Acetal crosslink

The polymer for this gel is common white glue (mostly poly[vinyl acetate]), crosslinked as above with borax. 

Schedli, N. Muenzel, and H. Holzarth, 1,3 dioxolyl acetals as powerful crosslinkers of pheno lie resin, Proc. SPIE 1925, 109 (1993) W. S. Huang, K.Y. Lee, R.K. J. Chen, and D. Schepsis, Negative tone resist system using vinyl cyclic acetal crosslinker, Proc. SPIE 2724, 315 (1996). H. Ito, Chemical amplification resists for microlithography, Adv. Polym. Sci. 172, 155 (2005). 

Phenyl acetate p-Quinone dioxime Toluene-2,4-diamine Tributyl phosphine 1,1,3-Triethoxy-3-methoxypropane Triethylene diamine Triethylenemelamine Trimethylolpropane tris-(B-(N-aziridinyl) propionate) Tris [1-(2-methyl-aziridinyl) phosphine oxide] Zinc acetylacetonate Zirconium acetate crosslinking agent, castings PEG-4 dimethacrylate crosslinking agent, coatings PEG-4 dimethacrylate... 

Biocompatible microgels for the delivery of protein and DNA biomolecules were developed using acrylamide monomer, a bisacrylamide acetal crosslinker and potassium persulphate initiator. Encapsulation was shown to provide protection from enzymatic degradation of the protein or DNA. These particles demonstrated pH sensitivity such that in an acidic environment, as in the lysosome, the polymeric carrier degraded and released the encapsulated biomolecule. 9 refs. 

Vinal fibers are made from polymers containing at least 50% vinyl alcohol units and in which at least 85% of the units are combined vinyl alcohol and acetal crosslink units. The fiber is inexpensive, resembles cotton in properties, and is produced in Japan. 

The use of degradable microgels for protein release, based on a bisacrylamide acetal crosslinker with a p-methoxy substituent as an acid degradable linkage [17], is shown schematically in Figure 2.8. 

Several authors have used glutaraldehyde (GTA) for HA crosslinking. GTA crosslinking needs to be performed under acidic conditions to obtain the acetal crosslinked product. Since this reaction is reversible under acidic pH, the acetal crosslinked hydrogel is obtained by neutralising the gel [41]. Another disadvantage of this strategy is the toxicity associated with GTA that limits its application in the biomedical field. 

Several approaches have been disclosed to make release coatings that can be printed with ink jet or laser jet printers (e.g., to make linerless labels). For example, Khatib and Langan [164] disclose a blend of two different acrylate functional silicones, one with a high level of acrylate functionality to provide the printability and one with a low level of acrylate functionality to provide easy PSA release. Lievre and Mirou [165] describe an aqueous blend of a crosslinkable silicone and poly(vinyl alcohol-vinyl acetate) resins while Shipston and Rice describe a blend of acrylic resin and a surfactant [166]. 

The resulting silanol group of a polymer chain condenses with acetoxy siloxy group of another polymer chain to form a siloxane (Si-O-Si) linkage (Scheme 8). Further similar reactions finally result in a crosslinked elastomer. Acetic acid is... 

A WBL can also be formed within the silicone phase but near the surface and caused by insufficiently crosslinked adhesive. This may result from an interference of the cure chemistry by species on the surface of substrate. An example where incompatibility between the substrate and the cure system can exist is the moisture cure condensation system. Acetic acid is released during the cure, and for substrates like concrete, the acid may form water-soluble salts at the interface. These salts create a weak boundary layer that will induce failure on exposure to rain. The CDT of polyolefins illustrates the direct effect of surface pretreatment and subsequent formation of a WBL by degradation of the polymer surface [72,73]. 

A similar type of condensation between a hydroxyl-containing polymer (such as secondary cellulose acetate) with VO(BrC6H4N=CHO CfiH4)2 CUVOL2CI] produces photoactive polymers [68]. When irradiated with UV light in the presence of styrene or MMA, grafted and crosslinked polymers were obtained ... 

Fig. I. Steady structure of crosslinked MA-EDMA copolymers obtained in solutions of acetic add of different concentrations. K — relative swelling coefficient, Ks — swelling coefficient (by a = 0 and a = 0.5, respectively)...

Chattopadhyay, S., Chaki, T.K., Bhowmick, A.K., Gao, G.J.P., and Bandyopadhyay, S., Structural characterization of electron-beam crosslinked thermoplastic elastomeric films from blends of polyethylene and ethylene-vinyl acetate copolymers, J. Appl. Polym. Sci., 81, 1936, 2001. 

Cortisone acetate has been incorporated into several polyanhydrides (15). The rates of release of cortisone acetate from microcapsules of poly(terephthaUc acid), poly(terephthaUc acid-sebacic acid) 50 50, and poly(carboxyphenoxypropane-sebacic acid) 50 50 are shown in Fig. 8. These microcapsules were produced by an interfacial condensation of a diacyl chloride in methylene chloride with the appropriate dicarboxylic acid in water, with or without the crosslinking agent trimesoyl chloride. This process produces irregular microcapsules with a rough surface. The release rates of cortisone acetate from these microcapsules varied correspondingly with the rate of degradation of the respective polyanhydrides. It can be expected that the duration of release of cortisone acetate from solid microspheres, such as those produced by the hot-melt process, would be considerably longer. 

Because this diketene acetal is so susceptible to cationic polymerization, acids cannot be used to catalyze its condensation with diols because the competing cationic polymerization of the diketene acetal double bonds leads to a crosslinked product. Linear polymers can, however, be prepared by using iodine in pyridine (11). Polymer structure was verified by 13c nmR spectroscopy as shown in Fig. 

To prepare crosslinked material, 2 eq of the diketene acetal is reacted with 1 eq of the diol and the resulting prepolymer is then reacted with a triol or a mixture of diols and triols. 

Because the ketene acetal-terminated prepolymer is a viscous Liquid at room temperature, therapeutic agents and the triol can be mixed into the prepolymer at room temperature and the mixture crosslink id at temperatures as low as 40°C. This allows incorporation of heat-sensitive therapeutic agents into a solid polymer under very mild conditions of thermal stress. However, because the prepolymer con-tedns reactive ketene acetal groups, any hydroxyl groups present in the therapeutic agent will result in the covalent attachment of the therapeutic agent to the matrix via ortho ester bonds (16). 

Polyvinyl alcohols may be applied as such or in crosslinked form [90]. Crosslinkers can be aldehydes (e.g., formaldehyde, acetaldehyde, glyoxal, glutaraldehyde), to form acetals, maleic acid or oxalic acid to form cross-linked ester bridges, or others (e.g., dimethylurea, polyacrolein, diisocyanate, divinyl sulfonate) [89,91]. 

The predominant RO membranes used in water applications include cellulose polymers, thin film oomposites (TFCs) consisting of aromatic polyamides, and crosslinked polyetherurea. Cellulosic membranes are formed by immersion casting of 30 to 40 percent polymer lacquers on a web immersed in water. These lacquers include cellulose acetate, triacetate, and acetate-butyrate. TFCs are formed by interfacial polymerization that involves coating a microporous membrane substrate with an aqueous prepolymer solution and immersing in a water-immiscible solvent containing a reactant [Petersen, J. Memhr. Sol., 83, 81 (1993)]. The Dow FilmTec FT-30 membrane developed by Cadotte uses 1-3 diaminobenzene prepolymer crosslinked with 1-3 and 1-4 benzenedicarboxylic acid chlorides. These membranes have NaCl retention and water permeability claims. 

Figure 3. Time dependence of the fraction R of unreacted aminostyrene residues during acetylation by 0.14 M acetic anhydride at 30°C. Methyl methacrylate copolymer in acetonitrile solution (0) linear poly-(methyl methacrylate-co-butyl methacrylate) swollen with acetonitrile Cd) methyl methacrylate copolymer crosslinked with 1 mole% ( ) and with 15 mole% ( ) ethylene dimethacrylate poly(methacrylate crosslinked with 3 mole% ethylene dimethacrylate containing entrapped poly(methyl acrylate-co-aminostyrene) ( ).

After 2 h incubation of the prepared antibody beads with UV-crosslinked extract in a cold room, the beads are washed 4 x with 100 /A RIPA buffer (50 mMTris-HCl pH 7.5, 150 rnMNaCl, 1% NP-40, 0.5% sodium deoxycholate, and 0.1% SDS) and lx with genomic DNA lysis buffer (50 mM Tris, pH 7.4, 10 mM EDTA, 500 mM NaCl, 2.5 mM DTT, 0.5 mM spermidine, 1% Triton X-100). Approximately 300 /(I of PK solution (1 mg/ml proteinase K in genomic DNA lysis buffer and 0.2 U//A RNase inhibitor) is added to the total lysate previously kept on ice and the beads are then incubated at 37° for 30 min. Gently flick the tubes to resuspend the beads every 10 min during the incubation. After removal of the proteinase K solution, 300 /A of RNA extraction solution (4 M guanidine thiocyanate, 0.5% sarkosyl, and 25 mM sodium citrate, pH7) is added to the beads, incubated for 10 min and the supernatant is mixed with 30 fig yeast tRNA (as a carrier) and 30 fil of 3 M sodium acetate. The RNA solution is phenol-chloroform extracted, ethanol-precipitated, and the pellet washed once with 70% ethanol. The dry pellet is used for 1st strand cDNA synthesis, followed by PCR analysis. The removal of proteins... 

M2C2H is slightly soluble in aqueous solutions, reportedly having a maximal solubility of 3.2 mg/ml in 0.1 M sodium acetate at pH 5.5. It is also soluble in organic solvents, which allows for the preparation of concentrated stock solutions to be made prior to addition of a small aliquot to an aqueous reaction mixture. The crosslinker is particularly stable in acetonitrile. 

Sulfo-SAMCA, sulfosuccinimidyl-7-azido-4-methylcoumarin-3-acetate, is a heterobifunctional reagent similar in design to SAED (Section 3.9, this chapter) (Thermo Fisher). One end of the crosslinker contains an amine-reactive sulfo-NHS ester, while the other end is an AMCA derivative (Chapter 9, Section 3) that contains a photosensitive phenyl azide group. Unlike... 

This technique has been applied to the concentration of organochlorine and organophosphorus insecticide [7,8] and various ethers, glycols amines, nitriles, hydrocarbons, and chlorinated hydrocarbons. Although this work was concerned with drinking water, it is a useful technique which may have application in seawater analysis. Cellulose acetate [9], ethyl cellulose acetate [6], and crosslinked polyethyleneinine [8] have been used as semi-permeable membranes. 

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