Noncovalent nonspecific solubilization of carbon nanotubes with common polymers without having any specific functionality is an important strategy for rendering debundled nanotube solutions for their ...processing and technological applications. Among the various polymers investigated thus far for noncovalent nonspecific nanotube solubilization, hyperbranched polyethylene (HBPE) featured with distinct highly compact dendritic chain architecture has been discovered to show outstanding performance in rendering stable nanotube solutions in common low-polarity organic solvents (including tetrahydrofuran (THF) and chloroform) at surprisingly high concentrations. To understand the mechanism of the nanotube solubilization with this unique class of polymers and to elucidate the effects of various macromolecular structural parameters, we have designed and synthesized in this work four sets of highly branched polyethylenes varying in chain topology, molecular weight, and end group. With these polymers, we have systematically investigated and compared their performance for the solubilization of multi-walled carbon nanotubes in common solvents including THF, chloroform, n-heptane, and toluene. We have found that these macromolecular structural parameters as well as the solvent play complex but sensitive roles in this noncovalent solubilization system. This work thus provides some valuable guidelines towards the design of optimum polymers for efficient noncovalent nonspecific solubilization of carbon nanotubes.
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We report in this article a new versatile surface-initiated ethylene “living” coordination polymerization technique for “grafting from” surface functionalization of silica nanoparticles with ...narrow-distributed branched polyethylene brushes of controllable length. The key to the success of this technique is the use of the acetonitrile Pd−diimine complex, (ArNC(Me)−(Me)CNAr)Pd(CH3)(NCMe)+SbF6 − (Ar = 2,6-(iPr)2 C6H3) (1), which possesses unique immobilization and polymerization chemistry. In this technique, complex 1 was immobilized covalently onto acryloyl-functionalized silica particle surface by reacting with the surface-tethered acryloyl groups, giving rise to Pd−diimine chelate complexes covalently tethered on silica surface through an ester linkage. The tethered Pd−diimine chelate complexes catalyzed successfully surface-initiated ethylene “living” polymerization at 5 °C and ethylene pressure of 400 psi, leading to narrow-distributed branched polyethylene chains covalently tethered on silica surface through the ester linkage. The branched polyethylene brushes, after cleaved off from the silica particles, were found to possess narrow molecular weight distribution (polydispersity index of about 1.18) and have a linear increase of their number-average molecular weight and relative mass content with the polymerization time. The covalent grafting of polymer brushes was confirmed by using characterization techniques including nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). To the best of our knowledge, this represents the first report on the use of surface-initiated ethylene “living” coordination polymerization technique for surface functionalization of inorganic particles with polyethylene brushes.
Abstract
Purpose
To explore the association between uric acid and urinary prostaglandins in male patients with hyperuricemia.
Methods
A total of 38 male patients with hyperuricemia in outpatients of ...Huadong Hospital from July 2018 to January 2020 were recruited. Serum uric acid (SUA), 24 h urinary uric acid excretion and other indicators were detected respectively. 10 ml urine was taken to determine prostaglandin prostaglandin D (PGD), prostaglandin E1 (PGE1), prostaglandin E2 (PGE2), 6-keto-PGF1α, thromboxane A2 (TXA2) and thromboxane B2 (TXB2). Fraction of uric acid excretion (FEua) and uric acid clearance rate (Cua) were calculated. According to the mean value of FEua and Cua, patients were divided into two groups, respectively. The independent-samples
t
test and the Mann–Whitney U test were applied for normally and non-normally distributed data, respectively.
Results
After adjusting confounding factors (age, BMI, eGFR, TG, TC, HDL and LDL), SUA was negatively correlated with urinary PGE1(
r
= -0.615,
P
= 0.009) and PGE2(
r
= -0.824,
P
< 0.001). Compared with SUA1 group (SUA < 482.6 mg/dl), SUA2 (SUA
$$\ge$$
≥
482.6 mg/dl) had lower urinary PGE1(
P
= 0.022) and PGE2(
P
= 0.019) levels. Cua was positively correlated with PGE2 (
r
= 0.436,
P
= 0.01). The correlation persisted after adjustment for age, BMI, eGFR, TG, TC, HDL and LDL by multiple linear regression analysis. In the Cua1 group (Cua < 4.869 mL /min/1.73 m
2
), PGE2 were lower than that in Cua2 (Cua
$$\ge$$
≥
4.869 mL /min/1.73 m
2
) group (
P
= 0.011).
Conclusions
In male patients with hyperuricemia, SUA was negatively correlated with urinary PGE2, Cua was positively correlated with urinary PGE2. Urinary PGE2 were significantly different between different SUA and Cua groups.
The flame-retardant properties of polyurethane (PU) containing ammonium polyphosphate (APP) and aluminum hydroxide (ATH) were investigated. Moreover, the flame retardant performance was investigated ...through thermogravimetric analysis, limiting oxygen index (LOI), vertical combustion (UL 94), and cone calorimeter. When 15 wt% APP and 5 wt% ATH were added together, the PU/15%APP/5%ATH sample shows better thermal stability and flame-retardant properties. When 15 wt% APP and 5 wt% ATH were added together, the LOI value of the PU/15%APP/5%ATH sample was 30.5%, and UL 94 V-0 rating was attained. Compared with PU, the peak heat release rate (PHRR), total heat release (THR), and average effective heat combustion (av-EHC) of the PU/15%APP/5%ATH sample decreased by 43.1%, 21.0%, and 29.4%, respectively. In addition, the flame-retardant mechanism was investigated through cone calorimeter. The APP/ATH addition simultaneously exerted condensed phase and gas phase flame retardant effects. APP and ATH have synergistic flame retardant properties.
Mounting studies have shown that hyperuricemia is related to kidney diseases through multiple ways. However, the application of urinary uric acid indicators in patients with reduced renal function is ...not clear. In this study, we aim to determine the effects of renal function on various indicators reflecting uric acid levels in patients with chronic kidney disease (CKD).
Anthropometric and biochemical examinations were performed in 625 patients with CKD recruited from Dept of Nephrology of Huadong hospital affiliated to Fudan University. Multiple regression analyses were used to study correlations of the estimated glomerular filtration rate (eGFR) with serum uric acid (SUA) and renal handling of uric acid. For further study, smooth curve plots and threshold effect analyses were applied to clarify associations between renal function and uric acid levels.
The nonlinear relationships were observed between eGFR and urinary uric acid indicators. The obvious inflection points were observed in smooth curve fitting of eGFR and fractional excretion of uric acid (FEur), excretion of uric acid per volume of glomerular filtration (EurGF). In subsequent analyses where levels of eGFR< 15 mL/min/1.73m
were dichotomized (CKD5a/CKD5b), patients in the CKD5a showed higher levels of FEur and EurGF while lower levels of urinary uric acid excretion (UUA), clearance of uric acid (Cur) and glomerular filtration load of uric acid (FLur) compared with CKD5b group (all P < 0.05). And there was no significant difference of SUA levels between two groups. On the other hand, when eGFR< 109.9 ml/min/1.73 m
and 89.1 ml/min/1.73 m
, the resultant curves exhibited approximately linear associations of eGFR with Cur and FLur respectively.
FEur and EurGF showed significantly compensatory increases with decreased renal function. And extra-renal uric acid excretion may play a compensatory role in patients with severe renal impairment to maintain SUA levels. Moreover, Cur and FLur may be more reliable indicators of classification for hyperuricemia in CKD patients.
We demonstrate in this paper the novel synthesis of multiarm star polyethylenes of well-defined arm lengths and controllable average arm numbers through the core-first multifunctional “living” ...polymerization protocol from ethylene stock. These novel star polymers are featured with a core−shell structure, having a hyperbranched polyethylene core joining multiple linear polyethylene arms bearing short branch structures. Utilizing the outstanding features of cationic Pd−diimine catalysts, a three-step synthesis procedure incorporating two sequential Pd−diimine catalyzed ethylene polymerization steps is employed. Hyperbranched polyethylenes bearing different numbers of pendant acryloyl groups (HPE1 and HPE2) were first synthesized with an acetonitrile Pd−diimine catalyst (2) by nonliving chain walking copolymerization of ethylene with 1,4-butanediol diacrylate at elevated concentrations. These two hyperbranched polymers having the specific acryloyl anchoring sites were used as the homogeneous support in the second step for the covalent immobilization of catalyst 2 to generate hyperbranched polyethylenes encapsulating multinuclear covalently tethered Pd−diimine catalysts (HPE-Pd-1 and HPE-Pd-2). Acting as the multifunctional initiating hyperbranched core in the third step, the two multinuclear hyperbranched Pd catalysts initiated and catalyzed successfully ethylene multifunctional “living” polymerization at 400 psi and 5 °C, and led to simultaneous multidirectional arm growth from the hyperbranched core to form two sets of star polymers of very high molecular weights (SPE1 and SPE2 sets, respectively, with number-average molecular weight M n up to 1,379 kg/mol). The arm growth catalyzed by the tethered Pd centers in the polymerization is confirmed to be “living”, with M n of both star polymers and the arms increases nearly linearly with polymerization time. Determined essentially by the average numbers of tethered acryloyl groups in HPE1 and HPE2, high average arm numbers (about 21 and 28 per star, respectively) were achieved in the star polymers, along with narrow-distributed tunable arm length (up to about 48 kg/mol). Study on dilute solution properties of these two sets of star polymers confirms their spherical chain conformation and resemblance of rigid spheres and high-generation dendrimers.
This communication reports the non-covalent, non-specific surface functionalization of multi-walled carbon nanotubes (MWCNTs) with a hyperbranched polyethylene (HBPE). The adsorption characteristics ...of the HBPE macromolecule on the MWCNTs were studied through an adsorption isotherm. Partial coverage of the nanotubes, estimated to be up to 25%, can be accomplished using this functionalization approach. The treated MWCNTs exhibited significantly improved dispersion within an ethylene–octene copolymer matrix, compared to the untreated fillers.
We report in this article the “arm-first” synthesis of core–shell-structured multiarm polyethylene (PE) star polymers having multiple linear-but-branched PE arms joined at a cross-linked ...polydivinylbenzene (polyDVB) core. This synthesis is achieved in two steps by coupling two mechanistically incompatible polymerization techniques, Pd-catalyzed coordinative ethylene “living” polymerization and atom-transfer radical polymerization (ATRP). Ethylene “living” polymerization was first carried out using a functionalized Pd–diimine catalyst, (ArNC(Me)–(Me)CNAr)Pd(CH2)3C(O)O(CH2)2OC(O)C(CH3)2Br+SbF6 – (Ar = 2,6-(iPr)2C6H3) (1), to directly synthesize narrow-distributed PE macroinitiators (MIs) containing an end-capping 2-bromoisobutyryl group active for initiating ATRP. Featured with controllable molecular weights at low polydispersity, the PE MIs are employed subsequently in the second step to initiate cross-linking polymerization of divinylbenzene (DVB) via ATRP to obtain the core-cross-linked star polymers. As a demonstration, three PE MIs at different lengths (number-average molecular weight of 7.3, 10.3, and 13.7 kg/mol, respectively) were specifically synthesized and employed for star construction. In the ATRP step, the effects of the various polymerization parameters, including MI concentration, the molar ratio of DVB to MI, and MI length, on the polymerization kinetics, star yield, average arm number, and average molecular weights of the star polymers were investigated systematically. By controlling the polymerization parameters, a range of PE star polymers having narrow-distributed arm lengths (7.3–13.7 kg/mol) and controllable average arm numbers (ca. 5–43 per star) have thus been successfully synthesized. A study on dilution solution properties of these star polymers having various structural parameters reveals their spherical chain conformation and resemblance of rigid spheres and high-generation dendrimers, with their intrinsic viscosity depending primarily on arm length while not on arm number or polymer molecular weight.
We demonstrate in this article the facile synthesis of a novel range of “treelike” polyethylene block polymers constructed uniquely with chain blocks of hybrid hyperbranched−linear chain topologies ...from sole ethylene stock. Though chemically identical, the blocks in the polymers are featured with distinctly different chain topologies, varying from hyperbranched to linear. This synthesis is achieved uniquely through one-pot stagewise chain walking ethylene “living” polymerization with a Pd−diimine catalyst, (ArNC(Me)−(Me)CNAr)Pd(CH3)(NCMe)+SbF6 − (Ar = 2,6-(iPr)2C6H3) (1), under varying conditions. It takes advantage of the combined outstanding features of the Pd−diimine catalyst in ethylene polymerizationthe “living” polymerization behavior at a broad range of ethylene pressure and temperature and the capability of topology tuning by changing both parameters. In this stagewise “living” polymerization technique, the polymerization condition (ethylene pressure and temperature) is varied from stage to stage to grow blocks of different desired topologies while with maintained “living” behavior. With this technique, diblock polymers, containing a hyperbranched first block and a linear second block with controllable narrow-distributed sizes, have been obtained through two-stage polymerizations using the growth order of “hyperbranched-first” with the first stage at 1 atm/15 °C and the second stage at 27 atm/5 °C. The distinct block structure in these diblock polymers is verified based on the fact that their intrinsic viscosity data follow consistently the combination rule found with conventional diblock polymers. In addition, the synthesis of triblock polymers, composed of a hyperbranched first block, a medium-compact second block, and a linear third block, is also demonstrated through three-stage polymerization involving the first stage at 1 atm/15 °C, the second at 3 atm/15 °C, and the third at 27 atm/5 °C.
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