Efficient dispersion of multi‐walled carbon nanotubes by in situ polymerization

Multi‐walled carbon nanotube (MWNT)‐reinforced polyimide nanocomposites were synthesized by in situ polymerization of monomers in the presence of acylated MWNTs. The acyl groups associated with the MWNTs participated in the reaction through the formation of amide bonds. This process enabled uniform dispersion of MWNT bundles in the polymer matrix. The resultant MWNT–polyimide nanocomposite films were optically transparent with significant mechanical enhancement at a very low loading (0.5 wt%). Evidence has been obtained for improved interactions between the nanotubes and the matrix polymer. Copyright © 2006 Society of Chemical Industry     

Preparation of polyimide/siloxane‐functionalized graphene oxide composite films with high mechanical properties and thermal stability via in situ polymerization

An effective approach to prepare polyimide/siloxane‐functionalized graphene oxide composite films is reported. The siloxane‐functionalized graphene oxide was obtained by treating graphene oxide (GO) with 1,3‐bis(3‐aminopropyl)‐1,1,3,3‐tetra‐methyldisiloxane (DSX) to obtain DSX‐GO nanosheets, which provided a starting platform for in situ fabrication of the composites by grafting polyimide (PI) chains at the reactive sites of functional DSX‐GO nanosheets. DSX‐GO bonded with the PI matrix through amide linkage to form PI‐DSX‐GO films, in which DSX‐GO exhibited excellent dispersibility and compatibility. It is demonstrated that the obvious reinforcing effect of GO to PI in mechanical properties and thermal stability for PI‐DSX‐GO is obtained. The tensile strength of a composite film containing 1.0 wt% DSX‐GO was 2.8 times greater than that of neat PI films, and Young's modulus was 6.3 times than that of neat PI films. Furthermore, the decomposition temperature of the composite for 5% weight loss was approximately 30 °C higher than that of neat PI films. © 2015 Society of Chemical Industry     

Polystyrene composites of single‐walled carbon nanotubes‐graft‐polystyrene

Single‐walled carbon nanotubes (SWCNTs) dispersed in N‐methylpyrrolidone (NMP) were functionalized by addition of polystyryl radicals from 2,2,6,6‐tetramethyl‐1‐piperidinyloxy‐ended polystyrene (SWCNT‐g‐PS). The amount of polystyrene grafted to the nanotubes was in the range 20‐25 wt% irrespective of polystyrene number‐average molecular weight ranging from 2270 to 49 500 g mol^?1. In Raman spectra the ratios of D‐band to G‐band intensity were similar for all of the polystyrene‐grafted samples and for the starting SWCNTs. Numerous near‐infrared electronic transitions of the SWCNTs were retained after polymer grafting. Transmission electron microscopy images showed bundles of SWCNT‐g‐PS of various diameters with some of the polystyrene clumped on the bundle surfaces. Composites of SWCNT‐g‐PS in a commercial‐grade polystyrene were prepared by precipitation of mixtures of the components from NMP into water, i.e. the coagulation method of preparation. Electrical conductivities of the composites were about 10^?15 S cm^?1 and showed no percolation threshold with increasing SWCNT content. The glass transition temperature (T_g) of the composites increased at low filler loadings and remained constant with further nanotube addition irrespective of the length and number of grafted polystyrene chains. The change of heat capacity (ΔC_p) at T_g decreased with increasing amount of SWCNT‐g‐PS of 2850 g mol^?1, but ΔC_p changed very little with the amount of SWCNT‐g‐PS of higher molecular weight. The expected monotonic decrease in ΔC_p coupled with the plateau behavior of T_g suggests there is a limit to the amount that T_g of the matrix polymer can increase with increasing amount of nanotube filler. Copyright © 2012 Society of Chemical Industry     

Dispersion of multi‐walled carbon nanotubes in poly(aryl ether ketone) obtained by in situ polymerization

BACKGROUND: Recently, much work has focused on the efficient dispersion of carbon nanotubes (CNTs) throughout a polymer matrix for mechanical and/or electrical matrices. However, CNTs used as enhancement inclusions in a high‐performance polymer matrix, especially in poly(aryl ether ketone) (PAEK), have rarely been reported. Therefore, multi‐walled carbon nanotube (MWNT)‐modified PAEK nanocomposites were synthesized by in situ polymerization of monomers of interest in the presence of pre‐treated MWNTs. RESULTS: This process enabled a uniform dispersion of MWNT bundles in the polymer matrix. The resultant MWNT/PAEK nanocomposite films were optically transparent with significant mechanical enhancement at a very low MWNT loading (0.5 wt%). CONCLUSION: These MWNT/polymer nanocomposites are potentially useful in a variety of aerospace and terrestrial applications, due to the combination of excellent properties of MWNTs with PAEK. Copyright © 2009 Society of Chemical Industry     

In situ polymerization of 3‐hexylthiophene with double‐walled carbon nanotubes: Studies on the conductive nanocomposite

Poly(3‐alkylthiophene)s represent a family of conjugated polymers that are soluble and processable, but still retaining the good electrical conductivity of the insoluble parent polymer thiophene ring backbone. Poly(3‐hexylthiophene) (P3HT) is reported to be a best candidate in the family for solar cell applications. In situ polymerization of 3‐hexylthiophene monomer with double‐walled carbon nanotubes (DWCNTs) has been attempted with the aim of addressing two main issues, namely, the interfacial bonding and proper dispersion of the carbon nanotubes in the polymer matrix to get a high‐performing polymer/nanocomposite. Fourier transform infrared spectroscopy, Raman, and X‐ray diffraction studies indicate the physical wrapping of the polymer on the nanotubes in the absence of any ground‐state interaction between them. The ultraviolet–visible measurements also support this view. The photoluminescence quenching indicates the effectiveness of the interface in the formation of the donor–acceptor‐type composite. The impressive conductivity values encourage the utility of the composites as photovoltaic material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Multiwalled carbon nanotube/polyacrylonitrile composite fibers prepared by in situ polymerization

Multi‐walled carbon nanotubes (CNTs) were mixed with polyacrylonitrile (PAN) by in situ polymerization or by mechanically mixing. The mixtures were then wet‐spun into fibers, respectively. The effects of mixing method on the interfacial bonding between the components in the fibers and the properties of the fiber were investigated by Raman spectroscopy, TEM, SEM, and tensile strength testing. By in situ polymerization mixing, a thin layer of PAN molecules is observed to cover the surface of the CNT, which increases the diameter of CNT evidently. Results of Raman spectroscopy indicate that the layer of PAN molecules are strongly attached onto the surface of CNT through grafting polymerization, leading to strong chemical bonding between CNTs and PAN matrix in the obtained fibers. In contrast, no obvious chemical interactions are observed between them in the fibers prepared by mechanically mixing. In both cases, the CNTs have significantly strengthened the PAN fibers. However, the fibers prepared from in situ polymerization mixing are much stronger because of the interfacial bonding effect between the PAN molecules and CNTs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Formation of Ziegler-type catalytic systems on the surface of multi-walled carbon nanotubes for the production of composite materials by in situ polymerization

The peculiarity of formation of Ziegler-type catalytic systems prepared using organoaluminum (AlR₃) and organomagnesium (MgR₂) on the surface of multi-walled carbon nanotubes (MWCNTs) was revealed. We have found first AlR₃ and MgR₂ interact with different sites on MWCNT surface. It was demonstrated by IR spectroscopy that organoaluminum compounds were immobilized on the hydroxyl-containing groups on MWCNT surface. Organomagnesium compounds were immobilized on the topological structural defects of MWCNTs; hydroxyl-containing groups were not required for their immobilization. Further interaction between TiCl₄ and organomagnesium compound immobilized on the MWCNT surface yielded a catalyst containing titanium and magnesium chlorides (an analogue of the known titanium–magnesium catalysts), which exhibits an enhanced activity in ethylene polymerization. The effect of polymerization conditions on molecular weight characteristics of polyethylene in the MWCNT/PE composite material produced by in situ polymerization over the catalyst immobilized on the MWCNT surface was studied. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48212.     

Carbon nanotubes‐reinforced PET nanocomposite by melt‐compounding

Poly(ethylene terephthalate) (PET) nanocomposites with single‐walled carbon nanotubes (SWNTs) have been prepared by a simple melt compounding method. With increasing concentration (0–3 wt %) of SWNTs, the mechanical and dynamic mechanical properties improved, corresponding to effective reinforcement. Melt rheological characterization indicated the effective entanglements provided by SWNTs in the melt state as well. Thermogravimetric analysis suggested no influence of SWNTs on the thermal stability of PET. Electrical conductivity measurements on the composite films pointed out that the melt compounded SWNTs can result in electrical percolation albeit at concentrations exceeding 2 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and properties of homogeneously dispersed polyamide 6/MWNTs nanocomposites via simultaneous in situ anionic ring‐opening polymerization and compatibilization

Toluene 2, 4‐diisocyanate (TDI) functionalized multiwalled carbon nanotubes (MWNTs‐NCO) were used to prepare monomer casting polyamide 6 (MCPA6)/MWNTs nanocomposites via in situ anionic ring‐opening polymerization (AROP). Isocyanate groups of MWNTs‐NCO could serve as AROP activators of ?‐caprolactam (CL) in the in situ polymerization. Fourier transform infrared (FTIR) showed that a graft copolymer of PA6 and MWNTs was formed in the in situ polymerization. MWNTs‐PA6 covalent bonds of the graft copolymer constituted a strong type of interfacial interaction in the nanocomposites and increased the compatibility of MWNTs and MCPA6 matrix. The nanocomposites were characterized for the morphology, mechanical, crystallization, and thermal properties through field emission transmission electron microscopy (FETEM), tensile testing, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). FETEM analysis showed that MWNTs were homogeneously dispersed in MCPA6 matrix. The initial tensile strengths and tensile modulus of the nanocomposite with 1.5 wt % loading of MWNTs were enhanced by about 16 and 13%, respectively, compared with the corresponding values for neat MCPA6. DSC analysis indicated that the crystallization temperature of the nanocomposites was increased by 8°C by adding 1.5 wt % MWNTs compared with pure MCPA6. Besides, it was found that the thermal stability of MCPA6 was improved by the addition of the MWNTs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyacrylate‐core/TiO2‐shell nanocomposite particles prepared by in situ emulsion polymerization

We report the preparation of polyacrylate‐core/TiO₂‐shell nanocomposite particles through in situ emulsion polymerization in the presence of nano‐TiO₂ colloid obtained by the hydrolysis of titanium tetrachloride. The resultant colloidal system can be stable for months without any precipitation. In a typical sample, the diameter of nanocomposite particles was about 150 nm, and the thickness of TiO₂‐shell was 4–10 nm. Only cetyltrimethylammonium bromide was employed to provide the latex particles with positive charge, which was enough for the formation of fine TiO₂ coatings. Three initiators were tested. Ammonia persulfate was the most suitable one, because the cooperative effect was formed by the negatively charged TiO₂ particles and the terminal anionic group (SO₄^2?, the fraction of Ammonia persulfate) of the polymer chain on the surface of latex particles to maintain the stability of nanocomposite system. The pH value played a vital role in obtaining a tight TiO₂ coating. Transmission electron microscopy, X‐ray diffraction and Atomic force microscopy were used to characterize this nanocomposite material. It was found that rutile and anatase coexisted in the nanocomposite film. This may suggest a potential application in the field of photocatalytic coating. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1466–1470, 2006     

Preparation of conductive polypyrrole composites by in‐situ polymerization

Two kinds of conductive polypyrrole composites were prepared by in‐situ polymerization of pyrrole in a suspension of chlorinated polyethylene powder or in a natural rubber latex using ferric chloride as oxidizing agent. The preparation conditions were studied and the results showed that it is better to swell the chlorinated polyethylene powder with the monomer first, followed by addition of the oxidant, than to add the oxidant first, and that conversion can reach 98% for 6 h at room temperature. The conductivity percolation threshold of the composite is about 12%. The composites can be processed repeatedly, exhibiting a maximum tensile strength over 9 MPa and a maximum conductivity near 1 S cm⁻¹. The polypyrrole/natural rubber composites were prepared successfully by using a nonionic surfactant (Peregal O) as stabilizer at pH less than 3 with a molar ratio of FeCl₃/pyrrole = 2.5 below 45 °C. The latter composites show a low conductivity percolation threshold about 6%, a maximum tensile strength over 10 MPa and a maximum conductivity over 2 S cm⁻¹. The composites were characterized by FTIR and TGA. The polypyrrole/chlorinated polyethylene composites are very stable in air and almost no decrease of conductivity was observed for over 10 months examined. © 1999 Society of Chemical Industry     

Ionomer covalent functionalization of single‐walled carbon nanotubes by radical polymerization of zirconium acrylate

A facile and efficient covalent functionalization of single‐walled carbon nanotubes (SWCNTs) via peroxide‐mediated free radical covalent attachment and polymerization of zirconium acrylate is reported. The resulting covalently functionalized SWCNTs exhibit improved solubility in organic solvents. The covalently functionalized SWCNTs are characterized by cross polarization magic angle spinning ¹³C NMR, differential scanning calorimetry, thermogravimetric analysis, x‐ray diffraction, Raman, and infrared spectroscopy. Infrared spectroscopy reveals that carboxylate groups of covalently attached ionomers chelate with zirconium ions and the participating carboxylate groups may be from different ionomer chains leading to cross‐linking the chains. The SWCNT topology, ionic clustering, and π‐electron clouds were explored by transmission electron microscopy. © 2014 American Institute of Chemical Engineers AIChE J, 60: 820–828, 2014     

In‐situ self reinforced polyimide for film materials

A novel polyimide (PI) with mesogenic units was synthesized by the reaction between the pendent hydroxyl group of PI and the epoxy group of a liquid crystalline (LC) compound in the presence of N,N‐dimethylaniline at 120–130 °C. As a result, a novel in‐situ self‐reinforced PI film materials was obtained. The macromolecular reaction between the hydroxyl group and epoxy group was investigated by a model reaction. The properties of PI were studied by WAXD, DSC and polarized optical microscopy, and the results indicate that the polyimides with mesogenic units exhibit a smectic phase, the mesogenic units level influencing the side‐chain crystallinity, and also the thermal and mechanical properties of the polymers; the enhanced PI films possess good solubility, higher thermal stability, higher tensile strength and modulus. © 2001 Society of Chemical Industry     

In situ polymerization and photophysical properties of poly(p‐phenylene benzobisoxazole)/multiwalled carbon nanotubes composites

Poly(p‐phenylene benzobisoxazole)/multiwalled carbon nanotubes (PBO‐MWCNT) composites with different MWCNT compositions were prepared through in situ polymerization of PBO in the presence of carboxylated MWCNTs. The nanocomposite's structure, thermal and photophysical properties were investigated and compared with their blend counterparts (PBO/MWCNT) using Fourier transform infrared spectra, Raman spectra, Wide‐angle X‐ray diffraction, thermogravimetric analysis, UV‐vis absorption, and photoluminescence. The results showed that MWCNTs had a strong interaction with PBO through covalent bonding. The incorporation of MWCNTs increased the distance between two neighboring PBO chains and also improved the thermal resistance of PBO. The investigation of UV‐vis absorption and fluorescence emission spectra exhibited that in situ PBO‐MWCNT composites had a stronger absorbance and obvious trend of red‐shift compared with blend PBO/MWCNT composites for all compositions. This behavior can be attributed to the efficient energy transfer through forming conjugated bonding interactions in the PBO‐MWCNT composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of biocompatible multi‐walled carbon nanotubes as potential tracers for sentinel lymph nodes

Carbon nanotubes (CNTs) are capable of traversing cellular membranes by endocytosis and are therefore promising materials for use in imaging and drug delivery. Unfortunately, pristine CNTs are practically insoluble and tend to accumulate inside cells, organs and tissues. To overcome the poor dispersibility and toxicity of pristine CNTs, hydrophilic functionalization of CNTs has been intensively investigated. Water‐soluble multi‐walled carbon nanotubes (MWCNTs) were prepared by in situ polymerization of acrylic acid in a poor solvent for poly(acrylic acid) (PAA). The solvent type influenced the grafted density and chain length of PAA. MWCNTs with a high grafted density of PAA (22 wt%) could be well dispersed in water, NaCl aqueous solution (0.9 wt%) and cell culture media. The in vitro cytotoxicity of these MWCNTs for endothelial cells is reasonably low even at high concentration of PAA‐g‐MWCNT (70 µg mL^?1). The experimental results show that the biocompatibility of these MWCNTs is sufficient for biological applications. PAA‐g‐MWCNTs were successfully utilized for lymph node tracing. Experimental results suggest that PAA‐g‐MWCNTs have potential to be used as a vital staining dye, which may simplify the identification of lymph nodes during surgery. Copyright © 2009 Society of Chemical Industry     

Carbon nanotube reinforced rigid‐rod polyimide

Multiwalled carbon nanotube/rigid‐rod polyimide composite films have been prepared by casting a solution of precursor polymer (polyamide acid) containing multiwalled carbon nanotubes (MWNTs) into thin films, followed by a thermal imidization treatment. The composite films were characterized by FTIR, TEM, DSC, TGA and TMA, and the film tensile properties were also examined. The presence of 1.0% MWNTs in the polymer matrix led to more than twofold increase in tensile strength of the rigid‐rod polyimide composite films and improved thermal stability, but reduced in thermal deformation. However, the tensile property did not show further increase when the film contained higher composition of MWNTs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

In situ polymerization of ethylene with functionalized multiwalled carbon nanotubes using a zirconocene aluminohydride system in solution

This study reports nanocomposite synthesis based on high-density polyethylene with carbon nanotubes through in situ polymerization by coordination, and the use of an aluminohydride zirconocene/MAO system as a catalyst. Nanocomposites of linear polyethylene exhibit higher molar masses than pure high-density polyethylene synthesized under similar conditions; where multiwalled carbon nanotubes (MWCNTs) acted as nucleating agents, shifting the crystallization temperature to higher values than neat high-density polyethylene. Well-dispersed MWCNTs in the HDPE matrices of the obtained nanocomposites are observed by SEM, where most of the nanocomposites showed an improvement in their thermal stability and electric conductivity, besides it is possible to obtain nanocomposites containing up to 41 wt% of nanofiller in the polymeric matrix. The aluminohydride complex n-BuCp₂ZrH₃AlH₂, activated with MAO at Al/Zr ratios of 2000, produced homogeneous HDPE/MWCNT composites under in situ polymerization conditions, at 70°C and 2.9 bar of ethylene pressure, with minimal residual alumina in the HDPE matrix.     

Effect of talc/MMA in situ polymerization on mechanical properties of PVC‐matrix composites

In this study, polymethyl methacrylate (PMMA)‐coated talc was produced by the in situ polymerization of methyl methacrylate on the talc surface. The polymerization reaction was performed by both batch and semicontinuous emulsion processes. The polymerization kinetics, particle size and distribution, grafting efficiency, and coated‐talc morphology were systematically investigated. It was found that the talc particles have no effect on the polymerization of PMMA. The PMMA produced was found to cover the talc surface well. However, only a small amount can be grafted onto the talc. The size distribution of talc particles treated by semicontinuous emulsion polymerization is more uniform than by batch polymerization. The treated talc was subsequently used as filler in a poly(vinyl chloride) (PVC) matrix, and mechanical properties of the PMMA‐coated‐talc/PVC composites were studied. Morphological structure of PVC‐matrix composites revealed that the PMMA coating on talc improved the dispersion of talc in the PVC matrix and enhanced the interfacial adhesion between the talc and PVC. The mechanical properties of the composites, especially the impact strength, were found to be improved. There appears to be a critical covering thickness of PMMA on the talc surface for optimum toughening. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2105–2112, 2001     

Studies on electro‐conductive yarns prepared by in situ chemical and electrochemical polymerization of pyrrole

This work deals with preparation, characterization, and performance of electro‐conductive yarns prepared by in situ chemical and electrochemical polymerization of pyrrole. Box‐Behnken design in conjunction with response surface analysis has been used to study the electrochemical polymerization process. The effect of electrochemical process parameters on the electrical resistivity has been reported. Further, the electrical and electromechanical behaviour of the electro‐conductive yarns thus produced has also been reported. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of pyrene‐capped polystyrene for dispersion of pristine single‐walled carbon nanotubes

Pyrene‐capped polystyrene (PyPS) with various molecular weights (M?_n) was synthesized through the anionic polymerization method and characterized using UV, Fourier transform infrared and NMR spectroscopy and gel permeation chromatography. The polymers were then used for non‐covalent functionalization of pristine single‐walled carbon nanotubes (SWNTs). The functionalization efficiency was assessed by measuring the SWNT dispersibility in chloroform. In the presence of PyPS, the dispersibility can be as high as 372.5 mg L^?1, and the dispersions containing more than 1.25 mg mL^?1 of PyPS are very stable with no solid deposits observed after being centrifuged at 5000 rpm for 15 min. Once the PyPS concentration is converted to the molar concentration of the pyrene unit and the dispersibility redefined as nanotube content per molar pyrene unit, the renewed dispersibility is found to be independent of M?_n of PyPS within the detected M?_n range. For a certain PyPS polymer, however, both nanotube dispersibility and dispersion stability are strongly dependent on the PyPS concentration. These results suggest that PyPS may be used as an excellent dispersant for subsequent preparation of polystyrene/SWNT composites. Copyright © 2011 Society of Chemical Industry