A Simple Route to Functional Highly Branched Structures: RAFT Homopolymerization of Divinylbenzene

Exploiting the Monomer-Feeding Mechanism of RAFT Emulsion Polymerization for Polymerization-Induced Self-Assembly of Asymmetric Divinyl Monomers

We exploited the monomer-feeding mechanism of reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization to achieve the successful polymerization-induced self-assembly (PISA) of asymmetric divinyl monomers. Colloidally stable cross-linked block copolymer nanoparticles with various morphologies, such as vesicles, were directly prepared at high solids. Morphologies of the cross-linked block copolymer nanoparticles could be controlled by varying the monomer concentration, degree of polymerization (DP) of the core-forming block, and length of the macro-RAFT agent. X-ray photoelectron spectroscopy (XPS) characterization confirmed the presence of unreacted vinyl groups within the obtained block copolymer nanoparticles, providing a landscape for further functionalization via thiol-ene chemistry. Finally, the obtained block copolymer nanoparticles were employed as additives to tune the mechanical properties of hydrogels. We expect that this study not only offers considerable opportunities for the preparation of well-defined cross-linked block copolymer nanoparticles, but also provides important insights into the controlled polymerization of multivinyl monomers.

Using temperature to modify the reaction conditions and outcomes of polymers formed using transfer-dominated branching radical telomerisation (TBRT)

Transfer-dominated Branching Radical Telomerisation (TBRT) enables the production of branched polymers with step-growth backbones using radical telomerisation chemistry. By conducting identical TBRTs over a broad temperature range, the role of temperature in telomer formation and branching has been evaluated. Elevated temperature limits telomer length, thereby allowing a >10% reduction in the amount of telogen required to produce near identical high molecular weight branched polymers.

Accessing new and scalable high molecular weight branched copolymer structures using transfer-dominated branching radical telomerisation (TBRT)

Three new synthesis strategies for branched statistical copolymers containing analogues of step-growth backbones are shown using free radical chemistries and transfer-dominated branching radical polymerisation (TBRT) conditions.

Quantification of branching within high molecular weight polymers with polyester backbones formed by transfer-dominated branching radical telomerisation (TBRT)

New branched polymerisations offer previously inaccessible macromolecules and architectural understanding is important as it provides insight into the branching mechanism and enables the determination of structure-property relationships. Here we present a detailed inverse gated 13C NMR characterisation of materials derived from the very recently reported Transfer-dominated Branching Radical Telomerisation (TBRT) approach to quantify branching and provide an insight into cyclisation.

Impact of multi-vinyl taxogen dimensions on high molecular weight soluble polymer synthesis using transfer-dominated branching radical telomerisation

The creation of branched polymers by TBRT is influenced by the molecular dimensions of the polymerising species. A mechanistic understanding is presented that includes a radical lifetime sphere model that is unique to telomerisation conditions used.

Regioselective, stereoselective, and living polymerization of divinyl pyridine monomers using rare earth catalysts

The first regioselective, stereoselective, and living polymerization of divinyl pyridine monomers, mediated by simple rare earth catalysts, is reported.

Hyperbranched polymers with step-growth chemistries from transfer-dominated branching radical telomerisation (TBRT) of divinyl monomers

The commercially relevant synthesis of novel materials with step-growth backbones has been achieved by applying conventional chemistries to the radical telomerisation of divinyl monomers leading to high molecular weight branched polymers.

Cross-linking polymerization-induced self-assembly to produce branched core cross-linked star block polymer micelles

Copolymerizing a cross-linker in the PISA process spontaneously produces branched core cross-linked block polymer micelles.

Highly efficient access to well-defined linear polymers with substantial vinyl pendants via ATRP of divinyl monomers

Reported herein is a highly efficient access to well-defined linear polymers with substantial vinyl pendants via ATRP of dissymmetric divinyl monomers by side armed bisoxazoline (SaBOX)/copper catalysts.

Tuning thermoresponsive network materials through macromolecular architecture and dynamic thiol-Michael chemistry

Synthesis of precision polymers crosslinked with dynamic thiol-Michael adducts is developed, and the materials are characterized to determine structure–property relationships.

Preparation and Properties of Branched Polystyrene through Radical Suspension Polymerization

Radical solvent-free suspension polymerization of styrene with 3-mercapto hexyl-methacrylate (MHM) as the branching monomer has been carried out using 2,2'-azobisisobutyronitrile (AIBN) as the initiator to prepare branched polymer beads of high purity. The molecular weight and branching structure of the polymers have been characterized by triple detection size exclusion chromatography (TD-SEC), proton nuclear magnetic resonance spectroscopy (¹H-NMR), and Fourier transform infrared spectroscopy (FTIR). The glass transition temperature and rheological properties have been measured by using differential scanning calorimetry (DSC) and rotational rheometry. At mole ratios of MHM to AIBN less than 1.0, gelation was successfully avoided and branched polystyrene beads were prepared in the absence of any solvent. Branched polystyrene has a relatively higher molecular weight and narrower polydispersity (Mw.MALLS = 1,036,000 g·mol-1, Mw/Mn = 7.76) than those obtained in solution polymerization. Compared with their linear analogues, lower glass transition temperature and decreased chain entanglement were observed in the presently obtained branched polystyrene because of the effects of branching.

Gel Point Suppression in RAFT Polymerization of Pure Acrylic Cross-Linker Derived from Soybean Oil

Here we report the reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylated epoxidized soybean oil (AESO), a cross-linker molecule, to high conversion (>50%) and molecular weight (>100 kDa) without macrogelation. Surprisingly, gelation is suppressed in this system far beyond the expectations predicated both on Flory-Stockmeyer theory and multiple other studies of RAFT polymerization featuring cross-linking moieties. By varying AESO and initiator concentrations, we show how intra- versus intermolecular cross-linking compete, yielding a trade-off between the degree of intramolecular linkages and conversion at gel point. We measured polymer chain characteristics, including molecular weight, chain dimensions, polydispersity, and intrinsic viscosity, using multidetector gel permeation chromatography and NMR to track polymerization kinetics. We show that not only the time and conversion at macrogelation, but also the chain architecture, is largely affected by these reaction conditions. At maximal AESO concentration, the gel point approaches that predicted by the Flory-Stockmeyer theory, and increases in an exponential fashion as the AESO concentration decreases. In the most dilute solutions, macrogelation cannot be detected throughout the entire reaction. Instead, cyclization/intramolecular cross-linking reactions dominate, leading to microgelation. This work is important, especially in that it demonstrates that thermoplastic rubbers could be produced based on multifunctional renewable feedstocks.

Controllable and Reversible Dimple-Shaped Aggregates Induced by Macrocyclic Recognition Effect

A novel dimethyl acrylate 18-membered macrocycle (DMECE), acting as both bifunctional monomer and cross-linker, was designed and synthesized, and thus employed to construct a series of macrocycle-containing amphiphilic hyperbranched polymers (HBPs). The macrocyclic recognition effect between the HBPs and alkali metal ions showed that Na(+) was introduced in 1:1 interactive mode, whereas K(+) and Rb(+) were in 2:1 ratio. Through the formation of the DMECE/K(+) = 2:1 rigid "sandwich" complex of amphiphilic hyperbranched polymers, dimple-shaped aggregates were observed by TEM, SEM and AFM. Moreover, the initial concentration, the nature of solvent, the mode and affinity of the macrocyclic recognition effect as well as the amount of K(+), were essential control factors for the formation of dimple-shaped aggregates. Most importantly, the macrocyclic recognition effect endows the reversibility of the dimple-shaped aggregates and the size controllability of its circular opening, which provides a new strategy for design novel macrocycle-containing HBPs and great potential application in the field of capture and release.

Water soluble hyperbranched polymers from controlled radical homopolymerization of PEG diacrylate

Hyperbranched PEG-based polymers were synthesized through homopolymerization of PEG diacrylate via enhanced intermolecular branching and showed a concentration-dependent thermoresponsive property.

Facile and cost-effective branched acrylic copolymers from multifunctional comonomers and multifunctional chain transfer agents

Branched acrylic copolymers were synthesised via facile conventional free-radical polymerisations taken to high conversion using comonomers containing 2-6 acrylate functional groups and chain transfer agents containing 1-8 thiol functional groups.

A rapid crosslinking injectable hydrogel for stem cell delivery, from multifunctional hyperbranched polymers via RAFT homopolymerization of PEGDA

A novel injectable hydrogel for stem cell delivery was prepared from multifunctional hyperbranched polyPEGDA and thiolated hyaluronic acid.

Monodisperse highly cross-linked “living” microspheres prepared via photoinitiated RAFT dispersion polymerization

Monodisperse highly Cross-linked “Living” microspheres were synthesized via photoinitiated RAFT dispersion polymerization of MMA using a bifunctional monomer or a trifunctional monomer as the cross-linker.

Hyperbranched polymers: advances from synthesis to applications

This review summarizes the advances in hyperbranched polymers from the viewpoint of structure, click synthesis and functionalization towards their applications in the last decade.

Controlled Divinyl Monomer Polymerization Mediated by Lewis Pairs: A Powerful Synthetic Strategy for Functional Polymers

Lewis pair cooperation provides a facile approach for polymerizing dissymmetric divinyl polar monomers such as 4-vinylbenzyl methacrylate in excellent regioselectivity and high reactivity at mild conditions, affording soluble polymers bearing pendant active vinyl groups with high molecular weight (up to 6.4 × 10⁵ g/mol) and narrow polydispersity (PDI < 1.5). ESI-TOF MS study demonstrated that the polymerization process only concerned the methacrylic double bond and selectively remained the pendant allylic or styrene C═C bond.

Combining ring-opening metathesis polymerization and thiol-ene coupling chemistries: facile access to novel functional linear and nonlinear macromolecules

The aim of this article is to highlight recent examples in which two powerful synthetic tools, namely ring-opening metathesis polymerization (ROMP) and thiol-ene (including the thiol-Michael variant) click chemistry have been combined to facilitate the preparation of novel functional materials of varying topology.

A facile one pot strategy for the synthesis of well-defined polyacrylates from acrylic acid via RAFT polymerization

Linear and hyperbranched polyacrylates were successfully synthesized by the combination of in situ esterification of acrylic acid with halogenated compounds promoted by 1,1,3,3-tetramethylguanidine (TMG) and RAFT polymerization.

Controlled multi-vinyl monomer homopolymerization through vinyl oligomer combination as a universal approach to hyperbranched architectures

The three-dimensional structures of hyperbranched materials have made them attractive in many important applications. However, the preparation of hyperbranched materials remains challenging. The hyperbranched materials from addition polymerization have gained attention, but are still confined to only a low level of branching and often low yield. Moreover, the complication of synthesis only allows a few specialized monomers and inimers to be used. Here we report a 'Vinyl Oligomer Combination' strategy; a versatile approach that overcomes these difficulties and allows facile synthesis of highly branched polymeric materials from readily available multi-vinyl monomers, which have long been considered as formidable starting materials in addition polymerization. We report the alteration of the growth manner of polymerization by controlling the kinetic chain length, together with the manipulation of chain growth conditions, to achieve veritable hyperbranched materials, which possess nearly 70% branch ratios as well as numerous vinyl functional groups.