Synthesis of polyaniline/multiwall carbon nanotube composite via inverse emulsion polymerization

The composite of polyaniline (PANI) and multiwall carbon nanotube carboxylated through acid treatment (c‐MWCNT) was synthesized by chemical oxidative polymerization in an inverse emulsion system. The resultant composites were compared with products from aqueous emulsion polymerization to observe the improvements in electrical conductivity, structural properties, and thermal stability obtained by this synthetic method. Prior to the inverse emulsion polymerization, MWCNT was treated with a strong acid mixture to be functionalized with carboxylic acid groups. Carboxylic acid groups on surfaces induced selective dispersibility between polar and nonpolar solvents because of the increase of hydrophilicity. As the content of c‐MWCNT was increased, the electrical conductivity was increased by a charge transport function from the intrinsic electrical conductivity of MWCNT and the formation of a highly ordered dense structure of PANI molecules on the surface of c‐MWCNT. The images observed with electron spectroscopy showed the capping of c‐MWCNT with PANI. The growth of additional ordered structures of PANI/c‐MWCNT composite, which was observed through wide‐angle X‐ray diffraction patterns, supported the capping by PANI. It was observed that the doping of the composite had a significant relationship with the concentration of dodecylbenzenesulfonic acid (DBSA). The thermal stability of PANI composite was improved by the addition of c‐MWCNT; this was thought to be related with structure ordering by inverse emulsion polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2255–2266, 2008     

Synthesis of poly(p‐phenylenediamine‐ co‐o‐aminophenol)/multi‐walled carbon nanotube composites by emulsion polymerization

Organic–inorganic composites composed of electrically conducting copolymer p‐phenylenediamine‐ co‐o‐aminophenol and carboxylic acid functionalized multi‐walled carbon nanotubes [poly(pPD‐co‐oAP)/c‐MWNTs] were prepared via in situ emulsion pathway using sodium dodecyl sulphate (SDS) as an emulsifier and potassium persulphate as an oxidant. Acid functionalized MWNTs were used as cores in the formation of tubular shells of the composites. TEM and FESEM analysis showed that a tubular layer of coated copolymer film of several nanometer thicknesses is present on the c‐MWNTs surfaces. FT‐IR spectra endorsed the formation of composites. TGA results indicated that the decomposition temperatures of composites were higher than the bare copolymer. UV‐visible absorption spectra of diluted colloidal dispersion of composites were similar to those of the bare copolymer. The composites were also confirmed by XRD and XPS. Room‐temperature conductivity increases with an increasing fraction of c‐MWNTs. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of silicone–acrylate copolymer latexes and their film properties

Emulsion copolymerization of silicones (octomethyl tetracyclosiloxane, D₄ and methacryloxypropyl trimethoxy silane, MATS) and acrylics was carried out using three different polymerization processes: semicontinuous monomer emulsion addition, batch and initiator solution addition. Results showed that only the semicontinuous process led to a stable latex with monodisperse particles. Various polymerizations were carried out through this process with varying silicone/acrylic ratios and MATS content. Films were obtained from different latexes: their properties are significantly influenced by silicone and MATS contents in copolymers.     

Modification of multiwall carbon nanotubes via soap‐free emulsion polymerization of acrylonitrile

A novel method for the synthesis of polyacrylonitrile (PAN)‐coated multiwall carbon nanotubes (MWCNTs) via a simple soap‐free emulsion polymerization is presented for the first time. The polymerization was initiated with conventional anionic ammonium persulfate (APS) at 65 °C. The modification of PAN on MWCNT surfaces was confirmed by Fourier‐transform infrared (FT‐IR) spectroscopy, X‐ray photoelectron spectra (XPS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and Raman spectroscopy. It is found that all the surfaces of the MWCNTs were coated by PAN chains, and the PAN coating thickness could be controlled by simply adjusting the polymerization time. The obtained PAN‐coated MWCNTs could be well dispersed in water. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2057–2062, 2010     

Multifunctional poly(2,5‐benzimidazole)/carbon nanotube composite films

The AB‐monomer, 3,4‐diaminobenzoic acid dihydrochloride, was recrystallized from an aqueous hydrochloric acid solution and used to synthesize high‐molecular‐weight poly(2,5‐benzimidazole) (ABPBI). ABPBI/carbon nanotube (CNT) composites were prepared via in situ polymerization of the AB‐monomer in the presence of single‐walled carbon nanotube (SWCNT) or multiwalled carbon nanotube (MWCNT) in a mildly acidic polyphosphoric acid. The ABPBI/SWCNT and ABPBI/MWCNT composites displayed good solubility in methanesulfonic acid and thus, uniform films could be cast. The morphology of these composite films was studied by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The results showed that both types of CNTs were uniformly dispersed into the ABPBI matrix. Tensile properties of the composite films were significantly improved when compared with ABPBI, and their toughness (～200 MPa) was close to the nature's toughest spider silk (～215 MPa). The electrical conductivities of ABPBI/SWCNT and ABPBI/MWCNT composite films were 9.10 × 10^?5 and 2.53 × 10^?1 S/cm, respectively, whereas that of ABPBI film was 4.81 × 10^?6 S/cm. These values are ～19 and 52,700 times enhanced by the presence of SWCNT and MWCNT, respectively. Finally, without acid impregnation, the ABPBI film was nonconducting while the SWCNT‐ and MWCNT‐based composites were proton conducting with maximum conductivities of 0.018 and 0.017 S/cm, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1067–1078, 2010     

Starch‐graft‐copolymer latexes initiated and stabilized by ozonolyzed amylopectin

A method is presented for synthesizing surfactant‐free latexes comprising a starch‐graft‐vinyl polymer, (1) starting with a suspension of the highly branched starch amylopectin, either native or degraded, (2) then using ozonolysis to create free‐radical initiation sites on this amylopectin scaffold, and (3) finally adding the monomer and inducing polymerization. The ozone simultaneously thins the starch and creates initiating/grafting sites on the starch, from which starch‐graft‐copolymer latexes can be grown. The encapsulation of starch inside the hydrophobic polymer particles created by a heterogeneous free‐radical polymerization process is demonstrated with energy‐dispersive spectroscopy; this is the first time that the particle morphology of such a latex has been so characterized. The data unambiguously prove that low‐molar‐mass degraded starch can be encapsulated within a latex particle. The underlying mechanisms have been explored, and data quantifying the rates of production of hydroperoxides by ozone, the thermal decomposition of the starch hydroperoxides so formed, and the degradation of amylopectin by ozone are reported. The activation energy for the thermal decomposition of the starch macroinitiator, determined in this work to be 125 ± 8 kJ mol⁻¹, is consistent with the proposition that the initiating species are mainly hydroperoxides. Colloidally stable poly(styrene‐co‐n‐butyl acrylate) latexes based on high‐molar‐mass amylopectin have been developed. These are stable against electrolytes (several months in 4 mol L⁻¹ NaCl), with 20% of the starch effectively grafted to the particles. Films cast from such latexes are more pliable than starch films and are readily redispersed in water. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5832–5845, 2006     

Synthesis of surfactant‐free carbon nanotube/poly(styrene‐co‐acrylamide) by dynamic interfacial emulsion polymerization under sonication

This paper describes a study on emulsifier‐free ultrasonically assisted in‐situ copolymerization method of acrylamide and styrene in the presence of CNT, resulting in stable and uniform dispersions. The dispersions prepared were found stable for several months. Thermogravimetric analysis (TGA) curves and conversion measurements provided an insight regarding the polymerization mechanism and the nanocomposites structure. Films prepared of the polymerization products resulted in some clear and transparent coatings. The polymerization method described is simple and very fast compared with the other literature reported methods. TGA was extensively used as an analytical tool for determination of the composition of acrylamide–styrene copolymers. TGA and differential scanning calorimetry indicate that the polymerization product is largely a poly(styrene‐co‐acrylamide), where the acrylamide fraction is attached to the CNT surfaces. The copolymer produced, with and without CNT, is essentially a block copolymer, where each block contains small amounts of the other comonomer. To the authors' best knowledge, this report is the first one describing the production of stable dispersions of CNT in surfactant‐free poly(styrene‐co‐acrylamide) emulsion. Copyright © 2013 John Wiley & Sons, Ltd.     

Solid‐state NMR study of cyclo‐olefin copolymer (COC)

In this article, we have applied solid‐state ¹³C NMR techniques, cross‐polarization/magic‐angle spinning (CP/MAS), and single‐pulse ¹³C NMR to characterize the NB conformation of the cyclo‐olefin copolymer. The copolymers containing higher NB contents produce more NB blocks according to ¹³C CP/MAS spectral analysis. In addition, NB‐dyad‐based conformations are able to induce peak splitting in the region of 49–52 ppm. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2554–2563, 2000     

Carboxylic‐group distribution of carboxylated acrylate copolymer latexes with their properties in the presence of acrylic acid and monobutyl itaconate

A series of carboxylated acrylate copolymer latexes were prepared via two different emulsion polymerization technologies with different carboxylic‐group distribution and morphologies. The effects of the emulsifier, the initiator, and the carboxylic monomers [acrylic acid (AA) or monobutyl itaconate (MBI)] on the total conversion of the monomers and the properties of acrylate latexes and films have been investigated. The distribution of carboxylic groups (?COOH) measured by conductometric titration shows that the concentration of surface –COOH (C_s) and embedded –COOH (C_b) both increase with the increase of the amount of carboxylic monomers. For the latexes containing AA, –COOH tends to distribute on the surface of latex particles and in the aqueous phase, whereas –COOH tends to concentrate inside the core of latex particles for the latexes containing MBI. Transmission electron microscopy demonstrates that the latex particles are regular with narrow size distribution and have significant differences in morphologies when different carboxylic monomers and polymerization technologies were used. The stability of latex is satisfactory through the results of common stability and zeta potential tests. Moreover, the water absorption and contact angle experiment tests also revealed that the water resistance of the latex films is good. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and characterization of polyaniline‐multiwalled carbon nanotube nanocomposites in the presence of sodium dodecyl sulfate

Polyaniline‐carboxylic acid functionalized multi‐walled carbon nanotube (PAni/c‐MWNT) nanocomposites were prepared in sodium dodecyl sulfate (SDS) emulsion. First, the c‐MWNTs were dispersed in SDS emulsion then the aniline was polymerized by the addition of ammonium persulfate in the absence of any added acid. SDS forms the functionalized counterion in the resulting nanocomposites. The content of c‐MWNTs in the nanocomposites varied from 0 to 20 wt%. A uniform coating of PAni was observed on the c‐MWNTs by field‐emission scanning electron microscopy (FESEM). The PAni/c‐MWNT nanocomposites have been characterized by different spectroscopic methods such as UV‐Visible, FT‐Raman, and FT‐IR. The UV‐Visible spectra of the PAni/c‐MWNT nanocomposites exhibited an additional band at around 460 nm, which implies the induced doping of the MWNTs by the carboxyl group. The FT‐IR spectra of the PAni/c‐MWNT nanocomposites showed an inverse intensity ratio of the bands at 1562 and 1480 cm^?1 as compared to that of pure PAni, which reveals that the PAni in the nanocomposites is richer in quinoid units than the pure PAni. The increase in the thermal stability of conductivity of the nanocomposites was due to the network structure of nanotubes and the charge transfer between the quinoid rings of the PAni and the c‐MWNTs. Copyright © 2008 John Wiley & Sons, Ltd.     

Nylon 610/functionalized multiwalled carbon nanotube composite prepared from in‐situ interfacial polymerization

Pristine multiwalled carbon nanotubes (P‐MWNTs) were functionalized with 4‐chlorobenzoic acid via “direct” Friedel‐Crafts acylation in polyphosphoric acid (PPA)/phosphorous pentoxide (P₂O₅) medium. The resultant 4‐chlorobenzoyl‐functionalized MWNTs (F‐MWNTs) were soluble in chlorinated solvents such as dichloromethane, chloroform, and carbon tetrachloride. A large scale of nylon 610/F‐MWNT composite could be conveniently prepared by in situ interfacial polymerization of 1, 6‐hexamethylenediamine (HMDA) in an aqueous phase, and sebacoyl chloride with F‐MWNTs in an organic phase. Similarly, nylon 610/P‐MWNT composite was also prepared for comparison. The state of F‐MWNTs dispersion in nylon 610 matrix was distinctively better than that of P‐MWNTs, which could be clearly discerned by both naked eye and scanning electron microcopy (SEM). As a result, the tensile strength of nylon 610/F‐MWNT composite was 4.9‐fold higher than that of nylon 610/P‐MWNT composite. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6041–6050, 2008     

The mechanism of core–shell inversion in two-stage latexes

In two-stage latexes where the first polymer is more hydrophilic than the second, inversion of the core and shell can occur. The mechanism of core–shell inversion during the initial and final intervals of the second-stage polymerization was investigated using model PMMA/PS systems. The phase behavior of polymer solutions intended to model the two-stage system during the initial interval of the second stage polymerization has yielded some insight into the thermodynamics of phase inversion. If the second stage monomer dissolves first stage polymer, the latter will tend to precipitate at the water/monomer interface, particularly in the presence of surfactant. The energy of the oil/water interface is thereby reduced. In the final interval, when much of the second monomer has polymerized, phase mobility is crucial to the inversion process.     

Synthesis of single‐core and multiple‐core core‐shell nanoparticles by RAFT emulsion polymerization: Lead sulfide‐copolymer nanocomposites

We report here a simple and direct route for the preparation of lead sulfide (PbS) quantum dots (QDs) embedded into polymeric nanospheres by emulsion polymerization. In this process, QDs are first dispersed in an aqueous solution containing a statistical oligomer constituted of five butyl acrylate and ten acrylic acid units prepared by reversible addition fragmentation chain transfer (RAFT) polymerization using a trithiocarbonate as RAFT agent. Then, the dispersion of PbS QDs is engaged into an emulsion polymerization process to form core‐shell nanoparticles. Transmission electron microscopy reveals the presence of single‐core core‐shell particles at low concentration of PbS QD, whereas multiple‐core core‐shell particles containing either well separated or aggregated PbS QDs are formed at high concentration of PbS QDs. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Chitosan and multi-walled carbon nanotube composite rods

<正>Multi-walled carbon nanotubes(MWNTs) and chitosan(CS) composite rods with layer-by-layer structure were prepared via in situ precipitation method.On the one hand,some MWNTs fragments with open tips played the role of nuclear agent to improve the crystallinity of CS.On the other hand,MWNTs embedded in CS matrix to absorb energy when the composite rods were destroying.Nanotubes pulled out from CS matrix,and lots of holes remained,so MWNTs could endure external stress effectively.The bending strength and bending modulus of CS/MWNTs rods(100/0.5,W/W) arrived at 130.7 MPa and 4.4 GPa respectively,increased by 34.3%and 7.3%compared with those of pure CS rods.Consequently, CS/MWNTs composite rods with excellent mechanical properties could be a novel device used for bone fracture internal fixation.     

Synthesis of novel cyclic olefin polymers with excellent transparency and high glass‐transition temperature via gradient copolymerization of bulky cyclic olefin and cis‐cyclooctene

Novel cyclic olefin polymers (COPs) with excellent transparency and high glass‐transition temperature (T_g) synthesized from bulky norbornene derivative, exo‐1,4,4a,9,9a,10‐hexahydro‐9,10(1',2')‐benzeno‐l,4‐methanoanthracene (HBMN), and cis‐cyclooctene (COE) by ring‐opening metathesis copolymerization utilizing the “first‐generation Grubbs” catalyst, RuCl₂(PCy₃)₂(CHPh), and subsequent hydrogenation was reported herein. To get amorphous copolymers, it was of great importance to control the feed ratios and the polymerization time for gradient copolymerization. All these copolymers showed very high T_gs (141.1–201.2 °C), which varied with the content of HBMN. The films of the gradient copolymers with only one T_g were highly transparent. On the contrary, all the block copolymers synthesized through sequential addition showed two thermal transition temperatures, T_g and melt temperature (T_m), and the films of these block copolymers were opaque. The mechanical performances of the COPs were also investigated. It is the first report that transparent COP could be prepared from bulky norbornene derivative and monocyclic olefin. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3240–3249     

Synthesis, modification and characterization of core-shell fluoroacrylate copolymer latexes

Core-shell fluoroacrylate copolymer latex, typically used for the protection of ancient stone monument, was synthesized in this paper by semi-continuous seed emulsion polymerization with butyl acrylate (BA) served as the core, methyl methacrylate (MMA), BA and dodecafluoroheptyl methacrylate (DFHMA, C₁₁H₈O₂F₁₂) served as the shell. At the same time, the above core-shell fluoroacrylate latex was modified by hydrolysis of tetraethyl orthosilicate (TEOS, Si(OC₂H₅)₄) in the presence of silane coupling agent dodecyltrimethoxysilane (DTMS, C₁₂H₂₅Si(OCH₃)₃). The chemical component of the final latex was analyzed by FT-IR. Morphology structure and the particle size of core-shell latex were determined by TEM. The effect of DFHMA and TEOS content on the latex and film properties was characterized by SEM-EDX, AFM, TEM, DSC and UV-vis. The analysis results indicated that the copolymer latex particle presented uniform sphere core-shell structure with 40-50 nm in diameter. About 30 wt% DFHMA gave favorable characteristics both in latex and in film properties. Compared with core-shell fluoroacrylate latex, the modified fluoroacrylate copolymer displayed, when TEOS was controlled in 2.2-3.8 wt%, sound performances in hydrophobic, mechanics, thermodynamics and resistance to ultraviolet.     

Polymerization of high‐solids‐content acrylic latexes using a nonionic polymerizable surfactant

Stable high‐solids‐content methyl methacrylate/butylacrylate latexes with small particle sizes (in the range of 150–180 nm) were obtained with a nonionic polymerizable surfactant (surfmer). Three percent of surfmer with respect to monomer was proven to be enough for the stabilization of the latexes. The influence of different operational variables on the stabilization of the final latex was analyzed, and the conditions needed to obtain coagulum‐free latex were assessed. The inorganic potassium persulfate/sodium metabisulfite initiator system provided better stability than the organic tert‐butyl hydroperoxide/ascorbic acid as a result of the end groups. In addition, the feeding of acrylic acid during the second half of the polymerization improved the stability of the final latex. The reduction of the feeding time was effective in the stabilization. Proof of the surfmer incorporation into the particles is presented. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1552–1559, 2002     

Starch‐graft‐(synthetic copolymer) latexes initiated with Ce4+ and stabilized by amylopectin

A method is presented for synthesizing surfactant‐free latexes comprising starch‐graft‐(vinyl polymer) starting with a suspension of amylopectin, either native or modified, then using cerium(IV) with either potassium persulfate or glucose to create grafting sites on the starch. Latex particles comprising polystyrene, poly(styrene‐co‐(n‐butyl acrylate)) and poly(vinyl acetate) grafted onto high molecular weight amylopectin were developed, with up to 80% of the starch effectively grafted to the particles. These latexes were colloidally stable against electrolyte (several months in 4 M NaCl). Reaction rates of Ce⁴⁺ with simple sugars and polysaccharides were investigated, as well as the gelation mechanism of the latex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4185–4192, 2007