Hydroxyhexafluoroisopropylnorbornene Block and Random Copolymers via Vinyl Addition Polymerization and Their Application as Biobutanol Pervaporation Membranes

Abstract

Vinyl addition polymers of substituted norbornene (NB) monomers possess very high glass-transition temperatures, making them useful in diverse applications; however, until very recently, the lack of an applicable living polymerization chemistry has precluded the synthesis of such polymers with controlled architecture, or copolymers with controlled sequence distribution. In the present work, block and random copolymers of NB monomers bearing hydroxyhexafluoroisopropyl and n-butyl substituents (HFANB and BuNB) are synthesized via living vinyl addition polymerization, using (η3-allyl)­Pd­(i-Pr3P)Cl activated by [Li­(OEt2)2.5]­B­(C6F5)4 as the initiator. Both series of polymers are cast into the selective skin layers of thin film composite (TFC) membranes, and these organophilic membranes are investigated for the concentration of n-butanol from dilute aqueous solution via pervaporation. The block copolymers show well-defined microphase-separated morphologies, both in bulk and as the selective skin layers on TFC membranes, while the random copolymers are homogeneous. Both block and random vinyl addition copolymers are effective as n-butanol pervaporation membranes, with the block copolymers showing a better flux-selectivity balance; the optimal block copolymer, containing 19 wt % BuNB, showed a process separation factor of 21 and a flux of 4300 g m–2 h–1 with a 1.00 wt % aqueous n-butanol feed, at a selective layer thickness of 1.3 μm. While polyHFANB has much higher permeability and selectivity than polyBuNB, incorporating BuNB units into the polymer (in either a block or random sequence) limits the swelling of the polyHFANB and thereby improves the n-butanol pervaporation selectivity. An analogous block copolymer derived from ring-opening metathesis polymerization, which shows much greater swelling than the vinyl addition polymers, shows a correspondingly higher flux and lower selectivity.

Thickness dependence of structural relaxation in spin‐cast polynorbornene films with high glass transition temperatures (>613 K)

“…BuNB‐r‐HFANB is promising for biobutanol membranes, so it is useful to examine the effect of film thickness on aging of BuNB‐r‐HFANB polymer films. Figure (a) shows the relative thickness change of BuNB‐r‐HFANB films cast from THF/toluene when aging at 333 K with initial thicknesses between 60 nm and 2.3 µm.…”

“…However, these thin film aging measurements have focused on polystyrene or its derivatives, while the aging of high free volume polymers is of particular interest for membrane applications . In this context, stiff polynorbornenes that contain a bicylic ring exhibit excellent performance in membranes for butanol–water separations . Similar polynorbornenes are not significantly impacted by confinement with no statistical decrease in T g or elastic modulus down to 10 nm, so one might expect that the aging of these polymers might be thickness independent to enable the use of ultrathin membranes for efficient separations.…”

Poly(trimethylsilylpropyne) Membranes for Removal of Alcohol Fermentation Products by Thermopervaporation with a Porous Condenser

“…The third type of materials which is being actively studied for the task of recovery of the ABE fermentation products is highly permeable glass-like polymers such as polyacetylenes (polytrimethylsilylpropyne (PTMSP) andpolymethylpentyne(PMP)) [35,[37][38][39], polymers with internal microporosity (PIM-1), and polynorbornenes [40,41]. Materials of such a type are capable of forming strong thin polymer films and possess a microporous structure formed by the elements of unrelaxed free volume [42].…”

Addition Homo‐ and Copolymerizations of Dicyclopentadiene and 5‐n‐Hexylnorbornene in the Presence of Pd‐N‐Heterocyclic Carbene Complexes

“…Norbornene and its derivatives are an unusual class of monomers that can be polymerized by various mechanisms forming polymers with different structures of main chains and properties . This feature, along with the ability to synthesize series of norbornenes with a regularly varying structure, has made these compounds attractive for the macromolecular design of polymers with desired properties and for the systematic study of the relationships “polymer structure‐properties.” Depending on the nature of the side substituents and the structure of the main chain, norbornene‐based polymers can have attractive optical properties, low moisture absorption, thermal and chemical stabilities, promising membrane characteristics, etc. Dicyclopentadiene (DCPD) is one of the most readily available norbornene derivatives, which is obtained by dimerization of cyclopentadiene—a component of light fraction of oil pyrolysis.…”