Hydrophilic polymeric dyes

Use of Sephadex Gels with Aqueous Pyridine Solvent to Determine Purity Levels of Hydrophilic Polymeric Dyes Containing Hydrophobic Impurities... 

In a reverse microemulsion, the hydrolysis and polymerization of the silicate precursor occur in the water droplet, therefore, to dope dyes in the silica nanoparticles they must be water soluble. However, a number of organic dye molecules are hydrophobic, requiring modifications prior to doping. Several methods are available to link a hydrophobic dye molecule to a water soluble group. A simple and effective example is to link a hydrophilic dextran to the dye molecules [8]. This modification can greatly enhance the water solubility of hydrophobic dye molecules, but will increase the cost of resultant DDSNs. 

Mechanism of Dyeing. Wool has a polymeric structure based on amino acids. It is dyed either in its neutral or in its nel positively charged form. As with cellulose, wool, heing a hydrophilic liher. is dyed with water-soluble dyes that contain sulfonic acid groups to impart solubility. 

Previous research aimed at removing pesticide residues from contaminated fabrics has been directed at removal of a particular pesticide chemical and/or formulation of pesticide, with no effect toward comparing the pesticide residue s composition to that of common soil. Fabric selection for this study allowed a comparison of both hydrophilic and hydrophobic fibers and the effect of fabric type on soil removal. Two fabrics were identified for the study. Denim was 100% cotton fabric of twill weave dyed with indigo dyes. This fabric was 14 ounce, comparable to the heavy weight denim found in jeans. The second fabric was Gore Tex, a three layer structure consisting of an outer layer of rip-stop nylon and an inner layer of nylon tricot laminated to a film. The film was a micro-porous, polymeric film or polytetrafluoroethylene (PTFE). Previous studies on pesticide penetration found Gore Tex to be impermeable to pesticides. Thermal comfort studies found it to be relatively comfortable, similar In comfort to the commonly worn denim jeans and a chambray shirt. 

Also aiming at biomedical applications are nanoscaled hydrogels, prepared in inverse miniemulsion. In crosslinked poly(oligo(ethylene glycol) monomethyl ether methacrylate) (POEOMA) nanogels hydrophilic dyes as the polymeric dye (rhodamine isothiocyanate (RITC) dextran) [41], rhodamine in combination with the drug doxorubicin [42] or gold nanoparticles with bovine serum albumin [43] could be encapsulated. 

Interfacial radical alternating copolymerization of hydrophilic vinylethers with hydrophobic maleates can be conducted in direct [181] and in inverse [182] miniemulsion, leading to encapsulation of organic liquids or water, respectively. Since the monomers do not homopolymerize, the alternating copolymerization can only take place at the interface where both monomers meet. The polymerization is initiated by an interfacially active azo initiator. The authors could show that the water soluble dye Rhodamine B can be encapsulated in the inverse miniemulsion process and released from the capsules [182]. 

Solid phase extraction (see Chapter 3) has been successfully used to extract Sudan dyes from spices using a surface-modified polymeric-based column that has hydrophilic, hydrophobic, or tt-tt retention mechanisms. This particular phase can be used to extract both polar and nonpolar compounds. An example of a Sudan red dye is given in Figure 11.7. 

It is possible to modify the interfaces between liquids with specific additives. This was discovered by andent and medieval investigators and applied in the form of soaps, and later in food technology and in the application of dyes. The mechanisms of these additives only came to be realized in about 1900. Such additives are generally molecules with hydrophobic and hydrophilic sedions that align along interfaces between the two liquid phases. They reduce interfadal tension and stabilize phase morphology to smaller dispersed phase sites. This phenomenon was realized by IG Farbenindustrie chemists who applied it in the late 1920s in emulsion polymerization that they used to produce synthetic rubber. 

The approach of enzymatically sensitive polymers is also widely used in the case of polymeric micelles that physically encapsulate their cargo and release it upon enzymatic degradation of the polymer of which they are composed. One example of this is the work of Mao and co-workers (Mao and Gan, 2009). They synthesized amphiphilic diblock copolymers based on poly(glyddol-WocA - -caprolactone) (PG-h-PCL) with well-controlled structure and pendant hydroxyl groups along the hydrophilic block. These copolymers formed 74-95 nm micelles that demonstrated enzymatically triggered release of the encapsulated dye (pyrene) in the presence of lipase, due to degradation of the PCL block, which resulted in micelle dissociation. 

Cell adhesion. For most applications the adhesion of cells is of fnndamental interest being the initial event of cell attachment. A simple method to quantify adherent cells is to incnbate cells over a snrface for a period of time snbsequently followed by the detachment of loosely adherent cells by gently washing the surface. Remaining cells can be labeled by flnorescent dyes and quantihed using flnorescent measnrements. Cell adhesion assays are also freqnently used to assess monocyte or platelet adhesion on polymeric snrfaces [215, 216]. In this context Hezi-Yamit et al. [217] did show that polymer hydrophilicity should be considered as a parameter to assess the biocompatibility of polymer surfaces. They showed that hydrophobic polymers such as PBMA or SIBS promote the adhesion of inflammatory activated monocytes while more hydrophilic polymers (e.g. PC (Phosphorylcholine) polymer) lead to less pro-inflammatory responses. 

Hyperbranched poly(aryl ether oxindole)s (hb-PAE-Oxns) with a DB of 100% were prepared by Fu et al. [176] from an isatin-based AB2 monomer (1—36, Scheme 12) by one-pot polymerization without using toxic organometaUics nor chromatographic purification. The hb-PAE-Oxns soluble in apolar solvents were able to encapsulate a hydrophilic dye from the same polymer. 

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