New polymorph of 4,4'-(Butadiyne-1,4-diyl)-bis-(2,2,6,6-tetramethyl-4-hydroxypiperidin-1-oxyl)

Journal ArticleA new polymorph of the title diradical has been characterized by X-ray diffraction, vibrational spectroscopy, and magnetic susceptibility; its radiation induced polymerization has not been achieved, but thermal treatment turns the crystals black and explosive decomposition occurs at-140 °C

PEGylation of Polyethylenimine Lowers Acute Toxicity while Retaining Anti-Biofilm and β-Lactam Potentiation Properties against Antibiotic-Resistant Pathogens

Bacterial biofilms, often impenetrable to antibiotic medications, are a leading cause of poor wound healing. The prognosis is worse for wounds with biofilms of antimicrobial-resistant (AMR) bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant S. epidermidis (MRSE), and multi-drug resistant Pseudomonas aeruginosa (MDR-PA). Resistance hinders initial treatment of standard-of-care antibiotics. The persistence of MRSA, MRSE, and/or MDR-PA often allows acute infections to become chronic wound infections. The water-soluble hydrophilic properties of low-molecular-weight (600 Da) branched polyethylenimine (600 Da BPEI) enable easy drug delivery to directly attack AMR and biofilms in the wound environment as a topical agent for wound treatment. To mitigate toxicity issues, we have modified 600 Da BPEI with polyethylene glycol (PEG) in a straightforward one-step reaction. The PEG–BPEI molecules disable β-lactam resistance in MRSA, MRSE, and MDR-PA while also having the ability to dissolve established biofilms. PEG-BPEI accomplishes these tasks independently, resulting in a multifunction potentiation agent. We envision wound treatment with antibiotics given topically, orally, or intravenously in which external application of PEG–BPEIs disables biofilms and resistance mechanisms. In the absence of a robust pipeline of new drugs, existing drugs and regimens must be re-evaluated as combination(s) with potentiators. The PEGylation of 600 Da BPEI provides new opportunities to meet this goal with a single compound whose multifunction properties are retained while lowering acute toxicity.We want to thank Dr. Phil Bourne and acknowledge the use of the Protein Production Core (PPC) at the University of Oklahoma, Norman. PPC is supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20GM103640. Open Access fees paid for in whole or in part by the University of Oklahoma Libraries.Ye

Cyclopolymerization of Unsaturated Paracyclophanes: Electrically Conducting Polymers (Flourescence).

Polymerization of (E,E)-{6.2}paracyclophane-1,5-diene (A) proceeds by an intra-intermolecular mechanism to give polymer B containing {3.2}paracyclophane repeat units. Polymerization occurs with free radical or cationic initiation; anionic initiation was unsuccessful. The cationic process is clearly favored and propagation proceeds through a stabilized carbonium ion inter-mediate. Molecular weight distribution can be controlled by varying the monomer to initiator ratio, temperature and polymerization medium. Polymer B is of interest because its structure allows alignment of adjacent cyclophane units. Such alignment and overlap of cofacial (pi)-systems leads to unusual optical and electronic properties. Fluores-cence studies indicate that energy migration may occur in B by formation of "extended excimers" consisting of several aligned repeat units. Electron spin resonance (ESR) studies indicate that oxidative "doping" of B occurs by formation of radical cations which become mobile within aligned (pi)-system segments. Doped B has considerable metallic character as evidenced by a Pauli-type temperature dependence of the ESR signal intensity over the range 100-300(DEGREES)K. The conductivity of oxidized B (ca. 10('-4) S(.)cm('-1)) places it in the semiconductor range. Films of B show good retention of physical integrity after oxidation and fair environmental stability. (E,E,E,E)-{6.6}paracyclophane-1,5,13,17-tetraene (C) was ther-mally polymerized in the solid state to give polymer D. Polymer D exhibits both enhanced bathochromic shifts in its fluorescence spectrum and increased conductivity on oxidation, relative to B, reflecting the higher degree of cofacial stacking of aromatic rings, as expected for its rigidly oriented structure.Ph.D.Polymer chemistryUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/160316/1/8502820.pd

Extended cooperative electronic effects in poly(( E , E )-[6.2]paracyclophane-1,5-diene)

Fluorescence spectroscopy of poly(( E , E )-[6.2]paracyclophane-1,5-diene) shows the existence of several emission maxima which appear at wavelengths longer than that of the [3.2]paracyclophane repeat-unit excimer. These maxima appear to be emission bands due to “extended excimer” fluorescence from multiples of electronically interacting repeat units. Oxidation of the polymer by exposure to iodine vapor results in a material which exhibits a strong, asymmetric electron-spin-resonance spectrum with g = ca. 2.00 and a DC conductivity of 5 X 10 —4 S-cm —1 . These results are interpreted by a model in which segments of interacting radical cation salts occur pendant to and along the polymer chains but are of random length and orientation in the bulk polymer. Similar results were obtained for a structurally related polymer containing [3.3]paracyclophane rings.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38821/1/080240512_ftp.pd