Phase Behaviors of Multi‐tailed B₂AB₂‐Type Regio‐isomeric Giant Surfactants at the Columnar‐Spherical Boundary^†

Abstract

Main observation and conclusion We report herein the precision synthesis and phase behaviors of multi‐tailed B2AB2‐type regio‐isomeric giant surfactants consisting of a hydrophilic polyhedral oligomeric silsesquioxane (POSS) head tethered with four hydrophobic polystyrene (PS) tails. The synthesis was accomplished through two sequential “click” reactions to give a series of regio‐isomeric giant surfactants S2DS2 (where S is short for PS tails and D for hydroxyl‐functionalized POSS) in para‐, meta‐, and ortho‐configurations. Their phase structures and phase behaviors at the columnar‐spherical boundary were investigated with a single PS tail molecular weight of 1.4 kDa. Specifically, the para‐ and meta‐isomers show hexagonally packed cylinders phases with slightly different order‐disorder transition temperatures (~120 °C and ~130 °C) and the ortho‐isomer exhibits an order‐order transition from a kinetically favored, metastable dodecagonal quasi‐crystal phase to a thermodynamically stable sigma phase at ~120 °C, as well as a further transition into the disordered state at ~140 °C. The phase diagram was constructed and their differences were rationalized based on the calculated interfacial area per molecule. This work demonstrates that tiny structural disparity could not only lead to unconventional phase formation in single‐component macromolecules, but also render dynamic and rich phase behaviors in these macromolecular assemblies.

Leveraging Macromolecular Isomerism for Phase Complexity in Janus Nanograins

“…Previously, we have shown that the reaction between octavinyl POSS and 1-thioglycerol gives a mixture of different adducts from which the three bifunctional POSS isomers can be isolated and fully identified. 22 These ortho-, meta-, and para-isomers of bifunctional POSS are ideal scaffolds for regioisomer design. 11 By replacing the soft building blocks in previous examples (e.g., polystyrene chains and noncrystalline POSS) with a crystalline BPOSS, we intended to introduce crystallization as a strong competing force to phase separation.…”

“…straightforward way to prepare such tetrafunctional POSS is via thiol−ene chemistry using thiolglycerol. 22 The bifunctional regioisomers (V 6 T 8 -4OH) were converted to V 6 T 8 -4yne and linked with four BPOSS through a copper-catalyzed alkyne− azide cyclization reaction to give B 2 VB 2 (Scheme 1, see Figures S1 and S2 for 1 H NMR and 13 C NMR characterizations). 24 Then, the vinyl groups were converted to hydroxyl groups to yield the Janus nanograins B 2 DB 2 by a second thiol−ene reaction (see Figures S3 and S4 for NMR characterizations).…”

“… Hence, we installed two hydroxyl groups on one vertex of bifunctional POSS for subsequent attachment of one BPOSS per hydroxyl group. A straightforward way to prepare such tetrafunctional POSS is via thiol–ene chemistry using thiolglycerol . The bifunctional regioisomers (V 6 T 8 -4OH) were converted to V 6 T 8 -4yne and linked with four BPOSS through a copper-catalyzed alkyne–azide cyclization reaction to give B 2 VB 2 (Scheme , see Figures S1 and S2 for 1 H NMR and 13 C NMR characterizations) .…”

Progress in the self-assembly of organic/inorganic polyhedral oligomeric silsesquioxane (POSS) hybrids

“…For example, the metaand para isomers showed HEX phase and the ortho-isomer formed metastable DQC phase. 152 Recently, porous organic polymers (POPs) have been attracting much attention because they possess high surface areas, low densities, high chemical and thermal stabilities, and tunable porosities; they can be classified into hypercrosslinked polymers, covalent organic frameworks, covalent triazine frameworks, and conjugated microporous polymers. [153][154][155][156][157][158][159][160][161][162][163] These POPs have a diverse range of applications in energy storage, gas capture and separation, photocatalysis, H 2 evolution, and optical devices.…”

“…For example, the meta - and para isomers showed HEX phase and the ortho -isomer formed metastable DQC phase. 152…”