Amphiphilic hyperbranched polyelectrolytes: a new type of polysoap

Hyperbranched hydrophobized polyelectrolytes of the ionene type are prepared. They are investigated as a new type of polysoap, with respect to viscosifying behaviour, surface activity and solubilization power. Compared to linear analogues, the visoasifying effect is reduced. Compared to classical polysoap architectures, such as analogous "tail-end-type" and "head-type" polysoaps, the hyperbranched polysoaps behave rather similarly to the "head-type" ones: they exhibit notable surface activity, whereas the solubilization capacity is moderate only

Tailoring of stimuli-responsive water soluble acrylamide and methacrylamide polymers

The tailoring of the lower critical solution temperature (LCST) polymers of acrylamide and methacrylamide in water is achieved by chemical modification of freely water soluble precursor polymers poly[N-2-hydroxypropylmethacrylamide], poly[N,N-bis(hydroxyethyl)acrylamide] and poly[N-(tris(hydroxymethyl)-methyl)acrylamide]. Two principal reactions, namely acetylation and cinnamoylation, are applied. By varying the acylating agent as well as the extend of acylation, the LCST can be tailored easily. The cloud points observed for the different polymer series do not correlate with the apparent hydrophilicity of the parent polymers according to the content of hydroxyl groups. The results thus exemplify the difficulties to predict the behavior of modified thermosensitive polymers by simply analysing the balance of hydrophilic to hydrophobic molecular fragments. Chemical modification by cinnamoylation provides photoreactive copolymers e.g susceptible to photocrosslinking. When the polymers are prepared by polymerization using a disulfide-functionalized azo-initiator efficient grafting of the modified copolymers on gold surfaces is possible to prepare ultrathin hydrogel films, as demonstrated by Surface Plasmon Resonance

Adsorption of polyelectrolyte multilayers on polymer surfaces

Different from the conventional use of charged supports, the assembly of thin coatings by alternate adsorption of oppositely charged polyelectrolytes was realized on a variety of uncharged standard polymers, such as poly(propylene), poly(styrene), poly(methyl methacrylate), and poly(ethylene terephthalate). For the multilayer buildup, the polyelectrolyte pair poly(styrenesulfonate)/poly(choline methacrylate) was used. The quality of the coatings was investigated by UV/vis spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), and X-ray photoelectron spectroscopy (XPS). The multilayer deposition on poly(propylene) (PP) and poly(ethylene terephthalate) (PET) was investigated in detail. On polar poly(ethylene terephthalate) supports, the regular growth of multilayer assemblies is evidenced. In contrast, on less polar supports, in particular on PP, the quality of the poly(styrenesulfonate)/poly(choline methacrylate) multilayers is inferior. However, if a hydrophobically modified poly(choline methacrylate) is employed instead, good quality multilayers are obtained even on PP. Thus, by appropriate choice of the polyelectrolytes used, even very hydrophobic and polar substrates become useful for the alternate adsorption technique

Influence of the Near Molecular Vicinity on the Temperature Regulated Fluorescence Response of Poly(N-vinylcaprolactam)

A series of new fluorescent dye bearing monomers, including glycomonomers, based on maleamide and maleic esteramide was synthesized. The dye monomers were incorporated by radical copolymerization into thermo-responsive poly(N‑vinyl-caprolactam) that displays a lower critical solution temperature (LCST) in aqueous solution. The effects of the local molecular environment on the polymers’ luminescence, in particular on the fluorescence intensity and the extent of solvatochromism, were investigated below as well as above the phase transition. By attaching substituents of varying size and polarity in the close vicinity of the fluorophore, and by varying the spacer groups connecting the dyes to the polymer backbone, we explored the underlying structure–property relationships, in order to establish rules for successful sensor designs, e.g., for molecular thermometers. Most importantly, spacer groups of sufficient length separating the fluorophore from the polymer backbone proved to be crucial for obtaining pronounced temperature regulated fluorescence responses

Polyelectrolyte multilayer assemblies containing nonlinear optical dyes

An ionene-type polycation incorporating a nonlinear optical chromophore was synthesized. It was employed for the assembly of alternating polyelectrolyte multilayers on charged and uncharged substrates, using different organic polyanions as well as montmorillonite clay as anionic counterparts. The assembly process was followed by UV/vis spectroscopy. The influences of the choice of anionic species and of variations in the layer architecture were studied, Different kinds of aggregation were observed for different species of polyanions employed, and the increase of absorbance with the number of layers proved to be dependent. on the specific multilayer composition. The degree of orientation of the chromophores was investigated by second-harmonic generation and the nonlinear response was found to depend strongly on the anionic species. This result demonstrates that polyelectrolyte multilayers do not necessarily have a centrosymmetric structure, as generally assumed

Polyelectrolyte multilayers containing photoreactive groups

The synthesis of a photocrosslinkable polycation and its use in the assembly of alternating polyelectrolyte multilayers are described. Characterization by UV/VIS spectroscopy and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) reveals the influence of the crosslinking on the physical properties of the build-ups. Remarkably, the assembly of such multilayer structures is not only possible on hydrophilic substrates, but also on apolar poly(propylene). In this case, the crosslinkable polycation turns out to be especially useful to obtain stable, solvent resistant coatings

Cationic polyacrylamide copolymers (PAMs): environmental half life determination in sludge-treated soil

Abstract Background Cationic polyacrylamide copolymers (PAMs) are used for sludge dewatering in municipal waste water treatment and might enter the environment by spreading of the sludge on agricultural land. Concern has been expressed since little is known about the degradation of PAMs in soils. To obtain detailed information on the polymer’s fate in the soil compartment, the degradation of 14C-radiolabelled PAM in an outdoor lysimeter was studied. Results No plant uptake and leaching of radioactivity was observed. There was practically no vertical movement of polymer and no transformation products found at the end of the study. For the top 10 cm soil layer, a mass balance was established throughout the study. About 10% of applied radioactivity was not extractable from soil even with a matrix destructive method, and this was concluded to be bound residue. Characterization of extractable radioactivity by means of GPC-analysis showed a significant decrease of the molecular weight of the PAM with time. The decrease in molecular weight indicates a breakdown of the polymer backbone (the C–C-chain), and is assumed to be primary degradation. The total radioactivity content in the 10 cm top soil layer was quantified every 6 months over a period of 3 years. The results show a significant decrease of the total radioactivity over time and this is defined as ultimate degradation following the definition of OECD and EPA. Based on the data, a half-life time of 2.0 × 103 days and a rate constant of 0.00035/day were calculated. With a χ 2 of 12.0 the results of the calculation are thus valid and reliable. The rate constant indicates a mineralization of 22.5% within a period of 2 years based on the total recovered radioactivity. This half-life time is solely based on mineralization and does not take into account the degradation of the polymer backbone, hydrolysis of the side chains, incorporation into the soil matrix, and thus is a conservative approach. Conclusions 14C-PAM degrades very slowly in soil after land-spreading as a component of sewage sludge. Even in a very conservative evaluation which only considered the loss of radioactivity, a half-life time of 5.4 years was determined

Smart bioactive surfaces

The purpose of this highlight is to define the emerging field of bioactive surfaces. In recent years, various types of synthetic materials capable of "communicating'' with biological objects such as nucleic acids, proteins, polysaccharides, viruses, bacteria or living cells have been described in the literature. This novel area of research certainly goes beyond the traditional field of smart materials and includes different types of sophisticated interactions with biological entities, such as reversible adhesion, conformational control, biologically-triggered release and selective permeation. These novel materials may be 2D planar surfaces as well as colloidal objects or 3D scaffolds. Overall, they show great promise for numerous applications in biosciences and biotechnology. For instance, practical applications of bioactive surfaces in the fields of bioseparation, cell engineering, biochips and stem-cell differentiation are briefly discussed herein