Microporosity Microporous polymers

Weber J, Su Q, Antonietti M et al (2007) Exploring polymers of intrinsic microporosity— microporous, soluble polyamide and polyimide. Macromol Rapid Commun 28 1871-1876... 

The microporosity of PIMs, like that of other microporous polymers, is composed by a covalent bonding framework. Actually, normal non-network polymers can pack the space densely because the polymer skeleton can twist and bend to maximise inter-chain interactions. However, it should be noted that some polymers can possess large amounts of voids, usually referred to as free volume. It can be anticipated that above a eertain amount of free volume, the voids would be interpenetrated, and therefore the polymer will behave as a conventional microporous compound despite the laek of a network structure. Thus, the polymer with interpenetrated voids ean be soluble like normal polymers, which could trigger solution proeessing, providing an advantage over other types of microporous compounds. ... 

Lewis-Acid Catalyzed. Recently, various Lewis acids have been examined as catalyst for the aldol reaction. In the presence of complexes of zinc with aminoesters or aminoalcohols, the dehydration can be avoided and the aldol addition becomes essentially quantitative (Eq. 8.97).245 A microporous coordination polymer obtained by treating anthracene- is (resorcinol) with La(0/Pr)3 possesses catalytic activity for ketone enolization and aldol reactions in pure water at neutral pH.246 The La network is stable against hydrolysis and maintains microporosity and reversible substrate binding that mimicked an enzyme. Zn complexes of proline, lysine, and arginine were found to be efficient catalysts for the aldol addition of p-nitrobenzaldehyde and acetone in an aqueous medium to give quantitative yields and the enantiomeric excesses were up to 56% with 5 mol% of the catalysts at room temperature.247... 

In addition, the polymers of intrinsic microporosity (PIMs), such as phthalocyanine networks and the Co phthalocyanine network-PIM (CoPc20), display high specific surface area, as confirmed by the N2 adsorption isotherm at 77 K, and by the adsorption of small organic probe molecules from aqueous solutions at 298 K [236], This material is basically microporous with an increased concentration of effective nanopores. 

Porosity is divided by IUPAC (Rouquerol et al. 1994), based on pore size, into the following groups macropores (>50 nm), mesopores (2-50 nm), and micropores (<2 nm). Microporosity may then be subdivided into three subsequent categories supermicropores (1.4-2.0 nm), micropores (0.5-1.4 nm), and ultramicropores (<0.5 nm). Both mineral and organic soil components have pores with different diameter. The holes and channels in the polymer chain of humic substances as well as the interlayer space of the layered mineral have an important role in determining the specific surface area. The size of the interlayer space of layered minerals in a dry state is a few tenths of nanometers, so they are considered as micropores. 

The polymers of intrinsic microporosity (PIMs). These are rigid macromolecules composed of a fused-ring subunit which cannot pack space efficiently and hence form microporous materials (Figure 2.5) [68]. 

Although typical FDU-1 silicas and other polymer-templated silicas with large cagelike mesopores tend to be significantly microporous, the FDU-1 sample calcined at 1000 °C appeared to be essentially free from microporosity, as can be inferred from the relation between its surface area, pore volume, and pore diameter. 

Membrane-like heteropoly acid-blended polymer film catalysts were prepared using a common solvent (or mixed solvents) and they were tested as fixed-bed catalysts for the ethanol conversion reaction in a continuous flow reactor. It was found that heteropoly acid catalyst was finely and uniformly distributed through the polymer matrix. All the film catalysts showed the higher selectivity to acetaldehyde than the bulk solid catalyst. Conversion and selectivity over the film catalysts were also affected by the nature of solvent and polymer. Microporosity of the film catalyst was controlled by the phase separation method. The microporous film catalyst could be regarded as a highly dispersed heteropoly acid catalyst supported on polymer matrix. The film catalysts were characterized by IR, TPD, SEM, EDX, DSC, and ESCA. 

The intensive search for other types of microporous materials that started less than a decade ago resulted in the development of polymers with intrinsic microporosity (PIMs see Chapter 9, Section 3.8) and... 

McKeown NB, Budd PM, Msayib KJ, GhanemBS, Kingston HI, TattershaU CE, Makhseed S, Reynolds KJ, Fritsch D. Polymers of intrinsic microporosity (PlMs) Bridging the void between microporous and polymeric materials. Chem Eur J 2005 11 2610-2620. 

Advanced organic and inorganic membranes and materials include polymers of intrinsic microporosity (PIMs), microporous PVDF, perovskite and palladium alloy membranes [45]. PIM membranes have displayed both high permeability with high selectivity for various gas mixtures. Major commercial and promising applications of membrane GS are delineated below [43—45] ... 

If the answer to both these questions is yes , then the polymer can be said to have intrinsic microporosity [3,4] intrinsic because it is a consequence of the molecular structure and microporosity because we are dealing with micropores in the sense defined by lUPAC [2], This chapter introduces a concept for creating just such polymer structures, outlines the properties of the archetypal polymer of intrinsic microporosity , PIM-1, and describes recent results for PIM-1 obtained in the course of a European collaborative research project [5]. 

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