Ending Aging in Super Glassy Polymer Membranes

Abstract

Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4‐methyl‐2‐pentyne) (PMP), and polymers with intrinsic microporosity (PIM‐1) reduces gas permeabilities and limits their application as gas‐separation membranes. While super glassy polymers are initially very porous, and ultra‐permeable, they quickly pack into a denser phase becoming less porous and permeable. This age‐old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO2 permeability for one year and improving CO2/N2 selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations.

Using intermolecular interactions to crosslink PIM-1 and modify its gas sorption properties

“…26 The pure N 2 , and CO 2 permeabilities were determined using a constant volume and variable pressure method. 26 The pure N 2 , and CO 2 permeabilities were determined using a constant volume and variable pressure method.…”

“…These modication approaches generally fall into two categories: modication of the polymer backbone, or crosslinking PIM-1 to form a network. Mixed matrix approaches 23 have been shown to be useful in enhancing the gas transport properties of PIM-1 and a range of different materials have been produced by blending PIM-1 with (amongst others) inorganic llers, 24 cage nanocrystals, 25 porous nanoparticles, 26 carbon nanotubes 27 and other polymers. 17 Crosslinking approaches have included thermal crosslinking of the polymer by the trimerisation of the nitrile groups to triazine, 13 UV radiation has been used to give an increase in the selectivity, rstly by Chung and co-workers who suggested that the modication in behaviour was due to chain rearrangement 21 while more recently Sivaniah and co-workers attributed the modication in properties to a photo-oxidative surface modication of the membrane.…”

Aging of polymers of intrinsic microporosity tracked by methanol vapour permeation

“…The decline of material permeability was lower than 10% of the initial permeability over one year for PIM-1 membrane with PAFs [25], lower than 60% for PIM-1 with cages [26] and about 40% over half a year for PIM-1 with HCP [27] , while the usual decline over one year is about 70% [26]. Furthermore, an increase in absolute permeability was observed for all the types of additives [27].…”

“…It was shown in recent works [23][24][25][26][27] that PIMs aging can be tackled using organic additives such as porous organic molecular crystals [28] (cages), porous aromatic frameworks [29] (PAFs) [28]or hypercrosslinked polystyrene fillers [27] (HCP). The decline of material permeability was lower than 10% of the initial permeability over one year for PIM-1 membrane with PAFs [25], lower than 60% for PIM-1 with cages [26] and about 40% over half a year for PIM-1 with HCP [27] , while the usual decline over one year is about 70% [26].…”

Recent developments in membranes for efficient hydrogen purification

“…introduced a novel and effective strategy to solve physical aging problem [225]. A very specific microporous filler, porous aromatic framework (PAF), was suggested to incorporate into three representative glassy polymers including poly(trimethyisilylpropyne) (PTMSP), poly(4-methyl-2-pentyne) (PMP) and PIM-1.…”