Free volume polymers PIMs

Emmler T, Heinrich K, Fritsch D, Budd PM, Chaukura N, Ehlers D, Raetzke K, Faupel F. Free volume investigation of polymers of intrinsic microporosity (PlMs) PIM-1 and PlMl copolymers incorporating ethanoanthracene units. Macromolecules 2010 43(14) 6075-6084. 

Reaction of a positron with an electron gives a metastable positronium (Ps) particle, which may have antiparallel spins (para-positronium, p-Ps) or parallel spins (ort/jo-positronium, o-Ps). Within a polymer, the longer lifetimes of o-Ps may be related to the size, concentration and distribution of free volume elements. There have been a number of studies of PIM-1 by positron annihilation lifetime spectroscopy (PALS) [33-36]. 

M. Heuchel, D. Fritsch, P. M. Budd, N. B. McKeown, D. Hofmann, Atomistic packing model and free volume distribution of a polymer with intrinsic microporosity (PIM-1), J. Membr. Sci., 318, 84-99 (2008). 

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. ... 

Xe nuclear magnetic resonance (NMR) experiments are a useful tool to explore the micropores lying on the frameworks of porous polymers. Emmler et al. studied Xe adsorption in PIMs (0-3 bar) to explore their microporosity. " High free volume copolymers, which form films, were synthesised when the proportion of the PIM-1 spiro-units were exchanged by ethanoanthracene (COl) units. PIMl-COl-40 has a 60 40 ratio of spiro-units to COl units and is used as a comparison with PIM-1. A systematic investigation was performed to compare the N2 sorption, Xe sorption, positron... 

The scope of discussions of porous polymers in this book is limited to polymers synthesized by the widely known concave-like monomers, which lead to high international molecular free volumes. The resulting free volume is interpenetrated and is fully open or accessible to make the polymer act as a host. The typical porous polymers discussed in this book are hyper-crosslinked polymers (HCPs), polymers of intrinsic microporosity (PIMs), covalent organic frameworks (COFs), conjugated mieroporous polymers (CMPs), and porous aromatie frameworks (PAFs). 

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