Polymers of Intrinsic Microporosity derived from a carbocyclic analogue of Tröger's base

Molecular insight into transport properties of Troger's base based polyimide membrane

Molecular Dynamics (MD) simulations were employed to investigate the transport properties of three polyimides comprising various diamines and dianhydrides. The diamines were 2,8-diamine-4,10-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (TB1) and 3,9-diamine-4,10-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (TB2); the dianhydrides were 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 4,4'-oxydiphthalic anhydride (ODPA). And the three polyimides were denoted as p-TB1-6FDA, p-TB1-ODPA and p-TB2-6FDA, respectively. The simulations provided the properties of the bulk polyimides such as glass transition temperature, fractional free volume, and solubility parameter. The results obtained were generally in consistent with experimental findings, which validated the quality of the model construction. Diffusion coefficient of carbon dioxide (CO2) in polyimide membrane was extracted based on mean square displacement analysis. Further research on backbone dihedral distribution and radial distribution function unveiled that Troger (TB1 or TB2) bases exerted strong influence on intra-chain mobility, 6FDA components were evenly distributed in polyimide matrix thus inhibiting inter-chain packing and CO2 molecules in free volume are surrounded by layers formed by Oxygen/Nitrogen atoms.

Incorporation of Carbocyclic Moieties into Polymer Structure: A Powerful Way to Polymers with Increased Microporosity

Microporous soluble polymers attract great attention as materials for membrane gas separation, gas storage and transportation, as sorbents, supports for catalysts, and matrices for mixed matrix membranes. The key problems in the development of this area of polymer chemistry include the search for methods of controlling the porous structure parameters and ensuring the stability of their properties over time. In this connection, a fruitful approach is to introduce bulky and rigid, often framework carbocyclic moieties into the polymer backbones and side chains. This review discusses the effect of carbocyclic moieties on gas transport properties, BET surface area, and FFV of glassy polymers, such as polyacetylenes, polynorbornenes, polyimides, and ladder and partially ladder polymers. In the majority of cases, the incorporation of carbocyclic moieties makes it possible to controllably increase these three parameters. Carbocyclic moieties can also improve CO2/gas separation selectivity, which is displayed for ladder polymers and polynorbornenes.

The effect of nanoparticles on gas permeability with polyimide membranes and network hybrid membranes: a review

Polyimide membranes and network hybrid membranes exhibit high permeability despite good thermal and chemical stability, and high selectivity in gas mixture separation. In this study, the effect of nanoparticle distribution on the network polymer network, and changes in permeability, selectivity, and structure of the composite lattice membrane are investigated. According to the obtained permeability results, this increase in permeability was due to the increase of polymer network free volume and the formation of cavities in the nanoparticle-polymer interface. The significant results were that the permeability growth of gases with larger molecular size such as methane and nitrogen was higher than other gases. A comparison of the permeability growth of gases with the increasing volume fraction of nanoparticles confirms the dominance of the molecular sieve mechanism and the type of membrane transport mechanism change over polyimide and network Hybrid.