Thin films with tunable properties are very interesting for potential applications as functional coatings with, for example, anti-icing or improved easy-to-clean properties. A novel "reactive layer stack" approach was developed to create covalently grafted mono- and multilayers of poly(glycidyl methacrylate)/poly(tert-butyl acrylate) di-block copolymers. Because these copolymers contain poly(glycidyl methacrylate) blocks they behave as self-cross-linking materials after creation of acrylic acid functionalities by splitting off the tert-butyl units. The ellipsometrically determined coating thickness of the resulting hydrophilic multilayers depended linearly on the number of applied layers. Amphiphilic films with tunable wettability were prepared using triblock terpolymers with an additional poly(methyl methacrylate) block. The mechanism of the formation of the (multi)layers was investigated in detail by studying the acidolysis of the surface-linked tert-butyl acrylate blocks by infrared reflection absorbance spectroscopy, accompanied by surface analysis using atomic force microscopy and contact angle measurements. In the case of the amphiphilic and switchable terpolymer layers this reaction was very sensitive to the used acidic reagent.

The adsorption of poly(vinylformamide) (PVFA) and its derivative statistical copolymer poly(vinyl-formamide-co-vinylamine) (PVFA-co-PVAm) on metallic copper and copper oxide particles as well as planar copper surfaces was studied as a function of the degree of hydrolysis of PVFA, the pH, and the polymer concentration in solution. The chemical composition and molecular structure of the PVFA-co-PVAm layers were investigated by surface-sensitive spectroscopic methods such as XPS, DRIFT spectroscopy, and ellipsometry. The findings allowed us to explain the adsorption mechanisms and the forces driving the PVFA-co-PVAm adsorption. It was shown that PVFA-co-PVAm layers thicker than 30 nm are able to protect the planar copper surface against corrosive attack.

Hydrogen-bonded complexation between high-molecular-weight poly(N-vinylpyrrolidone) (PVP, $\overline{M}_{\rm w}$ = 650 kDa) and poly(acrylic acid) (PAA) with weight-average molar weights between 0.9 and 50 kDa, is studied in dilute, salt-free aqueous solution. The onset of complexation, aggregation, and the structure of the formed particles are strongly influenced by PAA molecular weight, solution composition, and the method of sample preparation. With increasing poly(acrylic acid) chain length, IPCs show higher stability against aggregation. IPCs based on high-molecular-weight PAA show core-corona architecture ensuring good sterical stabilization, whereas for those containing the shortest polyacid a loose soft-sphere structure without distinct borders of different chain densities is found.

Poly(N-vinyl pyrrolidone) (PVP) is a widely used biocompatible polymer. PVP can be crosslinked by electron beam irradiation even in dry state. In contact with water it forms hydrogels. In a previous work we analyzed the crosslinking behavior of PVP bulk gels and thin PVP films on silicon wafers under electron beam irradiation. In this work, we applied the electron beam lithography on dry PVP films. Different patterns with a width of less than 100 nm were written into the film with the e-beam of a scanning electron microscope. The topography of the patterned film is investigated by atomic force microscopy. For further applications, we tried to create a gradient of crosslinking density within the film using a combination of e-beam irradiation and e-beam lithography. (C) 2007 Wiley Periodicals, Inc.

Biocompatible hydrogels based on poly(N-vinyl pyrrolidone) (PVP) were synthesized by electron beam irradiation of the dry polymer under various conditions. Sol–gel analysis of the bulk gel (in mm range) gave a dose of gelation of 94kGy. As seen for various other polymers, the network density rises with the increase in dose. At around 350kGy, PVP began to decompose. Based on these observations, films in μm range on a silicon wafer were synthesized by electron beam irradiation. Due to irradiation, the films adhered irreversibly on the wafer. Their swelling behavior was analyzed by ellipsometry.

Cross-linking of water-soluble polymers by high-energy irradation provides a clean method for the synthesis of hydrogels. some applications of stimuli-sensistive polymers need different patterns in the micro- and submicrometer range on a supporting material. A dry layer of poly(vinyl methyl ether), on a Si-wafer was cross-linked and patterned by irradiation with the electron beam of a modified electron microscope. The patterns in the micro- and submicrometer range show good adhesion on the supporting material without adhesion promoter. The deformation and the elastic behavior of the pattern were tested by AFM. The formed gel structures were sensitive against changes in environmental condition. This offers a wide range of applications.

Temperature-sensitive hydrogel films were synthesized by electron beam irradiation of poly(vinyl methyl ether) (PVME) on silicon (Si/SiO(2)) substrates and gold (Au) coated glass slides. The temperature-dependent swelling behavior of the films in aqueous solution was characterized by in situ spectroscopic ellipsometry and a combination of surface plasmon resonance (SPR) and optical waveguide spectroscopy (OWS). The results of both techniques are compared. The suitability of both techniques for the characterization of the swelling behavior of thin hydrogel films is demonstrated. The volume swelling degree in the swollen state decreases with increasing radiation dose D. This is explained by the fact that the number of formed polymeric radicals, and hence cross-linking density, increases with D. Above the phase-transition temperature, the swelling degrees were independent of D, slightly above 1. The swelling/deswelling process was fully reversible and is mainly directed perpendicular to the substrate surface. The phase-transition temperature was determined to be T(cr) approximately 33 degrees C. However, T(cr) slightly decreases with increasing D and increasing film thickness d.

Temperature-sensitive hydrogels based on poly(vinyl methyl ether) (PVME) with ferroelectric or ferromagnetic properties were synthesized by high-energy irradiation. Barium titanate and poly(vinylidene fluoride) (PVDF) were used as ferroelectric filler and Ni as ferromagnetic filler. The filled PVME hydrogels were synthesized by electron beam or gamma-ray irradiation (of a suspension with 5-50 wt % of filler (with respect to polymer mass) in a 20 wt % aqueous PVME solution). Filling of the gel reduces the absolute swelling degree at low temperatures, but do not influence the phase-transition temperature of the gel. The particle distribution of the fillers inside the gel was visualized by field emission scanning electron microscopy. The fillers were incorporated in the PVME network and fixed because of their size (inorganic particles), as well as by chemical bonds (PVDF). The ferroelectric or ferromagnetic properties of the filled gels were proved. Measurements in a corresponding alternating field provide the hysteresis loop, for both the ferromagnetic and ferroelectric gel. (c) 2005 Wiley Periodicals, Inc.

Hydrogel blends were synthesized by electron beam irradiation and gamma-irradiation of aqueous solutions of two polymers. Poly(vinyl methyl ether) (PVME) was used as a temperature-sensitive and poly(N-vinyl pyrrolidone) (PVP) as a biocompatible compound. Hydrogels of different composition were generated at different irradiation doses (40120 kGy).The hydrogels were characterized with regard to their sol content, swelling behavior in dependence on the temperature and network properties. Network characterization (determination of molecular weight of net chains, elastic moduli) was performed with compression measurements by using RET equation. (c) 2005 Elsevier B.V. All rights reserved.

A dilute aqueous solution of the temperature-sensitive polymer, poly(vinyl methyl ether) (PVME), was irradiated by a pulsed electron beam in a closed-loop system. At temperatures, below the lower critical solution temperature (LCST), intramolecular crosslinked macromolecules, nanogels, were formed. With increasing radiation dose D the molecular weights Mw increase, whereas the dimensions (radius of gyration Rg, hydrodynamic radius Rh) of the formed nanogels decrease. The structure of the PVME nanogels was analyzed by field emission scanning electron microscopy (FESEM) and globular structures with d=(10–30)nm were observed. The phase-transition temperature of the nanogels, as determined by cloud point measurements, decreases from Tcr=36°C (non-irradiated polymer) to Tcr=29°C (cp=12.5mM, D=15kGy), because of the formation of additional crosslinks and an increase in molecular weights. The same behavior was observed for a pre-irradiated PVME (γ-irradiation) with higher molecular weight due to intermolecular crosslinks. After pulsed electron beam irradiation the molecular weight again slightly increases whereas the dimension decreases. Above D=1kGy the calculated ρ-parameter (ρ=Rg/Rh) is in the range of ρ=0.5–0.6 that corresponds to freely draining globular structures.

Temperature-sensitive hydrogel beads were prepared by radiation crosslinking of poly(vinylmethylether) PVME spheres wrapped in Ca-alginate. The obtained gel beads have diameters in the sub-millimeter or millimeter range (depending on the PVME concentration). They were characterized by sol-gel analysis, swelling measurements, and differential scanning calorimetry.The gel content g increases with increasing radiation dose D. The swelling degree Q(V) decreases with increasing PVME concentration c(p) and increasing D. In comparison to PVME bulkgels the phase-transition temperature of the synthesized PVME gel beads is a little decreased.

An aqueous deoxygenated dilute PVME solution (cP = 0.5 mass %) was irradiated with gamma-rays at different radiation doses (D = 0.2-10 kGy). At these concentrations and doses contracted molecules are formed but no macroscopic networks. For the analysis of the structural changes, the irradiated samples were analyzed by size exclusion chromatography (SEC) with a triple detector system, static light scattering, and viscometry. SEC measurements necessitate for the application of the universal calibration principle the knowledge of the Kuhn-Mark-Houwink (KMH) parameters. To obtain these parameters commercially available poly(vinyl methyl ether) was fractionated and analyzed by the same means. We found at 30 degrees C a KMH relationship to [eta] = 0.0226 (mL/g) x Mw(0.67) in THF. We observed an increase in molar masses without any significant structural changing for D < 0.5 kGy. With increasing radiation dose, the intramolecular cross-linking reaction becomes more and more important. The results of viscosity measurements show a slight increase in contraction for 1.0 kGy. For irradiation dose higher than D > 1.5 kGy, a strong contraction occurs. For D > 5.0 kGy, the favored intramolecular reactions lead to the formation of microgels.

The submicrometer structure of the temperature-sensitive hydrogels was observed by field emission scanning electron microscopy (FESEM), using synthesized hydrogels of different outer size and shape. The hydrogel structure strongly depends on the homogeneity of the polymer chains during the crosslinking process. A porous structure of the poly(vinyl-methyl-ether) (PVME) bulkgel, synthesized by electron beam irradiation of a concentrated polymer solution, was observed in the swollen state because the phase transitions temperature is acquired through the crosslinking process. Photo-cross I inking reaction of the poly(N-isopropylacrylamide) (PNIPAAm) copolymer in the dry state to form PNIPAAm thin films leads to a rather homogeneous structure. In the shrunk state both gels possess structure being more compact than in the swollen state. We also synthesized PVME and PNIPAAm gels with small outer dimensions in the range of some 100 nm. Heating of the thermo-sensitive polymer in diluted solutions collapses the polymer chains or aggregates. The crosslinking reaction (initiated by electron beam or UV irradiation) of these phase separated structures produces thermo-sensitive microgels. These microgel particles of PVME and PNIPAAm are spherical shape having diameters in the range of 30 - 500 nm.

The paper reviews recent results of radiation crosslinking of poly(vinyl methyl ether) (PVME). It will give an overview of possible characterization methods for both, soluble and crosslinked PVME. The irradiation of aqueous low concentrated PVME solutions with γ-rays of low doses results in structural changes of PVME molecules. We are able to monitor changes in the chemical structure by spectroscopic methods (IR, NMR) as well as the changes of molecular parameters (e.g. molecular weight, molecular weight distribution, branches) by classical methods for polymer characterization (size exclusion chromatography with diverse detector systems, SLS, viscosimetry). The characterization of the network parameters (crosslinking density νc, molecular weight of the network chains Mc) of PVME bulkgels crosslinked by irradiation at high dose values by classical methods (swelling and compression measurements) provides incorrect results because of the high porosity of the gels. PVME microgel particles can be prepared by irradiation of a phase separated diluted aqueous PVME solution above their lower critical solution temperature. These microgels with decreased dimensions were characterized by SLS, DLS and field emission scanning electron microscopy.

Journal Article Determination of Hydrogel Structures by FESEM- Measurements Get access Daniel Theiss, Daniel Theiss Institute of Physical Chemistry and Electrochemistry, Dresden University of Technology, D- 1062 Dresden, Germany Search for other works by this author on: Oxford Academic Google Scholar Thomas Schmidt, Thomas Schmidt Institute of Physical Chemistry and Electrochemistry, Dresden University of Technology, D- 1062 Dresden, Germany Search for other works by this author on: Oxford Academic Google Scholar Dirk Kuckling, Dirk Kuckling Institute of Macromolecular Chemistry and Textile Chemistry, Dresden University of Technology, D- 1062 Dresden, Germany Search for other works by this author on: Oxford Academic Google Scholar Karl- Friedrich Arndt, Karl- Friedrich Arndt Institute of Physical Chemistry and Electrochemistry, Dresden University of Technology, D- 1062 Dresden, Germany Search for other works by this author on: Oxford Academic Google Scholar Rudolf Reichelt Rudolf Reichelt Institute of Biomedical Physics and Biophysics, University of Münster, D-48149 Münster, Germany Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 9, Issue S03, 1 September 2003, Pages 368–369, https://doi.org/10.1017/S1431927603027144 Published: 05 September 2003

Oxidative polymerization of pyrrole (Py) has been studied in the presence of poly(vinyl methyl ether) (PVME) and crosslinked PVME microgels using FeCl3 as oxidant and water or aqueous ethanol as a dispersion medium. The influences of the reaction medium and oxidant addition mode on the morphology as well as properties of final particles are discussed. SEM images of dispersions prepared in the presence of uncrosslinked PVME in water or water/ethanol mixtures indicate small spherical particles (40–100 nm). Large needle-like polypyrrole particles (approximately 400 nm long; aspect ratio 8:1) are formed in aqueous ethanol in the presence of crosslinked PVME microgels at Py/PVME ratio higher than 2:1.

A thermo-sensitive hydrogel was synthesized by irradiation of an aqueous solution of poly(methyl vinyl ether) (PMVE) with electrons. At high polymer concentration a bulk gel was formed. Irradiation of diluted polymer solution at a temperature above the phase transition temperature conserves the structure of the polymer in the phase-separated state. The micro-particles formed under irradiation conditions possess also typical thermo-sensitive properties. Their diameter roughly amounts to 300–500nm in the swollen state depending on the temperature of the solution. Static and dynamic light scattering were used to determine the dimension of the formed particles. The dry, swollen, and shrunk state were structurally characterized by field emission scanning electron microscopy (FESEM).