Nanoporous polymer foams porous structure

Table 9.1 Micro and nanoporous polymer foams obtained from nanostnictured polymers reported in the literature, with process conditions as well as nanostructure and porous structure characteristics [pore size ( p) and porosity (Vf)]... 

Most of the reported works are limited to the development of nanoporous structures in films or to particular processing parameters however, in the last years significant advances were performed in the production of bulk nanoporous polymer foams in a wide range of processing conditions, showing some of the best features reached, such as a nearly perfect correlation between the former nanostructure and the final porous structure. These advances are a promising step in the search of a continuous industrial process for the production of nanoporous polymer foams. 

The development of a continuous foaming production route able to produce nanoporous polymer foams with fine porous structures and medium-high porosities. 

Modification of the foaming processes, polymer precursors, or inclusion or an additional production step that allows connecting the inner open porous structures of some of these materials with the exterior of the sample. By this way a wide set of apphcations could be fulfilled by these nanoporous polymer foams. 

The types of nanostructured polymers used to date in the production of micro- and nanoporous foamed materials, the resulting porous structures, the experimental evidence between the pore structure and the nanostructure template, and the properties of this kind of materials are further described in the following sections. 

PS-b-PFMA films were foamed by a modified gas foaming process to obtain nanoporous polymers [83,84,88,91]. After the usual saturation stage (1 h at pressures between 7.5 and 30MPa and 60°C), the temperature was quenched to 0°C, maintaining the CO2 pressure, and then the pressure was released at a very low rate of 0.5 MPa/ min. The resulting porous structures were studied in thick films by SAXS and SEM, obtaining pore sizes between 10 and 30 nm and very high pore densities more than 10 pores/cm, but low porosity ( 30% Fig. 9.20). Moreover, they found that without... 

Some applications nonrelated to the properties of the nanoporous materials but to their porous structures are their use as filtration membranes, battery separators (hindering the diffusion of ions in the narrow channels), and catalyst supports (due to their high surface area) as well as gas capture and storage or light harvesting [72]. However, the common factor of all of these applications is the requirement of an open nanoporous structure not only inside the sample but also connected to the exterior of the sample. However, the CO2 foaming process from nanostructured polymers still has not allowed obtaining nanoporous samples with all of these features. Pinto et al. [102] proposed that 25/75 PMMA/MAM nanoporous foams present appropriate inner porous structures for these kinds of applications (bicontinuous nanoporous structures with tunable pore size), but further studies are required to connect effectively this inner porous structure with the exterior of the sample. 

This chapter provides a general overview of the different advances reported np to date in the production of nanoporous foamed polymers from nanostructured polymer blends. It has been demonstrated that the theoretical basis of this field has been confirmed experimentally, with the features proposed initially for ideal nucleating nanodomains reached by some different BCPs. Nanostructuration and the porous structure of the main works in this area were described, as well as a comprehensive explanation about the key evidence of the relationship between both structures was provided. 

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