Preparation and tribological properties of poly(methyl methacrylate)/styrene/MWNTs copolymer nanocomposites

Poly(methyl methacrylate)/styrene/multi‐walled carbon nanotubes (PMMA/PS/MWNTs) copolymer nanocomposites with different contents have been prepared successfully by means of in situ polymerization method. The structure and the microhardness of PMMA/PS/MWNTs copolymer nanocomposites were characterized. The tribological behaviors of the copolymer nanocomposites were investigated by a friction and wear tester under dry conditions. The relative humidity of the air was about 50% ± 10%. Comparing with pure PMMA/PS copolymer, the copolymer nanocomposites showed not only better wear resistance but also smaller friction coefficient. MWNTs could help the nanocomposites dramatically improve the wear resistance property. The mechanisms of the improvements on the tribological properties of the PMMA/PS/MWNTs copolymer nanocomposites were also discussed in detail. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Surface modification of MWNTs with BA‐MMA‐GMA terpolymer by single‐step grafting technique

In this article, a facile strategy was developed to prepare BA‐MMA‐GMA/MWNTs (multiwalled carbon nanotubes) hybrid nanoparticles as nanofillers in rubber by single‐step grafting technique. First, a new macromolecular surface modifier butyl acrylate (BA)‐α‐methyl methacrylate(MMA)‐glycidyl methacrylate (GMA) terpolymer was synthesized via radical copolymerization. Afterward, this terpolymer modifier was covalently grafted onto the surface of crude MWNTs by single‐step grafting technique. The structure, surface properties, and thermal stability of modified MWNTs were systematically investigated by FTIR, TGA, and TEM. FTIR results showed that BA‐MMA‐GMA terpolymer was successfully grafted onto the surface of MWNTs. TGA indicated that the optimum mass fraction of macromolecular modifier coated on the surface of MWNTs was 9 wt %. TEM images revealed that an organic coating layer was formed and the modified MWNTs showed good dispersibility in acetone. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A novel approach to prepare PBT nanocomposites with elastomer‐modified SiO2 particles

Poly(butylenes terephthalate) (PBT)/SiO₂ nanocomposites with uniform dispersion, strong interfacial adhesion, and improved mechanical properties have been prepared by a novel approach. Ethylene‐methyl acrylate‐glycidyl methacrylate (E‐MA‐GMA) elastomer chains were first chemically grafted onto the surface of SiO₂ nanoparticles. Fourier transform infrared spectra result shows that elastomer‐modified SiO₂ nanoparticles exhibit absorption at 2963–2862 cm⁻¹ of the stretching modes of C H, which suggests the reaction between the hydroxyl groups of SiO₂ surface and epoxy groups of E‐MA‐GMA. And the binding energy of Si2p and O1s of the elastomer‐modified SiO₂ shifts to lower binding energy, which further confirms the formation of Si O C bonds. This surface treatment allows SiO₂ nanoparticles homogeneously dispersing in PBT matrix. The morphology with loose aggregates contains networked SiO₂ particles with an interparticle distance ranging from 0 to 30 nm. As a result, the storage modulus and the tensile properties of PBT/E‐MA‐GMA‐SiO₂ nanocomposites are higher than those of pure PBT and PBT with untreated SiO₂. The incorporation of E‐MA‐GMA‐modified SiO₂ particles increases the tensile strength and modulus to 58.4MPa and 2661MPa respectively, which is 8% and 16% higher than those of pure PBT. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Towards transparent PMMA/SiO2 nanocomposites with promising scratch‐resistance by manipulation of SiO2 aggregation followed by in situ polymerization

Poly(methyl methacrylate) grafted silica (SiO₂‐g‐PMMA) was synthesized via in situ suspension polymerization. To achieve better uniform dispersion, hexadecyltrimethylammonium bromide (CTAB) was introduced into xylene to manipulate SiO₂ aggregation. SiO₂‐g‐PMMA or SiO₂ was incorporated into PMMA matrix by in situ polymerization to prepare PMMA‐based nanocomposites. The effect of CTAB amount, in the range 0–35 wt %, on the modification was evaluated by DLS, TGA, and FTIR. Furthermore, morphology, optical, mechanical, and thermal properties of PMMA nanocomposites was characterized by SEM, UV–vis, DMA, and TGA. Owing to surface functionalization, SiO₂‐g‐PMMA exhibited far more excellent compatibility and dispersion in matrix compared with SiO₂. Surface hardness and thermal properties of nanocomposites were enhanced significantly under the premise in high transparency. It is expected that transparent nanocomposites with promising scratch‐resistance could have wide applications, such as airplane shielding window and daily furniture. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44612.     

通过RAFT聚合制备经GMA偶联的PMMA/TiO2杂化纳米复合物

利用表面修饰法合成了常用单体甲基丙烯酸缩水甘油酯(GMA)修饰的TiO2纳米粒子。以甲基丙烯酸甲酯(MMA)为单体,S-1-十二烷基-S′-(α,α′-二甲基-α″-乙酸)三硫代碳酸酯(DDACT)为RAFT试剂,在纳米TiO2表面进行可逆加成-断裂链转移(RAFT)接枝聚合,PMMA"经表面接枝到(grafting through)"改性后的纳米TiO2表面。结果表明,随聚合时间的增加,纳米TiO2表面接枝聚合物PMMA的量增加,颗粒的团聚得到明显减缓。     

Synthesis and characterization of PMMA/SiO2 nanocomposites by in situ suspension polymerization

Poly(methyl methacrylate) (PMMA)/SiO₂ nanocomposites were prepared by in situ suspension polymerization. Two types of modified methods were used to modify nano‐SiO₂: one was modification by γ‐methacyloxypropyl trimethoxy silane (KH570) and lauryl alcohol (12COH) while the other was grafting PMMA onto the surface of KH570 treated SiO₂. Transmission electron microscopy (TEM) and Fourier transformed infrared (FTIR) were used to characterize the structures of the nanocomposites. The influence of synthetic conditions, for instance, surface modification, initial SiO₂ contents and reaction temperature, on the microsphere's size and molecular weight of the extracted PMMA were studied by gel permeation chromatograph (GPC) and optical microscopy (OM) in details. Thermal property of the nanocomposites was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicate that the presence and content of SiO₂ have a vital effect on the shape and size of the nanocomposite microspheres, as well as molecular weight of the extracted PMMA. Grafting polymer to the surface of SiO₂ is an effective way for the purpose of effective in situ suspension polymerization. Compared to pure PMMA, the thermal properties of the nanocomposites were improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of clay platelet dispersion as affected by the manufacturing techniques on thermal and mechanical properties of PMMA‐clay nanocomposites

In this work, the properties of Poly(methyl methacrylate) (PMMA)‐clay nanocomposites prepared by three different manufacturing techniques viz., solution mixing, melt mixing, and in‐situ bulk polymerization in presence of clay were studied. Morphological analysis revealed that the extent of intercalation and dispersion of the nanoclay were relatively higher in the in‐situ polymerized nanocomposites than those of solution and melt blended nanocomposites. Differential Scanning Calorimetric study indicated maximum increment in T_g of the PMMA in the in‐situ polymerized PMMA‐clay nanocomposites. Thermo gravimetric analysis showed improved thermal stability of PMMA in all the nanocomposites and the maximum improvement was for in‐situ polymerized nanocomposites. The storage moduli of all the nanocomposites were higher than the pure PMMA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(vinylbenzylchloride) beads grafted with polymer brushes carrying hydrazine ligand for reversible enzyme immobilization

Poly(glycidylmethacrylate), p(GMA), brush grafted poly(vinylbenzyl chloride/ethyleneglycol dimethacrylate), p(VBC/EGDMA), beads were prepared by suspension polymerization and the beads were grafted with poly(glycidyl methacrylate), p(GMA), via surface‐initiated atom transfer radical polymerization aiming to construct a material surface with fibrous polymer. The epoxy groups of the fibrous polymer were reacted with hydrazine (HDZ) to create affinity binding site on the support for adsorption of protein. The influence of pH, and initial invertase concentration on the immobilization capacity of the p(VBC/EGDMA‐g‐GMA)‐HDZ beads has been investigated. Maximum invertase immobilization onto hydrazine functionalized beads was found to be 86.7 mg/g at pH 4.0. The experimental equilibrium data obtained invertase adsorption onto p(VBC/EGDMA‐g‐GMA)‐HDZ affinity beads fitted well to the Langmuir isotherm model. It was shown that the relative activity of immobilized invertase was higher than that of the free enzyme over broader pH and temperature ranges. The K_m and V_max values of the immobilized invertase were larger than those of the free enzyme. After inactivation of enzyme, p(VBC/EGDMA‐g‐GMA)‐HDZ beads can be easily regenerated and reloaded with the enzyme for repeated use. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Property improvement of plasticized poly(vinyl chloride) by nano‐TiO2 and poly(methyl methacrylate)–encapsulated nano‐TiO2

To improve the physical properties of plasticized poly(vinyl chloride) (p‐PVC), the p‐PVC nanocomposites filled with four loading levels (3, 5, 7, and 9 parts per hundred of PVC resin) of either nanosized titanium dioxide (nTiO₂) or poly(methyl methacrylate)–encapsulated nTiO₂ (PMMA‐nTiO₂) were prepared by melt mixing on a two‐roll mill, followed by compression molding. The PMMA‐nTiO₂ used in this study was synthesized via in situ differential microemulsion polymerization. The resulting PMMA‐nTiO₂ exhibited core‐shell morphology (nTiO₂ core and PMMA shell) with an average diameter of 42.6 nm. The effects of nTiO₂ and PMMA‐nTiO₂ on the tensile properties, hardness, morphology, and thermal stability of the as‐prepared p‐PVC nanocomposites were then investigated and compared. The inclusion of either nTiO₂ or PMMA‐nTiO₂ nanoparticles increased the tensile strength, Young's modulus, hardness, and thermal stability of the nanocomposites in a dose‐dependent manner and reduced the elongation at break. However, the elongation at break was still higher than that for the neat p‐PVC. Moreover, the PMMA‐nTiO₂ nanocomposites had a higher enhancement of the tensile strength, Young's modulus, hardness, and thermal stability than the nTiO₂ nanocomposites at a similar loading level. Hence, the PMMA grafted on the nTiO₂ surface played an important role in toughening and increasing the thermal stability of the nanocomposites owing to the improved miscibility and interfacial adhesion between the encapsulated nanofiller and PVC matrix. J. VINYL ADDIT. TECHNOL., 22:433–440, 2016. © 2015 Society of Plastics Engineers     

Effect of the molecular chains grafted on graphene nanosheets on the properties of poly(l‐lactic acid) nanocomposites

We prepared thermally reduced graphene oxide (TRG) grafted with polymethyl methacrylate (PMMA) and polyvinyl acetate (PVAc) (TRG‐g‐PMMA and TRG‐g‐PVAc) by γ‐ray irradiation‐induced graft polymerization and studied their effects on poly(l ‐lactic acid) (PLLA) nanocomposites. PMMA and PVAc chains were proved to be grafted on the TRG surface successfully. TRG‐g‐PMMA and TRG‐g‐PVAc was found to restrict the crystallization behavior of PLLA compared with TRG. Moreover, tensile‐test results showed that TRG‐g‐PMMA and TRG‐g‐PVAc could enhance the elongation at break of PLLA nanocomposites without reducing the tensile strength and modulus compared with TRG, which indicated that the grafting of PMMA and PVAc chains on TRG could improve the toughness of PLLA nanocomposites. POLYM. COMPOS., 38:5–12, 2017. © 2015 Society of Plastics Engineers     

“胶乳共混法”制备天然橡胶／二氧化硅纳米复合材料及其性能

采用γ-甲基丙烯酰氧基丙基三甲氧基硅烷（KH570）改性纳米二氧化硅（SiO2）,然后通过乳液聚合接枝上聚甲基丙烯酸甲酯（PMMA）,再将其与甲基丙烯酸甲酯（MMA）改性的天然胶乳,通过胶乳共混法制备天然橡胶／二氧化硅纳米复合材料,结果显示,纳米二氧化硅表面接枝上了PMMA,二氧化硅在橡胶基体中分散良好,粒径在60～100nm之间,得到的胶膜力学性能有很大的提高。     

A novel route for well‐defined polystyrene‐grafted multiwalled carbon nanotubes via the radical coupling reaction

Multiwalled carbon nanotubes‐graft‐polystyrene (MWNTs‐g‐PS) was synthesized by atom transfer nitroxide radical coupling chemistry. MWNTs with 2,2,6,6‐tetramethylpiperidine‐1‐oxy (MWNTs‐TEMPO) groups was prepared first by esterification of 4‐hydroxy (HO)‐TEMPO and carboxylic acid group on the surface of MWNTs (MWNTs‐COOH); PS with bromide end group (PS‐Br) were then obtained by atom transfer radical polymerization using ethyl 2‐bromoisobutyrate as initiator and CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as catalyst. The MWNTs‐TEMPO was mixed with PS‐Br and heated to 90°C in the presence of CuBr/PMDETA to form MWNTs‐g‐PS. The product was characterized by FTIR, NMR, TGA, and TEM. TEM indicates that the MWNTs are enveloped by the polymer molecules. The content of grafted polymers is 46.7% by TGA measurements when the number‐average molecular weight (M_n) of PS‐Br is 10,200 g/mol. The as‐prepared nanocomposites exhibit relatively good dispersibility in solvents such as CH₂Cl₂, THF, and toluene. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Controlled atom transfer radical polymerization of MMA onto the surface of high-density functionalized graphene oxide

We report on the grafting of poly(methyl methacrylate) (PMMA) onto the surface of high-density functionalized graphene oxides (GO) through controlled radical polymerization (CRP). To increase the density of surface grafting, GO was first diazotized (DGO), followed by esterification with 2-bromoisobutyryl bromide, which resulted in an atom transfer radical polymerization (ATRP) initiator-functionalized DGO-Br. The functionalized DGO-Br was characterized by X-ray photoelectron spectroscopy (XPS), Raman, and XRD patterns. PMMA chains were then grafted onto the DGO-Br surface through a ‘grafting from’ technique using ATRP. Gel permeation chromatography (GPC) results revealed that polymerization of methyl methacrylate (MMA) follows CRP. Thermal studies show that the resulting graphene-PMMA nanocomposites have higher thermal stability and glass transition temperatures (T_g) than those of pristine PMMA.     

Grafting and properties of a porous poly(methyl methacrylate) film on a silicon surface by a one‐step dipping method

In this study, we prepared a porous poly(methyl methacrylate) (PMMA) film on an Si surface with a novel dipping method. We conducted the process by directly dipping the Si substrate into acidic aqueous media in a simple flask at 10 °C. First, 4‐nitrobenzene diazonium tetrafluoroborate (NBD) was spontaneously reduced at the Si surface. Then, the aryl radicals during the reduction of NBD were directly grafted onto the Si surface. Meanwhile, the aryl radicals initiated the polymerization of methyl methacrylate (MMA) monomers, and the radical‐terminated PMMA chains formed in the solution were grafted onto the Si surface. Because water was a poor solvent for MMA, the grafted PMMA chains easily aggregated together, and this resulted in a porous polymer film. The porosity of the film depended on the grafting time and the MMA concentration. Furthermore, the permittivity of the porous PMMA film was relatively low, and its dielectric dissipation factor was extremely small. Therefore, its excellent dielectric properties should allow the porous film to have many applications in industry. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44930.     

Structural characterization,thermal properties,and density functional theory studies of PMMA‐maghemite hybrid material

Maghemite (γ‐Fe₂O₃)‐poly(methyl methacrylate) (PMMA) nanocomposites were prepared by grafting 3‐(trimethoxy‐silyl) propyl methacrylate on the surface of maghemite nanoparticles, this process being followed by methyl methacrylate radical polymerization. Three different hybrids with 0.1, 0.5, and 2.5 wt% of maghemite nanoparticles were studied. The results indicate that these nanocomposites consist of a homogeneous PMMA matrix in which maghemite nanoparticles with a bimodal size distribution are embedded. The existence of covalent bonding between silane monomers and atoms on the maghemite surface was evidenced. AFM images showed a clear increase in surface roughness for increasing maghemite content. The thermal stability of PMMA‐maghemite nanocomposites is higher than that of pure PMMA and increases for increasing maghemite content. The results of our theoretical studies indicate that the electron density in the maghemite nanoparticle is not homogenous, the low electron density volumes being supposed to be radical trappers during PMMA decomposition, thus acting as a thermal stabilizer. POLYM. COMPOS., 51–60, 2016. © 2014 Society of Plastics Engineers     

Synthesis and characterization of polyimide/multi‐walled carbon nanotube nanocomposites

Polyimide/multi‐walled carbon nanotube (PI‐MWNT) nanocomposites were fabricated by an in situ polymerization process. Chemical compatibility between the PI matrix and MWNTs is achieved by pretreatment of the carbon nanotubes in a mixture of sulfuric acid and nitric acid. The dispersion of MWNTs in the PI matrix was found to be enhanced significantly after acid modification. The glass transition (T_g) and decomposition (T_d) temperature of PI‐MWNT nanocomposites were improved as the MWNT content increased from 0.5 to 15 wt%. The storage modulus of the PI/MWNT nanocomposites is nine times higher than that of pristine PI at room temperature. The tensile strength of PI doubles when 7 wt% MWNTs is added. The dielectric constant of the PI‐MWNT nanocomposites increased from 3.5 to 80 (1 kHz) as the MWNT content increased to 15 wt%. The present study demonstrates that enhanced mechanical properties can be obtained through a simple in‐situ polymerization process. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Use of a new natural clay to produce poly(methyl methacrylate)‐based nanocomposites

Nanocomposites of poly(methyl methacrylate) (PMMA) filled with 3 wt% of modified natural Algerian clay (AC; montmorillonite type) were prepared by either in situ polymerization of methyl methacrylate initiated by 2,2′‐azobisisobutyronitrile or a melt‐mixing process with preformed PMMA via twin‐screw extrusion. The organo‐modification of the AC montmorillonite was achieved by ion exchange of Na⁺ with octadecyldimethylhydroxyethylammonium bromide. Up to now, this AC montmorillonite has found applications only in the petroleum industry as a rheological additive for drilling muds and in water purification processes; its use as reinforcement in polymer matrices has not been reported yet. The modified clay was characterized using X‐ray diffraction (XRD), which showed an important shift of the interlayer spacing after organo‐modification. The degree of dispersion of the clay in the polymer matrix and the resulting morphology of nanocomposites were evaluated using XRD and transmission electron microscopy. The resulting intercalated PMMA nanocomposites were analysed using thermogravimetric analysis and differential scanning calorimetry. The glass transition temperature of the nanocomposites was not significantly influenced by the presence of the modified clay while the thermal stability was considerably improved compared to unfilled PMMA. This Algerian natural montmorillonite can serve as reinforcing nanofiller for polymer matrices and is of real interest for the fabrication of nanocomposite materials with improved properties. Copyright © 2009 Society of Chemical Industry     

Interfacial evaluation of epoxy/carbon nanofiber nanocomposite reinforced with glycidyl methacrylate treated UHMWPE fiber

Interface interactions of fiber–matrix play a crucial role in final performance of polymer composites. Herein, in situ polymerization of glycidyl methacrylate (GMA) on the ultrahigh molecular weight polyethylene (UHMWPE) fibers surface was proposed for improving the surface activity and adhesion property of UHMWPE fibers towards carbon nanofibers (CNF)‐epoxy nanocomposites. Chemical treatment of UHMWPE fibers was characterized by FTIR, XPS analysis, SEM, and microdroplet tests, confirming that the grafting of poly (GMA) chains on the surface alongside a significant synergy in the interfacial properties. SEM evaluations also exhibited cohesive type of failure for the samples when both GMA‐treated UHMWPE fiber and CNF were used to reinforce epoxy matrix. Compared with unmodified composite, a ～319% increase in interfacial shear strength was observed for the samples reinforced with both 5 wt % GMA‐grafted UHMWPE and 0.5 wt % of CNF. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43751.     

Synthesis of silica hybrid nanoparticles modified with photofunctional polymers and construction of colloidal crystals

Photofunctional polymer as silane coupling agent (PFD) was prepared by free radical copolymerization of 4‐vinylbenzyl N,N‐diethyldithiocarbamate (VBDC) and methyl methacrylate (MMA) in the presence of (3‐mercaptopropyl)trimethoxysilane (MPMS) as chain transfer agent. Next, silane (SiO₂; the average diameter D_n = 192 nm) nanoparticles was surface‐modified with PFD and 3‐(trimethoxysilyl)propyl methacrylate (γ‐MPS) by covalent bond formed between silanol groups and silane coupling agents. The PFD and γ‐MPS functionalizations changed the silica surface into hydrophobic nature and provided grafting initiation sites and methacrylate terminal groups respectively. We performed the construction of hybrid nanocomposites by using these modified SiO₂ nanoparticles. It was found from electron microscopy observations that SiO₂ particles were packed into repeating cubic arrangements in a poly(methyl methacrylate) (PMMA) matrix such as colloidal crystals. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of silica nanoparticles functionalized with poly(butyl acrylate‐co‐glycidyl methacrylate)‐g‐diaminodiphenyl sulfone on the mechanical and thermal properties of bismaleimide nanocomposites

The silica nanoparticles functionalized with poly(butyl acrylate‐co‐glycidyl methacrylate)‐g‐diaminodiphenyl sulfone (P(BA‐co‐GMA)‐g‐DDS)) were prepared via atom transfer radical polymerization and ring open reaction, and characterized by Fourier transform infrared and X‐ray photoelectron spectroscopy. Subsequently, the influence of SiO₂ content on the mechanical and thermal properties for the bismaleimide (BMI) resin nanocomposites modified with pristine SiO₂ and SiO₂‐P(BA‐co‐GMA)‐g‐DDS) was investigated. It was found that SiO₂‐P(BA‐co‐GMA)‐g‐DDS) was more effective as a modifier than pristine SiO₂. The most significant improvement of the impact strength (+108.7%) and flexural strength (+64.5%) was obtained with SiO₂‐P(BA‐co‐GMA)‐g‐DDS) at 0.5 wt% content. Moreover, the thermal properties of nanocomposites were distinctly improved with the addition of functionalized SiO₂. The reasons for these changes were discussed in this article. POLYM. COMPOS., 34:2154–2159, 2013. © 2013 Society of Plastics Engineers