Abstract: Poly(acrylicacid-co-allyl acrylate) statistical copolymers were synthesized in a controlled manner in two steps: first tert.butyl acrylate and allyl acrylate were polymerized via atom transfer radical polymerization (ATRP) and afterwords the tert.butyl protective groups were removed via hydrolysis. Samples of self cleaning glass (SCG) were coated with thin films of poly(acrylicacid-co-allyl acrylate) and cross-linked afterwards by UV irradiation (in the presence of a photoinitiator and an accelerator). Solution cast thin films were transparent and homogeneous before and after UV cross-linking. The irradiated samples were found to be hydrophilic (4 < 20°) and water insoluble. The coating prevented the spontaneous hydrophobization of the SCG by residual silicon exhaled from the sealing material. The TiO 2 photocatalyst that covers the glass surface was found to strip
Abstract: We describe the preparation of a poly(acrylicacid) (PAA) brush, polymerized by atom transfer radical polymerization (ATRP) of tert-butyl acrylate (tBA) and subsequent acid hydrolysis, on the flat gold surfaces of quartz-crystal microbalance (QCM) crystals. The PAA brushes were characterized by Fourier transform infrared (FT-IR) spectroscopy, ellipsometry and water contact angle analysis. The interaction of the PAA brushes with human serum albumin (HSA) was studied for a range of ionic strengths and pH conditions by quartz-crystal microbalance with dissipation monitoring (QCM-D). The quantitative analysis showed a strong adsorption of protein molecules onto the PAA brush. By increasing the ionic strength, we were able to release a fraction of the initially bound HSA molecules. This finding highlights the importance of counterions in the polyelectrolyte- mediated protein adsorption/desorption. A comparison with recent calorimetric studies related to the binding of HSA to polyelectrolytes allowed us to fully analyze the QCM data based on the results of the thermodynamic analysis of the binding process.
2.1. Bulk reticulation
The efficacy of low amounts of allylic groups along the backbone to generate crosslinked material was tested. A defined amount of polymer poly(acrylicacid-co-allyl acrylate) 90/10 was dissolved in THF to yield a concentration of 0.1g/mL followed by addition of photo-initiator 2 wt % as well as the addition of an accelerator 3 wt %. Complete dissolution preventing cross-linking was ensured by stirring the mixture at room temperature in the dark. After evaporation of the solvent, the sample was irradiated for four hours with a 300 W UV lamp; the distance between sample and lamp was 30 cm. After that, THF was added to the solid material and kept overnight in the dark. The solvent was removed and the sample was dried at 50 °C for four hours. By weighing the solid material it was found that 82 wt % of the polymer was cross-linked. For thin film preparation, the polymer was cross-linked according to the same procedure.
The results in Table 1 indicate that the elongation at break is significantly higher for the membranes prepared with AA and AMPS, despite the fact that in two cases the fraction of base material is lower than for GH170 and GH220. The good mechanical stability of these PEMs is suggested to be due to the fact that both monomers belong to the acrylate monomers, whereas GMA and HEMA are methacrylates. While the latter show only very little transfer to polymer, it is well known that radical polymerizations of acrylate monomers are associated with significant intra- and intermolecular chain transfer to polymer leading to branched polymer [ 51 ]. The branched material may explain the comparably high mechanical stability. This explanation is in line with a report by Faturechi et al., who observed that the presence of poly(acrylicacid) has a positive influence on the mechanical property of composite materials [ 52 ]. 3.3. Electrochemical Properties
oxides containing one or more of W, Cu, Co, Ni, Fe, Pb, Bi, Sn, Sb, or Si [10–12]. Contact time is kept to a minimum, at a few seconds, to avoid over-oxidation. Acrylicacid is isolated from the e ffluent gas of the second-stage oxidation by contact with water in an absorber column to give an aqueous solution of 20 to 70 wt% [13, 14]. After extraction with an organic solvent, such as ethyl acetate, butyl acetate, ethyl acrylate, 2-butanone or aromatic hydrocarbons, the acrylicacid can be further purified by distillation or re-crystallization before polymerization. To prevent unintentional polymerization of the acrylicacid monomer, dis- tillation is carried out in the presence of polymerization inhibitor, such as hydroquinone or hydroquinone monomethyl ether, at low temperature and reduced pressure .
Crude acrylicacid (99.7-99.8 % purity) is manufactured in a two stage oxidation process starting from propylene. By-products formed are maleic anhydride, propionic acid, acetic acid, furfural and sometimes traces of allyl acrylate and benzaldehyde. Crude acrylicacid is used in the production of commodity acrylates including methyl, ethyl, n-butyl, and 2- ethylhexyl acrylates. These acrylates are used to produce, e.g., coatings, adhesives, sealants, textiles, fibres, varnishes and polishes. Both crystallization and distillation are applied to purify crude acrylicacid. In its pure form, acrylicacid is a clear, colorless liquid with a characteristic acrid odor, presenting the following chemical properties: melting point at 285 K, boiling point at 412 K and ΔfH°gas = −330.7 ± 4.2 kJ·mol −1 . Glacial acrylicacid normally contains about 200 ppm of methyl ethyl hydrochinone to prevent polymerization during storage and transportation. Acrylicacid in its glacial form is used to produce homo- and copolymers of acrylic and methacrylic acid (“polyacrylic acid”), superabsorbent polymers (based on sodium polyacrylate) and detergent co- builders (chelating agents for the removal of alkaline earth ions).
The chemiluminescence inhibition by the test- com pounds is the highest when they contain an hydroxyl group in the p a ra position to the side chain o f the cinnamic acid, as com pared to com pounds having such a group in the orth o or m etha positions, or having m ethoxylated groups. Dihy drogenation of the double bond in the side chain abolishes the inhibition o f chemiluminescence al together, and even tends to enhance PMA-mediat- ed chemiluminescence. N o such m odulations were noticed in the control systems, when no luminol or PM A were added to the reaction test-tubes. A m ong the acrylicacid derivatives - 3-(4-imidazo- lyl)-acrylicacid was the m ost suppressive agent of the heterocyclic com pounds tested.
The application of derivatives of cam phor as chiral auxiliaries [1, 2] and starting m aterials [3-6] is a well investigated area in organic chemis try, and num erous reports on the general chemis try of this ketone exist. Surprisingly, only little work has been done on the isomeric fenchone (l,3,3-trimethylbicyclo[2.2.1]heptan-2-one) (1), al though it is available from the natural chiral pool in almost enantiom erically pure form as well. The main drawback, com pared with camphor, for the developm ent of its chemistry, is w ithout doubt the position of its carbonyl group betw een quaternary carbon atoms, first established by Semmler , which excludes derivatization in the a-position. Notew orthy among its reactions are the form ation of 3-isopropyl-toluene by treatm ent with phos phorus pentoxide above 100 °C , and of 3,4-di- m ethylacetophenone by heating with sulfuric acid . The mechanism of the latter rearrangem ent has been elucidated by means of labeling with 14C and involves a primary 1,2-methyl shift of the car- bocation formed by protonation of the carbonyl group . The isomeric cam phor is a by-product of this reaction. Thus, rearrangem ents can be ex
20 g of 4 were refluxed with 200 ml o f 6 M HC1 for 8 - 1 0 h. A fter cooling to —20 °C, the precipitated phthalic acid was rem oved by suction filtration and the clear filtrate brought to dryness in a vacuum d e siccator over KOH. The dry product was recrystal lized from m ethanol/isopropanol. Yield: 11.2 g (92%) o f white crystals, m .p. 147 °C.
discussed . According to the “preferential exclusion hypothesis”, established for protein stabilization, solutes are preferentially excluded from the surface resulting in the formation of a stabilizing solvent layer [17, 178-179]. However, it is questionable if this hypothesis can be adapted to nucleic acid nanoparticles, as the relatively high amounts of cryoprotectants required point to a nonspecific bulk stabilization [17, 178-179]. Based on the “glass formation or vitrification hypothesis”, nucleic acid nanoparticles are entrapped in the amorphous gassy matrix when the sample is cooled below the glass transition temperature (Tg`) limiting particle mobility and thus, preventing particle aggregation [17, 178]. As some sugars were able to preserve particle size at temperatures well above Tg` vitrification cannot be the only stabilization mechanism . The “particle isolation hypothesis” states that particles have to be sufficiently separated in the freeze-concentrate in order to inhibit particle aggregation, which is observed above a critical excipient to complex ratio . However, these three mechanisms are not suitable to solely explain the stabilization of nucleic acid nanoparticles during freezing. Thus, the influence of freezing on nucleic acid nanoparticles and underlying stabilization mechanisms during freezing will be addressed in detail in Chapter 6.
First, selective reduction of the carbonic acid to a prim ary alcohol with diborane or borane-dim ethyl- sulfide complex , and second, oxidation of the alcohol to an aldehyde function with pyridinium dichrom ate  or other approved reagents (Fig. 4). The reduction of 1 to the alcohol 6 was accomplished easily in 65% yield but the oxidation of 6 failed. T reatm ent of 6 with pyridinium dichrom ate yielded only overoxidized product 1 whereas 6 rem ained un changed by treatm ent with pyridiniumchlorochro- m ate . O th er reagents were not tried with regard to the acid lability of the protective groups.
Stizolobic acid was recrystallized from n-propa- nol/water (6:4, v/v) after adding the authentic amino acid (32 mg) dissolved in a minimum amount (3 —4 ml) of hot solvent and allowing the solution to stand overnight in a cold room. The crystals (specific activity 4.2 x 103 dpm//miol) were washed with ice-cold solvent and recrystallization were further repeated until the compounds show constant specific radioactivity (9 — 12 times).
The biosynthesis of carboxylic acids including fatty acids from biomass is central in envis- aged biorefinery concepts. The productivities are often, however, low due to product toxicity that hamper whole-cell biocatalyst performance. Here, we have investigated factors that influence the tolerance of Escherichia coli to medium chain carboxylic acid (i.e., n-hepta- noic acid)-induced stress. The metabolic and genomic responses of E. coli BL21(DE3) and MG1655 grown in the presence of n-heptanoic acid indicated that the GadA/B-based glu- tamic acid-dependent acid resistance (GDAR) system might be critical for cellular toler- ance. The GDAR system, which is responsible for scavenging intracellular protons by catalyzing decarboxylation of glutamic acid, was inactive in E. coli BL21(DE3). Activation of the GDAR system in this strain by overexpressing the rcsB and dsrA genes, of which the gene products are involved in the activation of GadE and RpoS, respectively, resulted in acid tolerance not only to HCl but also to n-heptanoic acid. Furthermore, activation of the GDAR system allowed the recombinant E. coli BL21(DE3) expressing the alcohol dehydro- genase of Micrococcus luteus and the Baeyer-Villiger monooxygenase of Pseudomonas
the degree o f form ation of the hydrogen bonds in Fig. 2 the absorbance of the continuum is shown as function of the added acid. This figure dem on strates that complete form ation of the hydrogen bonds with great proton polarizability occurs with the aspartic acid-aspartate systems at a mol ratio o f about 1.5 mol acid per mol salt, and with glut amic acid-glutam ate systems at a mol ratio of about 2.5. In the 1:1 mixtures in the case o f the aspartic acid-aspartate systems 95%, and in the case o f the glutamic acid-glutam ate systems 75% of the hydrogen bonds are formed.