Synthesis and characteristics of hyperbranched polymer with phosphonic acid groups for high-temperature fuel cells

Two different molecular weight hyperbranched polymers (HBP(L)-(PA)₂ and HBP(H)-(PA)₂) with two phosphonic acid groups as a functional group at the periphery and a low molecular weight hyperbranched polymer (HBP(L)-(PA)₂-Ac) with both two phosphonic acid groups and an acryloyl group as a cross-linker at the periphery were successfully synthesized as thermally stable proton-conducting electrolytes. A cross-linked electrolyte membrane (CL-HBP(L)-(PA)₂) was prepared by thermal polymerization of the HBP(L)-(PA)₂-Ac using benzoyl peroxide. Ionic conductivities of the HBP(L)-(PA)₂, the HBP(H)-(PA)₂, and the CL-HBP(L)-(PA)₂ under dry condition and their thermal properties were investigated, and also, the effect of the phosphonic acid group number on them was discussed. Ionic conductivities of the HBP(L)-(PA)₂ and the HBP(H)-(PA)₂ were found to be 1.5?×?10^?5 S cm^?1 at 150 °C and 3.6?×?10^?6 S cm^?1 at 143 °C, respectively, under dry condition, and showed the Vogel–Tamman–Fulcher type temperature dependence. The hyperbranched polymers and the cross-linked electrolyte membrane were thermally stable up to 300 °C, and the cross-linked electrolyte membrane (CL-HBP-(PA)₂) had suitable thermal stability as an electrolyte membrane for the high-temperature fuel cells under dry condition. Fuel cell measurement using a single membrane electrode assembly cell with the cross-linked membrane was performed.     

Synthesis and properties of polyurethane elastomers crosslinked with amine-terminated AB2-type hyperbranched polyamides

Amine-terminated AB₂-type hyperbranched polyamides of different molecular weights were prepared from 3,5-bis-(4-aminophenoxy)benzoic acid (AB₂ monomer) by fractional precipitation technique and characterized by FTIR, ¹H-NMR spectroscopies, DSC and GPC techniques. The degree of branching (DB) of hyperbranched polymers (HBP) was determined using ¹³C-NMR spectroscopy and it was found that the value increased with decrease in molecular weight of polymer considered. As the molecular weight distribution was narrow, the approximate number of end functional groups of each HBP was conveniently calculated. Three polymers were selected and used as crosslinkers in the preparation of polyurethanes. The incorporation of hyperbranched polyamide into the polyurethane chains was confirmed using FTIR and ¹H-NMR spectroscopic techniques. Among the range studied (1-6%), it was found that high tensile strength is attained with 1% of HBP. It was also found that the tensile strength decreases with increase in number of end functional groups and decrease in DB of HBP. However, glass transition temperatures and thermal stability of polyurethanes crosslinked with up to 6% of HBP, above which gelation occurred, were not affected and similar to the blank polymer prepared without AB₂ polymer.     

Novel hyperbranched polymers as host materials for green thermally activated delayed fluorescence OLEDs

A series of novel hyperbranched polymers(HBPs) consisting of a 2,7-subsituted 9-(heptadecan-9-yl)-9H-carbazole unit(A_2+A_2') and a tetra-substituted green thermally activated delayed fluorescence(TADF) dye of 2,3,5,6-tetra(9Hcarbazol-9-yl)-4-pyridinecarbonitrile(4CzCNPy, B4) have been synthesized via Suzuki cross-coupling reaction following an "A2+A2'+B_4" method. The polymers are named according to the polymerization ratio of 4CzCNPy monomer(5 mol%, 10 mol% and 15 mol% for HBPs of P2-P4 respectively, and 0 mol% for the control linear polymer P1). Their thermal, optoelectronic and electrochemical properties have been characterized by a combination of techniques. All the polymers exhibit high thermal stability with the decomposition temperatures(Td) above 400 ℃ and glass transition temperatures(Tg) up to 98 ℃. Unfortunately, the incorporation of TADF moiety into these HBP materials induced non-TADF characteristics. However, when the HBPs functionalized as the host for our previously developed 4CzCNPy TADF dopant in solution processed devices, maximum external quantum efficiency of 5.7% and current efficiency of 17.9 cd/A have been achieved in P3-based device, which is significantly higher than those of 1.5% and 4.2 cd/A for the linear polymer P1.     

Distribution of Dendritic,Terminal and Linear Units and Relationship between Degree of Branching and Molecular Weight of AB2‐Type Hyperbranched Polymer: A 13C‐NMR Study

Degree of branching (DB) of AB₂‐type hyperbranched polymer has been studied using ¹³C‐NMR spectroscopy. For this purpose, a series of hyperbranched polyamides based on 3,5‐bis(4‐aminophenoxy)benzoic acid differing in molecular weight was prepared by adopting a fractional precipitation technique. A model compound mimicking exactly the terminal and dendritic units present in the hyperbranched polymer (HBP) was also synthesized in high yield. ¹³C‐NMR spectra of the polymers and the model compound were recorded under exacting experimental conditions. With the help of ¹³C‐NMR spectrum of model compound and the integration values, peaks for terminal (T) units, dendritic (D) units and linear (L) units present in the HBP have been assigned. The spectra of low molecular weight fractions clearly showed that the linear unit is first formed and then the dendritic unit. Plots of mole fraction of individual unit against molecular weight (M_w) and DB against molecular weight (M_w) are constructed. For the first time, it is found that there is a critical molecular weight (the value calculated is between 3200–3500 for the chosen real system) below, which DB is dependent on molecular weight and above which it becomes independent. A new term T+D/L, which has a maximum value of 20 and minimum of 1, characterizing all AB₂‐type hyperbranched polymers in general, has been introduced.     

Surface-relief-grating formation behavior of two hyperbranched azo polymers

In this work,surface-relief-grating formation behavior was studied by using two hyperbranched azo polymers.The hyperbranched polymers containing pseudo-stilbene type azo chromophores throughout the hyperbranched structure were synthesized by step-growth polycondensation of AB₂ type monomers.The AB₂ monomer,4-（4’-（bis（2-chloroethyl）amino）-phenylazo） benzoic acid（BAA）,was prepared through azo-coupling reaction between N,N’-bis（2-chloroethyl）aniline and 4- aminobenzenic acid.The another AB₂ monomer,4-（4’-（bis（2-chloroethyl）amino）phenylazo）-3-nitro-benzoic acid（BANA）, was prepared through azo-coupling reaction between N,N-bis（2-chloroethyl）aniline and 3-nitro-4-aminobenzcnic acid.The hyperbranched polymers（PBAA and PBANA） were prepared through nucleophilic substitution reaction of BAA and BANA, respectively.The polymers synthesized were characterized by using spectroscopic methods and thermal analysis.The photoinduced dichroism and photo-induced surface-relief-grating（SRG） formation of the hyperbranched polymers were investigated upon irradiation with Ar⁺ laser at 488 nm.PBAA shows typical photoinduced dichroism SRG formation behavior.On the contrary,PBANA does not show the photoresponsive properties.The results indicate that the nitro at the ortho position of azo group of PBANA shows the effect of inhibiting the photoinduced variations.The effect can be attributed to the blockage of the trans-cis isomerization of the azobenzene moieties by the steric hindrance.     

Synthesis of novel hyperbranched polymers featuring oxazoline linear units and their application in fast‐drying solvent‐borne coating formulations

Novel acid‐terminated hyperbranched polymers (HBPs) containing adipic acid and oxazoline monomers derived from oleic and linoleic acid have been synthesized via a bulk polymerization procedure. Branching was achieved as a consequence of an acid‐catalyzed opening of the oxazoline ring to produce a trifunctional monomer in situ which delivered branching levels of >45% as determined by ¹H and ¹³C NMR spectroscopy. The HBPs were soluble in common solvents, such as CHCl₃, acetone, tetrahydrofuran, dimethylformamide, and dimethyl sulfoxide and were further functionalized by addition of citronellol to afford white‐spirit soluble materials that could be used in coating formulations. During end group modification, a reduction in branching levels of the HBPs (down to 12–24%) was observed, predominantly on account of oxazoline ring reformation and trans‐esterification processes under the reaction conditions used. In comparison to commercial alkyd resin paint coatings, formulations of the citronellol‐functionalized hyperbranched materials blended with a commercial alkyd resin exhibited dramatic decreases of the blend viscosity when the HBP content was increased. The curing characteristics of the HBP/alkyd blend formulations were studied by dynamic mechanical analysis which revealed that the new coatings cured more quickly and produced tougher materials than otherwise identical coatings prepared from only the commercial alkyd resins. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3964–3974     

Synthesis of aromatic hyperbranched PAMAM polymers

Our preliminary results towards the synthesis of hyperbranched polyamidoamine (PAMAM) polymers as ‘dendrimer equivalents’ is described. An aromatic AB₂ bis-amino acid monomer was polymerised at 165 °C (under vacuum) and the crude mixture purified by dialysis. Analysis by GPC and MALDI-TOF mass spectroscopy showed that the purified hyperbranched polymers possessed an M_n of 2000 and a PD of 3.2.     

UV-curable epoxy systems containing hyperbranched polymers: Kinetics investigation by photo-DSC and real-time FT-IR experiments

The effect of the presence of a hyperbranched OH-functionalized polymer (HBP) on the kinetics of cationic photopolymerization of an epoxy system was investigated employing two complementary techniques, photo-DSC and real-time FT-IR spectroscopy.Lower rates of cross-linking reactions and higher conversion degrees were obtained in photo-DSC experiments with respect to real-time FT-IR spectroscopy. A limited amount (10% wt) of HBP influenced to a certain extent the cure kinetics of the epoxy resin followed by RT-IR; a final conversion of epoxy groups equal to 100% was achieved by increasing the content up to 20% wt The addition of 10% wt of HBP leaves the cure kinetics of the CE resin studied by p-DSC almost unchanged. By increasing the HBP content, a slightly lower reaction rate is observed at lower reaction times. The presence of the HBP produced a continuous decrease of the T_g of the UV-cured epoxy resin but only modest reductions in its thermo-oxidative stability.     

Synthesis and in vitro antitumor activity of phthalimide-based polymers containing camptothecin

To improve the therapeutic efficacy of 20(s)-camptothecin (CPT) polymeric drugs containing CPT have been designed. A new CPT-conjugate, 3,6-endo-methylene-1,2,3,6-tetrahydrophthalimidoacetamidoglycine camptothecin ester (ETPA-gly-CPT), was synthesized by linking its hydroxyl group to the phthalimido monomer through a glycine-glycine spacer. Its homo- and copolymer with acrylic acid (AA) were prepared by photopolymerization using 2,2-dimethoxy-2-phenylacetophenone (DMP) as a photoinitiator. The monomer and its polymers were characterized by IR, ¹H- and ¹³C-NMR spectra. The ETPA-gly-CPT content in poly(ETPA-gly-CPT-co-AA) obtained by elemental analysis was 40 wt.%. The number-average molecular weights of the polymers determined by gel permeation chromatography were as follows: M_n=15,000 for poly(ETPA-gly-CPT), M_n=18,700 for poly(ETPA-gly-CPT-co-AA). The IC₅₀ values of ETPA-gly-CPT and its polymers against cancer cells were much larger than that of CPT.     

Fabricating Triple‐Sensitive Polymer Nano‐Aggregates via an Aqueous Iminoboronate Multicomponent Reaction

A triple‐sensitive polymer of poly(ethylene glycol)‐iminoboronate nitrobenzyl ethanediol chelate (PEG‐INEC) is efficiently fabricated via the convenient aqueous iminoboronate multi‐component reaction (MCR) of methoxypolyethylene glycol amine (mPEG‐NH₂), 2‐formylphenylboronic acid (FPBA), and bis(2‐nitrophenyl) ethanediol (BNPE, a photo‐cleavable nitrobenzyl alcohol derivate). The aqueous MCR synthetic procedure is followed using ¹H NMR and turbidity analysis. It is shown that polymer nano‐aggregates of PEG‐INEC in aqueous solution can be dissociated through the stimuli responsive reactions of the hydrophobic iminoboronate nitrobenzyl ethanediol chelates (INECs) when exposed to UV light, acid, and H₂O₂, respectively. Furthermore, upon the stimulation of combined triggers, the dissociation of polymer nano‐aggregates can be accelerated to different extents, resulting in the synergistic release of encapsulated hydrophobic molecules in water. The proposed facile and general method is quite desirable and of great importance in practical applications like drug and gene delivery.

     

Properties of composite solid polymer electrolyte using hyperbranched polymer with ether-linkage

The cross-linked composite solid polymer electrolytes composed of poly(ethylene oxide), lithium salt (LiN(SO₂CF₃)₂), and a hyperbranched polymer whose repeating units were connected by ether-linkage (hyperbranched polymer (HBP)-2) were prepared, and their ionic conductivity, thermal properties, electrochemical stability, mechanical property, and chemical stability were investigated in comparison with the non-cross-linked or cross-linked composite solid polymer electrolytes using hyperbranched polymers whose repeating units were connected by ester-linkage (HBP-1a, 1b). The cross-linked composite solid polymer electrolyte using HBP-2 exhibited higher ionic conductivity than the non-cross-linked and cross-linked composite solid polymer electrolytes using HBP-1a and HBP-1b, respectively. The structure of the hyperbranched polymer did not have a significant effect on the thermal properties and electrochemical stability of the composite solid polymer electrolytes. The tensile strength of the cross-linked composite solid polymer electrolyte using HBP-2 was lower than that of the cross-linked composite solid polymer electrolyte using HBP-1b, but higher than that of the non-cross-linked composite solid polymer electrolyte using HBP-1a. The HBP-2 with ether-linkage showed higher chemical stability against alkaline hydrolysis compared with HBP-1a with ester-linkage.     

Second-order nonlinear optical hyperbranched polymers via facile ring-opening addition reaction of azetidine-2,4-dione

A new hyperbranched polymeric structure was chosen as a nonlinear optical material. First, a difunctional chromophore, 4-(4′-nitrophenyl-diazenyl) phenyl-1,3-diamine (NDPD) was synthesized, which was then reacted with 4-isocyanato-4′(3,3-dimethyl-2,4-dioxo-azetidino)diphenylmethane (MIA) to form NDPDMIA (A₂ type monomer). The azetidin-2,4-dione functional groups exhibit selective reactivity, which can react only with primary amines under mild conditions. The hyperbranched polymers were synthesized via ring-opening addition reaction between azetidine-2,4-dione (A₂ type monomer) and primary amine (B₃ type monomer). This synthetic scheme comes with easy purification, high yield and rapid synthesis. Chemical structures of the hyperbranched polymers were characterized by FT-IR, ¹H NMR, and elemental analysis. The inherent viscosity of hyperbranched polymers in DMSO ranged from 0.15 to 0.22 dLg⁻¹. All of the obtained polymers were soluble in DMF, DMAc, and DMSO. Using in situ contact poling, r₃₃ coefficients of 6-16 pm/V and their temporal stability at 60 °C were obtained. Optical loss measurement was also achieved by a prism coupling setup.     

Poly(ε-caprolactone)-based hyperbranched polyurethanes prepared via A2 + B3 approach and its shape-memory behavior

Novel hyperbranched shape-memory polyurethanes based on ε-caprolactone were prepared via A₂ + B₃ approach with different molecular weights (M_w); the molecular weights ranged from 7.2 × 10⁴ to 32.3 × 10⁴ g/mol. The hard segment content was varied minimally and the B₃ monomer was also varied. The polymers were characterized by GPC, DSC, DMA, WAXD and shape-memory test. The crystallinity calculated from DSC and WAXD data indicated that the highly branched architecture does not affect the crystallization of these polymers. More interestingly the storage modulus ratios (E′ ratios) of hyperbranched polymers were found to be significantly high compared to the linear analogue. As a consequence, hyperbranched polymers show 100% more shape-recovery rate compared to their linear counterpart. Antimicrobial susceptibility tests confirmed that these polymers have good antimicrobial activity which is an essential requirement of medical implants.     

Effect of new hyperbranched polyester of varying generations on toughening of epoxy resin through interpenetrating polymer networks using urethane linkages

In this study, a previously unreported methodology is attempted to improve the inherent brittleness in diglycidyl ether of bisphenol-A based epoxy resin using hyperbranched polymers as toughening agents. Four different hyperbranched polyesters (HBPs) with increasing generations (1–4, denoted as HBP-G1 to HBP-G4) were synthesized by reacting calculated amount of dipentaerythritol (used as a core) and dimethylol propionic acid (AB₂ type monomer) through pseudo one-step melt polycondensation method. The newly synthesized HBPs were characterized using spectral, thermal and physical measurements, which confirmed the formation of highly branched structure and decreasing thermal stability with increasing HBP generations. Further, toughening of the epoxy resin is carried out by reacting each generation of the HBP with epoxy using hexamethylene diisocyanate as an intermediate linkage resulting in the formation of HBP-Polyurethane/Epoxy-g-Interpenetrating Polymer Networks (HBP-PU/EP-g-IPNs). A linear polyol-PU/EP-g-IPN is also synthesized for the purpose of comparison. It is found that the HBP modified epoxy samples exhibited higher toughness in comparison to that of neat epoxy and linear polyol based epoxy samples. On the other hand, flexural properties, thermal stability and glass transition temperature of the modified samples is lower than neat epoxy sample due to the existence of flexible urethane linkages and decrease in the cross-linking density of epoxy matrix. The toughening characteristics exhibited by the HBPs are corroborated from the existence of heterogeneous morphology using SEM data.     

Synthesis of novel low-viscosity liquid epoxidized aromatic hyperbranched polymers

Low-viscosity liquid epoxidized aromatic hyperbranched polymers are synthesized by the reaction between epichlorohydrin (ECH) and carboxy-end hyperbranched polymers prepared from low-cost products trimellitic anhydride (B₃ TMA) and dihydroxy alcohols (A₂). The low-viscosity property, especially the lowest viscosity of epoxidized aromatic hyperbranched polymers is only 350 cp which has not reported among epoxidized aromatic hyperbranched polymers before, make them can be used to coatings and adhesion fields without organic solvent hopefully. The properties of the epoxidized aromatic hyperbranched polymers are measured by GPC, FT-IR and viscometer.     

Synthesis and characterization of calcium containing poly(urethane-ether)s

Calcium containing poly(urethane-ether)s (PUEs) were synthesized by the reaction of hexamethylene diisocyanate or toluylene 2,4-diisocyanate (HMDI or TDI) with a mixture of calcium salt of mono(hydroxybutyl)phthalate [Ca(HBP)₂] and polyethylene glycol (PEG₂₀₀ or PEG₄₀₀). A series of calcium containing PUEs having different composition were synthesized by taking the mole ratio of Ca(HBP)₂:PEG₂₀₀ or PEG₄₀₀:diisocyanate (HMDI or TDI) as 3:1:4, 2:2:4 and 1:3:4 to study the effect of calcium content on the properties of the copolymer. The structure of the polymers were confirmed by IR, ¹H-NMR, ¹³C-NMR, and solid state ¹³C-CP-MAS NMR. The polymers were soluble in dimethyl sulfoxide and dimethyl formamide. The initial decomposition temperature of the polymers decreases with increase in calcium content. The T_g value of PUEs increases with increase in calcium content and decreases with increase in soft segment content and length. A single T_g value is observed for the calcium containing PUEs based on PEG₂₀₀ shows the presence of homogeneous phase. However, two T_g values for the PUEs based on PEG₄₀₀ for various composition of Ca(HBP)₂, PEG₄₀₀ and diisocyanate (HMDI or TDI) shows the presence of heterogeneous phase. The viscosity of the calcium containing PUEs increases with increase in the soft segment content as well as its length and decreases with increase in calcium content. X-ray diffraction patterns of the polymers show that the HMDI based polymers are partially crystalline and TDI based polymers are amorphous in nature. The dynamic mechanical analysis of the calcium containing PUEs based on HMDI shows that at any given temperature modulus (g^′ and g^″) increases with increase in the ionic content in the polymers.     

Hyperbranched conjugated polymers with donor-π-acceptor architecture as organic sensitizers for dye-sensitized solar cells

Three novel hyperbranched conjugated polymers (H-tpa, H-cya, and H-pca) with the same conjugated core structure and different functional terminal units were synthesized and applied in dye-sensitized solar cells (DSSCs) as photosensitizers. The photophysical, electrochemical and photovoltaic properties of the three hyperbranched conjugated polymers (HBPs) were investigated in detail. The results showed that donor-π-acceptor architecture in hyperbranched molecule benefited intramolecular charge transfer and consequently increased the generation of photocurrent. The three-dimensional (3D) steric configuration of HBPs could effectively suppress the aggregation of dyes on TiO₂ film, which is beneficial for achieving good photovoltaic performances. Among the three hyperbranched dyes, the highest power conversion efficiency (η) of 3.93% (J_sc = 8.78 mA/cm², V_oc = 0.65 V, FF = 0.688) was obtained with a DSSC based on H-pca dye upon the addition of the same mass ratio chenodeoxycholic acid (CDCA) as coadsorbent under AM 1.5 irradiation with 100 mW/cm² simulated sunlight.     

Synthesis and biological activity of medium molecular weight polymers of camptothecin

A new monomer, 3,6-endo-methylene-1,2,3,6-tetrahydrophthalimidohexanoylcamptothecin (ETHCPT) was synthesized from 3,6-endo-methylene-1,2,3,6-tetrahydrophthalimidohexanoic acid. Its homopolymer and copolymer with acrylic acid (AA) were synthesized and spectroscopically characterized. The ETHCPT content in poly(ETHCPT-co-AA) obtained by elemental analysis was 37 wt.%. The number-average molecular weights of the polymers determined by gel permeation chromatography were as follows: M_n=9700 for poly(ETHCPT), for poly(ETHCPT-co-AA). The IC₅₀ value of ETHCPT and its polymers against cancer cells was much larger than that of CPT. The in vivo antitumor activity of all polymers in Balb/C mice bearing the sarcoma 180 tumor cell line was greater than that of CPT at a dose of 100 mg/kg.     

Hyperbranched copolymers made from A2, B2 and BB′2type monomers (iv)

The new approach for synthesis of hyperbranched polymers from commercially available A₂ and type monomers was extended to synthesize hyperbranched copolymers. In this work, hyperbranched copoly(sulfone-amine) was prepared by copolymerization of divinyl sulfone (A₂) with 4,4′-trimethylenedipiperidine (B₂) and N-ethylethylenediamine (BB’₂). During the reaction, secondary-amino groups of B₂ and BB’₂ monomers react rapidly with vinyl groups of A₂ monomers within 35 s, generating a type of intermediate containing one vinyl group and two reactive hydrogen atoms. Now the intermediates can be regarded as a new type monomer, which further polymerizes to form hyperbranched copoly(sulfone-amine). The polymerization mechanism was investigated with FTIR and LC-MSD. The degree of branching (DB) of hyperbranched copolymers increased with decreasing the ratio of 4, 4′-trimethylenedipiperidine to N-ethylethylenediamine, so DB can be controlled. When the initial mole ratio of B₂ to BB′₂was equal to or higher than four,r≥4, resulted copolymers were semi-crystalline, while copolymers withr3 were amorphous.     

New epoxy thermosets modified with hyperbranched poly(ester-amide) of different molecular weight

The influence of hydroxy-functionalized hyperbranched poly(ester-amide) (HBP) of different molecular weight on the curing process of diglycidylether of bisphenol A (DGEBA) was studied using methyltetrahydrophthalic anhydride (MTHPA) as curing agent. By Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR) the curing reaction was monitored and the covalent incorporation of the modifier in the matrix was proved. By thermomechanical analysis (TMA) the reduction of the contraction after gelation on changing the HBP proportion was observed. The incorporation of HBP increased the glass transition temperature (T_g) and reduced the overall shrinkage. The modified materials showed a higher thermal degradability than neat DGEBA thermosets allowing reworkability. Thermal expansion coefficient, Young’s modulus, impact strength and microhardness were improved. The water uptake behavior was also evaluated.