Covalent organic frameworks (COFs) are highly modular porous crystalline polymers that are of interest for applications such as charge‐storage devices, nanofiltration membranes, and optoelectronic devices. COFs are typically synthesized as microcrystalline powders, which limits their performance in these applications, and their limited solubility precludes large‐scale processing into more useful morphologies and devices. We report a general, scalable method to exfoliate two‐dimensional imine‐linked COF powders by temporarily protonating their linkages. The resulting suspensions were cast into continuous crystalline COF films up to 10 cm in diameter, with thicknesses ranging from 50 nm to 20 μm depending on the suspension composition, concentration, and casting protocol. Furthermore, we demonstrate that the film fabrication process proceeds through a partial depolymerization/repolymerization mechanism, providing mechanically robust films that can be easily separated from their substrates.

Covalent organic frameworks (COFs) are highly modular porous crystalline polymers that are of interest for applications such as charge‐storage devices, nanofiltration membranes, and optoelectronic devices. COFs are typically synthesized as microcrystalline powders, which limits their performance in these applications, and their limited solubility precludes large‐scale processing into more useful morphologies and devices. We report a general, scalable method to exfoliate two‐dimensional imine‐linked COF powders by temporarily protonating their linkages. The resulting suspensions were cast into continuous crystalline COF films up to 10 cm in diameter, with thicknesses ranging from 50 nm to 20 μm depending on the suspension composition, concentration, and casting protocol. Furthermore, we demonstrate that the film fabrication process proceeds through a partial depolymerization/repolymerization mechanism, providing mechanically robust films that can be easily separated from their substrates.

4-Vinylphenyloxirane (4VPO) was homopolymerized under initiators for continuous activator regeneration atom transfer radical polymerization (ATRP) conditions using diethyl 2-bromo-2-methylmalonate, ethyl 2-bromoisobutyrate, as well as tri-, tetraand hexafunctional 2-bromisobutyrates as the initiators to yield well-defined linear and star-shaped epoxide-containinghomopolymers. In addition, the chain extension of Br-capped polystyrene with 4VPO afforded well-defined block copolymers. All polymerizations employed 2,2 ′ -azobisisobutyronitrile as the reducing agent and the Cu I and Cu II bromide complexes of tris(2-pyridylmethyl)amine as mediators at total concentration of Cu not exceeding ca. 46 ppm (by weight) or ca. 198 ppm (molar). Excellent polymerization control was observed even when the Cu concentration was decreased to ca. 12 ppm (by weight) or ca. 48 ppm (molar). The successful, well-controlled, low-catalyst-concentration ATRP of 4VPO in the absence of any external reducing agent is also demonstrated. In such systems, the epoxide groups present in the monomer and the polymer derived from it serve as internal reducing agents.

Polymers containing electrophilic moieties, such as activated esters, epoxides, and alkyl halides, can be readily modified with a variety of nucleophiles to produce useful functional materials. The modification of epoxide-containing polymers with amines and other strong nucleophiles is welldocumented, but there are no reports on the modification of such polymers with alcohols. Using phenyloxirane and glycidyl butyrate as low molecular weight model compounds, it was determined that the acid-catalyzed ring-opening of arylsubstituted epoxides by alcohols to form b-hydroxy ether products was significantly more efficient than that of alkylsubstituted epoxides. An aryl epoxide-type styrenic monomer, 4-vinylphenyloxirane (4VPO), was synthesized in high yield using an improved procedure and then polymerized in a controlled manner under reversible addition-fragmentation chaintransfer (RAFT) polymerization conditions. A successful chain extension with styrene proved the high degree of chain-end functionalization of the poly4VPO-based macro chain transfer agent. Poly4VPO was modified with a library of alcohols and phenols, some of which contained reactive functionalities, e.g., azide, alkyne, allyl, etc., using either CBr 4 (in PhCN at 90 8C for 2-3 days) or BF 3 (in CH 2 Cl 2 at ambient temperature over 30 min) as the catalyst. The resulting b-hydroxy ether-functionalized homopolymers were characterized using size exclusion chromatography, 1 H NMR and IR spectroscopy, and thermal gravimetric analysis.

4-Vinylphenyl glycidyl ether (4VPGE), an epoxide-containing styrenic monomer, was synthesized and then polymerized in a controlled fashion under reversible addition–fragmentation chain-transfer (RAFT) polymerization conditions using butyl 1-phenylethyl trithiocarbonate as the chain-transfer agent. The high degree of chain-end functionalization of the produced polymers was confirmed by chain extension reactions with styrene that afforded well-defined block copolymers. Phenyl glycidyl ether was utilized as a model compound to identify the optimal reaction conditions for alcoholysis of the glycidyl moiety using BF3 as a Lewis acid catalyst, and postpolymerization modifications were subsequently carried out on the epoxide groups of poly4VPGE with a library of structurally diverse alcohols to yield a number of β-hydroxy ether-functionalized polymers.