The preparation of multifunctional polymers and block copolymers by a straightforward one‐pot reaction process that combines enzymatic transacylation with light‐controlled polymerization is described. Functional methacrylate monomers are synthesized by enzymatic transacylation and used in situ for light‐controlled polymerization, leading to multifunctional methacrylate‐based polymers with well‐defined microstructure.
Surface‐initiated photo‐induced copper‐mediated radical polymerization is employed to graft a wide range of polyacrylate brushes from silicon substrates at extremely low catalyst concentrations. This is the first time that the controlled nature of the reported process is demonstrated via block copolymer formation and re‐initiation experiments. In addition to unmatched copper catalyst concentrations in the range of few ppb, film thicknesses up to almost 1 μm are achieved within only 1 h.
Diarylbutadiyne derivatives are ideal monomers for providing the π‐electron‐conjugated system of polydiacetylenes (PDAs). The geometrical parameters for diacetylene topochemical polymerization are known. However, control of the molecules under these parameters is yet to be addressed. This work shows that by simply tailoring diarylbutadiyne with amide side‐chain substituents, the arrangement of the substituents and the resulting hydrogen bond framework allows formation of π‐electron‐conjugated PDA.
Ethylene–propylene–methyl methacrylate (MMA) and ethylene–hexene–MMA A‐B‐C block copolymers with high molecular weight (>100 000) are synthesized using fluorenylamide‐ligated titanium complex activated by modified methylaluminoxane and 2,6‐di‐tert‐butyl‐4‐methylphenol for the first time. After diblock copolymerization of olefin is conducted completely, MMA is added and activated by aluminum Lewis acid to promote anionic polymerization. The length of polyolefin and poly (methyl methacrylate) (PMMA) is controllable precisely by the change of the additive amount of olefin and polymerization time, respectively. A soft amorphous polypropylene or polyhexene segment is located between two hard segments of semicrystalline polyethylene and glassy PMMA blocks.
Enzymatic catalysis and control over macromolecular architectures from reversible addition‐fragmentation chain transfer polymerization (RAFT) are combined to give a new method of making polymers. Horseradish peroxidase (HRP) is used to catalytically generate radicals using hydrogen peroxide and acetylacetone as a mediator. RAFT is used to control the polymer structure. HRP catalyzed RAFT polymerization gives acrylate and acrylamide polymers with relatively narrow molecular weight distributions. The polymerization is rapid, typically exceeding 90% monomer conversion in 30 min. Complex macromolecular architectures including a block copolymer and a protein‐polymer conjugate are synthesized using HRP to catalytically initiate RAFT polymerization.
Synthesis of a cyclodextrin (CD) polyrotaxane is achieved for the first time by simultaneous free radical polymerization of isoprene, threading by CD, and stoppering by copolymerization of styrene. This reaction is performed in an eco‐friendly manner in an aqueous medium similar to classical emulsion polymerization. Threaded CD rings of the polyrotaxane are cross‐linked by hexamethylene diisocyanate, leading to highly elastic slide‐ring gels.
In this work, the synthesis of various halogenated thiophenol derivatives is presented. These thiophenols are used as monomers in light‐initiated SRN1‐type radical polymerization reactions. The method provides easy access to industrially relevant poly(paraphenylene sulfide) and poly(metaphenylene sulfide). The influence of the halide leaving group and of other substituents in the thiophenol monomer on the polymerization process is investigated.
Cationic polyelectrolytes showing an upper critical solution temperature (UCST) are synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization in water at a temperature well above the UCST. The polymerization is well controlled by the RAFT process, with excellent pseudo‐first‐order kinetics. The cloud point is highly dependent on the polyelectrolyte concentration, molecular weight, and presence of added electrolyte. Alkylation of a neutral polymer is also conducted to obtain polyelectrolytes with different hydrophobic groups, which are shown to increase the cloud point.
An interesting cooperation between Candida antarctica Lipase B (CAL‐B) and alkaline protease from Bacillus subtilis (BSP) in the copolymerization of bulky ibuprofen‐containing hydroxyacid methyl ester (HAEP) and ε‐caprolactone (ε‐CL) is observed. This cooperation improved the of the polymers from 3130 (CAL‐B) to 9200 g mol–1 (CAL‐B/BSP). Experimental results clearly indicate that CAL‐B mainly catalyzes the ring‐opening polymerization (ROP) of ε‐CL under the initiation of HAEP to form the homopolymer of ε‐CL, while BSP catalyzes the subsequent polycondensation of the ROP product to yield the copolymer with increased molecular weight. Furthermore, using suitable chemo‐enzymatic methods, valuable polyesters with chiral (R)‐ or (S)‐ibuprofen pendants can be tailor‐made.
Self‐initiated photografting polymerization is used to couple the polymerizable initiator monomer 2‐(2‐chloropropanoyloxy)ethyl acrylate to a range of polymeric substrates. The technique requires only UV light to couple the initiator to surfaces. The initiator surface density can be varied by inclusion of a diluent monomer or via selection of initiator and irradiation parameters. The functionality of the initiator surface is demonstrated by subsequent surface‐initiated atom transfer radical polymerization. Surfaces are characterized by x‐ray photoelectron spectroscopy (XPS), ellipsometry, and atomic force microscopy (AFM), and UV‐induced changes to the initiator are assessed by 1H NMR and gel permeation chromatography (GPC). This is the first time this one‐reactant one‐step technique has been demonstrated for creating an initiator surface of variable density.
The accomplishments in the copolymerization of ethylene with cyclic olefins such as norborn‐2‐ene or cis‐cyclooctene via tandem ring‐opening metathesis polymerization (ROMP) – vinyl insertion polymerization (VIP) are outlined. This approach provides polyolefins with high molecular weight (600,000 < Mn < 4,500,000 g mol−1) and substantial amounts of double bonds along the polymer main chain. Olefinic moieties in ROMP‐derived polymers can be converted into hydroxyl, amino, silyl, ester, or carboxylate groups by different means including controlled radical polymerization‐based grafting. The underlying concept for the switch in polymerization mechanism, the resulting pre‐catalyst requirements, limitations and challenges and the chemistry developed for functionalizing unsaturated polymers are outlined in detail.
The application of cyclodextrin (CD)‐based host–guest interactions towards the fabrication of functional supramolecular assemblies and hydrogels is of particular interest in the field of biomedicine. However, as of late they have found new applications as advanced functional materials (e.g., actuators and self‐healing materials), which have renewed interest across a wide range of fields. Advanced supramolecular materials synthesized using this noncovalent interaction, exhibit specificity and reversibility, which can be used to impart reversible cross‐linking, specific binding sites, and functionality. In this review, various functional CD‐based supramolecular assemblies and hydrogels will be outlined with the focus on recent advances. In addition, an outlook will be provided on the direction of this rapidly developing field.
An acceleration effect and selective monomer addition during RAFT copolymerization of the oppositely‐charged ionic monomers in dilute aqueous solution at 25 °C are reported. The reaction is conducted using a non‐ionic water‐soluble polymer as a macromolecular chain transfer agent under visible light irradiation. A fast iterative polymerization can be induced, even in dilute solution, by the favorable ionic interactions and in situ self‐assembly of zwitterionic growing chains. Selelctive monomer addition is achieved in the statistical copolymerization due to the ion‐pairing of the oppositely‐charged monomers, such as precisely the same reaction rates at a 1:1 of monomer ratio, otherwise a faster reaction of the minor monomer component over the major one. These behaviors open up an avenue towards the rapid synthesis of sequence‐controlled zwitterionic polyelectrolytes that can satisfy the demands of emerging biological applications.
A novel one‐component type II polymeric photoinitiator, poly(vinyl alcohol)–thioxanthone (PVA–TX), is synthesized by a simple acetalization process and characterized. PVA–TX enables photopolymerization of methyl methacrylate and acrylamide in both organic and aqueous media. Photopolymerization proceeds even in the absence of a co‐initiator since PVA–TX possesses both chromophoric and hydrogen donating sites in the structure.
A facile method for the aqueous synthesis of monodisperse and micronmeter‐sized colloids with highly carboxylated surfaces is presented. The method is applied to three different monomers, styrene, methyl methacrylate, and 2,2,2‐trifluoroethyl methacrylate, and illustrate tuning of the size and monodispersity in the reactions. High surface density of carboxylic acids of up to 10 COOH nm−2 from potentiometric titrations, is achieved through copolymerization with itaconic acid. The versatility of this system is highlighted by creating highly fluorescent and monodisperse particles that can be index matched in aqueous solution and through surface modification via the carboxylic acid groups using standard amidation chemistry.
This work demonstrates a new halogenation reaction through sequential radical and halogen transfer reactions, named as “radical and atom transfer halogenation” (RATH). Both benzoxazine compounds and poly(2,6‐dimethyl‐1,4‐phenylene oxide) have been demonstrated as active species for RATH. Consequently, the halogenated compound becomes an active initiator of atom transfer radical polymerization. Combination of RATH and sequential ATRP provides an convenient and effective approach to prepare reactive and crosslinkable polymers. The RATH reaction opens a new window both to chemical synthesis and molecular design and preparation of polymeric materials.
The synthesis of two 4,7,12,15‐tetrakisalkoxy‐substituted [2.2.2]‐paracyclophane‐1,9,17‐trienes and their polymerization employing ring opening metathesis polymerization (ROMP) using Ru‐carbenes (third‐generation Grubbs catalyst) is reported. Phenylene ethynylene trimers are reduced via a Grignard reagent, followed by an intramolecular McMurry cyclization to give the cyclophenes. The cyclophenes are polymerized into soluble poly(para‐phenylene vinylene)s (PPV), which are analyzed in solution by NMR, UV–vis, and fluorescence spectroscopy. They are spin coated into amorphous, fluorescent thin films, and investigated by optical spectroscopy and cyclic voltammetry.
The synthesis of tetracene‐ and pentacene‐annulated norbornadienes, formed through the Diels–Alder reaction of a dehydroacene with cyclopentadiene is reported. Ring‐opening metathesis polymerization (ROMP) leads to polymers that are investigated with respect to their physical, optical, and electronic properties by gel permeation chromatography (GPC), UV–vis spectroscopy, and cyclic voltammetry. The pentacene‐containing polymer P1 is successfully integrated into an organic field‐effect transistor (OFET); the tetracene‐containing polymer P2 is integrated into an organic light‐emitting diode (OLED).
Natural macromolecules, i.e., sequence‐controlled polymers, build the basis for life. In synthetic macromolecular chemistry, reliable tools for the formation of sequence‐controlled macromolecules are rare. A robust and efficient chain‐growth approach based on the simultaneous living anionic polymerization of sulfonamide‐activated aziridines for sequence control of up to five competing monomers resulting in gradient copolymers is presented. The simultaneous azaanionic copolymerization is monitored by real‐time 1H NMR spectroscopy for each monomer at any time during the reaction. The monomer sequence can be adjusted by the monomer reactivity, depending on the electron‐withdrawing effect by the sulfonamide (nosyl‐, brosyl‐, tosyl‐, mesyl‐, busyl) groups. This method offers unique opportunities for sequence control by competing copolymerization: a step forward to well‐engineered synthetic polymers with defined microstructures.
Vinyl acetate is polymerized in the living way under the irradiation of blue light‐emitting diodes (LEDs) or sunlight without photocatalyst at ambient temperature. 2‐(Ethoxycarbonothioyl)sulfanyl propanoate is exclusively added and acts as initiator and chain transfer agent simultaneously in the current system. Poly(vinyl acetate) with well‐regulated molecular weight and narrow molecular weight distribution (Đ < 1.30) is synthesized. Near quantitative end group fidelity of polymer is demonstrated by nuclear magnetic resonance (NMR) and matrix‐assisteed laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS).
