Novel conjugated patterns of PBDT‐DTNT and PBDT‐TIPS‐DTNT‐DT complicated polymers onto graphenic nanosheets

The delicacy and connectivity of conductive patterns developed via poly[benzodithiophene‐bis(decyltetradecylthien)naphthothiadiazole] (PBDT‐DTNT) and poly[bis(triisopropylsilylethynyl)benzodithiophene‐bis(decyltetradecylthien)naphthobisthiadiazole] (PBDT‐TIPS‐DTNT‐DT) polymers were investigated on reduced graphene oxide (rGO) nanosheets. The principal driving force for assembly of PBDT‐DTNT and PBDT‐TIPS‐DTNT‐DT chains onto the rGO nanosheets was π‐stacking. In contrast to poly(3‐hexylthiophene) (P3HT), the surface modification of rGO limited the self‐assembly of PBDT‐DTNT and PBDT‐TIPS‐DTNT‐DT complicated polymers. The structure of PBDT‐DTNT and PBDT‐TIPS‐DTNT‐DT chains having fused and infused thiophenic and benzenic rings hindered their molecular ordering compared to P3HT, and therefore the selected area electron diffraction plots demonstrated rings instead of isolated growth planes. Although 2‐thiophene acetic acid (TAA) functional groups and poly(3‐dodecylthiophene) (PDDT) grafted onto rGO nanosheets did not alter the stacking type of the complicated polymers, it made their attachment more difficult. The thickness of π‐stacked patterns ranged from 55 to 70 nm. In the modified areas of rGO, the PBDT‐DTNT and PBDT‐TIPS‐DTNT‐DT chains were not capable of being deposited with a π‐interaction. Hence, the surface modification agents prevented the complicated polymers from interconnectedly assembling and, consequently, constructing longer and larger patterns. This hindrance was more noticeable for the supramolecules based on grafted rGO (rGO‐g‐PDDT) and PBDT‐TIPS‐DTNT‐DT. The conductivity of PBDT‐DTNT/rGO superstructures was the highest (14.61–14.89 S cm^?1). The patterned nanohybrids could be considered as potential super‐materials for morphology‐templating in the active layers of organic–inorganic photovoltaics. © 2018 Society of Chemical Industry     

Linear viscoelastic properties and crystallization behavior of multi‐walled carbon nanotube/polypropylene composites

Multi‐walled carbon nanotube/polypropylene composites (PPCNs) were prepared by melt compounding. The linear viscoelastic properties, nonisothermal crystallization behavior, and kinetics of PPCNs were, respectively, investigated by the parallel plate rheometer, differential scanning calorimeter (DSC), X‐ray diffractometer (XRD), and polarized optical microscope (POM). PPCNs show the typical nonterminal viscoelastic response because of the percolation of nanotubes. The rheological percolation threshold of about 2 wt % is determined using Cole‐Cole method. Small addition of nanotube can highly promote crystallization of PP matrix because of the heterogeneous nucleating effect. With increasing nanotube loadings, however, the crystallization rate decreases gradually because the mobility of PP chain is restrained by the presence of nanotube, especially at high loading levels. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Preparation and characterization of multi‐walled carbon nanotubes/polymer gradient composite films

BACKGROUND: Recently, much work has focused on the efficient dispersion of carbon nanotubes (CNTs) throughout a polymer matrix for mechanical and/or electrical enhancement. However, there are still only few reports about gradient distribution of CNTs in polymer matrices. In the work reported here, CNTs embedded in a polymer film with a gradient distribution were successfully obtained and studied. RESULTS: For composite films with gradient distributions of CNTs, the upper surface behaves as an intrinsic insulator, while the lower one behaves as a semiconductor, or even as a conductor. It is also found that with an increase of 1 wt% CNTs, the resistance of the bottom surface decreases by 2–3 orders of magnitude, as compared with pure polyarylene ether nitrile; furthermore, when the proportion of CNTs increases up to 5 wt%, the resistance of the bottom surface shows only very little change. As a result, sufficient matrix conductivity of the bottom surface could be achieved at a lower filler concentration with CNTs in a gradient distribution. Meanwhile, the thermal stability, glass transition temperature and tensile properties of the matrix are maintained. CONCLUSION: There is considerable interest in such gradient composite films, which could be applied in the electrical engineering, electronics and aerospace fields, for their excellent mechanical properties, thermal stability and novel electrical properties. Copyright © 2008 Society of Chemical Industry     

Nanocomposites of poly(L‐lysine) and single‐walled carbon nanotubes

BACKGROUND: Single‐walled carbon nanotubes have inspired research owing to their promise in a broad range of applications. The dispersion of carbon nanotubes is of key importance for the utilization of this interesting material for various potential applications. RESULTS: A novel and simple method was developed to fabricate polymer composites with single‐walled carbon nanotubes based on a solid‐state reaction, in which the nanotubes were reacted with poly(L ‐lysine) using high‐speed vibration milling. Fourier transform infrared and UV‐visible spectroscopy as well as thermogravimetry were employed to characterize the novel composites. The morphology and the dispersion of the carbon nanotubes were determined using scanning and transmission electron microscopy. CONCLUSION: The resulting composites were dispersable in water and are expected to have great potential for both molecular‐level studies and device applications of nanotubes. Copyright © 2007 Society of Chemical Industry     

Effect of covalent bonds on the mechanical properties of a multi‐walled carbon nanotube/cellulose composite

A multi‐walled carbon nanotube (MWCNT)/cellulose composite was synthesized to improve the mechanical strength of regenerated cellulose film. N,N‐carbonyldiimidazole was mixed with functionalized MWCNTs and sonicated at 60 °C for 12 h. The resulting MWCNT‐imidazolide was mixed with cellulose solution, and reacted at various temperatures for various times. The occurrence of covalent bonds between MWCNTs and cellulose was investigated using Fourier transform infrared spectroscopy and Raman spectroscopy. According to mechanical tensile tests, Young's modulus of the MWCNT/cellulose composite was found to be 11.2 GPa, an increase of approximately 110% with respect to regenerated cellulose film. Copyright © 2010 Society of Chemical Industry     

Thermal degradation behaviour of multi‐walled carbon nanotube‐reinforced poly(L‐lactide) nanocomposites

BACKGROUND: Polymer/multi‐walled carbon nanotube (MWCNT) composites are one of the most promising alternatives to conventional polymer composites filled with micrometre‐sized fillers. This approach can also be applied for the improvement of mechanical properties and thermal stability of biodegradable aliphatic polyesters, such as poly(L ‐lactide) (PLLA), which have been receiving increasing attention due to environmental concerns. Thermal degradation behaviour provides useful information for the determination of the optimum processing conditions and for identification of potential applications of final products. RESULTS: The PLLA/MWCNT composites investigated showed a higher thermal degradation peak temperature and onset temperature of degradation along with a higher amount of residue at the completion of degradation than neat PLLA. Moreover, PLLA/MWCNT composites with a greater MWCNT content showed higher activation energy of thermal degradation than those with a lower MWCNT loading, which confirmed the positive effect of MWCNT incorporation on the enhancement of PLLA thermal stability. CONCLUSION: This study explored the thermal degradation behaviour of PLLA/MWCNT composites by observing the weight loss, molecular weight and mechanical properties during non‐isothermal and isothermal degradation. The incorporation of MWCNTs into the PLLA matrix enhanced considerably the mechanical properties and thermal stability. Copyright © 2009 Society of Chemical Industry     

Interfacial conversion for poly(para‐phenylenevinylene) at a cholesteric liquid crystal surface

A new approach for the preparation of poly (para‐phenylenevinylene) (PPV) with an ordered structure is presented. PPV is synthesized by a precursor method using a cholesteric liquid crystal medium. The resultant PPV film is observed to have a cholesteric fingerprint‐like texture, indicating replication of the cholesteric liquid crystal medium. Infrared absorption measurements confirm that the PPV has essentially the same molecular structure as normal PPV film. Ultraviolet–visible absorption measurements show that the absorption band due to π?π* transition of the conjugated main‐chain is located at 402 nm. The conversion is found to occur at the interface with the cholesteric liquid crystal medium as a mechanical process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Dynamic mechanical and Raman spectroscopy studies on interaction between single‐walled carbon nanotubes and natural rubber

The effects of the incorporation of single‐walled carbon nanotubes (SWNTs) on the physical and mechanical properties of natural rubber (NR) are described. Characterization of these new materials has been performed by dynamic mechanical analysis, differential scanning calorimetry, and Raman spectroscopy to obtain information about of the possible interactions between both materials as well as the dispersion of SWNTs on elastomer matrix. The results are then compared with those obtained for NR–carbon black composites. Dynamic mechanical analysis indicates a stronger filler–matrix interaction in the case of SWNTs incorporation, showing a noticeable decrease of the height of tan δ peak, as well as a marked shift of T_g towards higher temperatures. In particular, the increase of the storage modulus indicates a beneficial effect of SWNTs incorporation with respect to NR filled with carbon black and the pristine polymer matrix. In addition, calorimetric analysis indicates that both fillers accelerate the NR vulcanization reaction, this effect being more evident when SWNTs are added into the matrix. Raman spectroscopy indicates that SWNTs dispersion into the elastomer matrix creates residual strain on the nanotubes bundle. We demonstrate that the Raman microprobe technique provides a means for load transfer effectiveness of SWNTs. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3394–3400, 2004     

Formation mechanism of polyaniline self‐assembled needles and urchin‐like structures assisted by magnesium oxide

The polyaniline (PANI) morphological structure is strongly correlated with the preparation procedure, yielding diverse geometries such as nano‐tubes, belts, rods, fibres and particles. In this study, the synthesis of a novel PANI morphology of consisting of hollow needles and urchin‐like structures is presented and its formation mechanism is explained. The polymer was synthesized by chemical oxidative polymerization of aniline in the presence of magnesium oxide as a structural directing agent. The morphological study of the urchin‐like PANI was conducted using scanning electron microscopy and in situ monitoring of needle growth was done using optical microscopy. The structure and functional groups of these novel structures were characterized using Fourier transform infrared spectroscopy. Additionally, the formation mechanism is modelled based on the multi‐layer theory where a core–shell structure exists between the polymer (shell) and the magnesium oxide particles (core). © 2014 Society of Chemical Industry     

Functionalization of multi‐walled carbon nanotubes with poly(ε‐caprolactone) using click chemistry

Multi‐walled carbon nanotubes (MWNTs) were covalently functionalized with poly(ε‐caprolactone) (PCL) using click chemistry. First, chlorine moiety‐containing PCL was synthesized by the copolymerization of α‐chloro‐ε‐caprolactone with ε‐caprolactone monomer using ring opening polymerization, and further converted to azide moiety‐containing PCL. The alkyne‐functionalized MWNTs were prepared with the treatment of p‐amino propargyl ether using a solvent free diazotization procedure. The covalent functionalization of alkyne‐derived MWNTs with azide moiety‐containing PCL was accomplished using Cu(I)‐catalyzed [3+2] Huisgen dipolar cycloaddition click chemistry. The PCL‐functionalization of MWNTs was confirmed by the measurements of Fourier transform infra‐red, NMR, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The morphology and thermal properties of multi‐walled carbon nanotube and poly(hydroxybutyrate‐co‐hydroxyvalerate) composite

Nanocomposites based on poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) and multi‐walled carbon nanotubes (MWNTs) were prepared by solution processing. Ultrasonic energy was used to uniformly disperse MWNTs in solutions and to incorporate them into composites. Microscopic observation reveals that polymer‐coated MWNTs dispersed homogenously in the PHBV matrix. The thermal properties and the crystallization behavior of the composites were characterized by thermogravimetric analysis, differential scanning calorimetry and wide‐angle X‐ray diffraction, the nucleant effect of MWNTs on the crystallization of PHBV was confirmed, and carbon nanotubes were found to enhanced the thermal stability of PHBV in nitrogen. Copyright © 2004 Society of Chemical Industry     

Preparation and characterization of polydiphenylamine/multi‐walled carbon nanotube composites

We describe the synthesis of methane sulfonic acid (MeSA)‐doped poly(diphenylamine) (PDPA) with carboxylic groups containing multi‐walled carbon nanotubes (c‐MWNTs) via in situ polymerization. Diphenylamine monomers were adsorbed on to the surface of c‐MWNTs and polymerized to form PDPA/c‐MWNT composites. SEM and TEM images indicated two different types of materials: the thinner fibrous phase and the larger globular phase. The individual fibrous phase had a diameter around 100–130 nm, which should be the carbon nanotubes (diameter 20–30 nm) coated with a PDPA layer. The structure of PDPA/c‐MWNT composites was characterized by FTIR, UV‐visible spectroscopy and X‐ray diffraction patterns. The electrical conductivities of PDPA/c‐MWNT composites were much higher than that of PDPA without c‐MWNTs. Copyright © 2006 Society of Chemical Industry     

Preparation and properties of the single‐walled carbon nanotube/cellulose nanocomposites using N‐methylmorpholine‐N‐oxide monohydrate

Single‐walled carbon nanotube (SWNT)/cellulose nanocomposite films were prepared using N‐methylmorpholine‐N‐oxide (NMMO) monohydrate as a dispersing agent for the acid‐treated SWNTs (A‐SWNTs) as well as a cellulose solvent. The A‐SWNTs were dispersed in both NMMO monohydrate and the nanocomposite film (as confirmed by scanning electron microscopy) because of the strong hydrogen bonds of the A‐SWNTs with NMMO and cellulose. The mechanical properties, thermal properties, and electric conductivity of the nanocomposite films were improved by adding a small amount of the A‐SWNTs to the cellulose. For example, by adding 1 wt % of the A‐SWNTs to the cellulose, tensile strain at break point, Young's modulus, and toughness increased ～ 5.4, ～ 2.2, and ～ 6 times, respectively, the degradation temperature increased to 9°C as compared with those of the pure cellulose film, and the electric conductivities at ? (the wt % of A‐SWNTs in the composite) = 1 and 9 were 4.97 × 10^?4 and 3.74 × 10^?2 S/cm, respectively. Thus, the A‐SWNT/cellulose nanocomposites are a promising material and can be used for many applications, such as toughened Lyocell fibers, transparent electrodes, and soforth. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fabrication of pH‐ or temperature‐responsive single wall carbon nanotubes via a graft from photopolymerization

An ultraviolet light initiated “graft from” polymerization method to fabricate polymer‐functionalized single wall carbon nanotubes (SWNTs) with pendant pH‐ and temperature‐responsive polymer chains is utilized. The attached polymer chains, formed from methacrylic acid and poly(ethylene glycol) methyl ether methacrylate monomers, are well established for its pH‐responsive swelling/deswelling behavior. This special property was utilized here to control the aqueous dispersibility of the carbon nanotubes. Furthermore, poly(N‐isopropylacrylamide), a temperature‐responsive polymer, was utilized in the fabrication of SWNTs whose dispersibility was dependent on solution temperature. The morphology of the polymer‐functionalized carbon nanotubes was characterized by scanning electron microscopy (SEM) before and after functionalization. Environmental SEM was used to further characterize the morphology of the functionalized SWNTs. In addition, covalent bonding of the polymer to the carbon nanotube surface was established using Raman and Fourier transform infrared spectroscopic techniques. The physical and chemical properties of the functionalized nanotubes were further characterized by energy‐dispersive X‐ray spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2980–2986, 2012     

Morphology and electrical properties of polymethylmethacrylate/poly(styrene‐co‐acrylonitrile)/multi‐walled carbon nanotube nanocomposites

Nanocomposites of blends of polymethylmethacrylate (PMMA) and poly(styrene‐co‐acrylonitrile) (SAN) with multi‐walled carbon nanotubes (MWCNTs) were prepared by melt mixing in a twin‐screw extruder. The dispersion state of MWCNTs in the matrix polymers was investigated using transmission electron microscopy. Interestingly enough, in most of the nanocomposites, the MWCNTs were observed to be mainly located at SAN domains, regardless of the SAN compositions in the PMMA/SAN blend and of the processing method. One possible reason for this morphology may be the π–π interactions between MWCNTs and the phenyl ring of SAN. The shift in G‐band peak observed in the Raman spectroscopy may be the indirect evidence proving these interactions. The percolation threshold for electrical conductivity of PMMA/SAN/MWCNT nanocomposites was observed to be around 1.5 wt %. Nanocomposites with PMMA‐rich composition showed higher electrical conductivity than SAN‐rich nanocomposites at a fixed MWCNT loading. The dielectric constant measurement also showed composition‐dependent behavior. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Functionalized multi‐wall carbon nanotubes/silicone rubber composite as capacitive humidity sensor

Functionalized multi‐wall carbon nanotubes (MWCNTs) treated by mixed acids have been used to develop a capacitive humidity sensor based on MWCNTs/silicone rubber (SR) composite film. The MWCNTs/SR composites were prepared through conventional solution processed method. The micrographs of MWCNTs/SR composites were observed by transmission electron microscopy (TEM) and scanning electron microscope. The FT‐IR spectra demonstrated the successfully grafting of ? OH groups on the treated MWCNTs. The sensing properties of the composite at different relative humidity (RH) and frequency were characterized and linear sensing responses of the MWCNTs/SR composites to RH were observed. The treated MWCNTs/SR composite film (Tr‐film) had higher sensitivity than that of the untreated MWCNTs/SR composite film (Un‐film). Experimental data indicate that the Tr‐film exhibits an excellent long‐term stability, small hysteresis, and fine reproducibility. The response and recovery time of the Tr‐film were 30 and 27 s, respectively. Thereby, such Tr‐film had potential applications as humidity sensors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40342.     

Wood/plastic composites co‐extruded with multi‐walled carbon nanotube‐filled rigid poly(vinyl chloride) cap layer

Wood/plastic composites (WPCs) can absorb moisture in a humid environment due to the hydrophilic nature of the wood in the composites, making products susceptible to microbial growth and loss of mechanical properties. Co‐extruding a poly(vinyl chloride) (PVC)‐rich cap layer on a WPC significantly reduces the moisture uptake rate, increases the flexural strength but, most importantly, decreases the flexural modulus compared to uncapped WPCs. A two‐level factorial design was used to develop regression models evaluating the statistical effects of material compositions and a processing condition on the flexural properties of co‐extruded rigid PVC/wood flour composites with the ultimate goal of producing co‐extruded composites with better flexural properties than uncapped WPCs. Material composition variables included wood flour content in the core layer and carbon nanotube (CNT) content in the cap layer of the co‐extruded composites, with the processing temperature profile for the core layer as the only processing condition variable. Fusion tests were carried out to understand the effects of the material compositions and processing condition on the flexural properties. Regression models indicated all main effects and two powerful interaction effects (processing temperature/wood flour content and wood flour content/CNT content interactions) as statistically significant. Factors leading to a fast fusion of the PVC/wood flour composites in the core layer, i.e. low wood flour content and high processing temperature, were effective material composition and processing condition parameters for improving the flexural properties of co‐extruded composites. Reinforcing the cap layer with CNTs also produced a significant improvement in the flexural properties of the co‐extruded composites, insensitive to the core layer composition and the processing temperature condition. Copyright © 2009 Society of Chemical Industry