The design, synthesis, and investigation of two series of side‐on dendrimers displaying nematic liquid crystal behavior at room temperature are described. The dendritic structures are derived from poly(amidoamine) (PAMAM‐(NH2)n) or poly(propylene imine) dendrimers (PPI‐(NH2)n) (with n = 4, 8, 16, 32, and 64) containing lateral attached mesogenic units in the periphery. The materials are characterized by 1H, 13C nuclear magnetic resonance (NMR) spectroscopy, matrix‐assisted laser desorption/ionization‐mass (MALDI‐TOF MS) spectrometry, differential scanning calorimetry (DSC), polarized optical microscopy (POM), and x‐ray diffraction spectroscopy. All dendrimers exhibit nematic mesophase behavior at room temperature. Conoscopic studies reveal that the nematic phase is uniaxial. The relationship between the structure of the two dendrimer series and the mesomorphic behavior is discussed.
AbstractPolyamidoamine (PAMAM) dendrimer is an extensively studied polymer in the biomedical research because of its low polydispersity, distinct molecular structure, and surface functionalities. Generally, a high-generational PAMAM dendrimer is used for gene delivery because transfection efficiency is dependent on charge density; however, an increase in charge density induces disruption of the cellular membrane, and damage to the membrane results in cytotoxicity. In this study, we selected PAMAM generation 2 to reduce the cytotoxic effect and conjugated RRILH and RRLHL sequences, nuclear localization signals (NLS) derived from herpesviridae to PAMAM generation 2. The transfection efficiency of RRILH-PAMAM G2 and RRLHL-PAMAM G2 was similar to that of polyethylenimine (PEI) in Neuro2A, HT22, and HaCaT cells, whereas their transfection efficiency was much higher than that of PEI in NIH3T3 cells. RRILH-PAMAM G2 showed relatively lower cytotoxicity than did RRLHL-PAMAM G2 in all cell lines, but the transfection capacity of the two polymers was similar. Our study shows that low-generational PAMAM dendrimer conjugated with NLS sequences has potential as an alternative to PEI in gene delivery. 相似文献
Three phosphorescent dendrimers ( IrC1 , IrC3 , and IrF2 ) with an iridium complex core and oligocarbazole or oligofluorene substituted ligands were synthesized and characterized. The structures of the oligocarbazole were designed to maintain high triplet energy of the ligands so that phosphorescence quenching in the resulting dendrimers can be prevented, while the oligofluorene in IrF2 resulted in undesired phosphorescence quenching. Best performance was obtained from an IrC3 based electrophosphorescent light‐emitting device with a maximum luminance of 13 060 cd · m?2 at a driving voltage of 11.5 V and a peak current‐efficiency of 4.3 cd · A?1 at a luminance of 3 400 cd · m?2, owing to its high PL efficiency, and efficient energy transfer between the iridium complex core and the ligands.
Summary: We have designed and synthesized novel diphenylamine‐substituted phenylazomethine dendrimers (DP‐Gn, n = 1, 2) as hole‐transport materials for organic light‐emitting diodes (OLEDs). These dendrimers similar to phenylazomethine dendrimers showed a stepwise metal complexation with metal ions. They have good multi‐redox properties attributed to the terminal amine moieties and excellent thermal stabilities. Double layer EL devices utilizing the dendrimers as a hole‐transport material and Alq3 as the emitting and electron transport materials were fabricated. The EL performances of the devices increased with higher dendrimer generations. Moreover, by using the metal ion (0.5 equiv. SnCl2)‐complexed DP‐G2 dendrimers, the luminance and EL efficiency of the devices were drastically increased by more than double and over 30%, respectively. These metal complexable phenylazomethine dendrimers are novel and promising materials for highly efficient OLEDs.
Structure of the diphenylamine‐substituted phenylazomethine dendrimer DP‐G2. 相似文献
The synthesis of a new potential anti-thrombogenic polymer is described. Limited halogenation of an aryloxysubstituted polyphosphazene, followed by quaternization with triethylamine yielded a polymer capable of forming polyelectrolyte complexes with sodium heparin. The results of preliminary clotting tests with bovine blood are presented. 相似文献
A series of ionic dendrimers is synthesized and used as conducting salt in carbonate‐based electrolytes for Li/S‐cells. The resulting electrolytes display increasing viscosity with increasing chain length of the side chains, both in the first‐ and second‐generation dendrimers. Higher conductivity is observed for the first‐generation dendrimers as compared to the second‐generation ones. While all cells show high cycle stability, the differences in dendrimer structure also influence the electrochemical behavior of the Li–S cells. Thus, discharge capacities of the corresponding Li–S cells correlate both with the viscosity and the conductivity of the electrolytes. The best electrolyte system is obtained with a first‐generation dendrimer having a short side chain, D1‐1, having the lowest viscosity and the highest conductivity, which delivers discharge capacities of 1150 mAh gsulfur?1 @ 0.5 C and 780 mAh gsulfur?1 @ 1 C. 相似文献
Microspheres of a hydrophobic and a hydrophilic poly(ether–ester) copolymer were evaluated for their in vitro and in vivo biocompatibility and degradation. The microspheres prior to and after sterilization were tested for in vitro cytotoxicity. The in vivo biocompatibility of the poly(ethylene glycol) terephthalate and poly(butylene terephthalate) (PEGT/PBT) microspheres was evaluated subcutaneously and intramuscularly for 24 weeks in rabbits. The in vivo degradation of the microspheres was studied microscopically and compared to the in vitro degradation. The in vitro and in vivo studies showed the biocompatibility of the microspheres of both the hydrophobic and the hydrophilic PEGT/PBT copolymer. Extracts of these microspheres showed no cytotoxic reactivity in the in vitro cytotoxicity test. Sterilization of the microspheres by gamma irradiation did not affect the cytotoxicity. PEGT/PBT microspheres injected subcutaneously and intramuscularly in rabbits showed a mild tissue response in vivo, in terms of the inflammatory response, the foreign body reaction and the granulation tissue response. Although an in vitro degradation experiment showed a decrease in molecular weight due to hydrolysis, the in vivo degradation of the microspheres was slower than previously published. 相似文献
Peripheral blood lymphocytes (PBL) were obtained from five patients with the acquired immune deficiency syndrome (AIDS), six homosexual males with lymphadenopathy, and five normal heterosexual controls. Modulation of virus-specific immunity was assayedin vitro by measuring the lymphocyte blastogenic response and the production of lymphokine (leukocyte inhibition factor; LIF) by PBL stimulated with herpes simplex virus (HSV) or cytomegalovirus (CMV) antigens in the presence or absence of interleukin-1 (IL-1) and interleukin-2 (IL-2). PBL from the control and lymphadenopathy subjects responded to both antigens in the lymphocyte transformation assay (LT) measured on day 7, and the responses were significantly enhanced in cultures grown in the presence of antigen and IL-2 (1 U/ml). PBL from the AIDS patients were unresponsive, but responsiveness was restored by the addition of IL-2. The addition of IL-1 (0.02 µg/ml) to antigen-stimulated PBL cultures failed to enhance the proliferative responses in all three study groups. LIF production was assayed in the supernatants from day 1 PBL cultures. LIF was not produced by PBL from AIDS patients grown in the presence of viral antigens, whereas three of five patients from the lymphadenopathy group, and three of five control subjects gave rise to positive responses. The addition of IL-1 to the antigenstimulated cultures enhanced LIF production in the control and lymphadenopathy groups but not in the AIDS patients. The addition of IL-2 did not modulate LIF production by antigen-stimulated PBL from the control oR AIDS patients while suppressing the LIF response of the similarly stimulated PBL from the lymphadenopathy patients. 相似文献
Novel biodegradable cross-linked co-polymers were prepared from poly(propylene glycol) diglycidylether (PPGDGE) and poly(ethylene imine) (PEI). PPGDGE and PEI were mixed at ambient temperature with varying PEI concentrations of 10, 15, 18.5, 25, 30, 40 and 50 wt%; the homogenous PPGDGE/PEI mixtures obtained were cured at elevated temperatures, resulting in formation of PPG–PEI cross-linked co-polymers via ring-opening reaction of PPGDGE with PEI. The physicochemical and biological properties of these co-polymers were dependent on the PEI content and the extent of curing reaction. The glass transition temperature of PPG–PEI cross-linked co-polymers varied in the range from ?14 to +42°C, while the co-polymers displayed composition-dependent mechanical behavior, from brittle to ductile with increasing PEI content from 18.5 wt% to 40 wt%. Chinese hamster ovary (CHO) cells were cultured on the PPG–PEI co-polymers; the MTT assay was used to measure cell viability and determine the cytotoxicity. The cell viability rate, relative to tissue-culture polystyrene (TCPS), increased from 49% to 125% with increasing PEI content from 18.5 wt% to 40 wt%. Although epoxy monomers usually exhibit cytotoxicity, the epoxy groups were exhausted via curing reaction in the fully cross-linked co-polymers. The PEI-cured PPG epoxy resin, i.e., PPG–PEI cross-linked co-polymers obtained in this study, showed excellent biocompatibility. 相似文献