Synthesis and Reversible Hydration of a Pseudoprotein, a Fully Organic Polymeric Desiccant by Multiple Single‐Crystal‐to‐Single‐Crystal Transformations

Abstract

Ad iphenylalanine derivative,N 3-Phe-Phe-NHCH2CCH, was designed for topochemical azide-alkyne cycloaddition (TAAC) polymerization. This dipeptide adopted b-sheet arrangement as designed, in its crystals,b ut the azide and alkyne were not fitly aligned for their topochemical reaction. However,t he voids present around these groups allowed them to attain ar eactive geometry upon heating and their consequent TAAC polymerization to ap seudoprotein in as ingle-crystal-to-single-crystal (SCSC) fashion. This motion led to the creation of channels in the product crystal and it absorbed water from the surroundings to fill these channels as H-bonded water wire.T he pseudoprotein undergo reversible hydration/dehydration in SCSC fashion many times under mild conditions:h ydration at lowr elative humidity and dehydration at lowt emperature.V apor sorption analyses suggest that this fully organic polymer might be useful as an energy-efficient desiccant material for controlling indoor humidity. Figure 4. A) SCSC dehydration of the PPH to PP showing the sliding of polymer chains. B) 30 cycles of TGA of the PPH showing complete and reversible hydration-dehydration.C)W ater adsorptiona nd desorption isotherms of the pseudoprotein at 20 8 8C, showing asigmoidal curve.

Topochemical synthesis of different polymorphs of polymers as a paradigm for tuning properties of polymers

“…1) terminally decorated with complimentary reacting groups viz. azide and alkyne for its topochemical polymerization via TAAC reaction 35 . In the crystals of DP obtained from a 1:1 mixture of MeOH and toluene (DP-I, rectangular plates, orthorhombic, P2 1 2 1 2 1 , Fig.…”

Topochemical Azide–Alkyne Cycloaddition Reaction

“…56 We synthesized the FF-based dipeptide, N 3 -Phe-Phe-CH 2 CCH (19), for TAAC polymerization assuming that this would adopt β-sheet arrangement in its crystal. 57 As expected, the dipeptide molecules were appropriately packed in the crystal lattice, forming β-sheets (Figure 11b) through two N−H•••O hydrogen-bonds and two supplementary C−H•••O hydrogen-bonds, and the adjacent sheets were arranged such that the molecules form a head-to-tail arrangement in the direction perpendicular to the β-sheet direction (Figure 11c). However, the CRGs were neither proximal nor in a ready-to-react TS-like orientation required for TAAC reaction.…”

Polyurethane Aerogels Based on Cyclodextrins: High-Capacity Desiccants Regenerated at Room Temperature by Reducing the Relative Humidity of the Environment

“…The most established class of polymeric desiccants is based on polyelectrolytes, whereas one of the attractive features of those materials is the fact that their hydrophilicity can be modified with −OH and −COOH groups. 13 Thus, polymeric desiccants can be based on poly(acrylic acid), 41,42 poly(lactic acid), 43 poly(quaternary ammonium salts), e.g., based on DABCO, 44 but also on pseudoproteins, 45 and on copolymers (e.g., epoxy-functionalized porous organic polymers via Diels−Alder reactions 46 ); even metal-oxide frameworks (MOFs) 16,17,47 are considered to belong in this class of materials, as well as certain xerogels (e.g., from the condensation reaction of resorcinol with formaldehyde 48 ) and polymer or biopolymer/inorganic composites, for example, polyethylene films with dispersed calcium oxide, 49 electrospun poly(vinyl alcohol)−LiCl membranes, 50 polyamide−LiCl membranes, 51 and chitosan-reinforced boehmite. 52 In an interesting variant of the last category of materials, a socalled solid (i.e., nonporous) superdesiccant combined the high adsorption capacity of a hygroscopic agent (LiCl) with the high liquid-withholding capacity of a superadsorbent polymer (sodium polyacrylate).…”

“…In that regard, dehydration under mild conditions (i.e., low temperature) is highly desirable. 45 The water sorption capacity of the two most commonly used materials, silica gel and zeolites, reaches 0.45 g of water per gram of material. 56,57 High surface area silica aerogels have demonstrated an even higher water uptake capacity than other forms of silica (reaching up to 1.35 g of water per gram of silica aerogel); 58 however, performance deteriorates rapidly because of hydrolysis of the silica framework by the adsorbed water.…”