Yongwen Zhang

Facile preparation and characterization of highly antimicrobial colloid Ag or Au nanoparticles

A series of colloid silver or gold nanoparticles (AgNPs or AuNPs) were successfully prepared by in situ reduction and stabilization of hyperbranched poly(amidoamine) with terminal dimethylamine groups (HPAMAM-N(CH(3))(2)) in water, and they all exhibited highly antimicrobial activity. The particle size could be controlled easily by adjusting the molar ratio of N/Ag (or N/Au) in feed. When the molar ratio was 2, some aggregates of the nanoparticles separated from the colloidal solution, which showed some limited antimicrobial activity with the bacterial inhibition ratio of below 15%. As the molar ratio increased from 10 to 30, the average particle diameters decreased (from ca. 7.1 to 1.0 nm for AgNPs and from ca. 7.7 to 3.9 nm for AuNPs, respectively) and they all showed high dispersion stability and excellent antimicrobial efficiency. All the bacterial inhibition ratios reached up to ca. 98% at the low silver content of ca. 2.0 microg/mL or at the low gold content of ca. 2.8 microg/mL. The AgNPs or AuNPs with smaller particle size can provide much more effective contact surface with the bacteria, thus enhancing their antimicrobial efficiency. Besides, the cationic HPAMAM-N(CH(3))(2) can also do some contribution to the antimicrobial activity through the strong ionic interaction with the bacteria.

Hyperbranched Polyamidoamines Containing β‐Cyclodextrin for Controlled Release of Chlorambucil

This work is focused on the controlled drug release behavior of hyperbranched HPMA in the presence of beta-CD. Hence, three HPMA-beta-CDs and a pure HPMA were synthesized by Michael addition polymerization. As a model drug, CLB (an anti-cancer drug) was loaded into them via a solution method for in vitro release studies. The DSC results indicate that the CLB/polymer interactions are at the molecular level. Loading CLB into these polymers results in an evident increase in their glass transition temperatures, and DeltaT(g) depends on the beta-CD content. The controlled-release experiments show that the presence of beta-CD can appropriately slow the release of CLB from HPMA-beta-CDs and adjust the ratio of CLB released in total drug loading.

A physical gel made from hyperbranched polymer gelator

A novel hyperbranched polymer gelator has been synthesized, which can self-assemble into the thermoreversible physical gel in DMF, DMAC, pyridine, DMSO or NMP with the driving force of hydrogen bonds among amide and amine groups of the highly branched macromolecules.

Complex self-assembly of hyperbranched polyamidoamine/linear polyacrylic acid in water and their functionalization.

This paper studied the complex self-assembly of hyperbranched polyamidoamine (h-PAMAM) and linear polyaryalic acid (l-PAA) by the facile mixing of their aqueous solutions. The complex self-assembly behavior and mechanism were investigated by the optical microscopy, UV-vis spectrometer, TEM, and zeta potential measurements. Interestingly, various self-assembled aggregates from micelles to microscaled vesicles were obtained by adjusting the solution pH. Moreover, the hollow structure of the vesicles was successfully stabilized by using glutaric dialdehyde (GDA) to cross-link the PAMAM layer. As expected, the resulting hollow spheres were able to capture different noble metal ions from their aqueous solution and reduce them into nanoparticles in situ, hence forming the hybrid hollow spheres. Such hybrid hollow spheres might have potential application in catalytic fields.

Preparation of the crosslinked polymer electrolyte membranes based on a hyperbranched poly(amidoamine) and their proton conductivity

Abstract A series of novel crosslinked polymer electrolyte membranes were successfully prepared based on the modification of a hyperbranched poly(amidoamine) with terminal vinyl groups. The membranes possessed the different contents of proton-generating sites (i.e., protonated tertiary amine groups) and triflate (Tf2N-) in the crosslinked network. They showed good mechanical and thermal stability. The water uptakes of them were ca. 8.4-24.5%. Their proton conductivity was of the order of ca. 10-5-10-2 S/cm in the range of 30-80 °C, and the proton conductivity increased with improving the protonation ratio. AFM results disclosed the micro-phase separation of the hydrophilic proton-generating sites and the hydrophobic domains of Tf2N- ions. The resulting locally continuous hydrophilic clusters could provide proton transport channels to produce the high proton conductivity. This kind of polymer electrolyte membranes may have potential applications in PEFCs and other electrochemical fields.