To gain insight into the mechanism treating formation of hyperbranched polylysines through the polymerization of N?-carbobenzoxylysine N-carboxyanhydride under conditions of the reductive removal of a N?-carbobenzoxy group, hyperbranched polylysine has been synthesized with the use of trifluoroacetic acid as a terminator in the polymerization of N-carboxyanhydride. The structure of the polymers is studied by capillary electrophoresis, low-pressure gel-permeation chromatography, circular dichroism, and enzymatic hydrolysis with trypsin. At the first stage of synthesis, a low-molecular-mass strongly branched core of the polymer is formed. At the second stage, polylysine chains are grafted via one point onto amino groups of N-terminal lysine moieties of the low-molecular-mass core through their carboxyl ends. 相似文献
A method for preparing hyperbranched poly(L-lysine) via the polymerization of N?-carbobenzoxy-L-lysine-N-carboxyanhydride has been developed in order to regulate the molecular mass and size of this polymer and to modify amino groups of its N-terminal lysine residues. This method includes the reductive removal of an N?-carbobenzoxy group by hydrogen over activated palladium in the presence of a chain termination agent, which is the activated ether of Nα-tert-butyloxycarbonylhistidine. The structure of the polymers has been studied by capillary electrophoresis, circular dichroism, and molecular hydrodynamics. 相似文献
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. 相似文献
Functionalized star polymers with tetraaniline on their surface have been successfully prepared by substitution reaction of N-succinimidyl-terminated star polymers with tetraaniline. A novel functional RAFT agent bearing N-succinimidyl group was used in the RAFT polymerization of styrene, and N-succinimidyl groups-terminated polystyrenes with narrow molecular weight distribution were obtained. The star polymers with reactive N-succinimidyl groups on their surface were synthesized via RAFT polymerization of DVB. Polymerization mechanism study by gel permeation chromatography displayed that complete disappearance of linear polymers in the products is difficult. The N-succinimidyl-terminated PSt, polymer stars with surface N-succinimidyl groups and the PSt-b-tetraaniline stars were characterized by 1H NMR spectroscopy, FT-IR and GPC. 相似文献
A series of novel well-defined chain-end-functionalized polystyrenes having 2, 4, 8, and 16 chiral ephedrine moieties dendritically distributed at their hyperbranched chain-ends were quantitatively synthesized. Their well-defined architectures were fully confirmed by elemental analysis, FTIR, SEC as well as by 1H and 13C NMR spectroscopies. These polymers were precisely controlled in the molecular weight and molecular weight distribution as well as well-defined in chain-end-functionalities. These dendritic chiral polymers serve as highly enantioselective chiral ligands in the enantioselective addition of diethylzinc to a series of N-diphenylphosphinoyl arylimines. Among them, chiral dendrimer having eight ephedrine moieties at the chain-ends afforded the corresponding enantiomerically enriched phosphinoylamides in good to high yields with enantioselectivities up to 93% ee. The obtained enantioselectivities are comparable with those obtained by using N-benzylephedrine and its corresponding copolymer as chiral ligands. 相似文献
Although poly(N-acyl dithieno[3,2-b:2′,3′-d]pyrrole)s have attracted great attention as a new class of conducting polymers with highly stabilized energy levels, hyperbranched polymers based on this monomer type have not yet been studied. Thus, this work aims at the synthesis of novel hyperbranched polymers containing N-benzoyl dithieno[3,23,2-b:2′,3′-d]pyrrole acceptor unit and 3-hexylthiophene donor moiety via the direct arylation polymerization method. Their structures, molecular weights and thermal properties were characterized via 1H NMR and FTIR spectroscopies, GPC, TGA, DSC and XRD measurements, and the optical properties were investigated by UV–vis and fluorescence spectroscopies.
Results
Hyperbranched conjugated polymers containing N-benzoyl dithieno[3,23,2-b:2′,3′-d]pyrrole acceptor unit and 3-hexylthiophene donor moiety, linked with either triphenylamine or triphenylbenzene as branching unit, were obtained via direct arylation polymerization of the N-benzoyl dithieno[3,23,2-b:2′,3′-d]pyrrole, 2,5-dibromo 3-hexylthiophene and tris(4-bromophenyl)amine (or 1,3,5-tris(4-bromophenyl)benzene) monomers. Organic solvent-soluble polymers with number-average molecular weights of around 18,000 g mol?1 were obtained in 80–92% yields. The DSC and XRD results suggested that the branching structure hindered the stacking of polymer chains, leading to crystalline domains with less ordered packing in comparison with the linear analogous polymers. The results revealed that the hyperbranched polymer with triphenylbenzene as the branching unit exhibited a strong red-shift of the maximum absorption wavelength, attributed to a higher polymer stacking order as a result of the planar structure of triphenylbenzene.
Conclusion
Both hyperbranched polymers with triphenylamine/triphenylbenzene as branching moieties exhibited high structural order in thin films, which can be promising for organic solar cell applications. The UV–vis absorption of the hyperbranched polymer containing triphenylbenzene as branching unit was red-shifted as compared with the triphenylamine-containing polymer, as a result of a higher chain packing degree.
The hydrodynamic and conformational properties of a hyperbranched polymethylallylcarbosilane in hexane solutions have been studied by light scattering, sedimentation, translational diffusion, and viscometry. Fractions with M = (1–75) × 103 have been used in experiments. The solution behavior of the hyperbranched polymer significantly differs from the properties of both spherical particles and linear polymers. The shape of hyperbranched polymethylallylcarbosilane macromolecules differs from spherical—the asymmetry factor is p ≤ 1.5. Polymethylallylcarbosilane macromolecules in solutions are characterized by compact structure—the hydrodynamic radius is not higher than 4 nm at M = 75 × 103. 相似文献
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% (Jsc = 8.78 mA/cm2, Voc = 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. 相似文献
Carboxylic acid terminated aromatic and semiaromatic hyperbranched polyamide-esters (HBPAEs) containing pyrimidine moieties were prepared by polycondensation of 4-hydroxy-2,6-diaminopyrimidine (CBB′) to a double molar ratio of various diacid chlorides (A2) without any catalyst. The products were soluble in organic solvents, such as N,N-dimethylformamide, N-methyl-2-pyrrolidone and displayed glass transition temperature (Tg) between 180 and 244 °C. The polymerization products have been investigated with FTIR, 1H and 13C NMR analyses and the degree of branching was higher than 60%. Amorphous polymers had inherent viscosity (ηinh) ranging between 0.21-0.28 dL/g and had excellent thermal stability with 10% weight loss at 346-508 °C. 相似文献
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. 相似文献
Novel hyperbranched shape-memory polyurethanes based on ε-caprolactone were prepared via A2 + B3 approach with different molecular weights (Mw); 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. 相似文献
Water-soluble acrylamide monomers N-(hydroxymethyl)acrylamide, N-(hydroxymethyl)methacrylamide, N,N-diethanolacrylamide, N,N-diethanolmethacrylamide, N,N-methylethanolacrylamide, and N,N-methylethanolmethacrylamide have been synthesized and characterized. The kinetics and thermodynamics of the free-radical polymerization of these monomers and of the model compounds N-isopropylacrylamide and acrylamide have been studied by the methods of isothermal and scanning calorimetry. The structure and the solubility of the said polymers in water and organic solvents have been investigated and their molecular-mass characteristics and temperatures of glass transition (Tg) and melting (Tm) have been examined by DSC, liquid chromatography, 1H NMR and IR spectroscopy, and chemical analysis of functional groups. Hydrogels and amphiphilic network polymers based on acrylamide monomers have been prepared and characterized. 相似文献
The hydrodynamic and conformational properties of hyperbranched polycarbosilanes with different lengths of branches, namely, poly(methyl(allyl)carbosilane) containing three CH2 groups between branching centers and poly(methyl(undecenyl)carbosilane) whose branches are composed of 11 CH2 groups, have been studied in dilute solutions in hexane using the methods of molecular hydrodynamics and optics. Fractions with M < 17.5 × 104 have been used in experiments. The hydrodynamic properties of the above polycarbosilanes differ significantly from those of linear polymers since hyperbranched macromolecules are compact and their shape differs only slightly from spherical. The lengthening of chains between branching centers causes a change in the hydrodynamic characteristics, and the difference between hyperbranched polymers and dendrimers becomes more pronounced. As the length of branches increases, their conformation changes from an extended trans chain to a more or less bent rod. 相似文献
The thermodynamics, kinetics, and mechanism of the anionic polymerization of a number of acrylamide monomers has been studied with the use of isothermal and scanning calorimetry, liquid chromatography, 1H NMR and IR spectroscopy, mass spectrometry, and chemical analysis of functional groups. It has been demonstrated that the polymerization system shows the living character and the interchain exchange reactions are absent. It has been shown that N,N-diethanolacrylamide and N,N-diethanol(meth)acrylamide are uninvolved in anionic polymerization. The causes of this phenomenon have been ascertained. The products of the anionic polymerization of acrylamides are hyperbranched copolymers containing heterochain and carbochain fragments. Macromolecules contain end amide and acrylamide groups; in some macromolecules, end tert-butoxide groups of the used polymerization initiator are detected. For the products of the anionic polymerization of the acrylamide monomers under study, the temperatures of glass transition and melting have been measured. 相似文献
Dendronized hyperbranched polymer (DHP) is a new kind of polymer, which combines the advantages of dendrimers and hyperbranched polymers. In this work, two dendronized hyperbranched polymers, DHPG0 and DHPG1, were successfully prepared through the simple “A3+B2” type Sonogashira coupling reaction. The nonlinear optical (NLO) effects of DHPG0 and DHPG1, characterized by the d33 values, were 183 and 220 pm V–1 respectively, higher than those of their analogues of dendronized polymers and dendrimers, thanks to the special topological structure. Also, the obtained polymers displayed excellent solubility, good processability, and high thermal stability. 相似文献