A well‐defined random copolymer of styrene (S) and chloromethylstyrene (CMS) featuring lateral chlorine moieties with an alkyne terminal group is prepared (P(S‐co‐CMS), = 5500 Da, PDI = 1.13). The chloromethyl groups are converted into Hamilton wedge (HW) entities (P(S‐co‐HWS), = 6200 Da, PDI = 1.13). The P(S‐co‐HWS) polymer is subsequently ligated with tetrakis(4‐azidophenyl)methane to give HW‐functional star‐shaped macromolecules (P(S‐co‐HWS))4, = 25 100 Da, PDI = 1.08). Supramolecular star‐shaped copolymers are then prepared via self‐assembly between the HW‐functionalized four‐arm star‐shaped macromolecules ( P(S‐co‐HW )) 4 and cyanuric acid (CA) end‐functionalized PS (PS–CA, = 3700 Da, PDI = 1.04), CA end‐functionalized poly(methyl methacrylate) (PMMA–CA, = 8500 Da, PDI = 1.13) and CA end‐functionalized polyethylene glycol (PEG–CA, = 1700 Da, PDI = 1.05). The self‐assembly is monitored by 1H NMR spectroscopy and light scattering analyses. 相似文献
Unmodified β‐cyclodextrin has been directly used to initiate ring‐opening polymerization of ϵ‐caprolactone in the presence of yttrium trisphenolate. Well‐defined cyclodextrin (CD)‐centered star‐shaped poly(ϵ‐caprolactone)s have been successfully synthesized containing definite average numbers of arms (Narm = 4–6) and narrow polydispersity indexes (below 1.10). The number‐average molecular weight ( ) and average molecular weight per arm ( ) are controlled by the feeding molar ratio of monomer to initiator. The prepared star‐PCL with of 2.7 × 103 is in fully amorphous and that with of 13.3 × 103 is crystallized. In addition, the obtained poly(e‐caprolactone) (PCL) stars with various molecular weights have different solubilities in methanol and tetrahydrofuran, which can be applied for further modifications. 相似文献
The electrochemical oxidation of bromide in the presence of ammonium ion (NH ) was studied by cyclic voltammetry and UV‐vis spectroscopy. The experimental results suggested that the anodically generated bromine (Br2) would be hydrolyzed to hypobromous acid (HBrO) at the pH range of 5–7 and was further disproportionate to hypobromite anion (BrO?) when pH was larger than 7. Both HBrO and BrO? were confirmed to be participated in the following homogeneous chemical reaction with the coexisted ammonium ion. However, HBrO is electroactive whereas BrO‐ is electroinactive at carbon electrode. Based upon the reaction of HBrO with NH , an indirect electrochemical method was proposed for determination of NH with dual‐electrode configuration in phosphate buffer solution (pH 7), where HBrO was produced at a generator electrode and the excess HBrO was subsequently detected at a collector electrode after a reaction with NH in a batch solution or in a micro flow injection analytical (micro‐FIA) system by using an interdigitated array (IDA) Pt microelectrode and a carbon film ring‐disk electrode (CFRDE), respectively. The decreasing of reduction current at the collector electrode was proportional to the concentration NH in both systems, with the detection limit below 3.0 μM. This approach shows the advantage of highly selectivity even in presence of a large amount of coexisted cations, and was successfully applied for the determination of NH in environmental water samples. 相似文献
The dilution of tert‐butylamine (tBA) with water and subsequent cooling leads to a large series of different crystalline hydrates by an in situ IR laser melting‐zone procedure. The crystal structures were determined for tBA?n H2O, with n=0, , 1, 7 , 7 , 9 , 11, and 17. For the two lower hydrates (n= , 1), one‐ and two‐dimensional hydrogen‐bonded networks are formed, respectively. The higher hydrates (n>1) exhibit a clathrate‐like three‐dimensional water framework with the tBA molecules as part of, or sitting inside, the cages. In all cases, tBA is hydrogen‐bonded to the H2O framework. In the intermediate range (1相似文献
The lamellar coordination polymer [(CuSCN)2(μ‐1,10DT18C6)] (1,10DT18C6 = 1,10‐dithia‐18‐crown‐6), in which staircase‐like CuSCN double chains are bridged by thiacrown ether ligands, may be prepared in two triclinic modifications 1 a and 1 b by reaction of CuSCN with 1,10DT18C6 in respectively benzonitrile or water. Performing the reaction in acetonitrile in the presence of an equimolar quantity of KSCN leads, in contrast, to formation of the K+ ligating 2‐dimensional thiocyanatocuprate(I) net [{Cu2(SCN)3}–] of 2 , half of whose Cu(I) atoms are connected by 1,10DT18C6 macrocycles. The potassium cations in [{K(CH3CN)}{Cu2(SCN)3(μ‐1,10DT18C6)}] ( 2 ) are coordinated by all six potential donor atoms of a single thiacrown ether in addition to a thiocyanate S and an acetonitrile N atom. Under similar conditions, reaction of CuI, NaSCN and 1,10DT18C6 affords [{Na(CH3CN)2}{Cu4I4(SCN)(μ‐1,10DT18C6)}] ( 3 ), which contains distorted Cu4I4 cubes as characteristic molecular building units. These are bridged by thiocyanate and thiacrown ether ligands into corrugated Na+ ligating sheets. In the presence of divalent Ba2+ cations, charge compensation requirements lead to formation of discrete [Cu(SCN)3(1,10DT18C6‐κS)]2– anions in [Ba{Cu(SCN)3(1,10DT18C6‐κS)}] ( 4 ). 相似文献
Macrocyclic and polymeric imines 5,5′ and 6,6′ are obtained in excellent yields by template‐free polycondensation of 1,6‐bis(4‐formylbenzoyloxy)hexane (1) with commercially available 4,4′‐methylene‐bis(cyclohexylamine) (2) and with bis(2‐amino‐2‐methylprop‐1‐yl)adipate dihydrochloride (4), respectively. The degree of macrocyclization during imine synthesis strongly depends on the diamine. Matrix‐assisted laser desorption–ionization time‐of‐flight (MALDI‐TOF) mass spectrometry analysis and gel permeation chromatography (GPC) measurements show that (2) leads to more macrocyclic adducts than (4). The subsequent meta‐chloroperoxybenzoic acid oxidation of polyimines 5,5′ and 6,6′ ( = 1650–11 200 g mol−1, = 3800–27 350 g mol−1) yields the corresponding polyoxaziridines 7,7′ and 8,8′ consisting of macrocyclic and linear polymeric structures ( = 1750–8050 g mol−1, = 3250–15 800 g mol−1). The synthesized polyoxaziridines are relatively stable and storable at room temperature. 相似文献
Iodostannates(II) with Anionic [SnI3]– Chains – the Transition from Five to Six‐coordinated SnII The iodostannates (Me4N) [SnI3] ( 1 ), [Et3N–(CH2)4–NEt3] [SnI3]2 ( 2 ), [EtMe2N–(CH2)2–NEtMe2] [SnI3]2 ( 3 ), [Me2HN–(CH2)2–NH–(CH2)2–NMe2H] [SnI3]2 ( 4 ), [Et3N–(CH2)6–NEt3] [SnI3]2 ( 5 ) and [Pr3N–(CH2)4–NPr3]‐ [SnI3]2 · 2 DMF ( 6 ) with the same composition of the anionic [SnI3]– chains show differences in the coordination of the SnII central atoms. Whereas the Sn atoms in 1 and 2 are coordinated in an approximately regular octahedral fashion, in compounds 3 – 6 the continuous transition to coordination number five in (Pr4N) [SnI3] ( 7 ) or [Fe(dmf)6] [SnI3]2 ( 8 ) can be observed. Together with the shortening of two or three Sn–I bonds, the bonds in trans position are elongated. Thus weak, long‐range Sn…I interactions complete the distorted octahedral environment of SnI4 groups in 3 and 4 and SnI3 groups in 5 and 6 . Obviously the shape, size and charge of the counterions and the related cation‐anion interactions are responsible for the variants in structure and distortion. 相似文献
A series of random copolymers and block copolymers containing water‐soluble 4AM and fluorescent VAK are synthesized by NMP. The homopolymerizations of 4AM and VAK and 4AM/VAK random copolymerization are performed in 50 wt% DMF using 10 mol% SG1, resulting in a linear increase in versus conversion, and final polymers with narrow molecular weight distributions ( < 1.4). Reactivity ratios rVAK = 0.64 ± 0.52 and r4AM = 0.86 ± 0.66 are obtained for the 4AM/VAK random copolymerization. In addition, a poly(4AM) macroinitiator is used to initiate a surfactant‐free suspension polymerization of VAK. After 2.5 h, the resulting amphiphilic block copolymer has = 12.6 kg · mol?1, = 1.48, molar composition FVAK = 0.38 with latex particle sizes between 270 and 475 nm.
The effect of a layer of electrochemically grafted 4‐diazo‐N,N‐diethylaniline (DEA) groups on the electron transfer kinetics of redox systems, displaying fast and slow heterogeneous electron transfer rate constants at edge and basal planes of carbon, was investigated. The properties of the modified electrode were characterized by cyclic voltammetry using four different inorganic redox systems (Fe(CN) , Co(phen) , Ru(NH3) , and IrCl in acidic, neutral, and basic media. Two distinct blocking behaviors and electrostatic effects were observed. More precisely, a strong blocking effect of the grafted layer on Fe(CN) and Co(phen) was found, whereas Ru(NH3) and IrCl showed to be rather unaffected by the presence of the DEA grafted layer. 相似文献
We describe the controlled fabrication of ultrathin multilayer films consisting of tri‐vanadium‐ substituted heteropolytungstate anions (denoted as P2W15V3) and a cationic polymer of quaternized poly (4‐vinylpyridine) partially complexed with osmium bis(2,2′‐bipyridine) (denoted as QPVP‐Os) on the 4‐aminobenzoic acid (4‐ABA) modified glassy carbon electrode (GCE) surface based on layer‐by‐layer assembly. Cyclic voltammetry and UV‐vis absorption spectrometry have been used to easily monitor the thickness and uniformity of thus‐formed multilayer films. The V‐centered redox reaction of P2W15V3 in the multilayer films can effectively catalyze the reduction of BrO and NO . The resulting P2W15V3/QPVP‐Os multilayer film modified electrode behaves as a much promising electrochemical sensor because of the low overpotential for the catalytic reduction of BrO and NO , and the catalytic oxidation of ascorbic acid. 相似文献
Self‐assembling systems based on ionic complexes of DNA fragments (36 base pairs), bcl‐2 antisense oligonucleotides (octadecamer), oligophosphates (25 phosphate groups) or acrylic oligomers (18 groups of phosphonic acid) with poly(L ‐lysine) (PLL) ( = 130 000 and 88 000) grafted with short poly[N‐(2‐hydroxypropyl)methacrylamide] (PHPMA) chains ( = 4 300 or 8 600) were studied by static and dynamic light scattering methods as systems suitable for gene therapy applications. The graft copolymers (GPLLs) with shorter PHPMA grafts ( = 4 300) provide polyelectrolyte complexes (PECs) with smaller and RH than the corresponding GPLLs with longer grafts ( = 8 600) and the same content of PLL. The lowest aggregation number of 2 was observed for PECs prepared from the GPLL with short grafts and 40 wt.‐% of PLL. The complexes of oligonucleotides and DNA fragments with GPLLs showed quite similar behavior to that with oligophosphates and acrylic oligomer. The complexes prepared from GPLLs containing 40 wt.‐% of PLL and at excess of oligophosphate were stable for at least 48 h under physiological conditions (0.15 M NaCl) and in bovine serum albumin solutions (1 mg · mL?1). Additionally, polyanion exchange reactions of the PECs in contact with poly(styrenesulfonate) and DNA were studied in 0.15 M NaCl solutions. The oligophosphates in complexes were at least partially substituted with high‐molecular‐weight polyanions. The structure of the initial PECs dominated the PEC structure after the exchange reaction.
The dependence of the molecular weight (a) and the hydrodynamic radius RH (b) of complexes of the oligophosphate (OPP) and four graft copolymers (GPLLi, i = 0–3) on the mixing ratio X. 相似文献
Summary: A novel chitosan derivative with polysarcosine side chains, i.e., chitosan‐graft‐polysarcosine [chitosan‐graft‐poly(N‐methylglycine)], was synthesized by ring‐opening polymerization of sarcosine N‐carboxyanhydride (NCA) with chitosan as a macroinitiator in the presence of carboxylic acids in dimethyl sulfoxide at 27 °C. Degree of substitution ( ) for polysarcosine side chains introduced to chitosan was controlled successfully by the feed amount of the additive nicotinic acid ( = 0.21–0.71). Independent of control, degree of polymerization ( ) for polysarcosine side chains was controlled by adjusting feed ratios of NCA monomer to chitosan ( = 14–43). Kinetic analysis of the propagation of sarcosine NCA was conducted by measuring CO2 evolution. Apparent kp values decreased with increased feed amounts of nicotinic acid, supporting the theory that propagation of NCA in the presence of nicotinic acid proceeds via equilibrium between active amine and dormant ammonium species.
Propagation mechanism of carboxylic acid‐mediated polymerization of sarcosine N‐carboxyanhydride. 相似文献