高内相比乳液的研究与应用进展

介绍了高内相比乳液(HIPEs)的研究概况,总结了HIPEs在聚合物多孔材料制备方面的研究与应用进展,展望了HIPEs作模板制备多孔材料的应用前景。     

Hydrophilic porous polymers based on high internal phase emulsions solely stabilized by poly(urethane urea) nanoparticles

Stable oil-in-water (o/w) Pickering high internal phase emulsions (HIPEs) having an internal phase of up to 95 vol% were prepared with a low-energy emulsification method. A poly(urethane urea) (PUU) aqueous nanodispersion was used as aqueous phase. The PUU nanoparticles of the aqueous nanodispersion acted as a mechanical barrier, and prevented droplet coalescence in the Pickering HIPEs. In addition, open porous hydrophilic polymer foams were obtained by polymerization of the Pickering HIPEs, and the morphology of the foams were tailored by changing the oil:water ratio, PUU nanoparticle and NaCl concentrations. The method used herein provides a simple way to prepare morphology controlled hydrophilic polymer foams using o/w Pickering HIPEs as template.     

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.     

有机硅含量对聚丙烯酸酯多孔材料性能的影响

以丙烯酸丁酯、丙烯酸异辛酯、二甲基丙烯酸乙二醇酯以及γ-甲基丙烯酰氧基丙基三甲氧基硅烷(MPtMS)为原料,采用高内相比乳液模板法制备了有机硅聚丙烯酸酯多孔材料,讨论了MPtMS对聚丙烯酸酯多孔材料的微观结构、热稳定性以及对有机染料罗丹明B水溶液的脱色效果的影响。结果表明:通过控制MPtMS含量,可有效控制多孔的形貌,获得泡孔规整、毛孔均匀分布的聚合物多孔材料;MPtMS的加入可提高聚合物多孔材料的热稳定性以及对罗丹明B水溶液的吸附性能。     

Preparation of organic/inorganic hybrid semi-interpenetrating network polymer electrolytes based on poly(ethylene oxide-co-ethylene carbonate) for all-solid-state lithium batteries at elevated temperatures

Organic/inorganic hybrid semi-interpenetrating network (semi-IPN) polymer electrolytes (HIPEs) based on poly(ethylene oxide-co-ethylene carbonate) (PEOEC) have been developed for all-solid-state lithium battery applications. In comparison to those of poly(ethylene oxide) (PEO), salient features of the PEOEC are the amorphous nature and high dielectric constant, which provide enhanced ionic conductivity. The organic/inorganic hybrid network matrix in the HIPEs is composed of different contents of photo-cross-linked octa-functional POSS acrylate (OA-POSS) and ethoxylated trimethylolpropane triacrylate (ETPTA). The effect of OA-POSS on solid-state electrolyte properties of the HIPEs is investigated in terms of the dimensional stability, thermal behavior, and ionic conductivity. Due to the presence of the rigid and bulky POSS moiety, the HIPEs exhibit improvement in ionic conductivity along with enhanced dimensional stability. The high capacity and good cycle performance of lithium batteries with the HIPEs demonstrate feasibility of applying the HIPEs to solid-state electrolytes for all-solid-state lithium batteries that can operate at elevated temperatures.     

Macroporous polymer nanocomposites synthesised from high internal phase emulsion templates stabilised by reduced graphene oxide

Reduced graphene oxide (rGO) is known to be electrically conductive and adsorb at oil–water interfaces. It has also been shown to mechanically reinforce bulk materials. This work combines these favourable characteristics of two-dimensional rGO to develop 3D macroporous polymer nanocomposites via emulsion templating. rGO proved to be an efficient emulsifier as only 0.2 mg/ml (with respect to the oil phase) of rGO was required to stabilise water-in-oil high internal phase emulsions (HIPE) of up to 80 vol.% internal phase. After polymerisation of the continuous minority monomer (styrene and divinylbenzene) phase, macroporous polymer nanocomposites with tuneable microstructures were obtained. The storage modulus of rGO-poly(styrene-co-divinylbenzene) HIPEs increased by almost an order of magnitude when the rGO concentration used to stabilise the HIPE template increased from 0.4 to 5.0 mg/ml. The adsorption and organisation of rGO at the o/w interface in HIPEs prior to polymerisation and partial aggregation in the polymer cell walls after polymerisation resulted in conductive nanocomposites with a rGO content of as low as 0.006 vol.% (with respect to bulk polymer volume or 0.8 mg/ml with respect to the monomer volume used in the emulsion template) compared to 0.1 vol.% for dense nanocomposites previously reported. This provided evidence for the efficient arrangement of rGO within the macroporous polymer nanocomposite, creating an electrically conductive network.     

Photopolymerised methacrylate-based emulsion-templated porous polymers

Highly porous and interconnected methacrylate-based porous materials were prepared by photopolymerisation of the continuous phase of high internal phase emulsion (HIPE) templates. The rapid cure afforded by photopolymerisation effectively ‘locks’ the emulsion morphology prior to emulsion destabilisation, in comparison to thermally-initiated HIPEs of similar compositions. Contrary to expectation, it was observed that fully cured photopolymerised polyHIPEs could be prepared with a thickness of up to 35 mm, despite the severe opacity of the parent emulsions. This is attributed to a photofrontal polymerisation process, where radicals generated on the surface propagate rapidly through the bulk of the emulsion. Homogeneous, well-defined polyHIPE materials of up to 95% nominal porosity were obtained by photopolymerisation of HIPEs containing up to 30 vol.% glycidyl methacrylate (GMA) in the monomer phase (the remaining monomers and crosslinker are acrylates). Surprisingly, poly(ethylene glycol) methacrylate (PEG-MA), a nonionic monomer that is miscible with both emulsion phases, could be added to such HIPEs after preparation. On polymerisation, hydrophilic, water-wettable porous materials were obtained. Finally, it was also demonstrated that all-methacrylate HIPEs could be prepared and cured to yield GMA-containing polyHIPEs. These findings demonstrate the versatility of photopolymerisation for the preparation of emulsion templated porous polymers.     

Characterization by solid-state NMR and selective dissolution techniques of anhydrous and hydrated CEM V cement pastes

The long term behaviour of cement based materials is strongly dependent on the paste microstructure and also on the internal chemistry. A CEM V blended cement containing pulverised fly ash (PFA) and blastfurnace slag (BFS) has been studied in order to understand hydration processes which influence the paste microstructure. Solid-state NMR spectroscopy with complementary X-ray diffraction analysis and selective dissolution techniques have been used for the characterization of the various phases (C₃S, C₂S, C₃A and C₄AF) of the clinker and additives and then for estimation of the degree of hydration of these same phases. Their quantification after simulation of experimental ²⁹Si and ²⁷Al MAS NMR spectra has allowed us to follow the hydration of recent (28 days) and old (10 years) samples that constitutes a basis of experimental data for the prediction of hydration model.     

The effects of nano-C-S-H with different polymer stabilizers on early cement hydration

A promising approach to accelerate cement hydration known as “seeding technology” has been discovered using nano-particles to provide additional nucleation sites for growing of C-S-H. Two different types of polymer, polycarboxylate (PCE) and polysulfonate (PSE) were used as stabilizer to synthesize nano-C-S-H via co-precipitation process. The obtained C-S-H-polymer composites were characterized by means of XRD, FTIR, thermogravimetric analysis (TGA), TEM, dynamic laser scattering (DLS), and BET. DLS measurement shows that the particle size of the obtained C-S-H-polymer suspension ranges from 82.6 to 589.9 nm. The results of DLS and BET show that the particle size of the C-S-H particles synthesized using PCE polymer as stabilizer is smaller than those synthesized with PSE polymer, and hence the specific surface area is much higher. FTIR and TGA results confirm the presence of the polymers in the obtained C-S-H composites particles. XRD results indicate that the presence of the polymers reduces the crystallinity of C-S-H due to the absence of the d002 peak at 2θ of 7°. The calorimetry results show that the main hydration peak of cement is dramatically increased by the addition of the C-S-H-polymer composites. It is interestingly found that the acceleration effect of the C-S-H-polymer composites is linearly proportional to the total surface area of the nanoparticles introduced into the cement pastes. At the same time, it is found that the secondary hydration peak, usually known as the sulfate-depletion peak, is greatly advanced by addition of the C-S-H nano-particles in comparison with the blank cement paste. The acceleration effect of the nano-C-S-H is further verified in a pure C₃S system.     

Grafting of nanospherical PMMA brushes on cross-linked PMMA nanospheres for addition in two-solution bone cements

Poly(methyl methacrylate) (PMMA) brushes were grafted to the surface of cross-linked PMMA nanospheres for use as the polymer phase in the preparation of the two-solution bone cement. PMMA chains grafted on the core of the cross-linked PMMA nanostructures were hypothesized to impart viscosity to the cement mixture, while providing entanglements with the matrix chains formed during cement cure. The first goal of this study was to develop a novel synthetic strategy to decorate the surface of nanoparticles with functional groups that allowed for grafting of PMMA brushes via radical polymerization. The grafting reactions were performed at specific combinations of monomer and initiator to produce a range of molecular weights adequate for the preparation of bone cements. The second goal was to investigate the ability of this novel methodology to produce high graft densities on the core surface from the analysis of the hydrodynamic properties of brushes. The synthetic pathway discussed enabled the synthesis of brushes with high graft densities and molecular weights tuned to provide optimal viscosities for preparation of brush-containing two-solution bone cements.     

Pore solution composition and alkali diffusion in inorganic polymer cement

Extraction of pore solutions from hardened inorganic polymer cement (“geopolymer”) paste samples shows that the pore network of these materials is rich in alkali cations and has pH > 13, with a relatively low dissolved Si concentration. However, there is little soluble Ca available in these materials to play a buffering role similar to Ca(OH)₂ or high-Ca C-S-H in hydrated Portland cements, meaning that preventing alkali loss is essential in ensuring the protection of reinforcing steel. It has been seen previously that calcium in an inorganic polymer cement binder is important in the formation of a low-permeability pore system; alkali diffusion measurements confirm these observations and highlight the role of Ca in reducing effective alkali diffusion coefficients by up to an order of magnitude. This is crucial for the durability of inorganic polymer concretes containing steel reinforcement, as it appears that the use of calcium-containing raw materials will be highly preferable.     

The encapsulation of Mg(OH)2 sludge in composite cement

A range of magnesium hydroxide waste sludges arising from the re-processing of nuclear fuel exist in the UK and require safe long-term disposal. Similar wastes undergo a cementation process in order to immobilise radioactive material prior to disposal. Simulant magnesium hydroxide sludges have been prepared and their subsequent interactions with composite cement systems based on the partial replacement of ordinary Portland cement with blastfurnace slag and pulverised fuel ash have been studied. This work has concluded that there was little reaction between the sludge and any of the composite cements during hydration. Apart from a small quantity of a hydrotalcite-type phase containing magnesium from the sludge, the main phases detected were C-S-H and unreacted brucite. This indicates that the magnesium in the sludges is encapsulated by the cement, rather than being immobilised or chemically bound within the hardened matrix.     

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.     

Rheology of foamed cement

Foams are being used in a number of petroleum industry applications that exploit their high viscosity and low density. Foamed cement slurries can have superior displacement properties relative to non-foamed cement slurries. This article presents results of an experimental study of foamed cement rheology. Viscosity curves of foamed cements were obtained using a flow-through rotational viscometer. Foamed cements with different foam qualities were generated under different pressures using a foam generator/viscometer apparatus. The foam qualities during the tests ranged from 0% to 30%, and the shear rate varied between 5 s^− 1 and 600 s^− 1. Experimental results indicate that: i) unlike conventional aqueous foams, low-quality cement foams have a lower viscosity than the base fluid; ii) as the cement foam quality (gas volumetric fraction) increases from 10% to 30%, the viscosity also increases; and iii) the viscosity of low-quality cement foam slightly increases after depressurization or expansion.     

Oxygen diffusion through hydrophobic cement-based materials

The oxygen diffusion coefficient through hydrophobic cement-based materials fully immersed in water was determined by potentiostatic measurements on concrete and by the use of a diffusion cell on cement pastes and mortars. The obtained results show that very high oxygen diffusion occurs through cement paste, mortar and concrete made with hydrophobic admixture as opposed to negligible diffusion through the reference cement matrix without admixture. Moreover, the oxygen diffusion coefficients measured through hydrophobic cement matrices immersed in water were comparable with those reported in literature for unsaturated cement materials in air. These experimental results appear to confirm that oxygen dissolved in water directly diffuses as a gaseous phase through the empty pores of a hydrophobic cement matrix. This could explain the severe corrosion of steel reinforcement embedded in cracked hydrophobic concrete immersed in an aqueous chloride solution observed in a previous work.     

Porous polymers prepared via high internal phase emulsion polymerization for reversible CO2 capture

A series of porous polymers with different pore volumes, pore sizes, and crosslinking densities were synthesized by high internal phase emulsion (HIPE) polymerization. The crosslinked polymerized HIPEs (polyHIPEs) were formed by the copolymerization of 4-vinylbenzyl chloride and divinylbenzene using water droplets in conventional or Pickering HIPEs as the templates. These porous materials were further modified by quaternization and ion exchange to introduce quaternary ammonium hydroxide groups. The resulting polyHIPEs were utilized as sorbents for reversible CO₂ capture from air using the humidity swing. The effect of pore structure on the CO₂ adsorption and desorption processes was studied. The polyHIPEs containing large pores and interconnected porous structures showed improved swing sizes and faster adsorption/desorption kinetics of CO₂ compared to a commercial Excellion membrane with similar functional groups.     

Cement hydration and microstructure formation in the presence of water-soluble polymers

Hardening of cement mortars modified with small amounts of water-soluble polymers implies both cement hydration and polymer film formation. In this paper, the effect of the presence of water-soluble polymers on the cement hydration reactions is investigated by means of isothermal calorimetry, thermal analysis, FT-IR spectroscopy and SEM investigation. In spite of an initial retardation of the hydration reactions, a higher degree of hydration is found after 90 days for 1% PVAA, MC and HEC modified mortars, due to a better dispersion of the cement particles in the mixing water. MC also affects the morphology of the Ca(OH)₂ crystals. Polymer bridges are detected between the layered crystals, gluing the layers together and strengthening the microstructure. Additionally, the internal cohesion of all bulk polymer modified cement pastes is improved. In the presence of the polymers, a more cohesive microstructure with a smaller amount of microcracks is created.     

Effect of polymer cement modifiers on mechanical and physical properties of polymer-modified mortar using recycled artificial marble waste fine aggregate

Various polymer-modified mortars using recycled artificial marble waste fine aggregate (AMWFA) were prepared and investigated for the purpose of feasibility of recycling. Styrene–butadiene rubber (SBR) latex and polyacrylic ester (PAE) emulsion were employed as polymer modifier, and compared each other. The replacement ratio of AMWFA was also changed to investigate the effect of it on physical properties. Adding polymer cement modifier into mortar reduced water–cement ratio, and PAE was the more effective polymer cement modifier to reduce water–cement ratio than SBR. PAE emulsion-modified mortar increased the air content entrained as the proportion of PAE was increased. There was little difference in water absorption between SBR latex and PAE emulsion. The compressive strength decreased in the presence of polymer cement modifiers compared to that of no polymer cement modifiers, but the compressive strength of 20% of polymer–cement ratio was higher than that of 10%. After the hot water resistance test, both compressive strength and flexural strength were decreased.     

Stability of surfactant-free high internal phase emulsions and its tailoring morphology of porous polymers based on the emulsions

Stable water-in-oil (w/o) high internal phase emulsions (HIPEs) having an internal phase of up to 95 vol% were prepared. The poly(styrene-methyl methacrylate-acrylic acid) (P(St-MMA-AA)) copolymer particles were used as stabilizer. The HIPEs prepared with addition of copolymer particles to the aqueous phase were stabilized by copolymer particles initially, followed by the mixture of copolymer particles and copolymer as the particles eventually dissolves in the organic phase, and finally by only copolymer. Stable w/o HIPEs having an internal phase of up to 92 vol% were also formed with P(St-MMA-AA) copolymer dissolved in the organic phase as the sole stabilizer. Porous polymers (polyHIPEs) were prepared based on these two types of surfactant-free HIPEs. The morphology of the polyHIPEs, such as the surface roughness of the voids and average void diameter, were tailored by tuning the internal phase volume fraction, NaCl, copolymer, and crosslinker concentrations.     

Polystyrene/magnetite hybrid foams prepared via 60Co γ-ray radiation of high internal phase emulsions

In this study, polystyrene (PS) solid foam with cell size of about 1 um and low polydispersity is prepared via γ-ray radiation induced high internal phase emulsions (HIPEs) at room temperature. The density of the foams can be as low as 0.05 g/cm³. The kinetics and molecule weight of styrene (S) polymerizing in continuous phase of HIPEs is studied. It is found that the molecule weight is greatly lower than the PS obtained from the polymerization in dispersed phase of emulsion. In addition, the authors study the mechanical properties of solid foam. The compression resistance of solid foam obtained from radiation method is better than these obtained from conventional method. At the same time, magnetite is added into the dispersed phase when prepared the HIPEs to fabricate magnetite hybrid PS foam. The saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) of the hybrid foam are 25 emu/g, 15 emu/g, and 350 Oe, respectively. The results revealed that the hybrid foams have some superparamagnetic.