Jingcheng Liu

Dispersion of carbon nanotubes in water by self-assembled micelles of branched amphiphilic multifunctional copolymers with photosensitivity and electroactivity

Noncovalent surface modification has been proved to be one of the effective strategies for enhancing the properties of multi-walled carbon nanotubes (MWCNTs). When a non-covalent modification method is appropriately designed, novel opportunities for better performance of CNTs can be expected. In this paper, a novel kind of branched amphiphilic photo-sensitive and electro-active copolymer (BP(VCz/VM-alt-MA); BPVCM) was synthesized through a simple one-pot free radical copolymerization with 7-(4-vinylbenzyloxy)-4-methyl coumarin (VM), maleic anhydride (MA), 4-vinylbenzyl thiol (VBT) and 9-(4-vinylbenzyl)-9H-carbazole (VCz) as monomers. The copolymer BPVCM can self-assemble into homogeneous spherical micelles along the side-walls of MWCNTs and efficiently disperse MWCNTs in aqueous solution. In addition, the photosensitive coumarin groups of the copolymer chain undergo crosslinking under UV-irradiation, which leads to the encapsulation of MWCNTs in the crosslinked micelles and greatly improves the stability of the obtained MWCNT suspension. More interestingly, the electroactive carbazole moieties of the BPVCM–MWCNT composites could polymerize via an electrochemical polymerization method and form a MWCNT based conducting coating on the modified glassy carbon electrode (GCE), which eventually increases the number of electroactive sites and significantly accelerates the electron transfer. This novel preparation method permits us to obtain carbon nanotube hybrids exhibiting high water-dispersibility and stability while preserving their outstanding electrical properties, and would be valuable for construction of microelectronics and electrochemical sensors.

Multiwalled carbon nanotubes noncovalently functionalized by electro-active amphiphilic copolymer micelles for selective dopamine detection

We have synthesized an electro-active amphiphilic copolymer with carbazole side chains via free radical polymerization using 7-(4-vinylbenzyloxy)-4-methyl coumarin and 9-(4-vinylbenzyl)-9H-carbazole as the monomers. The copolymer can self-assemble to form micelles (termed EACMs) in aqueous solution and can adsorb onto the surfaces of MWCNTs via π–π interactions and thereby cause the efficient dispersion of the MWCNTs in aqueous solution. The coumarin groups in the copolymer undergo UV-induced photo-crosslinking, which further improves the stability of the suspension. Moreover, the electro-active carbazole moieties in the EACMs can undergo electropolymerization to form a conducting network on the MWCNTs that significantly accelerates electron transfer. The EACM/MWCNTs hybrid was applied to the amperometric sensing of dopamine (DA) as a model analyte. After electropolymerization, the electrode exhibited good sensitivity and selectivity toward the determination of dopamine with a 0.2 μM detection limit and a wide linear range. The method described here provides a viable route to water-dispersible and stable carbon nanotubes while preserving their outstanding electrical properties. We presume that the composite described here represents a valuable tool for the construction of electrochemical sensors and electronics.

Self-assembled micelles based on branched poly(styrene- alt -maleic anhydride) as particulate emulsifiers

Branched copolymer self-assembled micelles, based on amphiphilic branched poly(styrene-alt-maleic anhydride) (BPSMA) synthesized by a one-pot method, are prepared and employed as particulate emulsifiers to stabilize the white oil-in-water Pickering emulsions. The influences of micelle concentration, branching degree, salinity, and oil type on the emulsifying performance of self-assembled micelles are comprehensively investigated, and the distinction between BPSMA micelles and linear poly(styrene-alt-maleic anhydride) (LPSMA) self-assembled micelles on the micellar structure and emulsifying performance is also studied. The results show that the branched structure of the copolymer plays an important role in emulsification. The emulsifying performance of BPSMA micelles is superior to that of LPSMA micelles, reflected in the emulsifying efficiency and the long-term stability of emulsions. It is attributed to the much better structural stability of BPSMA micelles compared to LPSMA micelles, which is probably due to the postponing of hydrolyzing of maleic anhydride and ionization of carboxyl to some extent caused by the introduction of the branched structure in copolymers. It is also worth noting that, salinity has a great effect on the emulsifying performance of LPSMA micelles, but little impact on that of BPSMA micelles. Additionally, BPSMA micelles can also well stabilize the oil-in-water emulsions with some other types of natural oils. Thus the findings are not only of theoretical interest but also of great practical application in the cosmetics area.

Humidity sensor fabricated by inkjet-printing photosensitive conductive inks PEDOT:PVMA on a paper substrate

In this study, 7-(4-vinylbenzyloxyl)-4-methylcoumarin (VM) and maleic anhydride (MA) were polymerized through free radical copolymerization to form a photosensitive alternating copolymer P(VM-alt-MA) (PVMA). PVMA was used as a soft template to achieve the oxidative polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). We obtained a stable PEDOT:PVMA photosensitive aqueous dispersion with an average diameter in the range of 140 to 210 nm. We then used this aqueous dispersion as the ink for fabricating humidity sensors through inkjet-printing on a paper substrate. The printed photosensitive conductive film PEDOT:PVMA could be cross-linked after photo-dimerisation of coumarin groups, leading to a small decrease of electrical conductivity, but also appreciable improvements in water resistance and sensor robustness. The humidity sensing ability of these PEDOT:PVMA/paper sensors was investigated by exposing them to a wide range of relative humidity, namely 11–97% at room temperature. These paper sensors could selectively and reversibly detect water vapor with a significant linear relationship. The response strength and the response/recovery time of the sensors show a substantial improvement compared with those of previous reports. The photo-dimerisation of PEDOT:PVMA improves the stability of humidity response and the response/recovery time of the sensors.

Preparation of surface self-concentration and contact-killing antibacterial coating through UV curing

A facile method to prepare surface self-concentration antibacterial coating with contact-killing mechanism was developed. Photo curable quaternary ammonium compound QAC bearing a 16-carbon alkyl chain and a terminal methacrylate was synthesized as reactive antibacterial additive. After UV irradiation, QAC was crosslinked in the soy-based coating matrix. With proper amounts of QAC, the UV cured coatings exhibited good properties such as high glossiness, good hardness and fine adhesion to cherrywood substrates. The self-concentration property of QAC on the cured coating surface, which is beneficial to reserve the physical properties of the bulk materials and to improve the surface antibacterial activity, was confirmed by fluorescence and X-ray photoelectron spectroscopy. Moreover, the introduction of QAC provided the coatings with superhydrophilicity property as well as good anti-fog capacity. The coatings with 8 wt% of QAC (charge density = 8.6 mol cm−2) exhibited almost 100% antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli by 5 log reduction. The contact-killing mechanism of coatings was confirmed via the zone of inhibition tests. The straightforward preparation combined with excellent antibacterial property makes the QAC containing coatings quite promising in antibacterial coatings realm and is suitable for industrial-scale manufacturing.

One-pot synthesis of branched alternating copolymers P(St-alt-MAn) via free radical polymerization in the presence of chain transfer monomer

Novel branched alternating copolymers poly(styrene-alt-maleic anhydride) (BPSMA) were synthesized through free radical polymerization with styrene, maleic anhydride, and chain transfer monomer, 4-vinyl benzyl thiol. The successful synthesis of BPSMA was confirmed by a triple detection system including gel permeation chromatography, multiangle laser light scattering, and differential viscosity detectors, as well as thermal analysis (differential scanning calorimetry). This methodology proposes good prospects for scaling-up and thereby offers a wide range of branched alternating copolymers at low cost.

Preparation and characterization of carboxylterminated poly (butadiene-co-acrylonitrile) -epoxy resin prepolymers for fusion-bonded-epoxy powder coating

Liquid carboxyl-terminated poly(butadiene-co-acrylonitrile)(CTBN)-epoxy resin(EP) prepolymers were prepared with different contents of CTBN. The chemical reactions between EP and CTBN were characterized by Fourier ransform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC). The scanning electron micrograph (SEM) and dynamic mechanical analysis (DMA) of curing films showed phase separation, and the rubber particles were finely dispersed in the epoxy matrix. Mechanical properties analysis of curing films showed that impact strength and elongation at break increased significantly upon the addition of CTBN, indicating good toughness of the modified epoxy resins. Thermogravimetric analysis (TGA) showed that the incorporation of CTBN had little effect on the thermal stability of EP. Fusion-bondedepoxy (FBE) powder coatings modified with CTBN-EP prepolymers were prepared. The experimental results demonstrate the ability of CTBN-EP prepolymers, toughening technology to dramatically enhance the flexibility and impact resistance of FBE coatings without compromising other key properties such as corrosion protection.

Synthesis and properties of UV-curable hyperbranched polyurethane and its application in the negative-type photoresist

UV-curable hyperbranched polyurethane (UV-HBPU) containing carboxyl groups was synthesized from isophorone diisocyanate (IPDI), diethanolamine (DEOA), polyethylene glycol (PEG-400), hydroxyethyl acrylate (HEA), and 2,2-bis (hydroxymethyl) propionic acid (DMPA). The UV-HBPU was used as a negative-type photoresist for a printed circuit board (PCB). Fourier-transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1HNMR) spectroscopy of UV-HBPUs indicated that the synthesis was successful. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that the thermal stability of the UV-HBPUs decreased as the HEA content increased. The polymer exhibited excellent photoresist properties, and the resolution of circuits based on this negative-type photoresist reached 10 μm.

Synthesis of fluorinated polycarbonate-based polyurethane acrylate for UV-curable coatings

Fluorinated polycarbonate-based UV-curable polyurethane acrylate (F-PCUA) was synthesized by incorporating 1H, 1H, 2H, 2H-Perfluoro-1-octanol to the end of polycarbonate-based PUA chains. The structure of F-PCUA was determined by 1H-NMR, 19F-NMR, and FTIR analyses. The physical, surface, and thermal properties of F-PCUA were also examined. The F-PCUA was used as a hydrophobic additive in PUA coatings, and the water and oil wettability of the UV-cured film was investigated by contact angle measurements. The results showed that the coating system had great hydrophobicity. Furthermore, X-ray photoelectron spectroscopy research confirmed that a hydrophobic fluorine-enriched surface was obtained in the coating system. Moreover, the mechanical and chemical properties of the hydrophobic coatings did not show deterioration with the introduction of elemental F.

Novel partially bio-based fluorinated polyimides from dimer fatty diamine for UV-cured coating

A series of novel partially bio-based fluorinated polyimides with double-bond end groups (BGPIs) from 4,4′-(hexafluoroisopropylidene) diphthalic anhydride, 4,4′-(hexafluoroisopropylidene) dianiline, Priamine 1074, 4-aminobenzoic acid, and glycidyl methacrylate were synthesized via a copolycondensation method in m-cresol. The chemical structure and performances of BGPIs were fully characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography, solubility test, X-ray diffraction, and differential scanning calorimetry. It was determined that the prepared BGPIs were in the amorphous phase and readily soluble in conventional aprotic polar solvents. Additionally, the properties of as-prepared UV-cured coatings based on BGPIs were also evaluated by real-time Fourier transform infrared, thermogravimetric analysis, UV–Vis spectroscopy, and so on. Results revealed that all coatings exhibited satisfactory curing, higher adhesion, lower water uptakes, outstanding optical transparency, and fairly favorable thermal stability under a high content of biomass up to 48.9%. Therefore, these bio-based polymers could be considered as a potential sustainable candidate for high-temperature UV-curable coatings in the microelectronic field.