Macromolecules desolvation

Gelatin and albumin nanoparticles have been prepared through desolvation of the dissolved macromolecules by either salts (e.g., sodium sulfate or ammonium sulfate) or ethanol [179-182], This is, in principle, similar to a simple coacervation method. The particles can then be insolubilized through cross-linking with an optimum amount of aldehydes. These phase separation methods avoid the use of oils as the external phase. 

The first applications of ESI in MS date from 1968. Dole et al. [5-6] investigated the possibility to transfer macromolecules from the liquid phase to the gas phase by electrospraying dilute solutions in a nitrogen bath gas. The hypothesis of Dole and cowoikers was that macro-ions can be produced by desolvating the charged droplets produced in electrospray. This ionization mechanism is called the charge residue model. 

Desolvation of water-insoluble macromolecules in nonaqueous solvents leads to the deposition of a coacervate layer around aqueous or solid disperse droplets. Table 8.13 lists both water-soluble and water-soluble macromolecules which have been used in coacervation processes. Desolvation, and thus coacervation, can be induced thermally and... 

Coacervation in aqneous phase can be classified into simple and complex. In simple coacervation, the polymer is salted ont by the action of electrolytes (sodium sulfate) or desolvated by the addition of an organic miscible water solvent, such as ethanol, or by increasing/decreasing temperature. In these cases, the macromolecule-macromolecule interactions are promoted, instead of the macromolecule-solvent interaction (Martins, 2012). Complex coacervation is defined as a Uqnid-liquid phase separation promoted by electrostatic interactions, hydrogen bonding, hydrophobic interactions, and polarization-induced attractive interactions occurring between two oppositely charged polymers in aqneons solution (Xiao et al., 2014). This technique is based on the ability of cationic and anionic water-solnble polymers to interact in water to form a liquid polymer-rich phase called complex coacervate (Martins, 2012). 

This theory also explains plasticization by nonsolvents (softeners). When introduced into the polymer mass, these molecules act by holding apart the polymer molecules and so breaking some unions between active centers on the polymer. It was also explained why internally plasticized systems behave worse with the temperature than the externally plasticized, since molecules of a separate plasticizer are free to solvate and desolvate the active centers on the resin macromolecules to a given extent, determined by the concentration, the temperature and the equilibrium involved in the system. Permanently bound side chains have no such freedom. Other properties such as the tear strength or the creep behavior of plasticized systems were also explained. 

---