No abstract

Well-defined" long-subchain hyperbranched poly(methyl methacrylate) (lsc-hp PMMA) was obtained under the reaction condition in disfavor of self-cyclization of seesaw macromonomer as well as triggered by the intrinsic hindrance of 1,1disubstituted chain ends of seesaw macromonomer. Firstly, seesaw-type alkynyl-(PMMA-Br)2 with one alkynyl group at the chain center and two bromine groups at each chain end was synthesized by atom transfer radical polymerization (ATRP). After the azidation of alkynyl-(PMMA-Br)2, seesaw macromonomer of alkynyl-(PMMA-N3)2 underwent click reaction under high concentration in a good solvent to produce lsc-hp PMMA, almost without intrachain cyclization of macromonomer. Compared with our previous reports, steric hindrance of 1,1-disubstituted MMA units endowed almost no self-cyclization of alkynyl-(PMMA-N3)2 macromonomer. Therefore, lsc-hp PMMA with exact subchain length were obtained except the polydispersity of overall molecular weight. The chemical structure of lsc-hp PMMA was fully confirmed through the combination of gel permeation chromatography (GPC) with different detectors, proton nuclear magnetic resonance spectroscopy and Fourier transform infrared analyses. Furthermore, the formation kinetics for lsc-hp PMMA was monitored based on GPC with multi-angle laser light scattering detector and followed the equation: ln[(DPw + 1)/2] = [A]0kAB,0(1 -e -αt )/α, where DPw is absolute weight-average amount of macromonomers in hyperbranched polymers."Well-defined" hyperbranched PMMA almost without self-cyclization was obtained through click reaction, facilitated by high concentration, good solvent and di-substituted chain-ends.

Net cationicity of membrane-disruptive antimicrobials is necessary for their activity but may elicit immune attack when administered intravenously. By cloaking a dendritic polycation (G2) with poly(caprolactone-b-ethylene glycol) (PCL-b-PEG), we obtain a nanoparticle antimicrobial, G2-g-(PCL-b-PEG), which exhibits neutral surface charge but kills >99.9% of inoculated bacterial cells at ≤8 μg/mL. The observed activity may be attributed PCL's responsive degradation by bacterial lipase and the consequent exposure of the membrane-disruptive, bactericidal G2 core. Moreover, G2-g-(PCL-b-PEG) exhibits good colloidal stability in the presence of serum and insignificant hemolytic toxicity even at ≥2048 μg/mL. suggesting good blood compatibility required for intravenous administration.

Long-subchain Janus-dendritic copolymers composed of PSt and PtBA half-dendrons, up to the third generation, were prepared under alternating chemical and local confinement. All the Janus-dendritic copolymers exhibited generation-dependent microphase separation.