Controlling porous properties of polymer monoliths synthesized by photoinitiated polymerization

Porous monoliths have been successfully prepared by photoinitiated polymerization of hydroxyethyl methacrylate and ethylene glycol dimethacrylate monomers in a porogenic solvent. By varying the composition of the starting solutions such as initiator fraction, monomer ratio and pore generator (porogen) fraction and type, as well as UV intensity, monoliths have been obtained with narrow pore size distribution and median pore size from about a few nanometres to a few micrometres. © 2012 Society of Chemical Industry     

Effect of porogenic solvent on the porous properties of polymer monoliths

Polymer monoliths with open pores and median pore size of about 15 nm–3 μm have been successfully synthesized by photoinitiated polymerization of butyl methacrylate and ethylene glycol dimethacrylate monomers. The solubility of the monomers in a porogenic solvent is determined by Hildebrand solubility parameter, and it is found that it has great effect on the pore size of the polymers synthesized. Polymers with larger pores are usually generated with poorer solvents for the monomers. However, polymers with different pore sizes and porosities have been obtained using porogenic solvents with similar Hildebrand solubility parameters. The evaporation rate of the porogenic solvents might be another critical factor affecting the properties of the polymer monoliths. Moreover, the effect of water as a cosolvent on the pore size and porosity of the polymers have also been investigated. Polymers with larger pore size have been prepared with the presence of water due to the occurrence of earlier phase separation in the polymerization. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and structural control of polyphenylene sulfide porous fibers via thermally induced phase separation method

The porous fibers are expected to be widely used in liquid filtration, environmental protection, and catalyst carrier field. Polyphenylene sulfide (PPS) porous fiber was prepared using polyethersulfone (PES) as pore-forming agent by a thermally induced phase separation method. The rheological behaviors, crystallization, compatibility of the PPS/PES blending resins and fibers were characterized by the tests of high pressure capillary rheology, differential scanning calorimetry, and dynamic thermodynamic analysis, and so on; meanwhile, the structure and properties of PPS porous fibers were studied through the tests of continuity, scanning electron microscope, mercury injection, and mechanical properties. The results shown that the pore structure of porous PPS fibers can be regulated by controlling the PES content. In the spinning process, the higher winding speed (R = 300 ~ 400) and the larger PES content (60%) are more conducive to the formation of an interpenetrating structure of PES in the blend system. After the extraction of PES, PPS fibers with PES contents of 30% and 40% formed pore structure with uniform shape and size. Nevertheless, a high PES fraction of 60% leads to the collapse of the pore structure, resulting in serious structural damage. The porous fiber with controllable pore dimension is obtained by selecting proper ratio of polymers and appropriate spinning conditions.     

Hydrophilic Porous Hydroxypropyl Methacrylate–Ethyleneglycol Dimethacrylate Packing Materials Suitable for Use in Size Exclusion Chromatography

Packing materials suitable for use in size exclusion chromatography (SEC) were produced by radical polymerization at 70°C for 1 hour. Hydroxypropyl methacrylate (HPMA) monomer, ethyleneglycol dimethacrylate (EDMA) cross-linker, 2, 2, azobis-2-methylpropionitrile (AIBN) initiator and the porogen dodecanol (DOD) were mixed and added to a polyvinyl alcohol (PVA) solution suspending medium. Elimination of the suspending medium by centrifugation was followed by filtering, rinsing with methanol, Soxhlet extraction and vacuum drying (60°C, 12 h) to yield polymeric spherical particles. The effect of increasing the concentrations of the porogen agent dodecanol was evaluated. Scanning electron microscopy (SEM) revealed regularly shaped spherical porous beads ranging in size from 10–20 m. Nitrogen Sorption Analysis (NSA) was employed to determine the specific surface area and pore size.     

Manufacture of Porous Cross-Linked HEMA Spheres for Size Exclusion Packing Material

2-Hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA) monomers and ethyleneglycol dimethacrylate (EDMA) as a cross-linker, were reacted with the initiator 2,2,azobis-2-methylpropionitrile (AIBN) in the presence of dodecanol. The effect of increasing concentrations of dodecanol, as a porogen agent, was evaluated. The radical polymerization was carried out using an in situ prepared Mg(OH)₂ gel, at 70°C for 5 h. Following polymerization, the suspension was eliminated by neutralization for recovery of beads. The spherical particles obtained were filtered, washed with methanol using simple extraction and using a Soxhlet thimble, and dried at 60°C under vacuum. Scanning Electron Microscopy (SEM) revealed regularly shaped spherical beads containing macropores. Nitrogen Sorption Analysis (NSA) and Mercury Intrusion Porosimetry (MIP) were performed for evaluation of surface area, pore size and pore volume.     

Novel fabrication route for porous silicon carbide ceramics through the combination of in situ polymerization and reaction bonding techniques

For the first time, an in situ polymerization technique was applied to produce mullite‐bonded porous SiC ceramics via a reaction bonding technique. In this study, SiC microsized particles and alumina nanopowders were successfully coated by polyethylene (PE), which was synthesized from the particle surface in a slurry phase reactor with a Ziegler–Natta catalyst system. The thermal studies of the resulting samples were performed with differential scanning calorimetry and thermogravimetric analysis. The morphology analysis obtained by transmission electron microscopy and scanning electron microscopy (SEM) confirmed that PE was successfully grafted onto the particle surface. Furthermore, the obtained porous ceramics were characterized in terms of their morphologies, phase composition, open porosity, pore size distribution, and mechanical strength. SEM observations and mercury porosimtery analysis revealed that the quality of the dispersion of nanosized alumina powder into the microsized SiC particles was strongly enhanced when the particles were coated by polymers with in situ polymerization. This resulted in a higher strength and porosity of the formed ceramic porous materials with respect to the traditional process. In addition, the X‐ray diffraction results reveal that the amount of mullite as the binder increased significantly for the samples fabricated by this novel method. The effects of the sintering temperature, forming pressure, and polymer content on the physical and mechanical properties of the final porous ceramic were also evaluated in this study. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40425.     

Effect of Viscosity on Preparation of Foamed Silica Ceramics by a Rapid Gelation Foaming Method

An environmentally benign preparation method for silica foam (the rapid gelation foaming method) was developed by combining sol-gel reactions and mechanical foaming without using organic polymers or monomers, in order to generate less CO₂ and harmful gases from the decomposition of organic compounds contained in the raw material. The viscosity of the silica sol during foaming affects the porous properties of the silica foam, i.e. the porosity and average pore size decrease with increasing viscosity. The pore structure of the silica foams depend on the viscosity of silica sol, two types of pore structure being formed. An open-pore structure is obtained by foaming low-viscosity sols, while a closed-pore structure is obtained by foaming high-viscosity sols. Since the viscosity of the silica sol affects the stability and foaming ability of the foam, the porous properties of the product can be controlled by controlling the viscosity of the silica during foaming.     

SPG膜乳化与界面聚合法制备单分散多孔微囊膜

小粒径单分散中空储库结构微囊膜的制备具有重要学术意义和实用价值。为此采用了SPG(Shirasu-Porous-Glass)膜乳化法和界面聚合法，对小粒径单分散多孔微囊膜的制备进行了较系统的实验研究，以期为进一步制备多孔内接枝环境感应型功能凝胶开关的小粒径单分散微囊型靶向式药物载体提供基体。研究结果表明，采用SPG膜乳化法可制得单分散性良好的乳液液滴，进而采用界面聚合法可得到单分散微囊。用膜乳化方法易于控制乳液液滴及微囊的大小，在研究中SPG膜乳化法制备的乳液液滴及微囊的平均粒径大约是所用膜孔径的3．6倍。微囊膜的多孔性可以靠改变溶剂和单体的成分来进行控制，扫描电镜检测结果表明所制备出的不同粒径级别的单分散微囊膜均具有良好的多孔结构。     

种子溶胀聚合制备苯乙烯-二乙烯苯多孔交联微球

以苯乙烯分散聚合制备单分散种子微球(PS),再用超声分散改进的二步种子溶胀聚合制备了聚苯乙烯-二乙烯苯(PSt-DVB)多孔微球。用光学显微镜、扫描电镜(SEM)和比表面积孔径分布测定仪(BET)等对种子微球和多孔微球的表面形貌及孔结构进行了表征。结果表明,随分散介质极性的增大,所得PS种子微球的粒径变小,相对分子质量增大;固定种子微球用量,随着DBP和DVB用量的增加,交联微球比表面积上升、孔径下降。以乙醇为介质制备种子微球,当DBP体积为1.0 mL,DVB体积为8~10 mL时,能够得到4~7μm单分散性良好的多孔PSt-DVB微球。     

Hierarchically porous polymeric materials from ternary polymer blends

Hierarchically porous polymers with controllable pore size were generated through a novel polymer blending strategy in an A/B/C–B–C ternary blend system. Polylactide/high-density polyethylene/poly(styrene-ethylene/butylene-styrene) triblock copolymer (PLA/HDPE/SEBS) was used as a model system to demonstrate this technique. During melt blending, the SEBS was driven into the HDPE phase owing to the presence of the PE block in the copolymer. With proper volume fractions of PLA/HDPE/SEBS (e.g., 50/25/25), a bi-modal, dual co-continuous morphology was obtained and hierarchically porous polymeric materials were further generated by selectively removing the PLA and SEBS phases. Annealing and compositional variation were further employed to control the pore size and it is shown that the length scales of the two co-continuous morphologies can be controlled independently.     

聚卟啉的制备及其在光氧化催化反应中的应用

通过Sonogashira Hagihara偶联聚合制备了一系列具有多孔结构的网状交联聚卟啉光催化剂,设计了双溴双炔卟啉和四溴卟啉两种结构的卟啉单体,通过双溴双炔卟啉自聚得到多孔有机聚卟啉(PPOP-1),通过四溴卟啉与含双炔基的单体(1,7-辛二炔、对苯二炔、联苯二炔)共聚得到聚卟啉PPOP-2、PPOP-3和PPOP-4.通过SEM和物理吸附仪观测聚合物的表面形貌和表征孔结构.结果显示,4种聚合物均具有均匀的颗粒形态和微孔结构,孔径约1 nm,比表面积分别为38.484、12.494、10.880和19.858 m2/g.以聚卟啉为异相光催化剂,通过可见光诱导二苄胺、缩硫酮、二苄基硫醚的有氧氧化证实了其对C—N和C—S键的氧化均具有优于单体催化剂的催化活性.PPOP-1(0.01 mmol)在可见光下催化二苄胺(0.1 mmol)的氧化反应,8 h后体系原料转化率和选择性均可达99％.经过4次循环催化后,PPOP-1仍保持较高的催化活性,原料转化率仍能达到99％.     

一种复合二氧化钛大孔共聚物的合成及其在扩张床吸附中的应用(Ⅰ)基质合成及其特性

以甲基丙烯酸缩水甘油酯和双甲基丙烯酸乙二醇酯作单体 ,在致孔剂存在下通过悬浮聚合将经过表面改性处理的二氧化钛超细颗粒包埋其中 ,制得一种密度增大的复合二氧化钛大孔共聚物 (GET) ,作为扩张床吸附基质 .研究了二氧化钛添加量、交联剂用量、致孔剂用量和配比对共聚物湿真密度和孔结构的影响     

一种复合二氧化钛大孔共聚物的合成及其在扩张床吸附中的应用（Ⅰ）基质合成及其特性

以甲基丙烯酸缩水甘油酯和双甲基丙烯酸乙二醇酯作单体，在致孔剂存在下通过悬浮聚合将经过表面改性处理的二氧化钛超细颗粒包埋其中，制得一种密度增大的复合二氧化钛大孔共聚物（GET），作为扩张床吸附基质.研究了二氧化钛添加量、交联剂用量、致孔剂用量和配比对共聚物湿真密度和孔结构的影响.     

偏氯乙烯聚合物基多孔炭的制备及应用研究进展

叙述了以偏氯乙烯聚合物为碳源,通过高温直接炭化制备微孔为主的多孔炭,及炭化、催化活化和模板法制备中孔-微孔复合多孔炭的研究进展,归纳了影响2种新型多孔炭制备过程中炭材料孔隙的主要因素.介绍了偏氯乙烯聚合物基微孔和中孔-微孔复合多孔炭材料在超级电容器电极、催化剂负载和吸附分离等方面的应用.认为偏氯乙烯聚合物基多孔炭属新型...     

Synthesis and characterization of porous polydimethylsiloxane structures with adjustable porosity and pore morphology using emulsion templating technique

Porous polydimethylsiloxane (PDMS) framework with adjustable pore structures has been fabricated by polymerization of the continuous phase in the emulsion templates. Different types of surfactants, including nonionic (Triton X-100), cationic (Benzalkonium chloride), anionic (sodium dodecyl sulfate), and silicone-based block copolymer were used to stabilize the water-in-oil emulsion system. Deionized water with a wide range of internal phases varying from 10% to 60% by weight was employed to make the low internal phase emulsion and medium internal phase emulsion. The effect of surfactant type, surfactant concentration, and the internal phase volume on the stability of the emulsion, pore morphology, and pore size distribution was explored. The stability of the emulsion was investigated by comparing the pore morphology of the cured sample at different set times, such as 0, 6, and 72 h. Scanning electron microscopy was employed for the characterization of the porous structures. The image analysis was conducted, and the pore size distribution, porosity, and open-cell ratio of each sample were calculated. Interconnected pores have been seen in the porous PDMS made from emulsions with an internal phase larger than 30%. The results demonstrated that the frequency of open-cell pores and the pore size is dependent on the surfactant types.     

离子液体聚合物CO_2吸附性能研究

为提高离子液体吸附CO_2的性能,通过自由基聚合制备了季铵盐类离子液体聚合物,采用两步种子溶胀法使该聚合物形成多孔结构,并通过扫描电子显微镜和差热-热重分析法对其形貌和热稳定性进行表征。研究了4种溶胀剂制备的多孔聚合物吸附CO_2的性能,试验结果表明:制备的多孔聚合物具有发达的微孔结构,孔径在0.4~0.8 nm内连续分布,且较集中于0.5~0.6 nm,达到38%以上;溶胀剂的种类对孔径分布及累计孔容有显著的影响,可归因于溶胀剂与聚合物的溶解度差异,采用混合溶胀剂得到的孔径分布更加均匀,而采用环乙烷溶胀剂得到的累计孔容明显减少;多孔聚合物的CO_2吸附量主要受累计孔容的影响,累计孔容相当的聚合物吸附CO_2的量也近似,在273 K、0.101 MPa条件下,约为1.1%。     

Macro and meso porous polymeric materials from miscible polysulfone/polyimide blends by chemical decomposition of polyimides

Novel macro and meso porous polysulfone materials were prepared from miscible blends of polysulfones with a phenylindane containing polyimide by selective chemical decomposition of the polyimide phase using a dilute hydrazine or tetraammonium hydroxide solution in methanol. It was found that the pore size of the material is affected by the backbone structure of the polysulfone selected. The compatibility between the polysulfones and the polyimide is influenced by the polysulfone structure. This in turn affects the pore size and the pore size distribution of the final porous material. Polyether sulfone was found to form most compatible blends that in turn leads to a porous material with the smallest pore size, a meso porous material. The meso porous polyether sulfones are transparent films, with uniform pore sizes in the range of 30 nm, while bisphenol A polysulfone based porous materials are opaque with pore sizes in the range of 200 nm.     

Synthesis and characterization of dense and porous cellulose films

Whereas cellulose‐derived polymers are routinely used as membrane materials, the cellulose polymer itself is not directly used to synthesize dense/porous films for membrane applications. Recently, N‐methylmorpholine N‐oxide (NMMO) and dimethylacetamide (DMAc)/lithium chloride (LiCl) have been successfully employed for dissolving unmodified cellulose. This provides a strong rationale for reexamining the possibility of cellulose membrane fabrication using these solvents. By judiciously selecting solvents, casting conditions, and solvent exchange steps, we successfully synthesized dense/asymmetric‐porous cellulose films. The pore size and porosity of the porous films decreased systematically with increasing cellulose concentration. SEM analysis of the cross sections revealed an asymmetric skinned structure with monotonically increasing pore size away from the skin. The measured pore diameters were in the range 1.8–4.8 μm. Mechanical testing indicated that the dense films possessed tensile properties comparable to those of cellulose acetate (CA) films. Though nitrogen permeability values were comparable for cellulose and CA dense films, cellulose film permeability depended upon the type of drying protocol employed. Overall, these results demonstrate that processability need not be a constraint in the use of cellulose polymer for membrane fabrication. In selected applications, cellulose membranes could become a cost‐effective, environmentally friendly alternative to other more commonly employed membrane polymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synthesis and characterization of reactive macroporous poly(glycidyl methacrylate‐triallyl isocyanurate‐ethylene glycol dimethacrylate) microspheres by suspension polymerization: Effect of synthesis variables on surface area and porosity

A novel macroporous poly(glycidyl methacrylate‐triallyl isocyanurate‐ethyleneglycol dimethacrylate) copolymer, hereinafter P_{GMA‐TAIC‐EGDMA}, of controlled bead size was prepared via free radical suspension copolymerization. The effects of varying the concentration of crosslinking agents and porogenic diluent on the average pore diameter, pore size distributions, specific surface area, and pore volume of the copolymer matrix were thoroughly investigated. The spherical beads were characterized by elemental analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The specific pore volume, average pore diameter, pore size distribution, and the specific surface area were measured by Mercury intrusion porosimetry and BET adsorption method, respectively. The porous properties of the polymer matrix are a direct consequence of the amount and quality of the porogenic solvent, the percentage of crosslinking monomers, and the ratio between the monomers and porogen phases. When the polymer was prepared at 30 and 40% crosslinking density, and 75 and 100% diluents, respectively, it showed a fine beads morphology, mechanical stability and pore size distributions. By comparing the copolymers P_{GMA‐TAIC‐EGDMA} and P_GMA‐EGDMA, it was found that the former is more stable both thermally and mechanically than its predecessor. The presence of epoxide functionalities of macroporous P_{GMA‐TAIC‐EGDMA} beads makes it a versatile carrier. The resulting polymers have the potential for wide applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Macrostructural design of highly porous SiOC ceramic foams by preceramic polymer viscosity tailoring

Highly porous SiOC ceramic foams with gradient or uniform macrostructures were obtained through polymer derived ceramic routes. Precuring of preceramic polymers and introduction of SiO₂ powders were used to tailor precursor viscosity and hence SiOC foam macrostructure. Effects of polymer viscosity on porosity, pore size, pore distribution were investigated by light microscopy and micro-computed tomography techniques. SiOC ceramic foams. Foams from one unmodified precursor, showed pore size gradient with small pores located at bottom and large pores at the top. To address this non-uniformity, the viscosity of the precursor was increased by pre-curing the preceramic polymer, which resulted in decrease of the average pore size and improvement in pore size uniformity. For a different system with a self-foaming preceramic polymer, because of the simultaneous release of foaming gases and rapid increase in viscosity during crosslinking, the foam had non-uniform macrostructure with large pores and thick struts at the bottom. By addition of SiO₂ fillers, the crosslinking reaction rate was reduced leading to homogeneous pore nucleation and uniform small pore size foams.