We report the synthesis and self-assembly of brush–linear diblock copolymers with variable side-chain length and density. Poly(pentafluorophenyl acrylate-g-ethylene glycol)-b-polystyrene ((PPFPA-g-PEG)-b-PS) brush–linear diblock copolymers are prepared by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization of PPFPA and PS, followed by postpolymerization reaction between the precursor PPFPA-b-PS diblock copolymer and amine-functionalized PEG. By controlling the PEG chain length and the degree of substitution, we obtained brush–linear diblock copolymers with different side-chain lengths and densities. The solid-state morphologies of the diblocks are then examined by small-angle X-ray scattering (SAXS). At low PEG side-chain density, the segregation of PEG and PS away from PPFPA leads to the formation of PEG and PS lamellar domains with PPFPA in the interface. At high PEG side-chain density, the segregation is between the PPFPA-g-PEG brush block and the PS linear block, and the domain morphology is determined by the composition of the brush block. A partial experimental phase diagram is presented, and it illustrates the importance of both side-chain length and density on the microdomain morphology of brush–linear diblock copolymers.

Surface modification offers an efficient and economical route to installing functional groups on a polymer surface. This work demonstrates that primary amine groups can be introduced onto a polymer surface via Buchwald–Hartwig amination, and the functionalized substrates can be chemically bonded to produce functional microfluidic devices. By activating the C-Cl bond in commercially used poly(chloro-p-xylylene) (parylene C) by Pd catalystand substituting Cl with the amine source, the amine groups are successfully
installed in a facile and recyclable manner. The substrates can be covalently bonded with each other via amine-isocyanate chemistry, providing much higher bonding strength compared to previous methods based on noncovalent adhesive coatings. As a result, transparent and flexible microfluidic channels can be fabricated that are compatible with organic solvents and high pressure. Retention of amine group reactivity in the channel suggests the potential of this methodology for the surface immobilization of functional
molecules for microfluidic reactors and biosensors.

We report the synthesis of thiopropionic acid-functionalized polymethacrylate-b-polystyrene (PMATA-b-PS) as a template for patterning Ag nanoarrays. Reversible addition-fragmentation chain transfer (RAFT) polymerization of silyl-protected propagyl methacrylate followed by chain extension with styrene produced a block copolymer precursor. Deprotection of the trimethylsilyl group and subsequent thiol-yne reaction afforded the target, PMATA-b-PS. While the entire series of the precursor was in the disordered phase, microphase separated morphologies were identified from PMATA-b-PS, indicating an increased interaction parameter (χ) as a result of introducing the acid groups. As a preliminary result, we show that an Ag nanoparticle array can be fabricated by selectively associating Ag+ ions to the PMATA cylinders in the thin film of PMATA-b-PS and removing the organic polymer layer by oxygen plasma treatment.

We developed a block polymer-based synthetic route to sulfonated porous composites (SPCs) with precisely controlled nanopore size. By reducing the pore size to <4 nm and introducing a high density of surface sulfonic acid, the permeation of vanadium ions was effectively suppressed. We employed a polymerization-induced microphase separation (PIMS) process, in which a polyethylene fiber mat impregnated with a liquid polymerization mixture was spontaneously transformed into a fiber-reinforced and cross-linked block polymer membrane. Selective etching and sulfonation then produced the target composite membrane. In a vanadium redox flow battery (VRFB) cell, an SPC with 3.6 nm-sized mesopores, 109 m2 g–1 of specific surface area, and 0.3 mL g–1 of mesoporosity outperformed a Nafion 212 membrane of similar thickness, providing higher proton conductivity and much lower vanadium permeability. Thanks to the composite reinforcement, the membrane demonstrated remarkably enhanced mechanical stability. The SPC membrane could be successfully operated up to 300 cycles. Compared with Nafion 212, the SPC exhibited higher energy efficiencies (EEs) and higher discharge capacity retention. These results suggest the promise of block polymer-based permselective membranes in advanced battery applications.

We propose the defunctionalization of vinyl polymers as a strategy to access previously inaccessible polyolefin materials. By utilizing B(C6F5)3-catalyzed deoxygenation in the presence of silane, we demonstrate that eliminating the pendent ester in poly(methyl acrylate) effectively leaves a linear hydrocarbon polymer with methyl pendants, which is polypropylene. We further show that a polypropylene-b-polystyrene diblock copolymer and a polystyrene-b-polypropylene-b-polystyrene triblock copolymer can be successfully derived from the poly(methyl acrylate)-containing block polymer precursors and exhibit quite distinct materials properties due to their chemical transformation. This unique postpolymerization modification methodology, which goes beyond the typical functional group conversion, can offer access to a diverse range of unprecedented polyolefin block polymers with a variable degree of functional groups.

We report the synthesis of microporous hyper-cross-linked polymers (HCPs) with increased specific surface area and porosity by the in situ removal of trimethylsilyl (TMS) groups during hyper-cross-linking. We synthesized poly(4-trimethylsilylstyrene-co-vinylbenzyl chloride-co-divinylbenzene)s (P(TMSS-co-VBzCl-co-DVB)s) with different compositions by reversible addition–fragmentation chain transfer copolymerization and converted them into HCPs by reacting with FeCl3 in 1,2-dichloroethane. The nearly quantitative removal of the TMS groups was observed during the reaction following the electrophilic aromatic substitution mechanism, where the TMS group shows higher reactivity than an aromatic hydrogen. Substantial enhancement in pore characteristics including surface area, microporosity, and mesoporosity was noticed up to a certain level of TMSS incorporation, compared with HCP derived from P(VBzCl-co-DVB). We suggest the porogenic TMS group increases porosity mainly by in situ removal via facilitated substitution reaction, which creates permanent voids in the hyper-cross-linked network. The use of TMSS provides a feasible and complementary route to tuning the pore characteristics of HCPs by varying DVB content, and is applicable to the synthesis of hierarchically porous polymers containing micropores within a mesoporous framework from block polymer precursors.

Controlled copolymerization of acryloyl chloride (AC), methacryloyl chloride (MAC), and vinylbenzoyl chloride (VBC) with styrene via the reversible addition–fragmentation chain transfer (RAFT) process was investigated. Copolymerization was conducted in 1,4-dioxane at 60 °C using azobisisobutyronitrile as an initiator and S-1-dodecyl-S′-(R,R′-dimethyl-R′′-acetic acid) trithiocarbonate as a chain transfer agent (CTA). The reactive copolymer was obtained by precipitating in hexanes. Methyl ester analogues of the reactive polymers were obtained by precipitating in methanol for analytical purposes and their 1H nuclear magnetic resonance spectroscopy and size exclusion chromatography analyses indicated that the best control was achieved for P(S-co-VBC) produced by copolymerization of styrene and VBC. Kinetics of the copolymerization of styrene and VBC was consistent with the RAFT mechanism. Reactive block polymers consisting of the P(S-co-VBC) block were also readily prepared using a macromolecular chain transfer agent. P(S-co-VBC) was successfully functionalized by reaction with alcohols or amines to form ester or amide linkages demonstrating its utility for the postpolymerization modification approach.