Hyperbranched polymers (HPs) are highly branched three-dimensional (3D) macromolecules. Their globular and dendritic architectures endow them with unique structures and properties such as abundant functional groups, intramolecular cavities, low viscosity, and high solubility. HPs can be facilely synthesized via a one-pot polymerization of traditional small molecular monomers or emerging macromonomers. The great development in synthetic strategies, from click polymerization (i.e., copper-catalyzed azide-alkyne cycloaddition, metal-free azide-alkyne cycloaddition, strain-promoted azide-alkyne cycloaddition, thiol-ene/yne addition, Diels-Alder cycloaddition, Menschutkin reaction, and aza-Michael addition) to recently reported multicomponent reactions, gives rise to diverse HPs with desirable functional/hetero-functional groups and topologies such as segmented or sequential ones. Benefiting from tailorable structures and correspondingly special properties, the achieved HPs have been widely applied in various fields such as light-emitting materials, nanoscience and technology, supramolecular chemistry, biomaterials, hybrid materials and composites, coatings, adhesives, and modifiers. In this review, we mainly focus on the progress in the structural control, synthesis, functionalization, and potential applications of both conventional and segmented HPs reported over the last decade.

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Polymerization-induced self-assembly (PISA) was achieved by conducting an initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) at low ppm of copper catalyst concentration. A poly(oligo(ethylene oxide) methyl ether methacrylate) 50 (POEOMA 50 ) macroinitiator and stabilizer was synthesized by an aqueous ICAR ATRP using Cu II Cl 2 /tris(pyridin-2-ylmethyl)amine (TPMA) complex. Subsequently, the dispersion polymerization of benzyl methacrylate (BnMA) in ethanol was realized with a Cu II Br 2 /TPMA complex either at room temperature or at 65 °C using V-70 or AIBN as radical initiators, respectively. The effect of catalyst concentration, radical initiators, targeted degree of polymerization (DP) of PBnMA, solids content, and temperature on the molecular characteristics and self-assembly behavior of block copolymers POEOMA−PBnMA was evaluated by gel permeation chromatography (GPC), transmission electron microscopy (TEM), and dynamic light scattering (DLS). Block copolymers assembled into spheres, wormlike aggregates, and vesicles with diameters ranging from 100 to 600 nm, depending on the temperature, solids content, and the DP of PBnMA. The effect of the temperature on the polymerization behavior and morphological evolution was attributed to the temperature-dependent plasticization of the core-forming PBnMA block above and below its glass transition temperature (T g = 54 °C).

A series of novel and narrowly polydispersed regular chain-segmented hyperbranched poly(tertiary amino methacrylate)s (HPTAM)s with hydrophilic core and hydrophobic shell were synthesized via the combination of self-condensing vinyl copolymerization (SCVCP) and reversible addition–fragmentation chain transfer (RAFT) methodology. 2-(Dimethylamino)ethyl methacrylate (DMAEMA) and 2-((2-(((dodecylthio)carbonothioyl)thio)-2-methylpropanoyl)oxy)ethyl acrylate (ACDT) at various molar feed ratios (γ, [DMAEMA]:[ACDT]) were chosen as monomers for linear segment formation of the structure. The copolymerization kinetics revealed that during the polymerization the real-time γ value kept almost constant and was consistent with the initial feed ratio. So HPTAMs possesses regular linear chains between every two neighboring branching units, which closely resemble HyperMacs in structure. Fast click-like Menschutkin reaction (i.e., quaternarization) of the segmented hyperbranched polymers with propargyl bromide and 2-azidoethyl 2-bromoacetate readily afforded water-soluble and clickable poly(propargyl quaternary ammonium methacrylate) (HPPrAM) and poly(azide quaternary ammonium methacrylate) (HPAzAM), respectively. Through Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC), the HPPrAMs were functionalized with 1-azidododecane and 2-azidoethyl 2-bromoisobutyrate, giving birth to amphiphilic hyperbranched polyelectrolytes (or hyperbranched surfactants) and hyperbranched ATRP macroinitiators, respectively. The HPAzAMs were efficiently decorated with monoalkynyl poly(ethylene glycol) (PEG-Alk) via CuAAC, generating dendritic polymer brushes, a novel architecture reported for the first time. In addition, core-functionazlied star-shaped HPPrAM-star-poly(tert-butyl acrylate) was synthesized by RAFT copolymerization and Menschutkin reaction.

Determination of how the properties of nanocarriers of agrochemicals affect their uptake and translocation in plants would enable more efficient agent delivery. Here, we synthesized star polymer nanocarriers poly­(acrylic acid)-block-poly­(2-(methylsulfinyl)­ethyl acrylate) (PAA-b-PMSEA) and poly­(acrylic acid)-block-poly­((2-(methylsulfinyl)­ethyl acrylate)-co-(2-(methylthio)­ethyl acrylate)) (PAA-b-P­(MSEA-co-MTEA)) with well-controlled sizes (from 6 to 35 nm), negative charge content (from 17% to 83% PAA), and hydrophobicity and quantified their leaf uptake, phloem loading, and distribution in tomato (Solanum lycopersicum) plants 3 days after foliar application of 20 μL of a 1g L–1 star polymer solution. In spite of their property differences, ∼30% of the applied star polymers translocated to other plant organs, higher than uptake of conventional foliar applied agrochemicals (<5%). The property differences affected their distribution in the plant. The ∼6 nm star polymers exhibited 3 times higher transport to younger leaves than larger ones, while the ∼35 nm star polymer had over 2 times higher transport to roots than smaller ones, suggesting small star polymers favor symplastic unloading in young leaves, while larger polymers favor apoplastic unloading in roots. For the same sized star polymer, a smaller negative charge content (yielding ζ ∼ −12 mV) enhanced translocation to young leaves and roots, whereas a larger negative charge (ζ < −26 mV) had lower mobility. Hydrophobicity only affected leaf uptake pathways, but not translocation. This study can help design agrochemical nanocarriers for efficient foliar uptake and targeting to desired plant organs, which may decrease agrochemical use and environmental impacts of agriculture.

Many common polymers, especially vinyl polymers, are inherently difficult to chemically recycle and are environmentally persistent. The introduction of low levels of cleavable comonomer additives into existing vinyl polymerization processes could facilitate the production of chemically deconstructable and recyclable variants with otherwise equivalent properties. Here, we report thionolactones that serve as cleavable comonomer additives for the chemical deconstruction and recycling of vinyl polymers prepared through free radical polymerization, using polystyrene (PS) as a model example. Deconstructable PS of different molar masses (∼20−300 kDa) bearing varied amounts of statistically incorporated thioester backbone linkages (2.5−55 mol %) can be selectively depolymerized to yield well-defined thiol-terminated fragments (<10 kDa) that are suitable for oxidative repolymerization to generate recycled PS of nearly identical molar mass to the parent material, in good yields (80−95%). A theoretical model is provided to generalize this molar mass memory effect. Notably, the thermomechanical properties of deconstructable PS bearing 2.5 mol % of cleavable linkages and its recycled product are similar to those of virgin PS. The additives were also shown to be effective for deconstruction of a cross-linked styrenic copolymer and deconstruction and repolymerization of a polyacrylate, suggesting that cleavable comonomers may offer a general approach toward circularity of many vinyl (co)polymers.

Solvent-free single-ion polymer electrolytes with high conductivity have historically been prepared in the form of block copolymer or polymer blends. In this work, single-ion homopolymer electrolytes consisting of poly­(poly­(ethylene oxide) methacrylate lithium sulfonyl­(tri­fluoro­methyl­sulfonyl)­imide), poly­(PEOMA-TFSI–Li+), were prepared for the first time by photoinduced metal-free atom-transfer radical polymerization. The PEO-based macromonomer PEOMA-TFSI–Li+ was synthesized via click chemistry, copper-catalyzed alkyne–azide cycloaddition. Because of the conductive, amorphous PEO phase in which the lithium ions are located, these polymers showed improved ionic conductivity (10–5–10–4 S/cm at 90 °C) and high transference number (0.97–0.99). A continued lithium plating–stripping experiment was performed at current density ≥0.1 mA/cm2 over 300 cycles at 90 °C. The potential dendrite-suppressing capability of the polymer with such high transference number was also estimated by employing a kinetic model using the measured transport and transference properties to study the current density at the dendrite tip. The analysis indicates that the synthesized polymers could have a high propensity to suppress dendrite growth.

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