Degree Of Branching Value Research Articles

Chemical Characterization and Antioxidant Properties of Cell Wall Polysaccharides from Antrodia cinnamomea mycelia

Fungal cell wall is composed of various polysaccharides with different structures and diverse bioactivities. Three polysaccharides coded as mycelia hot water-extracted fraction (AC-MHW), mycelia cold alkali-extracted fraction (AC-MCA) and mycelia hot alkali-extracted fraction (AC-MHA) were isolated and purified from the cell wall of Antrodia cinnamomea mycelia with yields of 3.82%, 39.13%, and 10.05%, respectively. The structure analysis showed that all of these polysaccharides were neutral hetero-polysaccharides with a high DB (degree of branching) value and presented as a spherical conformation in NaNO3 solution (0.1 M). Although with different sugar composition and glycosidic bonds, molecular weights of these polysaccharides were all over 107 g/mol. Besides, the results on antioxidant activity and IC50 values indicated that in vitro antioxidant activity of the AC-MCA and AC-MHA were much stronger than AC-MHW, which might be attributed to their greater contents of 1,3-glucosyl residues. It could provide a certain reference for the study and development of Antrodia cinnamomea polysaccharides as ingredients of functional foods.

Facile One-Pot Synthesis of Hyperbranched Glycopolymers in Aqueous Solution via a Hydroxy/Cu(III) Redox Process.

In this study, a self-condensing vinyl copolymerization/redox (SCVP/Redox) system was constructed to prepare hyperbranched poly(methyl-6-O-methacryloyl-α-D-glucoside) by using Cu(III) as the initiator in aqueous solution, in which the –OH group in C-2, C-3 and C-4 position on pyranose rings could be initiated by Cu(III). The branched and linear units were clearly distinguished by nuclear magnetic resonance (1H NMR) to estimate the degree of branching (DB). When the ratio of Cu(III) to monomer fixed at 0.5:1, the DB value reached 0.32, which was higher than the product initiated by Ce(IV). Moreover, the inhibition activity of the products on amyloid fibrillation was investigated by using the hen egg-white lysozyme (HEWL) as a model based on the difference of the initiation sites. The results showed that the –OH groups in C-4 position might play an important role in this process.

Ligand effect in the synthesis of hyperbranched polymers via copper‐catalyzed azide‐alkyne cycloaddition polymerization (CuAACP)

ABSTRACTCopper‐catalyzed azide‐alkyne cycloaddition polymerization (CuAACP) of AB2 monomers demonstrated a chain‐growth mechanism without any external ligand because of the complexation of in situ formed triazole groups with Cu catalysts. In this study, we explored the use of various ligands that affected the polymerization kinetics to tune the polymers’ molecular weights and the degree of branching (DB). Eight ligands were studied, including polyethylene glycol monomethyl ether (PEG350, Mn = 350), tris(benzyltriazolylmethyl)amine (TBTA), 2,6‐bis(1‐undecyl‐1H‐benzo[d]imidazol‐2‐yl)pyridine (Py(DBim)2), 2,2′‐bipyridyl (bpy), 4,4′‐di‐n‐nonyl‐2,2′‐bipyridine (dNbpy), N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA), N,N,N′,N″,N″‐penta(n‐butyl)diethylenetriamine (PBuDETA), and N,N,N′,N″,N″‐pentabenzyldiethylenetriamine (PBnDETA). All ligands except PEG350 exhibited stronger coordination with Cu(I) than the polytriazole polymer, which freed the Cu catalyst from polymers and resulted in dominant step‐growth polymerization with simultaneous chain‐growth feature. Meanwhile, the use of PEG350 ligand retained the confined Cu in the polymer, demonstrating a chain‐growth mechanism, but lower polymer molecular weights as compared with the no‐external‐ligand polymerization. Results indicated that aliphatic substituent groups on ligands had little effect on the molecular weights and DB of the polymers, but rigid aromatic substituent groups decreased both values. By varying the ligand species and amounts, hyperbranched polymers with DB value ranging from 0.53 ([TBTA]0/[Cu]0 = 5) to 0.98 ([PMDETA]0/[Cu]0 = 2) have been achieved. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2238–2244

Biobased Multifunctional Macroglycol Containing Smart Thermoplastic Hyperbranched Polyurethane Elastomer with Intrinsic Self-Healing Attribute

Smart biobased self-healable polymers are advanced sustainable materials. Thus, a thermoplastic hyperbranched polyurethane (HBPUR) elastomer was synthesized by using a biobased multifunctional macroglycol along with other required components, for the first time. This biobased macroglycol was obtained by stoichiometric controlled esterification reaction of dimer acid with glycerol. Fourier transform infrared, nuclear magnetic resonance spectroscopic, gel permeation chromatography, and X-ray diffraction studies confirmed the physicochemical structure of the synthesized macroglycol and HBPURs. The degree of branching value (0.78–0.91) of HBPURs varies with this macroglycol content. These thermoplastic PUR elastomers exhibited outstanding toughness (205 MJ.m–³), unprecedented high elongation at break (2810–3160%), good tensile strength (8.2–9.5 MPa), impact resistance (>17.3 kJ/m), scratch resistance (4.0–4.5 kg), durometer hardness (52–60 Shore A), adhesive strength (3.3–6.7 kPa), thermostability (241–249 °C), and chemical and UV-resistance. Notably, HBPURs also showed excellent repeatable intrinsic self-healing efficiency (100%) under exposure of microwave (450 W). Moreover, HBPURs exhibited outstanding thermoresponsive shape recovery (100%) within 50–56 s at 60 °C. In addition, HBPURs showed acceptable biodegradation under the exposure of Pseudomonus aeruginosa and Bacillus subtilus bacterial strains. Again, HBPUR demonstrated superior performance over linear analogous PUR. Thus, HBPUR has great potential as a smart sustainable self-healing thermoplastic elastomer for different applications.

Synthesis backbone-dual-responsive of hyperbranched poly(bis(N,N-ethyl acrylamide))s by RAFT

Hyperbranched poly(bis(N,N-ethyl acrylamide))s (HPNAMs) with many vinyls as terminal groups were synthesized successfully using reversible addition fragmentation chain transfer polymerization (RAFT). Detailed analyses, based on the molecular weight, α value, degree of branching (DB), and lower critical solution temperature (LCST) obtained from nuclear magnetic resonance (NMR), multi detector-size exclusion chromatography (MDSEC), ultravioletvisible (UV-vis) spectroscopy, and dynamic light scattering (DLS), indicate that we acquired backbone-temperature and pH responsive HPNAM. Factors, such as DB, molecular weight, and pH value, that affect the LCST were investigated. It was found that the molecular weights of the hyperbranched polymers show significant influence on the LCSTs. For the HPNAMs with low molecular weight, the LCSTs decreased as the DB increased, and the LCSTs can also be adjusted by changing the pH value of solutions. Furthermore, the result of cell cytotoxicity indicates that this new dual responsive hyperbranched polymer has low cytotoxicity and exhibits potential for biomedical applications.

Synthesis of highly branched sulfonated polymers and the effects of degree of branching on properties of branched sulfonated polymers as proton exchange membranes

Branched sulfonated polymers exhibit excellent properties as proton exchange membranes (PEMs). However, very few highly branched sulfonated polymers are reported as PEMs. The highly branched polymer, including the method to increase degree of branching (DB) and the effects of DB on the properties of PEMs, should be further studied. In this work, novel branched sulfonated poly(fluorenyl ether ketone sulfone)s with different DB value are synthesized by direct polycondensation reactions from bisphenol fluorene (A2), sulfonated 4,4′-difluorobenzphenone, 1,3,5-tris(4-(4-fluorophenylsulfonyl)phenyl)benzene (B3-3) and 4,4′-difluorodiphenyl sulfone. The highest DB with 10% branching agent is obtained using the B3-3 monomer. The method to increase the DB is discussed. It is found that B3 scaffold with long and hard arms can effectively increase the DB value. The effects of DB on the properties, including oxidative stability, proton conductivity, water uptake, swelling ratio, thermal stability, mechanical property and microstructure, are investigated. With increasing DB value, oxidative stability and proton conductivity of the membranes increase remarkably, but swelling ratio and tensile strength decrease slowly. The membrane with the highest DB value (10%) exhibits high proton conductivity (0.42 S cm−1) and oxidative stability (327 min), as well as relatively low swelling ratio (16.2%) at 80 °C.

One-step synthesis of multi-alkyne functional hyperbranched polyglycerols by copolymerization of glycidyl propargyl ether and glycidol

By copolymerization of glycidol with the alkyne-containing oxirane monomer glycidyl propargyl ether (GPE), hyperbranched polyglycerol (hbPG) with a defined number of alkyne functionalities (up to 38%) can be obtained in a one-step procedure. The number of alkynes can be adjusted by the glycidol/GPE ratio to provide multi-alkyne functional hbPGs, maintaining the highly branched polyether structure. Interestingly, the acidic proton of the alkyne moiety does not interfere with the proton exchange mechanism during the polymerization of glycidol. By specific modification of the synthesis procedure, crosslinking reactions can be suppressed. The polymers exhibit molecular weights ranging from 1800 to 5500 g mol−1 (determined by 1H NMR spectroscopy and SEC) with moderate polydispersities (Mw/Mn < 2.0, mostly <1.7). Using inverse gated 13C NMR spectroscopy and two-dimensional NMR techniques, the different repeat units of the copolymers can be assigned. The degree of branching value (DB) ranges from 0.58 to 0.50 for increasing GPE content, which is caused by an increased number of linear repeat units with increasing GPE content. The alkyne functionalities are readily available for derivatization reactions by copper-catalyzed azide–alkyne “click”-type cycloaddition reactions. The convenient synthesis and the broad applicability of the alkyne functionalities render these copolymers interesting building blocks for the preparation of complex polymer architectures by “click”-chemistry. This is exemplified by the attachment of hydrophobic azide end-functional polystyrene to yield amphiphilic branched copolymers containing exactly one hbPG block.

Synthesis and properties of highly branched sulfonated poly(arylene ether)s as proton exchange membranes

A series of branched sulfonated poly(arylene ether)s were successfully synthesized using 1,3,5-tris[4-(4-fluorobenzoyl)phenoxy]benzene (B3) as branching agent. The synthesized branched copolymers were soluble in polar organic solvents, such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc) and dimethylsulfoxide (DMSO), and could be cast to form tough and smooth films. The effect of degree of branching (DB) on the proton conductivity, swelling ratio and oxidative stability of the membranes was investigated. With increasing DB value, the proton conductivity and oxidative stability of the membranes increased. A maximum oxidative stability of the branched membrane with 4% of DB value was determined to be 3.4 times larger than that of the linear membrane. In addition, as the DB value increased, the swelling ratio of the membranes decreased from 13.51% to 9.09% at 80 °C. The results indicated that increasing DB value might be an effective way to improve the properties of proton exchange membranes.

Synthesis and Properties of Hyperbranched Polyurethane with a Long Chain Between the Branching Points

Hyperbranched polyurethane (HPU) with a long chain between the branching points was synthesized from isocyanate end-capped polycarbonatediols and diethanolamine via an oligomeric A2 + CB2 approach. The effects of the temperature and molar ratio of nPCDL/nNCO on the degree of branching (DB) were studied. The structure of the products was characterized by 13C-NMR. The results showed that the polymers had a hyperbranched structure and the DB value was 0.75 when the nPCDL/nTDI was 0.5 at 55°C. The thermal and adhesive properties were investigated by thermogravimetric analysis and tensile test, respectively. The HPUs could be used as hot melt adhesive, and the maximum lap shear strength was up to 6.5 MPa. Moreover, the effects of the length of the chain, reaction temperature and reaction time on the adhesive ability were investigated.

Degree of branching of hyperbranched polystyrenes via a controlled radical mechanism of an inimer: Determination by a kinetic approach

AbstractWe studied, with a kinetic approach, the living nature and degree of branching (DB) of the formation of hyperbranched polystyrene by the free‐radical photopolymerization of 2‐(N,N‐diethyldithiocarbamyl)methylstyrene in benzene. The free‐radical polymerization proceeded with a living radical mechanism. Subsequently, we treated the kinetics of the initiation and propagation steps of the active A* and B* (side‐group) sites with model compounds. The degradation rates of two types of dithiocarbamate groups at the A and B sites agreed well with theoretical trends for CS bond dissociation energies predicted by the density functional theory for model compounds. The reactivity of the initiating B* groups was greater than that of the propagating A* groups. DB of the hyperbranched polymers was estimated to be 0.31 with both reaction rates in terms of Müller's equation. This result supported the DB value (0.39) estimated from NMR data. The hyperbranched molecules obtained in this work were not perfectly dendritic but had somewhat defective structures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1810–1815, 2005

Synthesis of Hyperbranched Polysaccharide by Thermally Induced Cationic Polymerization of 1,6‐Anhydrohexopyranose

AbstractThe thermally induced cationic polymerizations of 1,6‐anhydro‐β‐D‐glucopyranose (1a), 1,6‐anhydro‐β‐D‐mannopyranose (1b) and 1,6‐anhydro‐β‐D‐galactopyranose (1c) as a latent cyclic AB4‐type monomer were carried out using (S‐2‐butenyl)tetramethylenesulfonium hexafluoroantimonate (2) as an initiator. The solution polymerization in propylene carbonate proceeded without gelation to produce the water‐soluble hyperbranched polysaccharides (3a‐c) with controlled molecular weights and narrow polydispersities. The degree of branching (DB), estimated by the methylation analysis of 3a‐c, was in the range of 0.38 – 0.49. The thermally induced cationic polymerization of 1a‐c using 2 is a facile method leading to a hyperbranched polysaccharide with a high DB value.

Synthesis of Hyperbranched Polysaccharide by Thermally Induced Cationic Polymerization of 1,6-Anhydro-β-d-mannopyranose

The thermally induced cationic polymerization of 1,6-anhydro-β-d-mannopyranose (1) as a latent cyclic AB4-type monomer was carried out using 2-butenyltetramethylenesulfonium hexafluoroantimonate (2) as the initiator. The solution polymerization in propylene carbonate proceeded without gelation to produce the water-soluble hyperbranched polysaccharides (3) with controlled molecular weights and narrow polydispersities. The weight-average molecular weight (Mw,SLS) values of 3 measured by static laser light scattering (SLS) varied in the range 6.5 × 103 to 6.4 × 105, which were significantly higher than the weight-average molecular weight (Mw,SEC) values by size exclusion chromatography (SEC). The viscosity of the solution of 3 was very low, and the intrinsic viscosities were from 0.032 to 0.047 dL·g-1. Polymer 3 was composed of α- and β-linked hyperbranched polysaccharides consisting of 19 kinds of d-mannopyranosyl and d-mannofuranosyl repeating units, which had numerous nonreducing d-mannopyranosyl terminal units. The degree of branching (DB), estimated by the methylation analysis of 3, was in the range of 0.38−0.44. The thermally induced cationic polymerization of 1 using 2 is a facile method leading to the hyperbranched polysaccharide with a high DB value.

Degree of branching in hyperbranched polymers. 2. Enhancement of the db: Scope and limitations

AbstractThe degree of branching (DB) as well as the ANB (average number of branches) of polymers obtained from polycondensation of AB2 and ABm‐type monomers in general is analyzed in detail on the basis of kinetic considerations. Various possibilities for the enhancement of the DB of hyperbranched polymers beyond the limit for a random ABm polycondensation (0.5 for AB2, 0.44 for AB3) are considered, i.e., (i) enhanced reactivity of linear vs. terminal units; (ii) polymerization of prefabricated, perfect dendritic units and (iii) the slow addition technique. For AB2 monomers, the formation of terminal (T), linear (L) and perfect dendritic (D) units in the course of the random one‐pot polymerization is calculated. Furthermore, the evolution of the DB and ANB with conversion is calculated for ABm monomers. It is shown that the definition of the DB for AB2 systems (DB = 2D/(2D+L)) derived in the first paper on the DB (Acta Polym. 1997, 48, 30) in the case of a random one‐pot polycondensation exhibits the same conversion dependence as the branching parameter α = 1/2PA, defined by Flory for AB2 polycondensations. The dilution principle is introduced, which is based on slow addition of ABm monomers to a core molecule Bf or an ABm‐type hyperbranched molecule with an arbitrary DB. It is shown that the maximum DB value obtainable from such a dilution/slow addition process is 0.67 for AB2 systems. Thus, the DB is considerably higher than in the case of a random one‐step polymerization (0.5). The DB for ABm‐type hyperbranched polymers prepared according to the dilution principle has been calculated to be m/(2m–1).