Synthesis of emulsion-templated porous polyacrylonitrile and its pyrolysis to porous carbon monoliths

PolyHIPEs are emulsion-templated polymers synthesized within high internal phase emulsions (HIPEs). The miscibility of acrylonitrile (AN) with water has made it difficult to synthesize PAN-based polyHIPEs. This paper describes the successful synthesis of PAN-based polyHIPEs by crosslinking through copolymerization with divinylbenzene (DVB), by stabilization with a polyglycerol polyricinoleate surfactant, and by initiation with both oil- and water-soluble initiators. The PAN-based polyHIPEs had porosities of over 86% and porous structures that were different from those of typical polyHIPEs. This paper also describes the production of porous carbon monoliths through the pyrolysis of these PAN-based polyHIPEs. Pyrolysis did not produce significant changes in the porous structures, which were quite similar to those of the original polyHIPEs. The porosities were around 95% and the carbon monoliths were largely macroporous and mesoporous, with some microporosity. These results indicate that PAN-based polyHIPE templates can be used for the a priori design of porous carbon monoliths.     

Emulsion-templated porous polymers: A retrospective perspective

PolyHIPEs are porous emulsion-templated polymers synthesized within high internal phase emulsions (HIPEs). HIPEs are highly viscous, paste-like emulsions in which the major, “internal” phase, usually defined as constituting more than 74% of the volume, is dispersed as discrete droplets within the continuous, minor, “external” phase. The surge in polyHIPE research and development parallels that of porous polymers in general and reflects the increasing number of potential applications (reaction supports, separation membranes, tissue engineering scaffolds, controlled release matrices, responsive and smart materials, and templates for porous ceramics and porous carbons). This review focuses upon the research and development in polyHIPEs through the prism of the work in our laboratory. The review includes an overview of the developments in polymerization chemistry, in the types of monomers, in the types of stabilization, in the generation of more complex polyHIPE-based systems (e.g. interpenetrating polymer networks, hybrids, bicontinuous polymers), and in unusual materials systems such as water-retaining polyHIPEs and shape-memory polyHIPEs.     

PolyHIPEs: Recent advances in emulsion-templated porous polymers

Porous polymers with well-defined porosities and high specific surface areas in the form of monoliths, films, and beads are being used in a wide range of applications (reaction supports, separation membranes, tissue engineering scaffolds, controlled release matrices, responsive and smart materials) and are being used as templates for porous ceramics and porous carbons. The surge in the research and development of porous polymer systems is a rather recent phenomenon. PolyHIPEs are porous emulsion-templated polymers synthesized within high internal phase emulsions (HIPEs). HIPEs are highly viscous, paste-like emulsions in which the major, “internal” phase, usually defined as constituting more than 74% of the volume, is dispersed within the continuous, minor, “external” phase. This review focuses upon the recent advances in polyHIPEs involving innovations in polymer chemistry, macromolecular structure, multiphase architecture, surface functionalization, and nanoparticle stabilization. The effects of these innovations upon the natures of the resulting polyHIPE-based materials (including bicontinuous polymers, nanocomposites, hybrids, porous ceramics, and porous carbons) and upon the applications involving polyHIPEs are discussed. The advances in polyHIPEs described in this review are now being used to generate new families of porous materials with novel porous architectures and unique properties.     

Recent developments in nanocellulose-based biodegradable polymers,thermoplastic polymers,and porous nanocomposites

Nanocellulose has generated a great deal of interest as a source of nanometer-sized reinforcement, because of its good mechanical properties. In the last few years, nanocellulose has also attracted much attention due to environmental concerns. This review presents an overview of recent developments in this area, including the production, characterization, properties, and range of applications of nanocellulose-based biodegradable polymers, thermoplastic polymers, and porous nanocomposites. After explaining the unique properties of nanocellulose and its various preparation techniques, an orderly introduction of various nanocellulose-reinforced biodegradable polymers such as starch, proteins, alginate, chitosan, and gelatin is provided. Subsequently, the effects of nanocellulose on the properties of thermoplastic polymers such as polyamides, polysulfone, polypropyrol, and polyacronitril are reported. The paper concludes with a presentation of new finding and cutting-edge studies on nanocellulose foam and aerogel composites. Three different types of aerogels, i.e., pristine nanocellulose-based aerogels, modified nanocellulose-based aerogels, and nanocellulose-based templates for aerogels, are discussed, as well as their preparation techniques and properties. In the case of foam composites, the research focus has been on two major preparation techniques, i.e., solvent-mixing/foaming and melt-mixing foaming, their respective challenges, and the properties of the final composites. In some cases, a comparison study between cellulose nanocrystals and cellulose nanofiber-reinforced biodegradable polymers, thermoplastics, and porous nanocomposites was carried out. Considering the vast amount of research on nanocellulose-based composites, special emphasis on such composites isprovided at the end of the review.     

Recent progress in porous organic polymers and their application for CO2 capture

Carbon capture, storage, and utilization (CCSU) is recognized as an effective method to reduce the excessive emission of CO₂. Absorption by amine aqueous solutions is considered highly efficient for CO₂ capture from the flue gas because of the large CO₂ capture capacity and high selectivity. However, it is often limited by the equipment corrosion and the high desorption energy consumption, and adsorption of CO₂ using solid adsorbents has been receiving more attention in recent years due to its simplicity and high efficiency. More recently, a great number of porous organic polymers (POPs) have been designed and constructed for CO₂ capture, and they are proven promising solid adsorbents for CO₂ capture due to their high Brunauer-Emmett-Teller (BET) surface area (S_BET), adjustable pore size and easy functionalization. In particular, they usually have rigid skeleton, permanent porosity, and good physiochemical stability. In this review, we have a detailed review for the different POPs developed in recent years, not only the design strategy, but also the special structure for CO₂ capture. The outlook of the opportunities and challenges of the POPs is also proposed.     

The potential of Kraft black liquor to produce bio-based emulsion-templated porous materials

Emulsion-templated porous monoliths based on castor oil-in-black liquor and on 1,2-dichloroethane-in-black liquor medium internal phase emulsions have been prepared in order to evaluate a possible valorisation of that undervalued by-product of the paper mill Kraft process. The cross-linking behaviour of the different polymers originally contained in the black liquor was investigated. It appears that both lignin and hemicellulose fragments are involved. Characterisation of the monoliths by scanning electronic microscopy and mercury intrusion porosimetry showed that using either castor oil or 1,2-dichloroethane allowed to obtain macrocellular morphology along with a high porosity. However, higher concentration of the internal phase is possible in emulsions prepared with 1,2-dichloroethane than with castor oil, leading to more attractive materials from both chemical and environmental aspects.     

锌酞菁基多孔有机聚合物催化CO2与环氧化物的环加成反应

基于环氧化物双重活化模型,以四氨基酞菁锌和均苯三甲醛为原料,通过席夫碱缩合反应,在溶剂热的条件下,制备了锌酞菁基多孔有机聚合物材料ZnPc-POP,采用FTIR、13C MAR NMR、XPS、TEM和氮气吸-脱附表征其结构,以环氧氯丙烷（ECH）和CO2的环加成反应为模型,以四丁基溴化铵（TBAB）为助催化剂,考察ZnPc-POP的催化性能、循环使用性和其催化不同环氧化物的底物适用性,并对催化机理进行探究。结果表明：ZnPc-POP具有丰富的介孔结构（孔容约为0.64 cm3/g,平均孔径约为20 nm）和高的比表面积（171.6 m2/g）;ECH在100 ℃和1.0 MPa的条件下生成环状碳酸酯的选择性＞99%,收率为96%,转化频率（TOF）高达533.3 h-1;ZnPc-POP至少可以循环使用5次,且催化活性无明显降低;ZnPc-POP催化不同环氧化物作为底物的环加成反应,选择性在95%~99%。环氧化物中三元环氧原子与ZnPc-POP的Lewis酸位点锌中心发生配位作用而被有效活化,助催化剂TBAB中溴离子通过亲核进攻促进环氧化物开环,此双重活化环氧化物开环是CO2环加成反应的控速步骤。     

Pullulanase immobilization on natural and synthetic polymers

This work describes the immobilization of pullulanase onto two different polymers; agarose activated with epichlorohydrin and trichlorotriazine and casein activated with epichlorohydrin, in addition to a synthetic copolymer, butylacrylate–acrylic acid (BuA/AAc). Immobilization by covalent binding yields stable enzyme activity. The operational stability of the free and immobilized enzymes showed that the enzyme immobilized by a crosslinking technique using glutaric dialdehyde (GA) showed poor durability and the relative activity decreased sharply due to leakage after repeated washing, while the enzymes immobilized by covalent bonds resulted in a slight decrease in most cases in the relative activity (around 20%) after being used 10 times. Storage for 4–6 months showed that the free enzyme lost most of its activity, while the immobilized enzyme showed the opposite behavior. Subjecting the immobilized enzymes to doses of γ‐radiation (0.5–10 Mrad) resulted in complete loss in the activity of the free enzyme at a dose of 5 Mrad, while the immobilized enzymes showed relatively high resistance to γ‐radiation up to a dose of 5 Mrad. Nuclear Magnetic Resonance (¹H NMR) and FTIR measurements were carried out to confirm the structure of the polymer as well as the immobilization process of the enzyme onto the polymeric carrier. The unique biochemical characteristics, mode of action and utility of the environmentally compatible pullulanase in starch conversion are well known. Using pullulanase with β‐amylase in starch saccharification processes can increase maltose yield by 20–25%. © 2001 Society of Chemical Industry     

Conjugated polymers with anionic dyes: Synthesis,properties, and sensing ability for nucleosides,DNA, and BSA

The reaction of N-(2,4-dinitrophenyl)pyridinium chloride (salt[Cl⁻]) with sodium salts of anionic dyes, such as acid red 52 (AR52), acid violet 49 (AV49), and coomassie brilliant blue G-250 (CBBG250) involves an anion exchange between the chloride anion of salt(Cl⁻) and sulfonium anion of the dyes, resulting in the generation of novel Zincke salts, namely, salt(AR52), salt(AV49), and salt(CBBG250), respectively. Reactions of salt(AR52), salt(AV49), and salt(CBBG250) with piperazine in the absence of catalysts resulted in the opening of the pyridinium ring to yield ionic polymers comprising units of 5-piperazinium-2,4-dienylideneammonium and the corresponding dye anion, namely polymer(AR52), polymer(AV49), and polymer(SBBG250), respectively. The corresponding model compounds for the polymers were also synthesized by reacting salt(AR52), salt(AV49), and salt(CBBG250) with piperidine. Polymer(AV49) and polymer(SBBG250) were found to be suitable for the detection of nucleosides, DNA, and proteins, realized by monitoring the changes in their UV–vis absorption spectra, arising from the anionic dyes within the polymers. The polymers and the model compounds were electrochemically oxidized in solution.     

A simple route to functionalize siloxane polymers for DMMP sensing

Hexafluoroisopropanol (HFIP) was the most widely used functional group for nerve agents detection. However, to incorporate HFIP group into a polymer backbone, highly toxic hexafluoroacetone gas was needed in a conventional synthetic route. In this article, a new route with low toxicity was proposed to synthesize a strong hydrogen‐bond acidic (HBA) siloxane polymer by using 2‐vinylhexfluoroisopropanol as the raw material in the hydrosilylation reaction. The synthesized fluoroalcoholic linear polysiloxane (LSFA) was characterized by FT‐IR, confirming its molecular structure was much similar to SXFA, a well‐established HBA polymer synthesized by the conventional route. TGA data verified the adduct's thermal stability. The dimethyl methylphosphonate (DMMP) sensing properties of LSFA and SXFA, along with PLF, were compared basing on the surface acoustic wave (SAW) platform. The results demonstrated that the conventional synthetic route was somewhat difficult to handle and control, while the new route was simpler, easier and was an effective and promising alternative. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4516–4520, 2013     

Functionalization of styrene–butadiene–styrene (SBS) triblock copolymer with glycidyl methacrylate (GMA)

A styrene–butadiene–styrene triblock copolymer (SBS) was functionalized with glycidyl methacrylate (GMA). Grafting reactions were carried out in an internal mixer at 170°C, using dicumyl peroxide (DCP) as an initiator. The effect of three variables, % GMA, % DCP, and reaction time, on grafting were studied using a factorial design to analyze the experimental data. GMA was grafted onto SBS and its incorporation increased with the % GMA added. The factors levels studied indicated that was an optimum % DCP point about 0.1% w/w to achieve the best incorporation and conversion values. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2074–2079, 2003     

Poly(aspartic acid) surface modification of macroporous poly(glycidyl methacrylate) microspheres

Novel macroporous, hydrophilic microspheres with a surface layer of crosslinked poly(aspartic acid) were synthesized. In this study, macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [poly(GMA-co-EGDMA)] microspheres with pore size around 370 nm were first obtained through the surfactant reverse micelle swelling method, and the poly(GMA-co-EGDMA) was aminated by ethylene diamine to form poly(GMA-NH₂). The polysuccinimide was grafted onto the surface of poly(GMA-NH₂) microspheres and crosslinked by hexamethylendiamine and γ-aminopropyltriethoxysilane, respectively, and then hydrolyzed to obtain the poly(aspartic acid)-functionalized macroporous microspheres. The functionalized hydrophilic microspheres were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, mercury porosimetry, and elemental analysis. The metal ion adsorption capacity was also studied. The FTIR, XPS, and elemental analysis confirmed the poly(aspartic acid) functionalization of the poly(GMA-co-EGDMA) microspheres. SEM and mercury porosimetry showed there was little effect of this surface chemical modification on microsphere porosity, and the obtained macroporous microspheres exhibited excellent thermal stability and adsorption for Ag(I), presenting great potential for applications in adsorption, fixation, and separation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47441.     

Effect of the synthesis initiation mode on the structure and properties of sulfadiazine molecularly imprinted polymers

In the presence of imprinting molecules of sulfadiazine, two kinds of molecularly imprinted polymers (MIPs) were synthesized by photoinitiated and thermally initiated polymerizations, respectively. The combination of sulfadiazine and α‐methyl acrylic acid and their composite ratio were studied by differential UV absorption spectrometry. The results show that a combined effect between the functional monomer and the imprinting molecule occurred in the solution. The structure and properties of these synthetic polymers were researched and compared with IR spectroscopy, transmission electron microscopy, and a balanced combination of static experiments. The polymer materials synthesized in these two ways had the same molecular structure, but their morphology was different. Furthermore, through the adsorption isotherm, Scatchard analysis, and evaluation of the imprinting efficiency, we determined that the lower temperature was a more suitable synthesis condition for the polymerization of the MIPs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Tailored dispersion of carbon nanotubes in water with pH-responsive polymers

In an effort to control the level of carbon nanotube exfoliation in water, pH-responsive polymers (i.e., weak polyelectrolytes) have been used as stabilizers in water. This noncovalent functionalization of single-walled carbon nanotubes (SWNTs) results in suspensions whose dispersion state can be altered by simply changing pH. In this study poly(acrylic acid), poly(methacrylic acid), poly(allylamine) and polyethyleneimine were used to stabilize aqueous SWNT suspensions. The results indicate that SWNTs stabilized with these polymers show a pH tailorable exfoliation and bundling in water, as evidenced by cryo-TEM images and shifts in suspension viscosity. Composite films prepared by drying these aqueous suspensions suggest that nanotube microstructure in the liquid state is largely preserved in the solid composites, with more bundled/networked structures showing higher electrical conductivity. A stabilization mechanism based upon the results obtained is proposed to explain the exfoliation and aggregation behavior of SWNTs. This method of controlling the microstructure of SWNTs in liquid state with pH could have a significant impact on the ability to tailor the microstructure and properties of composites.     

Competitive adsorption of uranyl ions in the presence of Pb(II) and Cd(II) ions by poly(glycidyl methacrylate) microbeads carrying amidoxime groups and polarographic determination

The adsorption capacity of UO in the presence of Pb(II) and Cd(II) ions was investigated with amidoximated poly(glycidyl methacrylate) (PGMA) microbeads with an average size of 135 μm packed in a glass column (0.5‐cm i.d. and 20‐cm length, flow rate = 3 mL/min) under competitive conditions. A differential pulse polarography technique was used for the determination of trace quantities of uptaken elements by the measurement of the reduction peak currents at ?200/?950, ?400, and ?600 mV (vs a saturated calomel electrode) for UO, Pb(II), and Cd(II) ions, respectively. When only UO was found in the eluate, its adsorption was 85.3% from a 50 μM initial solution. However, when there was UO with binary systems of Pb(II) or Cd(II), it was 78.2 and 76.3%, respectively. On the other hand, in a ternary mixture of UO with Pb(II) and Cd(II), the adsorption was found to be 75.2% with the same initial concentration. According to the results, the competitive adsorption studies showed that these amidoximated PGMA microbeads had good adsorption selectivity for UO with the coexistence of Pb(II) and Cd(II) ions. The ionic strength of the solution also influenced the UO adsorption capacity of the amidoximated PGMA microbeads. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4168–4172, 2007     

Preirradiation‐induced emulsion graft polymerization of glycidyl methacrylate onto poly(vinylidene fluoride) powder

An epoxy‐group‐containing monomer, glycidyl methacrylate (GMA), was grafted onto poly(vinylidene fluoride) powder via preirradiation‐induced emulsion graft polymerization. The existence of graft chains was proven by chemical structure characterization with Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy analysis. The degree of grafting was calculated by means of fluorine content analysis. A kinetic study indicated that, with the emulsion graft polymerization system, the GMA conversion rate was high, exceeding 80%. The variation in the molecular weight of the grafted polymer was measured by gel permeation chromatography, and its crystallinity was investigated with differential scanning calorimetry. The epoxy groups in graft chains were found to be suitable for further chemical modification. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Functional copolymers of p‐cumyl phenyl methacrylate and glycidyl methacrylate: Synthesis,characterization, and reactivity ratios

Free‐radical polymerization of p‐cumyl phenyl methacrylate (CPMA) was performed in benzene using bezoyl peroxide as an initiator at 80°C. The effect of time on the molecular weight was studied. Functional copolymers of CPMA and glycidyl methacrylate (GMA) with different feed ratios were synthesized by free‐radical polymerization in methyl ethyl ketone at 70°C, and they were characterized by FTIR and ¹H‐NMR spectroscopy. The molecular weights and polydispersity indexes of the polymers and copolymers were determined by gel permeation chromatography. The copolymer composition was determined by ¹H‐NMR. The glass‐transition temperature of the polymer and the copolymers was determined by differential scanning calorimetry. The reactivity ratios of the monomers were determined by the Fineman–Ross and Kelen–Tudos methods. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 336–347, 2005     

Fluoro-functionalized PLA polymers as potential water-repellent coating materials for protection of stone

A series of sixteen fluoro-functionalized poly(lactic acid)s were synthesised using two commercial fluorinated alcohols [3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-octanol and 4-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)benzyl alcohol] as co-initiators in the ring-opening polymerization of L-lactide and rac-lactide (the racemic mixture of L- and D-lactide) catalyzed by Tin(II) 2-ethylhexanoate. The polymers were characterized by NMR, IR, GPC, DSC and tested as potential protective coating for stone. The performances were comparatively evaluated in terms of water protection efficacy and colour changes of the treated stone. Furthermore, the photo-stability of nine selected polymers under Solar Box condition was also investigated. It has been shown that the presence of fluorine makes the stone more water-repellent. The polymers showed also interesting photo-stability and some of them provided a behavior close to PLA-FLK-PLA block copolymers recently reported in the literature, in spite of their lower fluorine content © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Photoluminescence and excimer emission of functional groups in light‐emitting polymers

Near‐UV and blue‐light‐emitting polymers were synthesized with luminescent functional groups in the side chains or in the polymer main chain. The unsubstituted fluorophores, 2,5‐diphenylfuran, 2‐phenylbenzoxazole, and triphenylamine, do not form excimers in solution; however, in the case of polymers, excimer emission was negligible only with 2‐phenylbenzoxazole derivatives. The monomers as well as the polymers, poly(2‐(4‐vinylphenyl)‐benzoxazole), poly{N‐(4‐benzoxazol‐2‐yl‐phenyl)‐N′‐[2‐(methacryloyloxy)ethyl]urea}, and the polyurea of 2‐(4‐aminophenyl)‐5‐aminobenzoxazole with 1,5‐diisocyanato‐2‐methylpentane, were strong blue emitters; photoluminescence shifted to longer wavelengths than that of 2‐phenylbenzoxazole. Light‐emitting polymers containing 2,5‐diphenylfuran derivatives, including poly[2‐(4‐vinylphenyl)‐5‐phenylfuran], poly[2‐(4‐vinylphenyl)‐5‐(4‐tert‐butylphenyl)furan], and poly(N‐[2‐(methacryloyloxy)ethyl]‐N′‐{4‐[5‐(4‐tert‐butylphenyl)‐2‐furyl]phenyl}urea), particularly in solid films, exhibited a strong blue excimer emission. The emission characteristics of polymers with triphenylamine side chains were influenced by the mode of attachment of the luminescent group. A longer spacer group between the lumophore and the polymer main chain successfully minimized excimer emission in poly{N‐[2‐(methacryloyloxy)ethyl]‐N′‐[4‐(N,N‐diphenylamino)phenyl]urea}, showing near UV/violet photoluminescence. Polymers with a shorter connecting group, such as poly[4‐(N,N‐diphenylamino)benzyl acrylate], displayed blue excimer emission. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1634–1645, 2003     

POSS‐based fluorinated azobenzene‐containing polymers: Photo‐responsive behavior and evaluation of water repellency

The photoresponsive polyhedral oligomeric silsesquioxanes (POSS) based fluorinated azobenzene‐containing polymers were prepared and characterized by NMR, FT‐IR, GPC, XRD, TG and UV–Vis spectra. The thermal property of the polymers was improved by the introduction of POSS cage. The trans‐cis photoisomerization of the polymers in solution was similar to that of the fluorinated azobenzene monomer and in accordance with the first‐order reaction kinetics equation within the first 250 seconds UV irradiation. The cotton fabrics coated with the polymers showed excellent water repellency and possessed switchable wettability under UV irradiation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43540.