Poly(2-alkyl-2-oxazoline)s can be regarded as pseudo-peptides or bioinspired polymers, which are available through living/controlled cationic polymerization and polymer ("click") modification procedures. Materials and solution properties may be adjusted via the nature of the side chain (hydrophilic-hydrophobic, chiral, bio-functional, etc.), opening the way to stimulus-responsive materials and complex colloidal structures in aqueous environments. Herein, we give an overview over the macromolecular engineering of polyoxazolines, including the synthesis of biohybrids, and the "smart"/bioinspired aggregation behavior in solution.
Measurements of trace metal species in situ in a softwater
river, a hardwater lake, and a hardwater stream were
compared to the equilibrium distribution of species calculated
using two models, WHAM 6, incorporating humic ion
binding model VI and visual MINTEQ incorporating NICA−Donnan. Diffusive gradients in thin films (DGT) and
voltammetry at a gel integrated microelectrode (GIME)
were used to estimate dynamic species that are both labile
and mobile. The Donnan membrane technique (DMT)
and hollow fiber permeation liquid membrane (HFPLM)
were used to measure free ion activities. Predictions of
dominant metal species using the two models agreed
reasonably well, even when colloidal oxide components
were considered. Concentrations derived using GIME were
generally lower than those from DGT, consistent with
calculations of the lability criteria that take into account
the smaller time window available for the flux to GIME. Model
predictions of free ion activities generally did not agree
with measurements, highlighting the need for further work
and difficulties in obtaining appropriate input data.
Several techniques for speciation analysis of Cu, Zn, Cd,
Pb, and Ni are used in freshwater systems and compared
with respect to their performance and to the metal
species detected. The analytical techniques comprise the
following: (i) diffusion gradients in thin-film gels (DGT);
(ii) gel integrated microelectrodes combined to voltammetric
in situ profiling system (GIME−VIP); (iii) stripping
chronopotentiometry (SCP); (iv) flow-through and hollow
fiber permeation liquid membranes (FTPLM and HFPLM); (v)
Donnan membrane technique (DMT); (vi) competitive ligand-exchange/stripping voltammetry (CLE−SV). All methods
could be used both under hardwater and under softwater
conditions, although in some cases problems with
detection limits were encountered at the low total
concentrations. The detected Cu, Cd, and Pb concentrations
decreased in the order DGT ≥ GIME−VIP ≥ FTPLM ≥
HFPLM ≈ DMT (>CLE−SV for Cd), detected Zn decreased
as DGT ≥ GIME−VIP and Ni as DGT > DMT, in agreement
with the known dynamic features of these techniques.
Techniques involving in situ measurements (GIME−VIP)
or in situ exposure (DGT, DMT, and HFPLM) appear to be
appropriate in avoiding artifacts which may occur
during sampling and sample handling.
Electrospinning of nanofibers with cyclodextrin inclusion complexes (CD-ICs) is particularly attractive since distinct properties can be obtained by combining the nanofibers with specific functions of the CD-ICs. Here we report on the electrospinning of poly(methyl methacrylate) (PMMA) nanofibers containing cyclodextrin-menthol inclusion complexes (CD-menthol-ICs). These CD-menthol-IC functionalized nanofibers were developed with the purpose of producing functional nanofibers that contain fragrances/flavors with high temperature stability, and menthol was used as a model fragrance/flavor material. The PMMA nanofibers were electrospun with CD-menthol-ICs using three type of CD: alpha-CD, beta-CD, and gamma-CD. Direct pyrolysis mass spectrometry (DP-MS) studies showed that the thermal evaporation of menthol occurred over a very high and a broad temperature range (100-355 degrees C) for PMMA/CDmenthol-IC nanowebs, demonstrating the complexation of menthol with the CD cavity and its high temperature stability. Furthermore, as the size of CD cavity increased in the order alpha-CDbeta-CD>alpha-CD.
Cataloged from PDF version of article.Poly(methyl methacrylate) (PMMA) nanofibers containing the inclusion complex forming beta-cyclodextrin (β-CD) were successfully produced by means of electrospinning in order to develop functional nanofibrous webs for organic vapor waste treatment. Electrospinning of uniform PMMA nanofibers containing different loadings of β-CD (10%, 25% and 50% (w/w)) was achieved. The surface sensitive spectroscopic techniques; X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) showed that some of the β-CD molecules are present on the surface of the PMMA nanofibers, which is essential for the trapping of organic vapors by inclusion complexation. Direct pyrolysis mass spectrometry (DP-MS) studies showed that PMMA nanowebs containing β-CD can entrap organic vapors such as aniline, styrene and toluene from the surroundings due to inclusion complexation with β-CD that is present on the fiber surface. Our study showed that electrospun nanowebs functionalized with cyclodextrins may have the potential to be used as molecular filters and/or nanofilters for the treatment of organic vapor waste and air filtration purposes
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