C. Adrian Figg

Closed‐System One‐Pot Block Copolymerization by Temperature‐Modulated Monomer Segregation

A biphasic one-pot polymerization method enables the preparation of block copolymers from monomers with similar and competitive reactivities without the addition of external materials. AB diblock copolymers were prepared by encapsulating a frozen solution of monomer B on the bottom of a reaction vessel, while the solution polymerization of monomer A was conducted in a liquid layer above. Physical separation between the solid and liquid phases permitted only homopolymerization of monomer A until heating above the melting point of the lower phase, which released monomer B, allowing the addition of the second block to occur. The triggered release of monomer B allowed for chain extension without additional deoxygenation steps or exogenous monomer addition. A method for the closed (i.e., without addition of external reagents) one-pot synthesis of block copolymers with conventional glassware using straightforward experimental techniques has thus been developed.

Mild and efficient synthesis of ω,ω-heterodifunctionalized polymers and polymer bioconjugates

This report describes the efficient preparation of ω,ω-heterodifunctionalized polymers and polymer bioconjugates under mild conditions using a recently introduced reagent, benzotrifuranone (BTF). Demonstrated is how BTF enables introduction of differentially “clickable” functional groups (e.g., alkenes and alkynes) to monomethyl ether poly(ethylene glycol) amine at ambient temperature using near-stoichiometric amounts of reagents, in contrast to conventional polymer heterofunctionalization approaches that may require high temperatures, significant excesses of reagents, and/or numerous synthetic steps. Showcasing the methodology is facile access to an ω,ω-heterodifunctional polymer bearing a fluorescent (coumarin) dye and biotin. Found, in addition to avidin binding by the polymer bioconjugate, is the unexpected disruption of avidin tetramer formation.

Modular and rapid access to amphiphilic homopolymers via successive chemoselective post-polymerization modification

Herein, we demonstrate a concise and modular preparation of homopolymers with both a hydrophilic and hydrophobic group on each monomer unit. Successive and chemoselective nucleophilic aromatic substitution of polymers derived from 2,4,6-trichloro-1,3,5-triazine allowed the step-wise installation of hydrophiles and hydrophobes and facilitated the systematic investigation of structure–property relationships for this new class of amphiphilic homopolymers.

Polymerization-Induced Self-Assembly of Micelles Observed by Liquid Cell Transmission Electron Microscopy

In this paper, we describe the use of liquid cell transmission electron microscopy (LCTEM) for inducing and imaging the formation of spherical micelles from amphiphilic block copolymers. Within the irradiated region of the liquid cell, diblock copolymers were produced which self-assembled, yielding a targeted spherical micellar phase via polymerization-induced self-assembly (PISA). Critically, we demonstrate that nanoparticle formation can be visualized in situ and that in the presence of excess monomer, nanoparticle growth occurs to yield sizes and morphologies consistent with standard PISA conditions. Experiments were enabled by employing automated LCTEM sample preparation and by analyzing LCTEM data with multi-object tracking algorithms designed for the detection of low-contrast materials.