Facile approach to prepare multi-walled carbon nanotubes/graphene nanoplatelets hybrid materials

A facile approach was developed to prepare multi-walled carbon nanotubes/graphene nanoplatelets hybrid materials through covalent bond formation. First, poly(acryloyl chloride) was grafted onto oxidized multi-walled carbon nanotubes through the reaction between the acyl chloride groups of poly and the hydroxyl groups of oxidized multi-walled carbon nanotubes. Second, the remaining acyl chloride groups of poly were allowed to react with the hydroxyl groups of hydroxylated graphene nanoplatelets. Scanning electron microscopy and transmission electron microscopy data showed that the multi-walled carbon nanotubes and graphene nanoplatelets were effectively connected with each other. And Fourier transform infrared spectroscopy data indicated the formation of covalent bonds between carbon nanotubes and graphene nanoplatelets. Conformational changes were monitored by Raman spectroscopy. This novel kind of carbon hybrid materials may have the potential application in a wide field, especially in increasing the toughness and strength of the matrix resin.     

Cationic graft polymerization of polymers from carbon fiber initiated by acylium perchlorate groups introduced onto the surface

The cationic graft polymerization of several monomers initiated by acylium perchlorate groups introduced onto the carbon fiber surface was investigated to modify the surface. The introduction of acylium perchlorate groups was successfully achieved by the reaction of silver perchlorate with acyl chloride groups, which were introduced by the reaction of surface carboxyl groups with thionyl chloride. It was found that the cationic polymerization of styrene is initiated by acylium perchlorate groups on the carbon fiber. In the polymerization, polystyrene was grafted onto the carbon fiber surface through the propagation of polystyrene from the surface. Ungrafted polymer was also formed by the chain transfer reaction of growing polymer cation to the monomer. The acylium perchlorate groups have the ability to initiate cationic ring-opening polymerization of tetrahydrofuran (THF) and ε-caprolactone (CL), polyTHF and polyCL being grafted onto the carbon fiber surface, respectively. Polyacetals, such as poly(1,3-dioxolane) and polyoxymethylene, were able to graft onto the carbon fiber by cationic ring-opening polymerization of the corresponding monomers.     

pH响应性聚合物修饰的空心介孔硅球的制备

将有机硅RAFT试剂三甲氧基硅基丙基三硫代羰基苄基酯（BTPT）固载于硅球表面,通过可逆加成-断裂链转移自由基聚合表面接枝法制备了pH值、温度双敏感聚合物聚甲基丙烯酸-2-（二甲氨基）乙酯（PDMAEMA）修饰的纳米硅球,通过表面保护法在常温下用氨水对该修饰过的硅球进行刻蚀,制得PDMAEMA修饰的纳米空心介孔硅球（HMS@PDMAEMA）。通过核磁、红外、GPC和透射电子显微镜等方法对其结构和表面形貌进行了表征,并用纳米粒度及zeta电位仪测试了其pH值响应行为,预测HMS@PDMAEMA在癌症药物的控制释放和基因递送等领域具有潜在的应用价值。     

Reactive carbon black having acyl imidazole or acid anhydride groups: Preparation and reaction with functional polymers having hydroxyl or amino groups

The introduction of acyl imidazole groups onto a carbon black surface was achieved by the reaction of the carboxyl groups on the surface with N N′-carbonyldiimidazole, the loading of acyl imidazole groups introduced was determined to be 0.28 mmol/g. In addition, reactive carbon black having acid anhydride groups was prepared by the reaction of phenolic hydroxyl groups with trimellitic anhydride chloride; the amount of acid anhydride groups introduced onto the surface was determined to be 0.20 mmol/g. The reaction of acyl imidazole groups on carbon black with commercially available polymers having hydroxyl or amino groups such resulted in polymers that were found to be grafted onto the surface via ester or amide bonds. The percentage of grafting of diol-type poly(propylene glycol) and diamine-type polydimethylsiloxane was increased to 27.2 % and 42.5 %, respectively. Furthermore, acid anhydride groups on carbon black also reacted with functional polymers having hydroxyl or amino groups to give polymer-grafted carbon blacks. The grafting reaction was accelerated by the addition of tertiary amines. These polymer-grafted carbon blacks produced a stable colloidal dispersion in good solvents for the grafted polymer, but readily precipitated in poor solvents.     

Grafting of branched polymers onto nano-sized silica surface: Postgrafting of polymers with pendant isocyanate groups of polymer chain grafted onto nano-sized silica surface

To control the surface wettability of nano-sized silica surface, the postgrafting of hydrophilic and hydrophobic polymers to grafted polymer chains on the surface was investigated. Polymers having blocked isocyanate groups were successfully grafted onto nano-sized silica surface by the graft copolymerization of methyl methacrylate (MMA) with 2-(O-[1′-methylpropylideneamino]caboxyamino)ethyl methacrylate (MOIB) initiated by azo groups previously introduced onto the surface. The blocked isocyanate groups of poly(MMA-co-MOIB)-grafted silica were stable in a desiccator, but isocyanate groups were readily regenerated by heating at 150 °C. The hydrophilic polymers, such as poly(ethylene glycol) (PEG) and poly(ethyleneimine) (PEI), were postgrafted onto the poly(MMA-co-MOIB)-grafted silica by the reaction of functional groups of PEG and PEI with pendant isocyanate groups of poly(MMA-co-MOI)-grafted silica to give branched polymer-grafted silica. The percentage of grafting increased with increasing molecular weight of PEG, but the number of postgrafted chain decreased, because of steric hindrance. The hydrophobic polymers, such as poly(dimethylsiloxane) were also postgrafted onto poly(MMA-co-MOI)-grafted silica. It was found that the grafting of hydrophobic polymer and the postgrafting of hydrophilic polymer branches readily controls the wettability of silica surface to water.     

Graft polymerization of vinyl monomers initiated by peroxycarbonate groups introduced onto silica surface by Michael addition

The introduction of peroxycarbonate groups onto a silica surface and the graft polymerization of vinyl monomers initiated by peroxycarbonate groups introduced onto a silica surface were investigated. The introduction of peroxycarbonate groups onto a silica surface was achieved by Michael addition of amino groups introduced onto the silica surface to t‐butylperoxy‐2‐methacryloyloxyethylcarbonate (HEPO). The amount of peroxycarbonate groups was determined to be 0.17 mmol/g. The graft polymerization of various vinyl monomers such as styrene (St), N‐vinyl‐2‐pyrrolidinone (NVPD), and 2‐hydroxyethyl methacrylate (HEMA) was initiated by peroxycarbonate groups introduced onto the silica surface to give the corresponding polymer‐grafted silicas. The percentage of poly(St)‐grafting reached about 120% after 5 h. This means that 1.20 g of poly(St) is grafted onto 1.0 g of silica. The surface of poly(St)‐grafted silica shows a hydrophobic nature, but the surfaces of poly(NVPD) and poly(HEMA)‐grafted silica show a hydrophilic nature. Furthermore, the poly(St)‐grafted silica was found to give a stable colloidal dispersion in a good solvent for the grafted polymer. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1491–1497, 1999     

Preparation of a carbon nanotube/carbon fiber multi-scale reinforcement by grafting multi-walled carbon nanotubes onto the fibers

To prepare a carbon nanotube (CNT)/carbon fiber multi-scale reinforcement (MSR), multi-walled carbon nanotubes (MWCNTs) functionalized at the end caps with hexamethylene diamine (HMD) are grafted onto the surfaces of carbon fibers treated with acyl chloride. The surface element concentrations, surface functional groups and morphology of the MSR were examined by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XPS spectra indicate that sp² and sp³ carbon atoms are major components in the MSR surface, and the carbon fiber surface structure is not destroyed. There is 17.41% of C-NH_x in the surface of the MSR, which suggests that MWCNTs are covalently grafted onto carbon fiber surfaces. SEM shows that the grafted MWCNTs stick to the carbon fiber surface at different angles, and are uniformly distributed along the outer edges of the grooves in the fiber surface. The grafted MWCNTs are 50-200 nm in length and around 14 nm in diameter. It was found that the grafting increases the weight of carbon fiber by 1.2%, which implied that a considerable amount of MWCNTs were grafted onto carbon fiber surfaces.     

Grafting polyamide 6 onto multi‐walled carbon nanotubes using microwave irradiation

Chemical reactions under microwave irradiation can be very efficient, with a significant shortening of reaction time. Few studies have reported the use of microwaves to functionalize carbon nanotubes. In the work reported, a new method of formulating functionalized multi‐walled carbon nanotubes (MWNTs) was developed by covalent grafting of polyamide 6 (PA6) chains onto the carbon nanotubes assisted by microwave irradiation. PA6 chains were grafted onto acidified MWNTs through condensation reaction between the carboxylic groups of the MWNTs and the terminal amine groups of PA6 using microwave radiation heating. The functionalized carbon nanotubes (MWNT‐g‐PA6) were characterized systematically using infrared and Raman spectroscopy, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). TEM showed that the surface of the MWNTs was covered with a layer of PA6. TGA results indicated that the MWNT‐g‐PA6 contained about 47 wt% of polymer. A novel, convenient and efficient functionalization approach is reported, involving covalently grafting PA6 chains onto MWNTs assisted by microwave irradiation. Copyright © 2010 Society of Chemical Industry     

A new route for organic-inorganic hybrid material synthesis through reactive processing without solvent

A new route to elaborate organic-inorganic hybrid materials is presented. It is based upon two successive steps, the former is the crosslinking of polymer which contains pendant ester groups such as poly(ethylene-co-vinyl acetate) (EVA) through ester-alkoxysilane interchange reaction in molten state in the presence of dibutyltin oxide as catalyst. The latter is the hydrolysis-condensation reactions of available alkoxysilane groups in the polymer network leading to the silica network co-grafted onto the organic network. More particularly the hydrolysis-condensation reactions in solid state leading to the silica network grafted and confined in the organic network are addressed in the present work. The progress of the hydrolysis-condensation reactions was investigated by gas chromatography, FT-IR spectroscopy, ²⁹Si solid NMR, volume swelling degree at equilibrium and dynamic mechanical analysis. Two side reactions have been evidenced leading to alcohol groups grafted onto EVA. The silanols and these alcohol groups can participate to hydrogen bonds between ester and silica domains. The organic-inorganic hybrids elaborated according to this new chemical route exhibit improved mechanical and thermomechanical properties with respect to the EVA while having an elastomeric behavior with respect to the nanocomposite synthesized by in situ polymerization of tetraethoxysilane.     

Surface grafting of polymers onto ultrafine silica: cationic polymerization initiated by benzylium perchlorate groups introduced onto ultrafine silica surface

Summary The cationic graft polymerization initiated by benzylium perchlorate groups introduced onto ultrafine silica surface was investigated. The introduction of benzylium perchlorate groups onto the surface was achieved by the reaction of silver perchlorate with surface benzyl chloride groups, which were introduced by the treatment of silica with 4-(chloromethyl)phenyltrimethoxysilane. The cationic graft polymerization of styrene and cationic ring-opening polymerization of -caprolactone were found to be initiated by the surface benzylium perchlorate groups and the corresponding polymers were grafted onto the surface. The percentage of grafting onto silica surface decreased with increasing polymerization temperature, because chain transfer reaction of growing polymer cation is accelerated with increasing polymerization temperature.     

Preparation of polymer/silica/polymer tri-layer hybrid materials and the corresponding hollow polymer microspheres with movable cores

Tri-layer poly(methacrylic acid-co-ethyleneglycol dimethacrylate)/silica/poly(ethyleneglycol dimethacrylate) (P(MAA-co-EGDMA)/SiO₂/PEGDMA) and P(MAA-co-EGDMA)/SiO₂/polydivinylbenzene hybrid microspheres were prepared by distillation precipitation polymerization of ethyleneglycol dimethacrylate (EGDMA) and divinylbenzene (DVB) in the presence of 3-(methacryloxy)propyl trimethoxysilane (MPS)-modified P(MAA-co-EGDMA)/SiO₂ microspheres as the seeds. The polymerization of EGDMA and DVB was performed in neat acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as initiator to coat the MPS-modified P(MAA-co-EGDMA)/SiO₂ seeds through the capture of EGDMA and DVB oligomer radicals with the aid of vinyl groups on the surface of modified seeds in the absence of any stabilizer or surfactant. Monodisperse P(MAA-co-EGDMA)/SiO₂ core-shell microspheres were synthesized by coating of a layer of silica onto P(MAA-co-EGDMA) microspheres via a sol-gel process, which were further grafted by MPS incorporating the reactive vinyl groups onto the surface to be used as the seeds for the construction of hybrid microspheres with tri-layer structure. Hollow poly(ethyleneglycol dimethacrylate) (PEGDMA) and poly(divinylbenzene) (PDVB) microspheres with movable P(MAA-co-EGDMA) core were subsequently developed after the selective etching of the silica mid-layer from the tri-layer hybrid microspheres in hydrofluoric acid. The morphology and structure of the tri-layer polymer hybrids and the corresponding hollow polymer microspheres with movable P(MAA-co-EGDMA) core were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra and X-ray photoelectron spectroscopy (XPS).     

A facile approach to covalently functionalized carbon nanotubes with biocompatible polymer

Biocompatible poly(l-lactic acid) (PLA) was successfully covalently grafted onto the convex surfaces and tips of the multi-walled carbon nanotubes (MWNTs) by one step based on in situ polycondensation of the commercially available l-lactic acid monomers. The functional groups in the carboxylic multi-walled carbon nanotubes (MWNT-COOH) showed active enough for participating the polycondensation of l-lactic acid. The resulting PLA-grafted-MWNTs were characterized with Raman spectroscopy, Fourier-transform IR (FTIR), UV-vis, ¹H NMR, thermogravimetric analyses (TGA) and transmission electron microscopy (TEM). Raman, FTIR and ¹H NMR spectroscopies revealed that the PLA was covalently attached to the MWNT. TGA showed that the grafted PLA content could be controlled by the reaction time. The core/shell structures with MWNT as the “hard” core and the PLA polymer layer as the “soft” shell can be clearly seen through HRTEM.     

PE膜表面接枝间苯二酚

Low density polyethylene film surface-grafted process. Firstly, acrylic acid was grafted to the surface grafting. Secondly, the carboxylic groups in poly （acrylic resorcinol was prepared by a sequential of low density polyethylene by UV photoacid） chains were transferred to acyl chloride groups by the reaction of carboxylic groups with thionyl chloride. The stability of acyl chloride groups in several solvents （alcohol, water, acetone, aqueous NaOH and in N2 atmosphere） was investigated, and N2 atmosphere and acetone were appropriate media to protect acyl chloride groups from side reaction. Finally, resorcinol monomer reacted with acyl chloride to append to the poly（acrylic acid） chains at room temperature. FT-IR ATR was used to characterize the change of carbonyl groups during each step of the grafting process. Furthermore, by the experimental data of gravimetric analysis the grafted resorcinol monomer on the surface of low density polyethylene film was verified to have undergone condensation with acetone further in the resorcinol/acetone solution at 56℃, which might be a useful feature for synthesizing a thermoplastic/thermosetting composition.     

Surface grafting of polymers onto aramid powder: graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface of aramid powder

The radical graft polymerization of vinyl monomers onto the surface of aramid powder, i.e., poly(p-phenylene terephthalamide) powder, initiated by azo groups introduced onto the surface was investigated. The introduction of azo groups onto the aramid surface was achieved by the reaction of surface acyl chloride groups, which were introduced by the treatment of aramid powder with adipoyl dichloride, with 2,2′-azobis[2-(2-imidazolyn-2-yl)propane] in the presence of pyridine: the amount of azo groups thus introduced onto the surface was determined to be 0.57 mmol/g by elemental analysis. It was found that the polymerizations of methyl methacrylate (MMA) and styrene were successfully initiated by the azo groups on the surface and that the corresponding polymers were grafted onto the surface. The percentage of surface grafting of polystyrene and poly(methyl methacrylate) (PMMA) increased up to 37.6 and 26.5%, respectively. Thermogravimetric analysis of polymer surface-grafted aramid powder confirmed that the grafting of polymers is limited on the surface. The polymerization rate was found to bear a first-order dependence on the concentration of aramid powder having azo groups. This suggests that in graft polymerization, unimolecular termination preferentially proceeds.     

Grafting onto carbon black by the reaction of reactive carbon black having acyl chloride group with several polymers

Summary Acyl chloride group introduced onto carbon black rapidly lost its activity by the moisture in air. However, the decrease of acyl chloride group content in vacuum was negligibly small. By the reaction of the acyl chloride group with several polymers having hydroxyl or amino group, such as polyethylene glycol (PEG), poly(vinyl alcohol)(PVA), and polyethyleneimine (PEI), these polymers were found to be effectively grafted onto carbon black; for instance, the grafting ratio of PEG (Mn=8.2×10³), PVA (Mn=2.2×10⁴), and PEI (Mn=2.0×10⁴) was 18.5%, 32.9%, and 45.8%, respectively. The number of polymer grafted onto carbon black decreased with an increase of its molecular weight.     

Preparation of doubly responsive polymer functionalized silica hybrid nanoparticles via a one‐pot thiol‐isocyanate click reaction at room temperature

Well‐defined poly(N‐isopropylacrylamide) and poly(2‐(diethylamino) ethyl methacrylate) were synthesized first by a reversible addition‐fragmentation chain transfer process. These polymers were then reduced to generate an end thiol group to react with isocyanate groups on the surface of silica nanoparticles, which were pretreated with toluene‐2,4‐diisocyanate, by a one‐pot “click” reaction to prepare temperature and pH responsive polymer functionalized hybrid silica nanoparticles. The polymer functionalized silica hybrid nanoparticles were characterized by a range of techniques such as Fourier transform infrared spectroscopy and dynamic light scattering. The doubly responsive polymer functionalized silica hybrid nanoparticles show both temperature and pH responsive behavior and their solution properties were dependent on the ratio of the two polymers on the surface of silica. Covalent functionalization of the silica nanoparticle with well‐defined temperature and pH responsive polymers was accomplished via a one‐pot thiol‐isocyanate click reaction. This reaction was found to be extremely efficient in producing doubly responsive polymer functionalized silica hybrid nanoparticle, even at relatively low reaction temperature and short reaction time. Thermogravimetric analysis indicated that the same ratio of poly(N‐isopropylacrylamide) and poly(2‐(diethylamino)ethyl methacrylate) functionalized silica hybrid nanoparticle consisted of 42.46 wt% polymer. POLYM. COMPOS., 38:1454–1461, 2017. © 2015 Society of Plastics Engineers     

磺化聚醚醚酮/接枝多壁碳纳米管复合膜的制备与表征

以浓硫酸为磺化剂,室温下制备了磺化聚醚醚酮(SPEEK)。以N,N-二环己基碳酰亚胺(DCC)为催化剂,将对氨基苯磺酸接枝到多壁碳纳米管(MWCNTs)的表面。采用溶液共混法制备了SPEEK/g-MWCNTs复合膜。采用傅里叶变换红外光谱仪(FT-IR)分析了复合膜的化学结构,采用光学显微镜以及扫描电子显微镜(FESEM)观察了膜的表面和断面结构,并采用交流阻抗法考察了膜的质子传导性能。结果表明:碳纳米管在复合膜中分散均匀,树脂基体包覆在碳管表面,复合膜的质子传导性和拉伸强度均优于磺化聚醚醚酮纯膜。     

Synthesis of Multiwalled Carbon Nanotubes–Poly(Methacrylic Acid) Nanohybrid Systems: Characterization,Thermal Properties,and In Vitro Release Studies of Naproxen as a Model Drug

Nanohybrid systems based on carbon nanotubes and pH-sensitive poly(methacrylic acid) were prepared through attaching polymer chains onto carbon nanotubes. First, polymerizable groups were attached onto carbon nanotube walls, then the polymerizable groups were copolymerized with different ratios of methacrylic acid. Obtained systems were studied and characterized through Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. A model drug (naproxen) was entrapped into the prepared materials and in vitro release studies were performed in pH 1 (simulated gastric fluids) and pH 7.4 (simulated intestinal fluids). It was noticed that release in simulated intestinal fluids was faster than simulated gastric fluids, therefore the prepared nanohybrid systems can be considered as appropriate carriers for colon-specific drug delivery.     

AC conductivity of conjugated polymer onto self-assembled aligned carbon nanotubes

This work focuses on the combination of the complementary properties of carbon nanotube (CNT) thin film and poly3-octylthiophene (P3OT), following a dielectric route to the characterization of a novel composite material. The structural and electrical characterization of a P3OT/CNTs hybrid system performed by X-ray diffraction, differential scanning calorimetry and a.c. impedance spectroscopy show interesting effects, including the tendency of the nanotube structure to nucleate crystal growth and substantial changes in the dielectric behavior of the polymer, due to the effect of the polymer on the nanotube conformation. Dielectric relaxation spectroscopy demonstrates that the crystallization of the polymer onto the nanotubes results into a different relaxation of the composite's electronic structure. The changes in the dielectric properties can be explained in terms of a reduced vibrational freedom of the polymer chains as a consequence of the intercalation of the polymer matrix into the nanotubes’ lattice.     

Modification of halloysite nanotubes with poly(styrene–butyl acrylate–acrylic acid) via in situ soap‐free graft polymerization

Halloysite nanotubes (HNTs) were grafted with poly(styrene–butyl acrylate–acrylic acid) (P‐SBA) via an in situ soap‐free emulsion polymerization. To introduce double bonds into the HNTs, N‐(β‐aminoethyl)‐γ‐aminopropyl trimethoxysilane was first used to modify the HNTs and render amino groups, and then, the double bonds were anchored through an amidation reaction between acryloyl chloride and amino groups. P‐SBA chains were grafted onto HNTs because of participating of double bonds in the copolymerization of styrene, butyl acrylate, and acrylic acid. Fourier transforms infrared spectroscopy, transmission electron microscopy, specific surface area measurements, and thermogravimetric analysis were used to characterize the HNTs grafted with P‐SBA. The results indicate that 25.21% of P‐SBA was grafted onto the outer walls of the HNTs and filled into the inner spaces of the HNTs. The modification dramatically decreased the surface area of the HNTs. The property study of the HNTs grafted with P‐SBA focused on the dispersion behavior in the biphase system. The results show that the grafted HNTs dispersed stably in the water/cyclohexane biphase system and were a potential emulsifier. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010