an in-situ free radical emulsion polymerization based on the silane coupling agent (Z-6030) modified ZrO2 nanoparticles, and the morphology, size and its distribution of nanocomposite particles are investigated. Scanning electron microscopy (SEM) images demonstrate that the methyl methacrylate (MMA) feeding rate has a significant effect on the particle size and morphology. When the MMA feeding rate decreases from 0.42ml·min-1 to 0.08ml·min-1 , large particles (about 200-550nm) will not form, and the size distribution become narrow (36-54nm). The average nanocomposite particles size increases from 34nm to 55nm, as the MMA/ZrO2 nanoparticles mass ratio increased from 4:1 to 16:1. Regular spherical ZrO2/PMMA nanocomposite particles are synthesized when the emulsifier OP-10 concentration is 2mg·ml-1. The nanocomposite particles could be mixed with VAc-VeoVa10 polymer matrix just by magnetic stirring to prepare the ZrO2 /PMMA/VAc-VeoVa10 hybrid coatings. SEM and atomic force microscopy (AFM) photos reveal that the distribution of the ZrO2 /PMMA nanocomposite particles in the VAc-VeoVa10 polymer matrix is homogenous and stable. Here, the grafted-PMMA polymer on ZrO2 nanoparticles plays as a bridge which effectively connects the ZrO2 nanoparticles and the VAc-VeoVa10 polymer matrix with improved comparability. In consequence, the hybrid coating with good dispersion stability is obtained.     

Preparation of Mesoporous Carbons from Acrylonitrile-methyl Methacrylate Copolymer/Silica Nanocomposites Synthesized by in-situ Emulsion Polymerization

Acrylonitrile-methyl methacrylate (AN-MMA) copolymer/silica nanocomposites were synthesized by in-situ emulsion polymerization initiated by 2,2'-azobis(2-amidinopropane) dihydrochloride absorbed onto colloidal silica particles, and the mesoporous carbon materials were prepared through carbonization of the obtained AN-MMA copolymer/silica nanocomposites, followed by HF etching. Thermogravimetric analysis of AN-MMA copolymer/silica nanocomposites showed that the carbon yield of copolymer was slightly decreased as silica particle incorporated. N₂ adsorption-desorption, scan electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the structure and morphology of the mesoporous carbon materials. Both SEM and TEM results showed that disordered mesopores were formed in the obtained carbon material mainly through templating effect of silica nanoparticles. The diameter of mesopores was mainly distributed in the range from 5 nm to 15 nm. The mean pore diameter and total pore volume of the material increased as the mass fraction of silica in the nanocomposites increased from 0 to 24.93%. The significant increase of the mean pore diameter and the decrease of surface area for the carbon material prepared from the nanocomposite with 24.93% silica were caused by partial aggregation of silica nanoparticles in the polymer matrix.     

Preparation and physical properties of transparent organic–inorganic nanohybrid materials based on urethane dimethacrylate

The aim of this study was to prepare transparent organic–inorganic nanohybrid materials with improved physical properties in comparison with the matrix polymer. Polymerizable silica nanoparticles were synthesized via the reaction of silanol groups on the surface of silica nanoparticles (particle diameter ≈ 12 nm) with isocyanate groups of 2‐(methacryloyloxy)ethyl isocyanate (MOI) in ethyl acetate. In addition, the matrix monomer, urethane dimethacrylate, was prepared by the reaction of an MOI isocyanate group with the hydroxyl group of 2‐hydroxyethyl methacrylate, and novel organic–inorganic nanohybrid materials were obtained at various silica contents with bulk polymerization. The surface treatment of the silica nanoparticles and preparation of the matrix monomer were carried out in a one‐pot reaction. The prepared hybrid materials retained high transparency, and the elastic modulus and surface hardness improved with increasing silica content. Moreover, the strength of the material containing 20 wt % silica was up to 30 MPa higher than that of the matrix polymer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Fabrication of highly refractive,transparent BaTiO3/poly(methyl methacrylate) composite films with high permittivities

Incorporation of crystalline barium titanate (BT) nanoparticles into poly(methyl methacrylate) (PMMA) was carried out to prepare highly refractive polymer nanocomposite films that have transparency and high permittivities. The BT nanoparticles were prepared by hydrolysis of a barium/titanium complex alkoxide in 2‐methoxyethanol, then surface‐modified with a silane coupling agent (3‐methacryloxypropyltrimethoxysilane) to improve their affinity for PMMA. The incorporation of the surface‐modified nanoparticles into PMMA was performed up to a nanoparticle content almost equivalent to particle close‐packing state. The refractive index of the composite films increased with nanoparticle incorporation, keeping the relative transmittance normalized with PMMA film above 90%. A high refractive index of 1.82 was reached at a nanoparticle content of 53 vol% with a dielectric constant as high as 36 and a dissipation factor as low as 0.05. The results demonstrate that the crystalline BT nanoparticles are useful fillers for effectively increasing both refractive index and dielectric constant of polymer nanocomposites. Copyright © 2011 Society of Chemical Industry     

Ultrasound assisted in situ emulsion polymerization for polymer nanocomposite: A review

This review covers an ultrasound assisted synthesis of polymer nanocomposites using in situ emulsion polymerization. First of all, surface modification of core nanoparticles with a coupling agent and surfactant has been employed for the synthesis of core–shell polymer nanocomposites. In addition to application of ultrasound for the synthesis of core–shell polymer nanocomposites, due to its influential efficiency, sonochemistry has been extensively used not only as an aid of dispersion for inorganic nanoparticles and organo-clay, but also acts as an initiator to enhance polymerization rate for synthesis of polymer nanocomposites. In situ emulsion polymerization of hydrophobic monomers, such as methyl methacrylate, butyl acrylate, aniline, vinyl monomers and styrene, using surfactant and water soluble initiator were carried out for a synthesis of core–shell polymer nanocomposite. This technique assists in preparation of stable and finely dispersed polymer nanocomposite with the loading of inorganic particles up to 5 wt.%. Recent developments in the preparation of core–shell polymer nanocomposites using an ultrasound assisted method with their physical characteristics such as morphology, thermal, and rheological properties and their potential engineering applications have been discussed in this review.     

Preparation of nano‐sized silica/poly(methyl methacrylate) composite latexes by heterocoagulation: comparison of three synthetic routes

Continuing earlier work, 2,2′‐azobis(isobutyramidine) dihydrochloride (AIBA) was used as a cationic initiator to generate positively charged polymers, and promote interaction of these polymers with the negatively charged surface of colloidal silica particles in aqueous solution. Three different synthetic routes have been investigated. In a first route, emulsion polymerization of MMA, initiated by AIBA, was performed directly in an aqueous suspension of the silica beads using a non‐ionic polyoxyethylenic surfactant (NP₃₀). In a second route, AIBA was first adsorbed on the silica surface, and the free amount of initiator was discarded from the suspension. The silica‐adsorbed AIBA adduct was suspended in water with the help of surfactant, and used to initiate the emulsion polymerization of MMA. In a third route, cationic PMMA particles were synthesized separately and subsequently adsorbed on the silica surface. Whatever the approach used for their elaboration, the colloidal nanocomposites were shown to exhibit a raspberry‐like morphology. Quantitative determination of the amount of surface polymer enabled us to evaluate the efficiency of the heterocoagulation process and establish a comparison among the three synthetic routes. Copyright © 2004 Society of Chemical Industry     

The effects of polymer‐nanofiller interactions on the dynamical mechanical properties of PMMA/CaCO3 composites prepared by microemulsion template

We prepared novel poly(methyl methacrylate) (PMMA)/CaCO₃ nanocomposites by using reverse micelle as a template. The nanoparticles of CaCO₃ were prepared by the reverse microemulsion with functional monomer, methyl methacrylate (MMA) as oily phase, and the PMMA/CaCO₃ nanocomposite was obtained via polymerization of MMA monomer. The SEM image showed that the nanoparticles of CaCO₃ were dispersed in the polymer matrix. Dynamic mechanical analysis (DMTA) was performed to investigate the interaction between the nanoparticles and the polymer chains. In the low‐temperature ripening process, two tan δ peaks were observed in the nanocomposite, corresponding to the glass transitions of the matrix and the interface layer. In the high‐temperature ripening process, only one tan δ peak was observed, suggesting that the interface layer forms a continuous phase. The nanoparticles behave as a physical crosslinker in the interface layer. Modification of the surface of nanoparticles with polyacrylamide and poly(N,N′‐methylenedisacrylamide) in the nanocomposite did not show an appreciable effect on the interaction of nanoparticles with the matrix. Upon removal of the aqueous phase around the nanoparticles, we obtained surface‐capped nanoparticles by using an improved reverse microemulsion technique. Another PMMA/CaCO₃ nanocomposite was also obtained with these modified nanoparticles. DMTA analysis of this nanocomposite demonstrated that the aqueous phase layer around the nanoparticles does not significantly affect the interaction between the nanoparticles and the polymer chains. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2739–2749, 2004     

Preparation of hydrophobic nanosilica-filled polyacrylate hard coatings on plastic substrates

Colloidal silica nanoparticles synthesized from tetraethoxysilane via a sol–gel process were surface-modified first by 3-(trimethoxysilyl)propyl methacrylate, and then by trimethylethoxysilane (TMES). The former agent acts both as a coupling agent and as a C=C provider, whereas the latter agent is used to prevent particle aggregation and to increase hydrophobicity of the coating. The modified silica particles were UV-cured together with the monomer, 2-hydroxyethyl methacrylate (2-HEMA), and the crosslinking agent, dipentaerythritol hexaacrylate (DPHA), to form highly transparent hard coatings on plastic (PMMA and PET) substrates. Both differential scanning calorimetric and thermal gravimetric analyses of the hybrid materials indicated enhanced thermal stability with respect to the neat HEMA–DPHA copolymer. Furthermore, due to the incorporation of TMES, hydrophobicity of the hybrid coating increased considerably with increasing modified silica content. In the extreme case, an antiabrasive hard coating (7H on PMMA) with a water contact angle of 99° was obtained at the silica content of 15 wt%.     

Preparation and properties of poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)]/silica nanocomposite latex prepared using an acidic silica sol

BACKGROUND: Polyacrylate/silica nanocomposite latexes have been fabricated using blending methods with silica nanopowder, in situ polymerization with surface‐functionalized silica nanoparticles or sol–gel processes with silica precursors. But these approaches have the disadvantages of limited silica load, poor emulsion stability or poor film‐forming ability. RESULTS: In this work, poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)] [P(St‐BA‐AA)]/silica nanocomposite latexes and their dried films were prepared by adding an acidic silica sol to the emulsion polymerization stage. Morphological and rheological characterization shows that the silica nanoparticles are not encapsulated within polymer latex particles, but interact partially with polymer latex particles via hydrogen bonds between the silanol groups and the ? COOH groups at the surface of the polymer particles. The dried nanocomposite films have a better UV‐blocking ability than the pure polymer film, and retain their transparency even with a silica content up to 9.1 wt%. More interestingly, the hardness of the nanocomposite films increases markedly with increasing silica content, and the toughness of the films is not reduced at silica contents up to 33.3 wt%. An unexpected improvement of the solvent resistance of the nanocomposite films is also observed. CONCLUSION: Highly stable P(St‐BA‐AA)/silica nanocomposite latexes can be prepared with a wide range of silica content using an acidic silica sol. The dried nanocomposite films of these latexes exhibit simultaneous improvement of hardness and toughness even at high silica load, and enhanced solvent resistance, presumably resulting from hydrogen bond interactions between polymer chains and silica particles as well as silica aggregate/particle networks. Copyright © 2009 Society of Chemical Industry     

Synthesis of nanosize poly(methyl methacrylate) microlatexes with high polymer content by a modified microemulsion polymerization

Summary Nanosize poly(methyl methacrylate) (PMMA) microlatexes with high PMMA/surfactant ratio have been successfully prepared by a modified microemulsion polymerization, i.e., continuous and slow addition of monomer (MMA) to the polymerizing MMA microemulsion with mild stirring. Number-average diameters of 33–46 nm with narrow polydispersity (D_v/D_n= 1.1) and polymer content of 6–24 wt% were achieved using low levels of surfactant (dodecyltrimethylammonium bromide, DTAB) — less than 1 wt% of the reaction mixture. Particle diameter depended on polymerization temperature, MMA content, and concentrations of initiator and surfactant. Larger particles wereformed when temperature was too high, initiator concentration was too high, or surfactant concentration was too low. Received: 24 February 1998/Accepted: 24 March 1998     

Preparation and characterization of UV-curable epoxy/silica nanocomposite coatings

To enhance the interfacial interaction in silica nanoparticles filled polymer composites, the silica surface was firstly treated with glycidoxypropyl trimethoxysilane (GPTMS), and its structure was analyzed by ¹³C NMR and FTIR spectrophotometry. Then a series of GPTMS-modified silica/cycloaliphatic epoxy nanocomposite coatings with 0–6 wt% silica content were prepared by UV-induced cationic polymerization in the presence of a diaryliodonium photoinitiator and thioxanthone photosensitizer. The physical and mechanical properties such as hardness, adhesion, gloss, impact as well as tensile strength were examined. As a result, these composites demonstrated superior tensile strength and tensile modulus with increasing proportion of modified silica up to a certain level. An increase in abrasion resistance of nanocomposites with the addition of modified silica was observed. The thermal stability of nanocomposites was not enhanced with the addition of silica particles. SEM studies indicate that silica particles were dispersed homogenously through the polymer matrix.     

Effect of tethering chemistry of cationic surfactants on clay exfoliation, electrospinning and diameter of PMMA/clay nanocomposite fibers

We examine the influence of tethering chemistry of cationic surfactants on exfoliation of montmorillonite (MMT) clay dispersed in methyl methacrylate (MMA) followed by in-situ polymerization to form poly(methyl methacrylate) (PMMA) nanocomposites, the effect of exfoliation and clay loading on the rheology of polymer/clay dispersions in dimethyl formamide, and the diameters of nanocomposite fibers formed from these dispersions by electrospinning. Incorporation of an additional reactive tethering group of methacryl functionality significantly improves the intercalation and exfoliation of clays in both in-situ polymerized PMMA nanocomposites and the corresponding electrospun fibers. The proper surfactant chemistry also increases the dispersion stability, extensional viscosity, extent of strain hardening and thus the electrospinnablity of the nanocomposite dispersions, especially at low nanocomposite concentrations. The degree of the enhancement in electrospinnability by clays with proper tethering chemistry is at least the same as or greater than that obtained with three times higher loading level of clay particles without proper tethering chemistry in the nanocomposites. These results suggest a new strategy to produce smaller diameter fibers from very dilute polymer solutions, which are otherwise not electrospinnable, by incorporating a small amount of well-exfoliated clays.     

Synthesis and characterization of poly(methyl methacrylate)‐grafted silica microparticles

A procedure to synthesize poly(methyl methacrylate)‐grafted silica microparticles was developed by using radical photopolymerization of methyl methacrylate (MMA) initiated from N,N‐diethyldithiocarbamate (DEDT) groups previously bound to the silica surface (grafting “from”). The functionalization of silica microparticles with DEDT groups was performed in two steps: introduction of chlorinated functions onto the surface of silica particles, and then nucleophilic substitution of chlorines by DEDT functions via a S_N2 mechanism. The study was performed with a Kieselgel® S silica which was initially chlorinated in surface, either by direct chlorination of silanols with thionyl chloride, or by using a condensation reaction between silanols and a chlorofunctional trialkoxysilane reagent, 4‐(chloromethyl)phenyltrimethoxysilane and chloromethyltriethoxysilane, respectively. Three types of DEDT‐functionalized silica microparticles were prepared with a good control of the reactions, and then characterized by solid‐state ¹³C and ²⁹Si CP/MAS NMR. Their ability to initiate MMA photopolymerization was studied. The kinetics of MMA photopolymerization was followed by HPLC and ¹H‐NMR. Whatever the silica used the grafting progresses very slowly. On the other hand, the conversion of MMA in PMMA grafts is depending on the structure of the DEDT‐functionalized Kieselgel® S used. Poly(methyl methacrylate)‐grafted silica microparticles bearing high length grafts ( about 100) were synthesized. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The influence of oxide nanoparticles on the kinetics of free radical methyl methacrylate polymerization in bulk

A series of poly(methyl methacrylate) (PMMA) nanocomposites were synthesized using free radical polymerization in bulk, by addition of 1 vol% of oxide nanoparticles (silica, alumina, and titania), differing in the nature and type. The influence of nanofiller presence on the kinetics of methyl methacrylate (MMA) free radical polymerization was investigated. For this purpose, the kinetic model that includes the contribution from the first‐order reaction and the autoacceleration was applied on data obtained following the isothermal polymerization at 70°C by differential scanning calorimetry (DSC). The effect of the size and the surface nature of nanofillers on the interfacial layer thickness (d), as well as the influence of d on the glass transition temperature (T_g) of PMMA hybrid materials was studied. It was found that hydrophilic particles accelerated the initiator decomposition and affected the monomer polymerization on the surface, which caused the formation of thicker interfacial layer compared to the one around hydrophobic fillers. The addition of smaller nanoparticles size decreased the glass transition temperature of pure poly(methyl metacrylate). The linear increase of PMMA T_g value with increasing the polymeric interfacial layer was determined. The T_g values of pure PMMA and PMMA nanocomposite with d of 1.4 nm were estimated to be the same. POLYM. COMPOS. 34:1342–1348, 2013. © 2013 Society of Plastics Engineers     

Synthesis of CaCO3–P(MMA–BA) nanocomposite and its application in water based alkyd emulsion coating

As part of broader effort to synthesize a new class of water-based composite, hybrid emulsion polymerization was carried out with acrylic monomers [methyl methacrylate (MMA), n-butyl acrylate (BA)]. Nanocomposite of P(MMA–BA)/nano CaCO₃ was synthesized by in situ emulsion polymerization. Water-based alkyd coating with various proportions nano CaCO₃, P(MMA–BA) and its nanocomposite was formulated. Extent of polymerization with and without nano CaCO₃ was measured using gravimetric method. Thermal properties of neat polymer, nanocomposite and coating films were evaluated by TGA and DSC, DTA analysis. Uniform dispersion of nano CaCO₃ in polymer matrix was ensured from SEM/TEM images. Incorporation of nanoparticles to hybrid polymer and nanocomposite to alkyd emulsion showed significant enhancement in mechanical and thermal properties. Dual role of nanocomposite in coating; as a partial binder and a filler to improve property profile of neat coating has been reported.     

Effects of mesoporous silica particles on the emulsion polymerization of methyl methacrylate

Rod‐like and spherical mesoporous SBA‐15 silica particles were synthesized as pure silicas and surface modified by organosilane coupling agents firstly, and then the effects of these mesoporous materials on the critical micelle concentration (CMC) of sodium dodecylsulfate (SDS), the stabilities of batch and semi‐continuous MMA emulsion polymerizations, and the molecular weights and molecular weight distributions of the polymer products were studied. The incorporation of both unmodified and silane‐modified forms of the mesoporous silica particles in the polymerization reaction increased the CMC of SDS. The presence of the unmodified mesoporous silica in the polymerization process led to instability in the batch emulsion polymerization process, as indicated by the formation of increased amounts of coagulum, and a decrease in the molecular weight of the polymer product. However, in comparison to the polymer formed in the absence of particle additives the molecular weight of the PMMA polymer increased with the amount of emulsifier and the addition of silane‐modified SBA‐15 particles, suggesting the growth of the polymer chains is facilitated at least in part by reaction in the pores of the particles. The improvement in molecular weight indicates that semi‐continuous MMA emulsion polymerization is best suited for the preparation of PMMA–mesoporous silica composites. POLYM. ENG. SCI., 54:2746–2752, 2014. © 2013 Society of Plastics Engineers     

Preparation and properties of transparent PMMA/ZrO2 nanocomposites using 2-hydroxyethyl methacrylate as a coupling agent

Transparent PMMA/ZrO₂ nanocomposites were prepared by in-situ bulk polymerization of methyl methacrylate (MMA)/ZrO₂ dispersions that were firstly synthesized using nonaqueous synthesized ZrO₂ nanocrystals and the function monomer, 2-hydroxyethyl methacrylate (HEMA), as the ligand. The dispersion behavior of ZrO₂ nanoparticles in MMA, structure, mechanical and thermal properties of the PMMA/ZrO₂ nanocomposites were investigated comprehensively. It was found that ZrO₂ nanoparticles were well dispersed in MMA with HEMA ligand, but the MMA/ZrO₂ dispersions easily destabilized in air as well as at elevated temperatures. The destabilization temperature of the dispersion is raised by increasing the molar ratio of HEMA/ZrO₂ to match the bulk polymerization temperature. The PMMA/ZrO₂ nanocomposites showed an interesting chemical structure (namely, highly cross-linked structure even at ZrO₂ content as low as 0.8 wt% and hydrogen bonding interaction between polymer matrix and ZrO₂ nanoparticles), with enhanced rigidity without loss of the toughness and improved thermal stability. The relationship between the structure and the properties of the PMMA/ZrO₂ nanocomposites based on the HEMA coupling agent was discussed.