Hyperbranched Star Polymers Research Articles

Confining Hyperbranched Star Poly(ethylene oxide)-Based Polymer into a 3D Interpenetrating Network for a High-Performance All-Solid-State Polymer Electrolyte.

The original poly(ethylene oxide)-based polymer electrolytes normally show low ionic conductivity and inferior mechanical property, which greatly restrict their practical application in all-solid-state lithium-ion batteries (LIBs). In this work, a hyperbranched star polymer with poly(ethylene glycol) methyl ether methacrylate flexible chain segments is embedded into a three-dimensional (3D) interpenetrating cross-linking network created by the rapid one-step UV-derived photopolymerization of the cross-linker (ethoxylated trimethylolpropane triacrylate) in the presence of lithium salt. The rigid 3D network framework provides the polymer electrolyte with not only enhanced mechanical behavior, including film-forming and dendrite-inhibiting capabilities, but also nanoconfinement effects, which can speed up polymer chain segmental dynamics and reduce the crystallinity of the polymer. Depending on this unique rigid-flexible coupling network, the prepared solid polymer electrolyte shows enhanced ionic conductivity (6.8 × 10-5 S cm-1 at 50 °C), widened electrochemical stability window (5.1 V vs Li/Li+), and enough mechanical stability to suppress the growth of uneven Li dendrite (the Li symmetrical cells can operate steadily at both current densities of 0.05 and 0.1 mA cm-2 for 1000 h). Moreover, the assembled LiFePO4//Li cell also exhibited good cycle performance at 50 °C, making the hyperbranched star polymer electrolyte with a nanoconfined cross-linking structure to have potential application in high-safety and high-performance LIBs.

Electrochemical performances of a new solid composite polymer electrolyte based on hyperbranched star polymer and ionic liquid for lithium-ion batteries

A new composite polymer electrolyte membrane composed of hyperbranched star polymers (HBPS-(PMMA-b-PPEGMA)30 (the hyperbranched star polymer with hyperbranched polystyrene as core and polymethyl methacrylate block poly(ethylene glycol) methyl ether methacrylate) as arms)), ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4) or 1-butyl-3-methylimidazolium hexafluorophosphate (BMImPF6)), and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) has been fabricated by solution casting method. This type of solid polymer electrolyte membrane shows an excellent flexibility, transparency, and free-standing properties. Room temperature ionic conductivity of composite electrolytes with 40 wt% BMImBF4 or 40 wt% BMImPF6 can reach 2.5 × 10−4 and 4.1 × 10−5 S cm−1, respectively. The HBPS-(PMMA-b-PPEGMA)30/BMImPF6/LiTFSI (the composite polymer electrolyte with 1-butyl-3-methylimidazolium hexafluorophosphate) composite polymer electrolyte displays better performances including a good thermal stability with decomposition temperature of 350 °C, a wide electrochemical window with oxidation potential of 4.3 V, and the excellent interfacial compatibility with lithium electrode. Moreover, the Li/LiFePO4 batteries based on HBPS-(PMMA-b-PPEGMA)30/BMImPF6/LiTFSI electrolyte retain about 96% of their highest discharge capacity (120.5 mAh g−1) after 100 cycles under a current density of 0.1 C at 60 °C, exhibiting the excellent reversible cyclability.

A New All-Solid-State Hyperbranched Star Polymer Electrolyte for Lithium Ion Batteries: Synthesis and Electrochemical Properties

A new hyperbranched multi-arm star polymer with hyperbranched polystyrene (HBPS) as core and polymethyl methacrylate-block-poly(ethylene glycol) methyl ether methacrylate(PMMA-b-PPEGMA) as arms was firstly synthesized by atom transfer radical polymerization. The obtained hyperbranched multi-arm star polymer (HBPS-(PMMA-b-PPEGMA)x) exhibited good thermal stability with a thermal decomposition temperature of 372°C. The transparent, free-standing, flexible polymer electrolyte film of the blending of HBPS-(PMMA-b-PPEGMA)x and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) was successfully fabricated by a solution casting method. The ionic conductivity of the hyperbranched star polymer electrolyte with a molar ratio of [EO]/[Li] of 30 could reach 8.3×10−5Scm−1 at 30°C (with the content of PPEGMA of 83.7%), and 2.0×10−4Scm−1 at 80°C (with the content of PPEGMA of 51.6%). The effect of the concentration of lithium salts on ionic conductivity was also investigated. The obtained all-solid-state polymer electrolyte possessed a wide electrochemical stability window of 4.7V (vs. Li+/Li), and a lithium-ion transference number (tLi+) up to 0.31. The interfacial impedance of the fabricated Li│polymer electrolyte│Li symmetric cell based on hyperbranched star multi-arm polymer electrolyte exhibited good interfacial compatibility between all-solid-state polymer electrolyte and electrodes. The excellent properties of the hyperbranched star polymer electrolyte made it attractive as solid-state polymer electrolyte for lithium-ion batteries.

A new hyperbranched star polyether electrolyte with high ionic conductivity

Hyperbranched poly(glycidol) containing hydroxyl groups was firstly synthesized via anionic polymerization and then reacted with 2-bromoisobutyl bromide to form macroinitiator HPG-Br. Finally, a hyperbranched star polymer (HPG-PPEGMA) was successfully prepared by atom transfer radical polymerization (ATRP) of poly(ethylene glycol) methyl ether methacrylate using HPG-Br as macroinitiator. The structures and properties of the obtained polymers were characterized by 1H NMR, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The ionic conductivity of the polymer electrolytes composed of HPG-PPEGMA and lithium bis(trifluoromethanesulfonimide) (LiTFSI) was investigated via electrochemical impedance spectroscopy. The results showed that the room temperature ionic conductivity of the prepared hyperbranched star polymer electrolytes had a higher ionic conductivity. When [EO]/[Li] was 20, the ionic conductivity of the hyperbranched star polymer electrolyte was up to 1 × 10−4 Scm−1 at 30 °C. The onset decomposition temperature of the hyperbranched star polyether could reach 374 °C, indicating that the hyperbranched star polymer had a good thermal stability. The XRD results showed that the structure of the hyperbranched star polymer was beneficial to improve the ionic conductivity due to possessing a low degree of crystallinity.

Preparation and ionic conductivity of composite polymer electrolytes based on hyperbranched star polymer

Hyperbranched star polymer HBPS-(PPEGMA) x was synthesized by atom transfer radical polymerization (ATRP) using hyperbranched polystyrene (HBPS) as macroinitiator and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as monomer. The structure of the prepared hyperbranched star polymer was characterized by 1H NMR, ATR-FTIR, and GPC. Polymer electrolytes based on HBPS-(PPEGMA) x , lithium salt, and/or nano-TiO2 were prepared. The influences of lithium salt concentration and type, nano-TiO2 content, and size on ionic conductivity of the obtained polymer electrolytes were investigated. The results showed that the low crystallinity of the prepared polymer electrolyte was caused by the interaction between lithium salt and polymer. The addition of TiO2 into HBPS-(PPEGMA) x /LiTFSI improved the ionic conductivity at low temperature. The prepared composite polymer electrolyte showed the highest ionic conductivity of 9 × 10−5 S cm−1 at 30 °C when the content of TiO2 was 15 wt% and the size of TiO2 was 20 nm.

Multi-responsive Hyperbranched Star Copolymer: Synthesis, Self-assembly and Controlled Release

Multi-responsive (temperature, pH and redox) hyperbranched star polymers, poly(2-(2-methoxyethoxy)ethyl methacrylate)-star-poly(dimethylaminoethyl methacrylate) (H-PMEO2MA-star-PDMAEMA) have been successfully synthe- sized by self-condensing vinyl polymerization of disulfide-based inimer and MEO2MA first, and subsequently atom transfer radical polymerization of DMAEMA with H-PMEO2MA as macroinitiator. The Mn and Mw/Mn of the H-PMEO2MA were 8300 g/mol and 2.61, respectively. H-PMEO2MA-star-PDMAEMAs with different molecular weights were obtained by ad- justing the polymerization time. The molecular weight of the hyperbranched star copolymer increased but the polydispersity index (PDI) decreased with increasing polymerization time. Since the PDI of the PDMAEMA formed by ATRP is low, with the molecular weight increase of the PDMAEMA, the relative amount of H-PMEO2MA in the hyperbranched star copoly- mers becomes less; as a result, the influence of the core H-PMEO2MA's PDI on the hyperbranched star copolymers de- creases. UV/Vis TU-1901 spectrophotometer was used to investigate the lower critical solution temperature (LCST) of the resultant polymer. The LCST of H-PMEO2MA is relatively low (2—10 ℃). The effects of the compositions and pH of the solution on LCST of the hyperbranched star copolymers were studied. The LCST increased with the chain length increase of PDMAEMA. The pH of the solution has a significant impact on the LCST of the hyperbranched star copolymers. With de- crease of the pH value, the protonation degree of PDMAEMA increased, the repulsion between the chain segments enhanced, making the aggregation of the H-PMEO2MA-star-PDMAEMA molecules become difficult, and as a result, the wa- ter-solubility of the hyperbranched star copolymers enhanced. In addition, when temperature of the aqueous solution raised from 2 ℃ to room temperature, the spherical micelles with H-PMEO2MA as core and PDMAEMA as shell were formed. During the formation of spherical micelles in the aqueous solution of H-PMEO2MA-star-PDMAEMA and Nile Red, the Nile Red was successfully encapsulated in the micelles. The controlled release of this system, in which Nile Red was used as model drug, was investigated, the results showed that this system is pH and redox-responsive, and may have potential appli- cation in drug delivery. Keywords self-condensing vinyl polymerization (SCVP); atom transfer radical polymerization (ATRP); hyperbranched star copolymer; multi-responsive; controlled release

Effect of amphiphilic hyperbranched-star polymer on the structure and properties of PVDF based porous polymer electrolytes

An amphiphilic hyperbranched-star polymer (HPE-g-MPEG) was synthesized by grafting methoxy poly(ethylene glycol) to the end of the hyperbranched polyester (HPE) molecule using terephthaloyl chloride (TPC) as the coupling agent. The synthesized amphiphilic hyperbranched-star polymer was blended with poly(vinylidene fluoride) (PVDF) to fabricate porous membranes via typical phase inversion process, and then the membranes were filled and swollen by a liquid electrolyte solution to form polymer electrolytes. The influences of HPE-g-MPEG on the morphology, crystallinity, liquid electrolyte uptake, mechanical properties of the porous membranes and the electrochemical properties of the activated membranes were investigated. It was found that the addition of HPE-g-MPEG resulted in a significant increase in porosity and a considerable reduction in crystallinity of the blend membranes, which favored the liquid electrolyte uptake and, consequently, led to a remarkable increase in ion conductivity at ambient temperature. The maximum ion conductivity observed in this study was 1.76 × 10 − 3 S/cm at 20 °C for the blend membrane with a HPE-g-MPEG/PVDF ratio of 3/10 (w/w).

Facile synthesis and self-assembly of multihetero-arm hyperbranched polymer brushes

A facile methodology was presented for scalable synthesis of hyperbranched-star polymers with tens of hydrophilic and hydrophobic hetero-arms, in merely two steps starting from monomers. Self-condensing atom transfer radical polymerization (SC-ATRP) of a clickable initiator-monomer (click-inimer), 3-azido-2-(2-bromo-2-methylpropanoyloxy)propyl methacrylate, resulted in a hyperbranched polymer with azido and bromo multihetero-groups. Subsequently orthogonal one-pot “grafting onto” azide-alkyne click coupling and “grafting from” ATRP with the core of hyperbranched polymer afforded targeted miktoarm globular binary brushes. The brushes could readily assemble into superstructures of 150–300 nm spheres and micro-scale sheets. Furthermore, hyperbranched copolymer possessing azido, hydroxyl and bromo trihetero-groups were synthesized by self-condensing atom transfer radical copolymerization of the click-inimer and 2-hydroxyethyl methacrylate (HEMA). Hyperbranched trinity brushes were then facilely prepared via a one-pot multigrafting strategy by a combination of click chemistry, esterification, and ATRP. The trinity brushes could assemble into superstructures of micron-scale dendritic tubes.

Synthesis and Characterization of Hyperbranched Polymers from the Polymerization of Glycidyl Methacrylate and Styrene Using Cp2TiCl as a Catalyst

Hyperbranched poly(glycidyl methacrylate) (PGMA) and poly(GMA-co-styrene) have been synthesized by the self-condensing vinyl polymerization of GMA and the copolymerization of GMA and St. Cp 2 Ti(III)Cl catalyzed the epoxy groups to produce initiating radicals and Cu(II)X 2 (X = Br or Cl) was used for control of the polymerization. The resultant polymers were characterized by GPC and 1 H NMR, and the molecular weights, the molecular weight distribution and the degree of branching were determined. The branching structure of the polymers was further confirmed by a hydrolysis test. Hyperbranched star polymers with HPGMA as the core and PSt as the arms were synthesized by the atom transfer radical polymerization of St using HPGMA as a macroinitiator. The resultant products were analyzed by GPC and 1 H NMR. Their morphology in solution was investigated by TEM. The hyperbranched polymers were modified by various acids and amines, and the variation in solution properties was investigated.

Porous membranes modified by hyperbranched polymers II.: Effect of the arm length of amphiphilic hyperbranched-star polymers on the hydrophilicity and protein resistance of poly(vinylidene fluoride) membranes

Amphiphilic hyperbranched-star polymers (HPE- g-MPEG) with different arm length were synthesized by grafting methoxy poly(ethylene glycol)s (MPEGs, M ¯ n = 350 , 750 and 2000 , respectively) to the hyperbranched polyester (HPE) molecule using terephthaloyl chloride (TPC) as the coupling agent, and blended with PVDF to fabricate porous membranes via phase inversion process. Membrane morphologies were observed by scanning electron microscopy (SEM) and atomic force microscope (AFM), and chemical composition changes of the membrane surfaces were measured by X-ray photoelectron spectroscopy (XPS). Water contact angle, static protein adsorption, and filtration experiments were used to evaluate the hydrophilicity and anti-fouling properties of the membranes. It was found that, with the increase in MPEG arm length, the MPEG segments of HPE- g-MPEG enriched at the membrane surfaces substantially, resulting in a significant decrease in water contact angle. Furthermore, the blend membranes containing longer arm HPE- g-MPEGs showed lower static protein adsorption, higher protein solution fluxes, and better protein solution flux recovery than the pure PVDF membrane.

Improving Hydrophilicity and Protein Resistance of Poly(vinylidene fluoride) Membranes by Blending with Amphiphilic Hyperbranched-Star Polymer

To endow hydrophobic poly(vinylidene fluoride) (PVDF) membranes with reliable hydrophilicity and protein resistance, an amphiphilic hyperbranched-star polymer (HPE-g-MPEG) with about 12 hydrophilic arms in each molecule was synthesized by grafting methoxy poly(ethylene glycol) (MPEG) to the hyperbranched polyester (HPE) molecule using terephthaloyl chloride (TPC) as the coupling agent and blended with PVDF to fabricate porous membranes via phase inversion process. The chemical composition changes of the membrane surface were confirmed by X-ray photoelectron spectroscopy (XPS), and the membrane morphologies were measured by scanning electron microscopy (SEM). Water contact angle, static protein adsorption, and filtration experiments were used to evaluate the hydrophilicity and anti-fouling properties of the membranes. It was found that MPEG segments of HPE-g-MPEG enriched at the membrane surface substantially, while the water contact angle decreased as low as 49 degrees for the membrane with a HPE-g-MPEG/PVDF ratio of 3/10. More importantly, the water contact angle of the blend membrane changed little after being leached continuously in water at 60 degrees C for 30 days, indicating a quite stable presence of HPE-g-MPEG in the blend membranes. Furthermore, the blend membranes showed lower static protein adsorption, higher water and protein solution fluxes, and better water flux recovery after cleaning than the pure PVDF membrane.

Tandem reactions of Friedel–Crafts/aldehyde cyclotrimerization catalyzed by an organotungsten Lewis acid

The tris(2-pyridyl)phosphine complex [P(2-py) 3W(CO)(NO) 2](BF 4) 2 acts as a Lewis acid catalyst precursor for the tandem reactions of Friedel–Crafts/aldehyde cyclotrimerization, which lead to the formation of a series of hyper-branched star polymers.

Disaccharide synthesis on a soluble hyperbranched polymer

A hyperbranched star polymer was employed as a soluble support for disaccharide synthesis as a practical alternative to a dendrimer support. The large number of terminal groups present on the support permit very high loading levels to be possible. Polymer bound intermediates could be directly analyzed by MALDI-TOF mass spectrometry due to the presence of a photolabile linker that is cleaved by the MALDI-TOF laser.

New polymer syntheses, 79. Hyperbranched poly(ester‐amide)s based on 3‐hydroxybenzoic acid and 3,5‐diaminobenzoic acid

AbstractThe reaction of 3‐acetoxybenzoyl chloride (4) with N,N′,O‐tris(trimethylsilyl)‐3,5‐diaminobenzoic acid (5) proceeds by highly selective and almost quantitative acylation of both amino groups. The resulting 3,5‐bis(3‐acetoxybenzamido)benzoic acid (6a), or its silylated derivative (6b), was polycondensed in bulk. The silylated monomer yielded the higher molecular weights. The condensation of 3,5‐diacetoxybenzoyl chlorides with diamines containing aliphatic protons yielded acetylated tetraphenols which served as “star centers” for polycondensation. The polycondensation of silylated 3,5‐bis(3‐acetoxybenzamido)‐benzoic acid (6b), with these “star centers” yieled in turn hyperbranched star polymers. The feed ratio of monomers and “star centers” allows the control of the molecular weight. 1H NMR spectroscopy of these hyperbranched star polymers was used to determine the average degree of polymerization (DP) and the average degree of branching (DB). 1H and 13C NMR spectroscopy also revealed that all polycondensations involve a significant extent of ester‐amide interchange reactions.