Synthesis and Properties of Indan-Based Polyacetylenes That Feature the Highest Gas Permeability among All the Existing Polymers

Abstract

Acetylenic monomers containing indan and other groups (1a-m) were polymerized with TaCl 5n-Bu 4 Sn catalyst to give high molecular weight polymers. Most polymers were soluble in common organic solvents including toluene and chloroform, and they afforded free-standing membranes by the solution casting method. The onset temperature of weight loss of the polymers were over 400 °C, indicating high thermal stability. Despite the absence of bulky spherical groups, polymethylated indan-containing polymer membranes showed extremely high gas permeability. In particular, the oxygen permeability coefficients of polymers having 1,1,3,3tetramethylindan and either p-fluorophenyl or p,m-difluorophenyl groups (2b and 2e) reached 17 900 and 18 700 barrers, respectively, which are even larger than that of the most permeable polymer known, poly(1-trimethylsilyl-1-propyne).

Synthesis and gas permeation properties of poly(diarylacetylene)s having substituted and twisted biphenyl moieties

“…Based on the above experimental findings, the following discussions are possible about the gas permeability of the present polymers: (i) the twisted biphenyl structure26, 38 induced by methyl, chlorine, or tert ‐butyl groups at the ortho position(s) is favorable for the generation of excess free volume; (ii) the large local mobility of tert ‐butyl groups promotes the diffusion of gases through the membrane;39 and (iii) intersegmental packing of the polymer chain of 2d is inhibited by the repulsion of highly electronegative chlorine atoms to produce a sparse structure in the polymer matrix. Similar and even obvious effects have been observed in previous studies of poly(diarylacetylene)s carrying indanyl/fluorenyl groups 40–42…”

Review of Membranes for Helium Separation and Purification

“…This is because of the strong solubility of CH 4 in silicone-based polymers which dominates permeability through this class of polymer [23]. For both gas pairs, the highest permeable polymers are poly (trimethylsilylpropyne) (PTMSP) and substituted polyacetylenes, which are well known to have high fractional free volumes, which are almost microporous in structure [24,25]. Alternatively, high selectivity for both gas pairs is achieved for dense polymers such as polypyrrolone.…”

Polymers of Intrinsic Microporosity

“…It should be noted that several members of wellestablished classes of nonnetwork polymers can possess significant intrinsic microporosity as demonstrated by very fast gas permeabilities (e.g., polyacetylenes [24][25][26], fluorinated polymers [27][28][29], polynorbornanes [30,31], and polyimides [32]), and these are exploited in the polymer membrane field where they are more commonly described as high free volume or ultrapermeable polymers [33]. However, with the exception of some polyimides that have structural similarities to the PIMs (i.e., those termed PIM polyimides), these polymers will only be dealt with indirectly when comparisons of their properties with those of PIMs are instructive.…”