As a continued study on combined use of different antibacterial chemistries, N-chloramine and short chain Quaternary ammonium compound (QAC) were immobilized on modified poly (ethylene terephthalate) (PET) surface in various ratios via “click” chemistry. In this study, contribution of surface bound QAC to the conversion of cyclic and acyclic N-H to N-Cl, fastest recharging chlorination as well as the most effective antibacterial efficacy was investigated. Surface bound positive charge at the density of 8.4x1016charges/cm2 achieved highest equilibrium conversion and facilitated a nine-fold increase in conversion of sterically hindered acyclic N-H to N-Cl from 0.39 to 3.92%. Within the range of 2.8x1016 to 8.4x1016charges/cm2, highest active chlorine loading within first five minutes of chlorination was observed on sample loaded with 4.6x1016charges/cm2.As it comes to PET surface grafted with a cyclic N-chloramine precursor, the presence of 2x1016charges/cm2 enabled a five-fold increase in the conversion of cyclic N-H to N-Cl. The highest biocidal efficacy was observed for sample loaded with cyclic N-chloramine/QAC 17.2:10 which presented total kill of E.coli (5.8 log reduction) in 10 minutes compared to 1.9 log reduction for other ratios (22.8/10, 75.5/10) tested at a similar level of active chlorine(223±6ppm respectively). / October 2016

A burn is a type of injury to the skin caused by fire, heat, electricity, chemicals, radiation or friction. It occurs in all age groups. Burn wound infection remains the leading cause of skin graft failure and one of the leading causes of burn injury related mortality. Dressings impregnated with silver compounds are the mainstay of treatment for burn wounds to prevent or combat the infection. However, most commercially available silver based wound dressings cause trauma upon removal because of adhesion to the wound bed. A recent study has shown that burn dressing related pain is linked to more severe depressive and posttraumatic stress symptoms. Furthermore, emerging resistance associated with silver based wound dressings is a growing concern. Organic N-chloramines have been in clinical use for over 180 years thanks to their effectiveness toward a broad spectrum of microorganisms, and no resistance has been yet reported. This study aimed to develop an “ideal” wound dressing with both antibacterial and atraumatic properties. Poly(ethylene terephthalate) (PET) fabrics are among the most representative base materials in burn wound dressings and thus were chosen as the substrate. Specifically, a very thin layer of polyacrylamide (PAm) hydrogel was deposited onto the surface of PET fabric via plasma activation and photopolymerization. The treated PET fabric (termed as “PET-PAm”) was characterized with attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and water contact angle measurement. We adapted an in vitro wet-gelatin adherence model to evaluate the effect of hydrogel deposition on reducing the adherence of PET. The deposited hydrogel layer was found to lower the adherence of PET fabrics. The peeling energy of PET decreased drastically from 2231.5 J/m2 to nearly 250 J/m2 after the deposition of hydrogel. On the other hand, we have also synthesized a series of new “composite” biocides with both N-chloramine and quaternary ammonium (QA) moieties. Those “composite” biocides exert boosted killing efficiency against methicillin-resistant Staphylococcus aureus (MRSA) and multi-drug resistant (MDR) Pseudomonas aeruginosa. The deposited hydrogel layer can also serve as the reservoir for the loading of the novel N-chloramine based “composite” biocides, to achieve a both non-adherent and antibacterial wound dressing.

Three advanced methodologies for the preparation of extremely sterically hindered tertiary alkyl amines have been developed. The syntheses of 28 novel tertiary alkylamines that accommodate unusual steric hindrance are detailed. The electrophilic amination of alkyl Grignard reagents with N-chlorodialkylamines, in the presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA) as a key additive, gives a variety of unprecedentedly sterically hindered tertiary alkylamines in good yields. Alternative strategy to 1-adamantyl-substituted (1-Ad) sterically hindered tertiary amines, which involved instead an SN1 reaction between 1-Ad cation with various secondary amines, is described. A complementary strategy to 1-Ad-based sterically hindered tertiary amines, which involves an iminium salt intermediate, is also reported. Salient features of the three protocols that are detailed here include unusual tolerance of steric hindrance, mild reaction conditions employed, ease of product isolation-purification, and absence of catalysts/transition metals. The molecular structures of two faithful examples of extremely sterically hindered tertiary alkylamines were determined by single crystal X-ray diffraction, and the height “h” of nitrogen pyramid of these compounds were measured. The NMR spectra show a restriction in rotation at room temperature among many hindered tertiary amines, and some of them exhibit two complete sets of peaks for two non-equivalent rotamers at room temperature. 15N NMR has been applied to study the structural changes in highly sterically hindered tertiary amines. Most of these compounds have been shown to undergo Hofmann type elimination reaction upon thermolysis at 100 degree in inert solvents, like toluene. / In der vorliegenden Arbeit wurden drei Methoden zur Synthese von tertitären Aminen mit extremer sterischer Hinderung entwickelt und zur Synthese von 28 neuen tertiären Alkylaminen mit entsprechender sterischer Hinderung angewendet. Die elektrophile Aminierung von Grignard-Reagenzien mit N-Chlordialkylaminen, unter Zusatz von N,N,N′,N′-Tetramethylethylendiamin (TMEDA) als Schlüsselkomponente, ermöglicht einen einfachen Zugang zu einer Vielzahl von tertiären Aminen mit extremer sterischer Hinderung mit guten Ausbeuten. Eine alternative Synthesestrategie unter SN1-Bedingungen führt zu sterisch-gehinderten 1-Adamantyl-substituierten (1-Ad) tertiären Aminen durch die Reaktion eines 1-Ad-Kations mit unterschiedlichen sterisch-gehinderten sekundären Aminen. Angelehnt an die zuvor beschriebene Reaktion können auch sterisch gehinderte Imine über eine Iminium-Salz-Zwischenstufe zu sterisch-gehinderten 1-Ad-substituierten tertiären Aminen umgesetzt werden. Auch in diesen Fall zeichnet sich die Reaktion durch eine bemerkenswerte Toleranz gegenüber sterischer Hinderung, milden Reaktionsbedingungen, leichte Produktisolierbarkeit und die Abwesenheit von Übergangsmetallkatalysatoren aus. Die molekulare Struktur zweier repräsentativer tertiärer Alkylamine mit extremer sterischer Hinderung wurde mittels Röntgeneinkristallstrukturanalyse untersucht und die Höhe “h” ihrer Stickstoff-Pyramide bestimmt. Die NMR-Spektren zeigen bei RT eine Einschränkung der freien Rotation um die N-C-Bindungsachse, teilweise führt dies zu vollständig getrennten Signalsätzen für die einzelnen Rotamere. 15N-NMR-Spektroskopie wurde ebenfalls zur Untersuchung von Strukturveränderungen genutzt. In inerten Lösungsmitteln, wie Toluol, zeigen die Verbindungen bei 100 °C in den meisten Fällen eine Hofmann-Eliminierung.