Aerogels and Polymorphism of Isotactic Poly(4-methyl-pentene-1)

Abstract

Monolithic and highly crystalline aerogels of isotactic poly(4-methyl-pentene-1) (i-P4MP1) have been prepared by sudden solvent extraction with supercritical carbon dioxide from thermoreversible gels. The cross-link junctions of i-P4MP1 gels, depending on the solvent, can be constituted by pure polymer crystalline phases (I or III or IV) or by polymer-solvent cocrystalline phases (for cyclohexane and carbon tetrachloride gels). Gels with cocrystalline phases lead to aerogels exhibiting the denser crystalline form II, whereas all the other considered gels lead to aerogels exhibiting the thermodynamically stable form I. Aerogels obtained from form I gels, which do not undergo a crystalline phase transition during the CO(2) extraction process present the high structural stability most suitable for the preparation of porous membranes. The effect of solvents on the aerogel pore structure and morphology has been also investigated by scanning electron microscopy and N(2) sorption measurements. In all cases, the aerogels present highly porous interconnected structures with macropores and mesopores presenting a large size distribution and a vanishing presence of micropores.

Advanced materials based on polymer cocrystalline forms

“…Monolithic high porosity s‐PS aerogels exhibiting three‐dimensional networks of highly crystalline nanofibers can be easily obtained by supercritical CO 2 extraction of the solvent present in physical gels 144–146. Similar polymeric aerogels have been also obtained for polysaccarides,147–149 poly(vinylidenefluoride‐ co ‐hexafluoropropylene),150 polyvinylidenefluoride,151 and isotactic poly‐4‐methyl‐pentene‐1 64…”

“…Polymeric cocrystalline forms are quite common for several regular and stereoregular polymers, such as, for example, isotactic21–23 and syndiotactic polystyrene (s‐PS),24–40 syndiotactic poly‐ p ‐methyl‐styrene,41–47 syndiotactic poly‐ m ‐methyl‐styrene,48, 49 syndiotactic poly‐ p ‐chloro‐styrene,50 syndiotactic poly‐ p ‐fluoro‐styrene,51 polyethyleneoxide,52–55 poly(muconic acid),56, 57 polyoxacyclobutane,58 poly(vinylidene fluoride),59, 60 syndiotactic polymethylmethacrylate,61–63 isotactic poly‐4‐methyl‐1‐pentene,64 or poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPO) 65–68…”

ROMP crosslinkers for the preparation of aliphatic aerogels

“…A review of the literature concerning CH-based aerogels highlights styrene/divinylbenzene [17], RF [14], graphene [18], dicyclopentadiene (DCPD) [13,19,20] and poly(4-methylpentene) [21]. Notably, poly(4-methylpentene) retains a CH balance of CH 2.0, though the final aerogel densities are high (ca.…”

“…200 mg mL − 1 ) and the microporous volume is less than ca. 3% of the total pore volume [21]. We previously reported [22] that hydrogenation of polydicyclopentadiene (pDCPD) gels and supercritical drying to aerogels give low density aerogels (40-50 mg mL −1 ) of an overall NCH 1.5 atom balance with high surface areas (ca.…”

Crystalline Nanoporous Materials Based on Poly(2,6‐dimethyl‐1,4‐phenylene)oxide

“…structures where a polymeric host and a low‐molecular‐mass guest are co‐crystallized, has been reported for many polymers like e.g. isotactic and syndiotactic polystyrene (s‐PS), syndiotactic poly‐ p ‐methyl‐styrene, syndiotactic poly‐m‐methyl‐styrene, polyethyleneoxide, poly(vinylidene fluoride), syndiotactic polymethylmethacrylate, isotactic poly‐4‐methyl‐1‐pentene or poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPO)…”