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31.
Hiroaki Shimomoto Dai Fukami Tomomi Irita Ken‐ichi Katsukawa Takabumi Nagai Shokyoku Kanaoka Sadahito Aoshima 《Journal of polymer science. Part A, Polymer chemistry》2012,50(8):1547-1555
Various types of fluorine‐containing star‐shaped poly(vinyl ether)s were successfully synthesized by crosslinking reactions of living polymers based on living cationic polymerization. Star polymers with fluorinated arm chains were prepared by the reaction between a divinyl ether and living poly(vinyl ether)s with fluorine groups (C4F9, C6F13, and C8F17) at the side chain using cationogen/Et1.5AlCl1.5 in a fluorinated solvent (dichloropentafluoropropanes), giving star‐shaped fluorinated polymers in high yields with a relatively narrow molecular weight distribution. The concentration of living polymers for the crosslinking reaction and the molar feed ratio of a bifunctional vinyl ether to living polymers affected the yield and molecular weight of the star polymers. Star polymers with block arms were prepared by a linking reaction of living block copolymers of a fluorinated segment and a nonfluorinated segment. Heteroarm star‐shaped polymers containing two‐ or three‐arm species were synthesized using a mixture of different living polymer species for the reaction with a bifunctional vinyl ether. The obtained polymers underwent temperature‐induced solubility transitions in various organic solvents, and their concentrated solutions underwent sol–gel transitions, based on the solubility transition of a thermoresponsive fluorinated segment. Furthermore, a slight amount of fluorine groups were shown to be effective for physical gelation when those were located at the arm ends of a star polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
32.
Chen He Ban‐Kun Jin Wei‐Dong He Xue‐Song Ge Jing Tao Jing Yang Sheng‐Qi Chen 《Journal of polymer science. Part A, Polymer chemistry》2013,51(10):2142-2149
Long‐subchain hyperbranched polystyrene (lsc‐hp PSt) with uniform subchain length was obtained through copper‐catalyzed azide‐alkyne cycloaddition click chemistry from seesaw macromonomer of PSt having one alkynyl group anchored at the chain centre and two azido group attached to both chain ends [alkynyl‐(PSt‐N3)2]. After precipitation fraction, different portions of lsc‐hp PSt having narrow overall molecular weight distribution were obtained for further grafting with alkynyl‐capped poly(N‐isopropylacrylamide) (alkynyl‐PNIPAM), which was obtained via single‐electron transfer living radical polymerization of NIPAM with propargyl 2‐bromoisobutyrate as the initiator and grafted onto the peripheral azido groups of lsc‐hp PSt via click chemistry. Thus, amphiphilic lsc‐hp PSt grafted with PNIPAM chains (lsc‐hp PSt‐g‐PNIPAM) was obtained and would have star‐like conformation in tetrahydrofuran (THF). By replacing THF with water, lsc‐hp PSt‐g‐PNIPAM was dissolved at molecular level in aqueous solution due to the hydrophilicity of PNIPAM and exhibited thermal induced shrinkage of PNIPAM arms. The water‐insoluble lsc‐hp PSt would collapse densely and could be served as a reservoir to absorb hydrophobic chemicals in aqueous solution. The influence of overall molecular weight of lsc‐hp PSt on the absorption of pyrene was studied. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
33.
34.
We provide a new class of interior solution of a(2+1)-dimensional anisotropic star in Finch and Skea spacetime corresponding to the BTZ black hole. We develop the model by considering the MIT bag model EOS and a particular ansatz for the metric function grrproposed by Finch and Skea [M.R. Finch and J.E.F. Skea, Class. Quantum.Grav. 6(1989) 467]. Our model is free from central singularity and satisfies all the physical requirements for the acceptability of the model. 相似文献
35.
Seung Hyun Sung William B. Farnham Heidi E. Burch Yefim Brun Kai Qi Thomas H. Epps 《Journal of Polymer Science.Polymer Physics》2019,57(24):1663-1672
We demonstrate the directional alignment of perpendicular‐lamellae domains in fluorinated three‐armed star block polymer (BP) thin films using solvent vapor annealing with shear stress. The control of orientation and alignment was accomplished without any substrate surface modification. Additionally, three‐armed star poly(methyl methacrylate‐block‐styrene) [PMMA‐PS] and poly(octafluoropentyl methacrylate‐block‐styrene) were compared to their linear analogues to examine the impact of fluorine content and star architecture on self‐assembled BP feature sizes and interdomain density profiles. X‐ray reflectometry results indicated that the star BP molecular architecture increased the effective polymer segregation strength and could possibly facilitate reduced polymer domain spacings, which are useful in next‐generation nanolithographic applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1663–1672 相似文献
36.
A star edge coloring of a graph is a proper edge coloring such that every connected 2-colored subgraph is a path with at most 3 edges. Deng et al. and Bezegová et al. independently show that the star chromatic index of a tree with maximum degree is at most , which is tight. In this paper, we study the list star edge coloring of -degenerate graphs. Let be the list star chromatic index of : the minimum such that for every -list assignment for the edges, has a star edge coloring from . By introducing a stronger coloring, we show with a very concise proof that the upper bound on the star chromatic index of trees also holds for list star chromatic index of trees, i.e. for any tree with maximum degree . And then by applying some orientation technique we present two upper bounds for list star chromatic index of -degenerate graphs. 相似文献
37.
Yoshiki Shibuya Ryoichi Tatara Yivan Jiang Yang Shao‐Horn Jeremiah A. Johnson 《Journal of polymer science. Part A, Polymer chemistry》2019,57(3):448-455
The properties of polymeric materials are dictated not only by their composition but also by their molecular architecture. Here, by employing brush‐first ring‐opening metathesis polymerization (ROMP), norbornene‐terminated poly(ethylene oxide) (PEO) macromonomers ( MM‐n , linear architecture), bottlebrush polymers ( Brush‐n , comb architecture), and brush‐arm star polymers ( BASP‐n , star architecture), where n indicates the average degree of polymerization (DP) of PEO, are synthesized. The impact of architecture on the thermal properties and Li+ conductivities for this series of PEO architectures is investigated. Notably, in polymers bearing PEO with the highest degree of polymerization, irrespective of differences in architecture and molecular weight (~100‐fold differences), electrolytes with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as an Li+ source exhibit normalized ionic conductivities (σn) within only 4.9 times difference (σn = 29.8 × 10?5 S cm?1 for MM‐45 and σn = 6.07 × 10?5 S cm?1 for BASP‐45 ) at a concentration of Li+ r = [Li+]/[EO] = 1/12 at 50 °C. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 448–455 相似文献
38.
Ikhlas Gadwal Prakash P. Wadgaonkar Amol B. Ichake Shivshankar R. Mane 《Journal of polymer science. Part A, Polymer chemistry》2019,57(2):146-156
A new approach was developed for synthesis of certain A3B3‐type of double hydrophilic or amphiphilic miktoarm star polymers using a combination of “grafting onto” and “grafting from” methods. To achieve the synthesis of desired miktoarm star polymers, acetyl protected poly(ethylene glycol) (PEG) thiols (Mn = 550 and 2000 g mol?1) were utilized to generate A3‐type of homoarm star polymers through an in situ protective group removal and a subsequent thiol–epoxy “click” reaction with a tris‐epoxide core viz. 1,1,1‐tris(4‐hydroxyphenyl)ethane triglycidyl ether. The secondary hydroxyl groups generated adjacent to the core upon the thiol–epoxy reaction were esterified with α‐bromoisobutyryl bromide to install atom transfer radical polymerization (ATRP) initiating sites. ATRP of N‐isopropylacrylamide (NIPAM) using the three‐arm star PEG polymer fitted with ATRP initiating sites adjacent to the core afforded A3B3‐type of double hydrophilic (PEG)3[poly(N‐isopropylacrylamide)] (PNIPAM)3 miktoarm star polymers. Furthermore, the generated hydroxyl groups were directly used as initiator for ring‐opening polymerization of ε‐caprolactone to prepare A3B3‐type of amphiphilic (PEG)3[poly(ε‐caprolactone)]3 miktoarm star polymers. The double hydrophilic (PEG)3(PNIPAM)3 miktoarm star polymers showed lower critical solution temperature around 34 °C. The preliminary transmission electron microscopy analysis indicated formation of self‐assembly of (PEG)3(PNIPAM)3 miktoarm star polymer in aqueous solution. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 146–156 相似文献
39.
Marcin Libera Petr Formanek Leonard Schellkopf Barbara Trzebicka Andrzej Dworak Manfred Stamm 《Journal of polymer science. Part A, Polymer chemistry》2014,52(24):3488-3497
Dendritic copolymers comprising a hydrophobic core and hydrophilic shell with nearly equal numbers of hydroxyl groups in the shell and different densities in the core were prepared by a multi‐step process based on anionic ring‐opening polymerization. The diversity in the core density was obtained by using copolymer stars with poly(tert‐butyl‐glycidylether)‐block‐polyglycidol arms with nearly equal length of hydrophobic blocks and numbers of hydroxyl groups of polyglycidol but different numbers of arms as macroinitiators. The ability of the dendritic copolymers to serve as a nanocontainer for a ruthenium complex Ru(NH3)3Cl3 with anticancer properties was studied. The possibility of improving the water solubility of this poorly soluble drug by loading it onto dendritic copolymers was investigated. The hydroxyl groups of the dendritic copolymers were used for complexation of the ruthenium compound to the shell. The loading efficiency was analyzed by UV–vis spectroscopy. The dendritic nanoparticles in their hydrated state were visualized using cryo‐TEM. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3488–3497 相似文献
40.
Cui‐Wei Wang Chao Liu Xiao‐Wei Zhu Zi‐Ying Yang Hong‐Fan Sun De‐Ling Kong Jing Yang 《Journal of polymer science. Part A, Polymer chemistry》2016,54(3):407-417
Well‐defined star‐shaped hydrophobic poly(ε‐caprolactone) (PCL) and hydrophilic poly(ethylene glycol) (PEG) amphiphilic conetworks (APCNs) have been synthesized via the combination of ring opening polymerization (ROP) and click chemistry. Alkyne‐terminated six arm star‐shaped PCL (6‐s‐PCLx‐C?CH) and azido‐terminated PEG (N3‐PEG‐N3) are characterized by 1H NMR and FT‐IR. The swelling degree of the APCNs is determined both in water and organic solvent. This unique property of the conetworks is dependent on the nanophase separation of hydrophilic and hydrophobic phases. The morphology and thermal behaviors of the APCNs are investigated by SEM and DSC respectively. The biocompatibility is determined by water soluble tetrazolium salt reagents (WST‐1) assay, which shows the new polymer networks had good biocompatibility. Through in vitro release of paclitaxel (PTX) and doxorubicin (DOX), the APCNs is confirmed to be promising drug depot materials for sustained hydrophobic and hydrophilic drugs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 407–417 相似文献