Mesoporous polymer

Still, this theory is over-simplified, and holds only for a limited part of the sorption isotherm, which is usually the case for relative pressures between 0.05-0.30, and the presence of point B (Fig. 1.14). Thus, isotherms of Types II (macroporous polymer supports) and IV (mesoporous polymer supports), but not Type I and III, are those amenable to BET analysis [21, 80]. Attention should also be paid to the constant C, which is exponentially related to the enthalpy of adsorption of the first layer. A negative or high value of C exceeding 200-300, is likely to indicate the presence of micropores and the calculated surface area should be questioned since the BFT theory would not be applicable [79, 80]. 

As discussed in Section 1.4.2.1, the critical condensation pressure in mesopores as a function of pore radius is described by the Kelvin equation. Capillary condensation always follows after multilayer adsorption, and is therefore responsible for the second upwards trend in the S-shaped Type II or IV isotherms (Fig. 1.14). If it can be completed, i.e. all pores are filled below a relative pressure of 1, the isotherm reaches a plateau as in Type IV (mesoporous polymer support). Incomplete filling occurs with macroporous materials containing even larger pores, resulting in a Type II isotherm (macroporous polymer support), usually accompanied by a H3 hysteresis loop. Thus, the upper limit of pore size where capillary condensation can occur is determined by the vapor pressure of the adsorptive. Above this pressure, complete bulk condensation would occur. Pores greater than about 50-100 nm in diameter (macropores) cannot be measured by nitrogen adsorption. 

Note 4 Porous polymers with pore diameters from ca. 2 to 50 nm are called mesoporous polymers. 

Mesoporous polymers (SiO, template) Triton N-101/ cyclohexane/ hexanol/water/... 

The work of Mallouk et al. (39) offers an interesting extension of the microemulsion sol-gel technique. In this case, microemulsion-derived silica nanoparticles were used as templates for preparing ordered mesoporous polymers with tailored pore sizes. Utilizing the Triton N-101/cyclohexane/hexanol/water/ammonia microemulsion, monodisperse silica nanoparticles were first synthesized. The silica product... 

Ordered mesoporous polymers have been produced by filling with divinylbenzene, ethyleneglycol dimethacrylate, or a mixture of the two the pores of a colloidal crystal are formed by silica spheres of 35 nm of diameter. Thereafter, the polymerization and subsequent dissolution of the silica template leave a polycrystalline network of interconnected pores [235],... 

Monodispersed 35 nm colloidal silica spheres were used to template a periodic mesoporous polymer [71]. Divinylbenzene was used to make a cross-linked rigid polymer replica, ethylene glycol dimethacrylate ensured that it was flexible and shrinkable, while mixtures of the two were used to vary the degree of shrinkage. In addition, the mesoporous polymer replicas were themselves... 

Johnson S. A., Ollivier P. J., and Mallouk T. E., Ordered mesoporous polymers of tunable pore size from colloidal silica templates. Science 283 (1999) pp. 963-968. 

Adsorption of inflammatory cytokines and endotoxin by mesoporous polymers and activated carbons... 

F.Q. Zhang, Y. Meng, D. Gu, Y. Yan, C.Z. Yu, B. Tu, and D.Y. Zhao, A Facile Aqueous Route to Synthesize Highly Ordered Mesoporous Polymers and Carbon Frameworks with Ia3d Bicontinuous Cubic Structure. J. Am. Chem. Soc., 2005, 127, 13508-13509. 

Titirici MM, Hall AJ, Sellergren B (2002) Hierarchically imprinted stationary phases mesoporous polymer beads containing surface-confined binding sites for adenine. Chem Mater 14(l) 21-23... 

In conclusion, it should be also said that the origin of the hysteresis loop of the adsorption—desorption isotherms of porous polymers is stiU debated and can be interpreted in different ways. For example, there exists an opinion that hysteresis is not related to traditional capillary condensation in the pores, but may be a consequence of the out-of-equihbrium character of phase transitions in real disordered mesoporous polymers [255]. A failure to reach equilibrium under the given experimental conditions may be caused by the slow diffusion rate of the sorbate [256] or slow swelling of the polymeric sorbent on adsorption and slow relaxation of its swollen structure on desorption. Quite often, a subsequent adsorption on the same material results in larger adsorption capacity values. It is the so-called conditioning effect [256] that may imply a nonequihbrium character of the process. Even the reproducibihty of the shape and location of a hysteresis loop of the isotherms may indicate the estabhshment of fast... 

The mechanical strength of the mesoporous polymers was found to be good. Each bead of 0.4 mm in diameter could tolerate a load as high as 300—450 g before destruction. This is an important parameter, because crushed particles and fines released from an adsorbent bed could embolize into the patient s circulation. The optimal bead size of the polymeric adsorbent was found to be 0.3—0.8 mm, which prevented high back pressures at moderate to high flow rates of viscous liquids, such as whole blood and plasma, through a 200—300 mL cartridge packed with the polymer. 

Figure 15.1 Selectivity of protein sorption on the hypercrosslinked mesoporous polymer in dynamic in vitro experiment with plasma. Experimental conditions the polymer to plasma ratio is 1 20 (v/v) 37°C initial concentrations of proteins are as follows (1) P2-microglobulin 6.35mg/dL, (2) albumin 3.15 g/dU (3) prealbumin 30 mg/dL, (4) transferrin 317 mg/dL, (5) total protein 6.2 g/dL (After [357].)...

Zhao and co-workers have made major advances in the soft-template synthesis of mesoporous carbons. They reported the self-assembly of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) and resol mixtures and successful removal of the templates including F127, F108 and P123 at a series of temperatures to produce mesoporous polymer and carbon materials. " ° Eigure 4.10 illustrates the five-step synthesis procedure reported by Meng et Low-... 

Figure 4.10 Scheme for the preparation of ordered mesoporous polymer resins and carbon frameworks.Reprinted with permission from Y. Meng, D. Gu, F. Zhang, Y. Shi, L. Cheng, D. Feng, Z. Wu, Z. Chen, Y. Wan, A. Stein and D.Y. Zhao, Chem. Mater., 18, 4447. Copyright (2006) American Chemical Society... 

The pore size of mesoporous carbon is of importance with respect to practical applications. When mesoporous carbon is synthesised via soft-template methods, the self-assembly of organic-organic species and pore size can be influenced by synthesis conditions, including surfactant type and concentration, and synthesis temperature. For example, Meng et al. observed that the pore size of mesoporous carbon derived from soft-templated mesoporous polymer composites decreased from 7.4 to 5.9 nm when the pyrolysis temperature increased from 400 to 800 How-... 

S.A. Johnson, P.J. OUivier, and T.E. Mallouk, Ordered mesoporous polymers of tunable pore size from colloidal sihca templates. Science, 283(5404), 963 965 (1999). 

A novel sulfonated Pd-phthalocyanine modified FDU-15 mesoporous polymer has been efficiently applied as a heterogeneous photocatalyst for the degradation of 4-chlorophenol, under visible-light irradiation in the presence of H2O2. The material is promising for the removal of organic pollutants under sunlight irradiation. Luminescent... 

Fig. 7.11 Scheme for the preparations of the ordered mesoporous polymer resins and carbon frameworks [78] (Reprinted by permission of the publisher)... 

Zhang F, Meng Y, Gu D, Yan Y, Yu C, Tu B, Zhao D (2(X)5) A facile aqueous route to synthesize highly ordered mesoporous polymers and carbon frameworks with Ia3d bicontinuous cubic structure. J Am Chem Soc 127 13508-13509... 

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