Block Copolymer Vesicles in Liquid CO₂

Abstract

Two polylactide-b-poly(perfluoropropylene oxide) (PLA-PFPO) diblock copolymers were synthesized via a coupling reaction of acid chloride end-functionalized poly(perfluoropropylene oxide) and hydroxyterminated polylactide. The solubility of these materials in CO 2 was measured using a variable-volume highpressure cell. At a concentration of 1 wt %, the PLA-PFPO copolymers were found to be soluble at modest pressures (<500 bar) over the temperature range of 30-65°C. The size of the resulting micelles in solution was characterized by high-pressure dynamic light scattering. These measurements indicated the formation of predominantly small, spherical micelles for the block copolymer with a PFPO volume fraction of 0.49 and large aggregates with hydrodynamic radii of 100 nm for PLA-PFPO with a PFPO volume fraction of 0.37. By kinetically trapping the aggregates in CO 2 through vitrification of the PLA cores, redispersing them in an analogous PFPO selective solvent, and imaging them using transmission electron microscopy, we confirmed the formation of block copolymer vesicles in liquid CO 2 .

Structure–Property Relationships in CO2-philic (Co)polymers: Phase Behavior, Self-Assembly, and Stabilization of Water/CO2 Emulsions

“…Lodge and co-workers synthesized two examples of poly­(lactide)- block -poly­(hexafluoropropylene oxide) (PLA- b -PFPO, M n around 10 000 g mol –1 ) with varying CO 2 -philic/CO 2 -phobic balances (see Figure ). The self-assembly of these copolymers in CO 2 at 25 °C and 400 bar was studied by DLS. A 1 wt % solution of a copolymer ( M n,PLA = 4000 g mol –1 , M n,PFPO = 6000 g mol –1 ) was found to self-assemble into spherical aggregates with a hydrodynamic radius ( R h ) of 4 nm.…”

“…As a consequence of their high solubility, perfluoropolyethers have been used to synthesize highly soluble amphiphilic copolymers. This includes various polymeric architectures such as poly­(lactide)- b- poly­(hexafluoropropylene oxide) block copolymers and Krytox-based copolymers grafted from either a poly­(methyl methacrylate- co -hydroxyethyl methacrylate) backbone or a hyperbranched poly­(ethylene imine) core …”

Stabilization of Chitosan Aggregates at the Nanoscale in Solutions in Carbonic Acid

“…This is not very surprising because it is rather challenging to reveal the conformation of the macromolecules in solutions, which exist only at high pressure, by means of the commonly used methods for conformational characterization. There are only several works about the possibility to perform the similar characterization of macromolecular conformation for other macromolecules in solutions in supercritical CO 2 at high pressure by light, , small-angle neutron, , and small-angle X-ray , scattering. The main challenge in these experiments is the construction of suitable transparent windows sustaining fairly high pressures.…”

Solution self-assembly of fluorinated polymers, an overview

“…In 2007, Lodge et al synthesized two polylactide-b-poly(perfluoropropylene oxide) diblock copolymers via coupling of acid chloride end-functionalized PFPOs and hydroxy-terminated PLAs. 151 The solubility of these materials in scCO2 was measured using a variable-volume highpressure cell. At a concentration of 1 wt %, the diblock copolymers were found to be soluble at modest pressures (< 500 bar) over the temperature range of 30−65 °C.…”