Binding of highly branched poly(N-isopropylacrylamide) with vancomycin end groups to Staphylococcus aureus induced a coil-to-globule phase transition. The polymers aggregated this gram-positive bacteria (but not gram-negative bacteria) over a wide range of temperatures, but cooling to 24-26 degrees C progressed the polymer-bound bacteria through a globule-to-coil phase transition, after which the bacteria were released.

No abstract

Polymyxin peptide conjugated to the end groups of highly branched poly(N-isopropyl acrylamide) was shown to bind to a Gram negative bacterium, Pseudomonas aeruginosa . The nonbound polymer had a lower critical solution temperature (LCST) above 60 °C. However, binding caused aggregation, which was disrupted on cooling of the bacteria and polymer mixture. The data indicate that polymer binding of bacteria occurred by interaction of the end groups with lipopolysaccharide and that the binding decreased the LCST to below 37 °C. Cooling then progressed the polymer/bacteria aggregate through a bound LCST into an open polymer coil conformation that was not adhesive to P. aeruginosa .

This investigation reports controlled ring-opening polymerization of a vinylcyclopropane via copper-mediated atom transfer radical polymerization which leads to predominantly 1,5 ring-opening polymerization.

This paper describes a novel synthetic strategy for the preparation of thiol end-functionalized poly-(ethylene glycol) (PEG)-b-polyesters. Block copolymers containing an internal disulfide bond were prepared through the ring-opening polymerization of DL-lactide (LA) and -caprolactone (CL) employing a PEG disulfide [(PEG-S) 2 ] as the macroinitiator. This initiator was synthesized from R-tert-butanethio-ω-hydroxy-PEG (tBu-S-PEG) through the deprotection of tBu and the subsequent formation of a disulfide. The disulfide bond of the block copolymers was cleaved by reduction using tributylphosphine to generate block copolymers bearing a thiol at the PEG chain end. Thiolated PEG-b-PLA and PEG-b-PCL with number-average molecular weights (M n ) in the range of 3300-5800 and 3600-4600, respectively, were thereby obtained. The PLA and PCL contents could be varied according to the feed ratio and ranged between 20-47 and 15-30 mol %, respectively. Aqueous solutions of the disulfide block copolymers formed degradable gels at high concentration and underwent a gelsol transition upon an increase in temperature. The gels were liquefied by treating with dithiothreitol, indicating that the triblock configuration is essential for the gelation.